JP2007057622A - Optical element, manufacturing method thereof, method for manufacturing shape transfer mold for optical element, and transfer mold for optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element of a phase modulation type having high light availability by attaining phase modulation of transmission light by means of a low aspect ratio structure like a sub-wavelength structure having a single height. <P>SOLUTION: The optical element changes the phase of transmission light by spatially modulating the height of at least a part of structures 2, has a finer structure than the wavelength of usage light and, therefore, attains the phase modulation of transmission light by using a fine structure having a narrower period than incident wavelength with different heights. Further, when wavelength of usage light is λ, incident angle is θ, refractive index of an incident medium is n1 and refractive index of a structure 2 is n2, the period of the structure is λ/(n1sinθ+n2) or less, thereby, the occurrence of transmission light due to higher order diffraction is eliminated and the optical element having high light availability is attained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin optical element used for a laser recording apparatus, a display apparatus, an image forming apparatus, optical communication, optical information processing, and the like, in particular, an optical element having functions such as condensing, branching, diffraction, and hologram, The optical element has a lens function, demultiplexing / multiplexing function, light intensity distribution conversion function, polarization separation function, or a combination of these functions. Furthermore, it has a multistage or continuous structure, and has a high diffraction efficiency. And a surface relief type diffractive optical element. Furthermore, the present invention relates to a method for manufacturing the optical element, and further relates to a method for manufacturing a shape transfer mold for an optical element used when manufacturing the optical element, and a shape transfer mold for an optical element manufactured by the manufacturing method. .

  In recent years, a structure in which two media having different refractive indexes (for example, one is air and the other isotropic medium) has a periodic structure smaller than the wavelength of light (SWS = Subwavelength Structure) is used. Such optical elements have been widely developed. These structures range from the resonance diffraction region to the equivalent refractive index region in the diffraction theory, and exhibit characteristics that are largely different from the diffractive optical element in the structure having a wavelength longer than that in the conventional scalar diffraction theory.

  A diffraction grating whose period is shorter than the wavelength is called a sub-wavelength grating. Among them, a grating having a period that is shorter and has only a 0th-order diffracted light in both transmission and reflection is called a 0th-order grating. Since these zero-order diffractive elements do not contain high-order diffracted light, it is possible to realize an element with high light utilization efficiency that does not cause energy loss due to high-order diffracted light in a diffractive optical element having a structure with a wavelength longer than that of the conventional. It is believed that there is.

  It is known that the 0th-order diffracted light transmitted through these sub-wavelength structures undergoes phase modulation due to refractive index change caused by the grating structure, and as shown in FIG. 35, the width of the structure is the same at the same height and pitch. The element which condenses light is implement | achieved by modulating only (fill factor modulation) (for example, nonpatent literature 1 (Journal of the Optical Society of America A, Vol14 (4), 901-906 (1997). ))reference).

Further, in Patent Document 1 (Japanese Patent Laid-Open No. 2001-318217), a diffractive optical element in which only the fill factor of the structure is modulated and the phase of the structure is spatially modulated by dividing the region of the structure is realized. is doing.
Further, in Patent Document 2 (Japanese Patent Laid-Open No. 2004-61905), a columnar sub-wavelength structure is used, and similarly, only the width (area) of the structure is modulated to realize a phase modulation optical element.

[Subwavelength structure manufacturing method]
The manufacturing method of the structure below the wavelength of the incident light varies greatly depending on the wavelength used. For a region where the wavelength is considerably longer than 1 micron (μm), many manufacturing methods such as photolithography, machining, and etching can be used.
However, in the wavelength region of the order of visible light, the period of the structure is on the order of submicrons, and the manufacturing method is limited. In particular, as a manufacturing method of a structure of about several hundred nm, an interference exposure method using an interference of laser light and an electron beam exposure method have been mainly used.

In the laser interference exposure method, a laser beam of blue to ultraviolet is usually interfered and irradiated to a photosensitive polymer material (resist) to form a structure of the interference pitch. At this time, the structure is formed in the resist, and the height is defined by the resist thickness.
Further, in the electron beam exposure method, an electron beam is condensed and scanned to irradiate the resist material, thereby producing a fine structure of the resist material. Similarly, the height is defined by the resist thickness.
When a fine structure is produced in a material other than a resist by these techniques, the structure is produced using a technique such as reactive dry etching or metal vapor deposition using this resist structure.

[Microstructure manufacturing method using laminated thin film]
In the method of manufacturing an optical element described in Patent Document 3 (Japanese Patent Application Laid-Open No. 2003-181678), a fine structure having flat surfaces with different heights is obtained by irradiating a transmission / absorption thin film arranged in multiple layers with laser light. Form. At this time, a diffractive optical element having a binary structure is formed by controlling the processing position of the fine structure.

In these conventional optical elements having a subwavelength structure, the height of the structure is made constant, and the phase of transmitted light is modulated by the width or area of the structure. FIG. 35 shows a conventional phase modulation type sub-wavelength element. In this way, only the fine fill factor having a constant pitch is modulated to control the phase of transmitted zero-order light.
It is known that the refractive index of a material in this subwavelength region is approximated by the following effective refractive index method (Equation 1) in many cases.

(Formula 1)
n _TE = √ {fn ₂ ² + (1-f) n ₁ ² }
n _TM = √ {[n ₁ ² n ₂ ² ] / [fn ₁ ² + (1-f) n ₂ ² ]}
f = w / p

Here, n _TE represents a refractive index with respect to a vertical polarization component in which the electric field vibrates parallel to the structure in FIG. 36, and n _TM represents a refractive index with respect to a component in which the electric field vibrates in a direction perpendicular to the structure. f represents a fill factor which is a ratio between the width w of the structure and the period (pitch) p.

FIG. 37 shows the effective refractive index (n) according to the fill factor when n1 = 1 and n2 = 1.5. Thus, it can be seen that both the TE wave and the TM wave can be controlled by the fill factor from n1 to n2. At this time, the effective refractive index of incident light having different polarizations is an intermediate value between the effective refractive indexes of the TE wave and TM wave depending on the polarization component.
At this time, the phase modulation of the transmitted zero-order light uses the effective refractive index n, the incident light wavelength is λ, and the transmitted optical path length is d.
φ = 2πnd / λ (Formula 2)
Given in.

At this time, for example, consider the structure of FIG. When the wavelength λ of the incident light is 800 nm, the pitch p of the structure is 400 nm, the refractive index is n1 = 1, n2 = 1.5, and a phase modulation of 2π is applied between a fill factor f of 1 and 0.2. In this case, the height d is about 2 microns. When the fill factor is 0.2, the width of the structure is 80 nm, and a structure with a very high aspect is required. It is very difficult to produce such a structure, and it has been difficult to obtain a large phase modulation of transmitted light only by modulation using a conventional fill factor. The phase modulation optical element in the sub-wavelength region often requires such a fine and high structure, which has been a big problem.
Furthermore, the structure having such a high aspect has a problem that it has weak mechanical strength and is weak against external force.

[Problems of manufacturing method]
In order to realize elements having fine structures with different heights, a conventional fine structure manufacturing method using laser interference is a method of forming a binary structure of a region having a high interference intensity and a region having a low interference intensity, Usually, since the processing height is defined by the resist thickness, there is a problem that it is difficult to control the height.
In the conventional electron beam exposure method, the height can be controlled by the exposure amount, but the processing speed is very slow because it is basically processing by point drawing, and it takes days to form a structure of several mm square. This has been a major problem in manufacturing.
In addition, these methods can produce the structure only in the resist, and when producing the structure with other materials, it is necessary to use another process such as reactive dry etching, which is complicated and costly. However, the problem is that the shape is changed and the shape is changed.

[Diffraction optical element, manufacturing method thereof, and problems in conventional manufacturing methods]
The diffractive optical element controls the spatial phase distribution of the laser light incident on the element, thereby controlling the light in various forms such as a beam condensing function, an intensity distribution conversion function, and a beam demultiplexing / combining function. It is an element capable of performing the above. The manufacturing method according to the present invention is directed to a surface relief type diffractive optical element having a multi-stage structure or a continuous and smooth structure capable of obtaining a high diffraction efficiency. Hereinafter, this is simply referred to as a diffractive optical element.

  An example of a diffractive optical element having a multistage structure according to the present invention is shown in FIG. The structure of the multi-stage diffractive optical element includes a structure based on a diffraction grating as shown in FIG. 25A and a structure where steps are randomly arranged two-dimensionally as shown in FIG. In general, a diffractive optical element has a structure with a height of several hundred nm to several μm and is formed with a pitch of several hundred nm to several tens of μm. It is several tens nm to 1 μm and several tens nm in the height direction.

The diffractive optical element and the manufacturing method thereof are described in detail in Non-Patent Document 2 (Latest diffractive optical element technology complete technical information association (2004) pp107-160).
The manufacturing method and problems in each manufacturing method will be briefly described below.

  As a manufacturing method of a diffractive optical element, it has been generally performed by machining using a diamond tool or the like. However, in the technique by machining, since the in-plane resolution is defined by the size of the tip of the cutting tool, it is difficult to achieve high resolution. In addition, it is difficult to machine a brittle material such as glass or a soft material such as resin with high accuracy.

  On the other hand, in recent years, as a technique having a high in-plane resolution, a technique using lithography, which is a semiconductor manufacturing technique, has been adopted. Examples of the lithography method include the following.

(1) Manufacturing Method by Photolithography This is a technique for producing a multi-stage structure by repeating a series of processes such as resist coating, mask pattern transfer by photolithography, pattern development, etching, and resist removal a plurality of times.
However, this manufacturing method has a large number of steps and is expensive. In addition, precise alignment is necessary when lithography is repeated a plurality of times, and alignment errors cause deterioration in device performance.

(2) Manufacturing method using gray scale mask
In contrast to the method of (1), there is a method using a gray scale mask as a method of manufacturing a diffractive optical element in one photolithography process. Gray scale masks have spatially different light transmittances with gradations, so that a resist having a three-dimensional shape can be produced by one-time mask pattern transfer.

(3) Production method by electron beam exposure This is a method of forming a pattern by condensing an electron beam, irradiating the resist, and moving the condensing point, and by producing while modulating the intensity of the electron beam, A three-dimensional shape whose depth direction differs depending on the location can be produced.

(4) Manufacturing method by condensing scanning of laser light By using laser light (mainly laser light in the ultraviolet region) instead of the electron beam, it is possible to manufacture the shape more easily.

With respect to the above methods (1) and (2), a mask is necessary.In particular, a gray scale mask is expensive, and is a diffractive optical element that is less likely to produce the same type in large quantities compared to a semiconductor element. It was not suitable for production.
In addition, regarding the manufacturing methods (2) to (4), the sensitivity of the resist is generally not linear with respect to the intensity of the laser beam or electron beam, and it is very difficult to precisely control the height. there were.

As a method for precisely controlling the height direction while maintaining high in-plane resolution as in these methods, a method using a multilayer structure has been proposed as follows.
For example, Patent Document 4 (Japanese Patent Laid-Open No. 5-333204) discloses a method of performing multiple exposures after applying multiple types of resists in multiple layers.
A method for producing a multi-stage shape by preparing a multilayer structure in advance and selectively removing them by laser ablation is disclosed in the above-mentioned Patent Document 3 (Japanese Patent Laid-Open No. 2003-181678).
In these methods using a multilayer structure, the depth of the structure can be precisely controlled, but a process is required to produce a multilayer film, and the number of layers of the multilayer structure is limited. There is a problem that the resolution is limited because the resolution depends on the accuracy when the multilayer film is manufactured.

JP 2001-318217 A JP 2004-61905 A JP 2003-181678 A JP-A-5-333204 JP-T-2004-503413 JP 2001-158050 A Journal of the Optical Society of America A, Vol 14 (4), 901-906 (1997) The latest diffractive optical element technology collection Technical Information Association (2004) pp107-160 Appl.Phys.Lett.83, 819-821 (2003) Opt.Lett. 22,132-134 (1997) Appl.Phys.Lett.74, 786-788 (1999) Appl.Opt. 33,863-867 (1994) Opt.Eng. 19, 297-305 (1980)

The present invention has been made in view of the above-mentioned problems of the background art, and the first problem is to solve the above-mentioned problem of the element structure and to transmit the same transmitted light as in the single-wavelength sub-wavelength structure. An object of the present invention is to provide an optical element that realizes phase modulation with a low aspect structure.
The second problem is to provide an optical element with high light utilization efficiency in addition to the first problem.
A third problem is to provide a phase modulation type optical element structure that is simple in design and easy to manufacture in addition to the first and second problems.
A fourth problem is to provide an optical element that is flexible to an incident angle change and easy to design and manufacture in addition to the first to third problems.
The fifth problem is to provide a diffractive optical element and a hologram optical element by phase modulation of transmitted light in addition to the first to fourth problems.
The sixth problem is to provide an optical element capable of realizing large phase modulation with a stable structure and more complicated modulation by two phase modulations in addition to the first to fifth problems.
A seventh problem is to provide an optical element that can be easily used as a condenser lens and a projection lens in addition to the first to sixth problems.
The eighth problem is to provide a condensing optical element such as a flat plate, a thin condensing lens, and a projection lens by using the phase modulation function in addition to the first to seventh problems.
A ninth problem is to provide a flat plate or a thin diffractive optical element that divides and shapes incident light using the phase modulation function in addition to the first to seventh problems.
The tenth problem is to provide a thin aberration correcting optical element by utilizing the phase modulation function in addition to the first to seventh problems.

An eleventh problem is to provide a method for manufacturing an optical element made of a fine structure having a plurality of heights with high speed and high accuracy, or a method for manufacturing a shape transfer mold for an optical element.
A twelfth problem is to provide a method for manufacturing an optical element composed of a fine structure having a plurality of heights at high speed and high accuracy, or a method for manufacturing a shape transfer mold for an optical element. It is to provide a manufacturing method capable of directly manufacturing an optical element or a shape transfer mold for an optical element without applying.
A thirteenth problem is to provide a method for manufacturing an optical element composed of a fine structure having a plurality of heights with high speed and high accuracy, or a method for manufacturing a shape transfer mold for an optical element. An object is to provide a manufacturing method of an optical element having a high controllability and a flat processed surface or a manufacturing method of a shape transfer mold for an optical element.
A fourteenth problem is to provide a method for manufacturing an optical element composed of a fine structure having a plurality of heights with high accuracy at high speed or a method for manufacturing a shape transfer mold for an optical element, and further, has a high aspect ratio. It is to provide a method for manufacturing an optical element having a fine structure or a method for manufacturing a shape transfer mold for an optical element.
A fifteenth problem is to provide a method for manufacturing an optical element composed of a fine structure having a plurality of heights at high speed and high accuracy, or a method for manufacturing a shape transfer mold for an optical element. An object of the present invention is to provide an optical element manufacturing method or a shape transfer mold manufacturing method for an optical element that is easily miniaturized and has high structure controllability.

In recent years, various methods using a two-photon or multi-photon process have been proposed as processing methods having three-dimensional spatial resolution.
For example, as shown in Non-Patent Document 3 (Appl. Phys. Lett. 83, 819-821 (2003)), by using a multiphoton process, a structure smaller than the diffraction limit in ordinary laser processing can be obtained. It is possible to produce. In addition, a structure having a high aspect ratio that is long in the vertical direction of the substrate and short in the horizontal direction of the substrate is formed by a single focused irradiation.
In Non-Patent Document 4 (Opt. Lett. 22, 132-134 (1997)) and Patent Document 5 (Japanese Translation of PCT International Publication No. 2004-503413), the focal position is changed by moving the stage, and the structure is drawn with a single stroke. A method of making an object, in particular a waveguide, is shown.
Furthermore, in Non-Patent Document 5 (Appl. Phys. Lett. 74, 786-788 (1999)), after the structure is produced by moving the stage in the horizontal direction of the substrate, the stage is moved in the vertical direction of the substrate, and then again in the horizontal direction. A layered three-dimensional shape manufacturing method is shown in which the process of creating a structure is repeated.
Further, Patent Document 6 (Japanese Patent Laid-Open No. 2001-158050) discloses a method for producing a structure at a higher speed by combining a mirror scanner and a stage.

In these methods, a method for controlling the height of a structure to be manufactured is realized by stacking the structures to be manufactured. In this method, since it is necessary to stack, it takes time to manufacture, and since the height of the structure is limited by feeding at the time of stacking, it is further necessary to manufacture a structure having high resolution in the height direction. It will take time.
Accordingly, the following problem is to solve these problems and to provide a method of manufacturing a structure whose height is easily controlled with high accuracy using multiphoton absorption. Here, multiphoton absorption refers to an absorption process of two or more photons.

More specifically, the sixteenth problem of the present invention is that a multistage or continuous surface relief type diffractive optical element or shape transfer mold for an optical element whose height is precisely controlled by utilizing multiphoton absorption. It is to provide a manufacturing method that makes it possible to manufacture the substrate with a small number of steps.
A seventeenth problem is to provide a more accurate method for manufacturing a diffractive optical element or a method for manufacturing a shape transfer mold for an optical element in addition to the sixteenth problem.

  By the way, since the multiphoton absorption process is a non-linear process, a high-power laser that is difficult to occur normally is required. However, by locally condensing a high-power laser, phenomena such as bubbles are generated in the photoreactive material and the material is destroyed by ablation, which adversely affects the structure to be produced. .

  Accordingly, the eighteenth problem, in addition to the sixteenth and seventeenth problems, is a method for producing a diffractive optical element that does not require high power, or a method for producing a shape transfer mold for an optical element, which causes a multiphoton absorption process more efficiently. It is to provide a method, and further to provide a method for manufacturing a diffractive optical element having a finer structure in the horizontal direction or a method for manufacturing a shape transfer mold for an optical element.

By the way, when the condensing point of the laser beam is scanned in the horizontal direction, if the relationship between the amount of horizontal movement of the condensing point and the width of the structure formed by one scan is not optimal, the structure A groove is formed between the two, and the manufactured structure has a structure as shown in FIG. In contrast to a structure that obtains only desired diffracted light as shown in FIG. 31A, this structure produces unnecessary diffracted light as shown in FIG. 31B, which adversely affects the performance of the optical element.
Further, depending on the manufacturing method, as shown in FIG. 32, depending on the manufacturing conditions, fine unevenness may be formed on the top of the structure without such a groove. This also generates unnecessary diffracted light.

Therefore, the nineteenth problem is to make a structure that does not affect the optical performance of the produced optical element even if such a groove exists, and to produce a diffractive optical element with a higher performance or a shape for an optical element. It is to provide a transfer mold manufacturing method.
Furthermore, in addition to the nineteenth problem, the twentieth problem is to provide a method for manufacturing a diffractive optical element having higher optical performance or a method for manufacturing a shape transfer mold for an optical element.
A twenty-first problem is to provide a method for manufacturing an optical element having a more complex function or a method for manufacturing a shape transfer mold for an optical element in addition to the nineteenth and twentieth problems.
A twenty-second object is to provide a method for producing a high-performance diffractive optical element with high diffraction efficiency or a method for producing a shape transfer mold for an optical element in addition to the nineteenth to twenty-first problems.

In order to solve the above problems, the present invention employs the following technical means.
The first means of the present invention is an optical element having a fine structure, characterized in that the phase of transmitted light is changed by spatially modulating the height of at least a part of the structures (claims). Item 1).
The second means of the present invention is characterized in that the optical element of the first means has a structure finer than the wavelength of light to be used (claim 2).

According to a third means of the present invention, in the optical element of the second means, when the wavelength of light to be used is λ, the incident angle is θ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2, The period of the structure is λ / (n1sinθ + n2) or less (claim 3).
According to a fourth means of the present invention, in the optical element of the second or third means, when the wavelength of light to be used is λ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2, The height difference Δh of the structure is
Δh = 2√2λ × √ (n1 ^ 2 + n2 ^ 2) / (n1 + n2) ^ 2
(Claim 4).

According to a fifth means of the present invention, in the optical element of any one of the first to fourth means, the fine structure is a substantially rectangular lattice, a columnar structure or a multistage structure having the same period. Item 5).
According to a sixth means of the present invention, in the optical element according to any one of the second to fifth means, a fine structure having a wavelength equal to or less than a wavelength to be used is divided into a plurality of regions, and the structure in the region is The pitch is the same and the height is the same (Claim 6).

According to a seventh means of the present invention, in the optical element of any one of the first to sixth means, the fine structure is formed on both surfaces of the element (claim 7).
According to an eighth means of the present invention, in the optical element of any one of the first to seventh means, the fine structure is formed on a curved surface (for example, on a lens) ( Claim 8).

According to a ninth means of the present invention, in the optical element of any one of the second to eighth means, the phase of incident light is modulated by a structure having a wavelength or less, and at least a part of the incident light is condensed. (Claim 9).
According to a tenth means of the present invention, in the optical element of any one of the second to eighth means, the phase of the incident light is modulated by a structure having a wavelength equal to or less than the wavelength, thereby shaping the transmitted light beam. (Claim 10).
Furthermore, the eleventh means of the present invention is the optical element of any one of the second to ninth means, wherein the phase of incident light is modulated by a structure having a wavelength equal to or shorter than the wavelength provided on at least one surface, The light aberration is corrected (claim 11).

  A twelfth means of the present invention uses a laser interference exposure method in which a structure is formed by laser interference in a manufacturing method for manufacturing an optical element of any one of the first to eleventh means, and the interference light intensity. The height of the structure is spatially modulated by modulating the intensity of the interference light by the modulating means to form a fine structure (claim 12).

  A thirteenth means of the present invention uses a laser ablation processing method for forming a fine structure by a laser ablation method in a manufacturing method for manufacturing an optical element of any one of the first to eleventh means. Further, the processing laser beam is caused to interfere, and the interference intensity is modulated by the interference light intensity modulating means, whereby the height of the structure is spatially modulated to form a fine structure (claim 13).

  A fourteenth means of the present invention uses a laser ablation processing method for forming a fine structure by a laser ablation method in a manufacturing method for manufacturing an optical element of any one of the first to eleventh means. A fine structure is formed by irradiating a processing laser beam to a structure in which a thin film that is transparent to processing laser light and a thin film that absorbs light is laminated, and the thin film is spatially removed. (Claim 14).

  According to a fifteenth means of the present invention, in the manufacturing method for manufacturing the optical element according to any one of the first to eleventh means, the structure is obtained by condensing light and curing the material in the vicinity of the condensing point. Using the photocuring method to be formed, the structure is formed by multiphoton absorption of the irradiation laser light, and the fine structure is formed by modulating the height of the structure (claim 15).

  According to a sixteenth means of the present invention, in the optical element manufacturing method according to any one of the thirteenth to fifteenth means, the processing laser beam is an ultrashort pulse laser having a pulse width of 10 picoseconds or less. (Claim 16).

  According to a seventeenth means of the present invention, in the manufacturing method for manufacturing an optical element according to any one of the first to eleventh means, a photoreactive material is applied onto a substrate, and laser light is applied to the material. This is a method in which multi-photon absorption occurs only in the vicinity of the condensing point, and a fine structure is formed on the substrate surface by scanning the condensing point on the substrate surface. By changing the distance from the surface, the height of the structure to be formed is changed, and structures having spatially different heights are produced (claim 17).

According to an eighteenth means of the present invention, in the optical element manufacturing method according to the seventeenth means, the power of the laser light and the scanning speed of the condensing point are substantially constant during the irradiation with the laser light. (Claim 18).
According to a nineteenth means of the present invention, in the optical element manufacturing method of the seventeenth or eighteenth means, the position of the substrate and the focal point is constantly monitored during the irradiation with the laser beam, The position of the condensing point is adjusted from the result (claim 19).

According to a twentieth means of the present invention, in the optical element manufacturing method according to any one of the seventeenth to nineteenth means, the laser light is an ultrashort pulse laser light.
According to a twenty-first means of the present invention, in the method for manufacturing an optical element according to any one of the seventeenth to twentieth means, an immersion objective lens as a means for condensing a laser beam in the photoreactive material. Is used (claim 21).

According to a twenty-second means of the present invention, in the method of manufacturing an optical element according to any one of the seventeenth to twenty-first means, the pitch of the structure to be produced in at least part of the plane (the minimum distance between the structure and the structure) The width is set to be equal to or smaller than the wavelength (claim 22).
According to a twenty-third means of the present invention, in the optical element manufacturing method of the twenty-second means, the structures are produced at an equal pitch in a region functioning as an optical element. .
The twenty-fourth means of the present invention is the method for manufacturing an optical element according to any one of the seventeenth to twenty-third means, wherein the structure is formed on a structure having a curved surface at least partially. (Claim 24).

  A twenty-fifth means of the present invention is an optical element, which is manufactured by the optical element manufacturing method of any one of the twelfth to twenty-fourth means (claim 25).

  The twenty-sixth means of the present invention is used when manufacturing the optical element of any one of the first to eleventh means, and in the method of manufacturing a shape transfer mold for optical elements for transferring the fine structure, A laser interference exposure method in which a structure is formed by interference is used, and the height of the structure is spatially modulated by modulating the intensity of the interference light by means of interference light intensity modulating means to form a fine structure (claims) Item 26).

  The twenty-seventh means of the present invention is used when manufacturing an optical element of any one of the first to eleventh means, and in the method for manufacturing a shape transfer mold for an optical element for transferring the fine structure, The laser ablation method is used to form a fine structure by the modulation method, the laser beam for processing is made to interfere, and the interference intensity is modulated by the interference light intensity modulation means to spatially modulate the height of the structure and A structure is formed (claim 27).

  A twenty-eighth means of the present invention is used in manufacturing an optical element of any one of the first to eleventh means, and in the method for manufacturing a shape transfer mold for an optical element for transferring the fine structure, Using a laser ablation method that forms a fine structure by the irradiation method, a processing laser beam is irradiated to a structure in which a thin film that shows transparency and a thin film that absorbs laser light is laminated. The fine structure is formed by spatially removing the thin film (claim 28).

  A twenty-ninth means of the present invention is used when manufacturing an optical element of any one of the first to eleventh means, and in the method for manufacturing a shape transfer mold for an optical element for transferring the fine structure, light is emitted. Using a photocuring method that forms a structure by condensing and curing the material in the vicinity of the focal point, forming the structure by multiphoton absorption of the irradiated laser light, and modulating the height of the structure A structure is formed (claim 29).

  According to a thirtieth aspect of the present invention, in the method for manufacturing a shape transfer mold for an optical element according to any one of the twenty-seventh to twenty-ninth means, the processing laser beam has an extremely short pulse width of 10 picoseconds or less. It is a pulse laser (claim 30).

  A thirty-first means of the present invention is used when manufacturing an optical element of any one of the first to eleventh means, and is a method for manufacturing a shape transfer mold for optical elements that transfers the fine structure. A photoreactive material is coated on the substrate, the laser beam is condensed in the material, multiphoton absorption occurs only in the vicinity of the condensing point, and the fine structure is formed on the substrate surface by scanning the condensing point on the substrate surface. In this method, the height of the structure to be formed is changed by changing the distance between the focal point center and the substrate surface during scanning, thereby producing structures having spatially different heights. (Claim 31).

According to a thirty-second means of the present invention, in the method for producing a shape transfer mold for optical elements of the thirty-first means, the power of the laser light and the speed at which the condensing point is scanned are substantially constant during irradiation with the laser light. (Claim 32).
According to a thirty-third means of the present invention, in the method for producing a shape transfer mold for optical elements of the thirty-first or thirty-second means, the position of the substrate and the condensing point is constantly monitored during the irradiation with the laser beam. The position of the condensing point is adjusted from the monitoring result (claim 33).

According to a thirty-fourth means of the present invention, in the method for manufacturing a shape transfer mold for optical elements according to any one of the thirty-first to thirty-third means, the laser beam is an ultrashort pulse laser beam. Item 34).
The thirty-fifth means of the present invention is the means for concentrating laser light in the photoreactive material in the method for producing a shape transfer mold for optical elements according to any one of the thirty-first to thirty-four means. An immersion objective lens is used (claim 35).

According to a thirty-sixth aspect of the present invention, in the method for manufacturing a shape transfer mold for an optical element according to any one of the thirty-first to thirty-fifth means, the pitch of the structure to be fabricated (at least in a plane) The minimum distance width of the object is set to a wavelength or less (claim 36).
According to a thirty-seventh means of the present invention, in the method for producing a shape transfer mold for an optical element according to the thirty-sixth aspect, the structure is produced at an equal pitch in a region functioning as an optical element ( Claim 37).
The thirty-eighth means of the present invention is the method of manufacturing a shape transfer mold for optical elements according to any one of the thirty-first to thirty-seventh means, wherein the structure has a curved surface at least partially. (38th means).

The thirty-ninth means of the present invention is a shape transfer mold for optical elements, and is manufactured by the method for manufacturing a shape transfer mold for optical elements according to any one of the twenty-sixth to thirty-eighth means ( Claim 39).
The 40th means of the present invention is an optical element, wherein the fine structure is transferred to an optical material using the optical element shape transfer mold of the 39th means, and is manufactured (claim). 40).

In the optical elements of the first and second means, the phase modulation of the transmitted light can be realized by a structure having a shorter period than the incident wavelengths having different heights.
Here, in the periodic structure with different heights, as described above, when the effective refractive index n is used and the incident light wavelength is λ and the transmitted optical path length is d, the phase modulation amount φ is
φ = 2πnd / λ (Formula 2)
Therefore, when the pitch and fill factor are the same, phase modulation depending only on the height is possible. As a result, phase modulation is possible even in a structure having the same pitch and the same fill factor. This corresponds to, for example, setting the phase difference of transmitted light to π by setting the height to ½. For example, phase modulation equivalent to making a structure with an equal pitch fill factor of 0.2 into a structure with a height of 1/2 and a fill factor of about 0.6 is possible, and the aspect can be greatly reduced. It becomes. Thereby, large phase modulation is possible even in a structure with a low aspect, and an optical element having a stable structure can be realized.

  Moreover, in addition to the configuration of the optical elements of the first and second means, the generation of transmitted light due to higher-order diffraction can be achieved by setting the wavelength and incident angle used and the refractive index of the medium as the conditions of the third means. Thus, an optical element with high light utilization efficiency can be realized.

Further, in the optical element of the fourth means, in addition to the configuration of the second or third means, the wavelength of the light to be used is λ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2. The difference in body height Δh is
Δh = 2√2λ × √ (n1 ^ 2 + n2 ^ 2) / (n1 + n2) ^ 2
The vicinity of. That is, the difference between the maximum height and the minimum height of the sub-wavelength structure is the above relationship.

As can be seen from FIG. 37, the effective refractive index of TE polarized light, which is incident light parallel to the structure, is higher than the effective refractive index of perpendicular TM polarized light having the same fill factor. Phase modulation is defined by a structure having this average refractive index and a fill factor of 0.5.
This condition is a value shown in (b) of (Expression 3) below from (Expression 1) described above. Thereby, when using incident light of circularly polarized light or random polarized light, or when it has a centrally symmetric structure, phase modulation of 2π can be realized with a structure having a fill factor of 0.5. This makes it possible to realize an optical element having a stable structure with a low aspect and the easiest structure to design and manufacture.

(Formula 3)
n1sinθ _i + n2sinθ _o = m (λ / p) (a)
_{p ≦ λ / (n1sinθ i +} n2) (b)
θi: incident angle of light to the structure n1: refractive index of the incident medium n2: refractive index of the structure p: pitch of the structure m: diffraction order θo: diffraction angle

  In the optical element of the fifth means, in addition to the configurations of the first to fourth means, the structure is a substantially rectangular lattice structure having the same period, a columnar structure having the same period, or a multistage structure having the same period. As a result, it is possible to realize an element that can be easily manufactured and can be stably manufactured. Furthermore, phase modulation that satisfies the above-described expression of the effective refractive index described in (Expression 1) can be realized. Furthermore, since it has a symmetrical structure, there is little change due to the incident direction, and a stable optical element can be realized.

  In the optical element of the sixth means, an arbitrary phase modulation region is formed at an arbitrary position in the structure of any one of the second to fifth means. Thus, phase modulation for each region can be performed by spatially dividing the phase modulation. By using the phase modulation for each region, it is possible to perform the same function as that of a binary type diffractive optical element that is currently generally used. This can be used not only as a single element but also as a diffractive optical element in combination with other lenses.

  In the optical element of the seventh means, the structure of any one of the first to sixth means is formed on both surfaces of the transmissive substrate. This may be the same structure or a different structure. Since transmitted zero-order light is used, phase modulation on both surfaces can be the sum of phase modulation amounts on each surface in the transmitted light path. As a result, the amount of phase modulation on one side can be increased, thereby realizing phase modulation with a stable structure having a lower fill factor and realizing complicated phase modulation by adding phase modulation.

  In the optical element of the eighth means, in addition to the structure of any one of the first to seventh means, the fine structure is formed on the curved surface (for example, on the lens), so that the fine structure is added to the power of the lens. The phase modulation of the transmitted light using the phase modulation due to the above becomes possible. This has the same effect as the addition of phases. Thereby, for example, it can be used as an integral diffractive optical element in which a fine structure is combined with a lens.

  In the optical element of the ninth means, in addition to the structure of any one of the second to eighth means, the phase of the transmitted light is spatially modulated to form an equiphase surface in a certain point or line. By adjusting the phase modulation amount, the transmitted light can be condensed. Thereby, a thin and condensable optical element can be realized by a structure having a height on the order of wavelength.

  In the optical element of the tenth means, in addition to the structure of any one of the second to eighth means, the phase of the transmitted light is spatially modulated, and a plurality of points on a certain plane or an arbitrary phase plane It is possible to shape the beam shape of the transmitted light by adjusting the phase modulation amount so as to form. Thereby, a thin diffractive optical element can be realized by a structure having a height on the order of wavelength.

  In the eleventh means, in addition to the configurations of the second to ninth means, the phase of the transmitted light is spatially modulated, and the phase of the arbitrary spatial position is modulated. Accordingly, the phase of the light can be controlled by the structure having the height of the wavelength order, and an optical element for aberration correction in which the wavefront of the propagating light is controlled can be realized.

  In the optical element manufacturing method of the twelfth means or the shape transfer mold manufacturing method of the optical element of the twenty-sixth means, the interference intensity of the laser light is modulated when the laser light interference is performed, preferably positive. Exposure is performed in a space-selective manner using a mold resist. Here, the interference intensity indicates the ratio of the maximum interference intensity, the minimum interference intensity, and the non-interference intensity in FIG. 39, and is a value that can be changed according to the interference condition. As a result, a fine structure having a thickness equal to or smaller than the resist thickness can be manufactured.

  In the optical element manufacturing method of the thirteenth means or the optical element shape transfer mold manufacturing method of the twenty-seventh means, a laser having a high peak intensity is caused to interfere, and a fine structure is formed by a laser ablation method. As a result, a fine structure can be manufactured in a large area at high speed. In addition, the process is simple and can be made directly on many materials, leading to a significant cost reduction. Furthermore, this method has the advantage that it can perform processing at a significantly higher speed than the electron beam exposure method, and is a clean process that does not require solution processing or gas.

  In the optical element manufacturing method of the fourteenth means or the optical element shape transfer mold manufacturing method of the twenty-eighth means, selective laser irradiation is performed on the multilayer structure material. By alternately arranging a layer that absorbs the processing laser beam and a layer that transmits light in the multilayer film, it is possible to selectively process the removal layer. Further, by repeating the laser irradiation while controlling the irradiation position, it is possible to manufacture a fine structure having a spatially different height. At this time, the controllability of the height is high as compared with the normal ablation method, and a flat processed shape can be obtained. Furthermore, since the layer is removed with one pulse of laser light, high-speed processing can be realized. Further, a multi-stage structure can be formed by adjusting the thickness of each layer to the initial value.

  In the optical element manufacturing method of the fifteenth means or the optical element shape transfer mold manufacturing method of the twenty-ninth means, the multi-photon absorption process at the condensing point of the laser beam is used for the fine structures having different heights. Created by photocuring method. This makes it possible to manufacture a fine structure capable of controlling the height with high accuracy at high speed.

  In the optical element manufacturing method of the sixteenth means or the shape transfer mold manufacturing method for the optical element of the thirty means, the processing laser in the thirteenth to fifteenth means or the twenty-seventh to 29th means is 10 ps or less. The ultrashort pulse laser is used. As a result, processing with a low energy light source and processing with high energy use efficiency are possible, and a fine structure with high accuracy can be formed.

  In the manufacturing method of the optical element of the seventeenth means or the method of manufacturing the shape transfer mold for optical elements of the thirty-first means, as shown in FIG. In this method, multi-photon absorption is caused only in the vicinity of the condensing point, and a fine structure is formed on the substrate surface by scanning the condensing point on the substrate surface. By changing the distance between the point center and the substrate surface, the height of the structure to be formed is changed, and a structure having a spatially different height is produced. As shown in Non-Patent Document 3, By using the multiphoton process, it is possible to produce a structure smaller than the diffraction limit in normal laser processing. In addition, a structure having a high aspect ratio that is long in the vertical direction of the substrate and short in the horizontal direction of the substrate is formed by a single focused irradiation. Furthermore, in the manufacturing method of the present invention, it is possible to produce structures having spatially different heights with a smaller number of steps than in the conventional method as shown in FIGS.

  In the research by the present inventors, a laser beam having a wavelength of 800 nm is condensed by an objective lens having a numerical aperture (NA) of 0.8, thereby producing a structure having a horizontal width of about 400 nm and a vertical direction of about 2 μm. Is possible. Since the height of the structure is defined by (Equation 4) below, for example, if the wavelength to be used for the diffractive optical element is 650 nm, phase modulation of 2π can be obtained if the height is 1.3 μm. Therefore, it can be said that the structure manufactured by the method of the present invention is sufficient.

(Formula 4)
h (x, y) = [λ / (n−1)] × [φ (x, y) / 2π]
h (x, y): height of diffractive optical element at arbitrary position x, y φ (x, y): phase modulation amount at arbitrary position x, y of light to be controlled n: refractive index of material λ: Wavelength of light used as a diffractive optical element

The height of the structure to be manufactured is determined by the distance between the condensing point of the laser and the substrate. For this reason, for example, if a piezo stage is used, since the position resolution of the stage is several nm, the height of the manufactured structure can be formed with an accuracy of several nm.
This makes it possible to manufacture a diffractive optical element having high performance or a shape transfer mold for optical elements.

In the optical element manufacturing method of the eighteenth means or the shape transfer mold manufacturing method for the optical element of the thirty-second means, in addition to the manufacturing method of the seventeenth means or thirty-first means, the intensity and scanning of the laser beam. By keeping the speed constant, a structure having the same height can be accurately produced. As a result, the distance between the focal point and the substrate accurately corresponds to the height of the structure to be fabricated. This correspondence can be expressed as follows.
When the maximum value of the height of the structure manufactured by one scan is H, the distance between the condensing point and the substrate is H / 2. When the distance between the focal point and the substrate is d, the height h of the structure to be formed is
h = H / 2 + d (when -H / 2 <d <H / 2)
It becomes.

Here, since only the relative height in the plane affects the characteristics of the diffractive optical element, when the diffractive optical element is manufactured by the method of the present invention, only the change due to the location of the distance d between the condensing point and the substrate is present. Affects properties.
That is, it becomes possible to manufacture a diffractive optical element having desired characteristics regardless of the maximum height H of the structure manufactured by one scan.
The value of H is a value that is difficult to reproduce because it changes depending on environmental factors such as ambient temperature and humidity. However, in the method of the present invention, since it is not affected by the value of H, it is a manufacturing method that is more advantageous for environmental changes. is there.

  In the manufacturing method of the optical element of the nineteenth means, or the manufacturing method of the shape transfer mold for optical elements of the thirty-third means, the manufacturing method of the seventeenth or eighteenth means, or the manufacturing method of the thirty-first or thirty-second means. In addition, by measuring the distance between the substrate and the condensing point and feeding back the result to the amount of converging point movement in the vertical direction of the substrate, it is not affected by the warp or undulation of the substrate, and more accurate diffraction. An optical element or a shape transfer mold for an optical element can be produced.

  In the manufacturing method of the optical element of the twentieth means, or the manufacturing method of the shape transfer mold for optical elements of the thirty-fourth means, the manufacturing method of any of the seventeenth to nineteenth means, or any of the thirty-first to thirty-third methods. In addition to the above manufacturing method, a so-called ultrashort pulse laser having a pulse width of 1 ps or less can be used as a light source, whereby a structure can be manufactured with lower power. As a result, it is possible to avoid the generation of bubbles and the destruction due to the ablation of the structure caused by condensing high-intensity laser light.

  In the manufacturing method of the optical element of the twenty-first means, or the manufacturing method of the shape transfer mold for optical elements of the thirty-fifth means, the manufacturing method of any of the seventeenth to twentieth means or any of the thirty-first to thirty-fourth In addition to the above manufacturing method, a structure with finer horizontal resolution can be produced by using an immersion objective lens as means for condensing laser light in the photoreactive material.

By the way, in the manufacturing method of the 17th to 21st means or the manufacturing method of the 31st to 35th means, when the condensing point of the laser beam is scanned in the horizontal direction, the amount of horizontal movement of the condensing point is When the width of the structure formed by one scan is small, a groove is formed between the structures, resulting in a structure as shown in FIG. Due to the presence of such grooves, unnecessary diffracted light is generated, resulting in a problem that the diffraction efficiency is lowered.
On the other hand, in the manufacturing method of the optical element of the twenty-second means or the manufacturing method of the shape transfer mold for optical elements of the thirty-sixth means, the pitch of the structure (structure By setting the minimum distance width of the structure to be equal to or less than the wavelength, the pitch of the structure to be manufactured is smaller than the wavelength used.
In such a structure, even if a periodic pitch structure exists, no diffracted light is generated, but the phase distribution of incident light can be changed (in addition, spatial phase distribution control using a sub-wavelength structure) Is described in Patent Document 1).
That is, in the manufacturing method of the present invention, the pitch of the structure to be manufactured is a structure finer than the wavelength, so that even if a groove exists between the structures at the time of manufacture, the desired diffracted light is not generated. A diffractive optical element or a shape transfer mold for an optical element capable of obtaining the above functions can be manufactured.

In the above manufacturing method, particularly when the intensity of the focused laser beam is the same and the scanning speed is the same, the width of the structure to be manufactured is always constant, and so-called duty ratios with different pitches change. When the duty ratio changes, the effective refractive index changes, so that the height of the structure to be manufactured needs to be corrected.
Therefore, in order to more easily control the function of the diffractive optical element only by the height, in the manufacturing method of the optical element of the twenty-third means or the manufacturing method of the shape transfer mold for optical elements of the thirty-seventh means, In addition to the manufacturing method of the twenty-second means or the manufacturing method of the thirty-sixth means, the structure is formed at an equal pitch in a region functioning as an optical element.

  In the manufacturing method of the optical element of the twenty-fourth means or the manufacturing method of the shape transfer mold for optical elements of the thirty-eighth means, any one of the manufacturing methods of the seventeenth to twenty-third means, or any of the thirty-first to thirty-seventh aspects. In addition to the manufacturing method of the means, the structure can be produced on the curved surface by changing the condensing point along the curved surface. This makes it possible to make a structure on a spherical lens and make it aspherical, or to make a diffraction grating and add a function to correct chromatic aberration of the lens. Can be produced.

  In the optical element of the twenty-fifth means, a fine structure that is finer than the wavelength of light to be used and spatially different in height is manufactured by the manufacturing method of any one of the twelfth to twenty-fourth means. Thus, it is possible to easily obtain the optical element having the high-performance optical element.

In the shape transfer mold for optical elements of the thirty-ninth means, which is manufactured by the manufacturing method of any one of the twenty-sixth to thirty-eighth means, it is finer and spatially higher than the wavelength of light to be used. A shape transfer mold for optical elements having different microstructures can be easily obtained.
Further, in the optical element of the 40th means, the fine structure is transferred to the optical material by using the optical element shape transfer mold of the 39th means and manufactured, so that the space is finer than the wavelength of the light to be used. Therefore, optical elements having fine structures with different heights can be easily and inexpensively duplicated, and high-performance optical elements can be provided at low cost.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on the embodiments shown in the drawings.

[Example 1]
One embodiment of the optical element of the first and second means will be described with reference to FIG. This optical element has a structure finer than the wavelength of light to be used, and changes the phase of transmitted light by spatially modulating the height of at least some of the structures 2.
Specifically, as shown in FIG. 1, fine structures 2 having different heights below the wavelength to be used are formed on a substrate 1 made of glass or transparent polymer. The microstructure 2 may be made of a material different from that of the substrate 1 or the same material as that of the substrate 1. By making light incident on the structure 2, the transmitted light is not normal high-order diffracted light but mainly zero-order diffracted light. At this time, by spatially modulating the phase of the 0th-order diffracted light (transmitted light), the same effect as that of the lens and the diffraction grating is obtained. When the incident light has polarized light, the height of the structure 2 is determined from the above (Equation 1) so as to obtain an effective refractive index n matched to the polarized light, so that light can be condensed or diffracted. it can. Here, the structure 2 modulates only the height, but it can also be modulated with the same width as in the prior art (for example, Non-Patent Document 1, Patent Documents 1 and 2, etc.). Thereby, an optical element using 0th-order diffracted light that can be easily processed and replicated can be realized.

[Example 2]
An embodiment of the optical element of the third means will be described with reference to FIG. In this example, in the optical element having the microstructure 2 as shown in FIG. 1, the wavelength of light to be used is λ, the incident angle is θ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2. In this case, the period of the structure is configured to be λ / (n 1 sin θ + n 2) or less.
Here, as shown in FIG. 2, when the incident angle of light to the structure 2 formed on the substrate 1 is θi, the diffraction angle is the refractive index of the medium n1 and the refraction of the structure 2 from the diffraction formula. When the rate is n2, the diffraction order is m, and the structure pitch is p, the light propagates to the angle indicated by (a) in (Equation 5) below. At this time, the condition that the + 1st order diffracted light is not generated is that θi is positive and the diffraction angle θo at m = + 1 is 90 degrees or more. From this, the condition of (b) in the following (formula 5) is Led. By adopting the structure of the third means in this way, it is possible to realize a phase modulation optical element with transmitted zero-order light without loss of incident light due to high-order diffraction.

(Formula 5)
_{n1sinθ i + n2sinθ o = m (} λ / p) (a)
_{p ≦ λ / (n1sinθ i +} n2) (b)
θi: incident angle of light to the structure n1: refractive index of the incident medium n2: refractive index of the structure p: pitch of the structure m: diffraction order θo: diffraction angle

[Example 3]
An embodiment of the optical element of the fourth means will be described with reference to FIG. In this example, in the optical element of Example 1 or Example 2, when the wavelength of light used is λ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2, the height of the structure is The difference Δh is
Δh = 2√2λ × √ (n1 ^ 2 + n2 ^ 2) / (n1 + n2) ^ 2
It is comprised so that it may become near.
From the viewpoint of ease of processing and design, when creating a fine structure, a structure having an equal pitch and an equal width is desirable. When the height is modulated under this condition, the phase difference is given by 2πnΔh / λ by the above height difference Δh, where n is the effective refractive index of light. By setting the minimum height and the maximum height of the created structure to this value, 2π modulation, which is a necessary amount of phase modulation, can be performed.

  When this value is realized by the subwavelength element, if the incident light is randomly polarized light or circularly polarized light, anisotropy does not appear and an average value of the refractive index may be used. Similarly, the average value can be used when the structure is the central object. Such a structure can be realized by setting the phase modulation of 2π obtained from the above-described (Equation 1) as the value of this embodiment. As a result, a structure having the necessary phase modulation can be realized with a simple structure.

[Example 4]
An embodiment of the optical element of the fifth means will be described with reference to FIG. In this embodiment, in addition to the structure of any one of the optical elements of Embodiments 1 to 3, the fine structure is a substantially rectangular lattice, columnar structure or multistage structure having the same period.
FIG. 4 shows an example of the shape of the fine structure, and the fine structure 2 having a wavelength equal to or smaller than the wavelength for phase modulation is typically a rectangle as shown in FIG. 4A, but need not be a rectangle. 4B, a structure having different widths in the vertical direction, a structure close to a quadrangular prism as shown in FIGS. 4C to 4E, a cylindrical structure not shown, or a stepped shape not shown. A multistage structure or the like can be used.
By arranging these structures 2 spatially at different heights, it is possible to modulate the phase of transmitted zero-order light. Further, such a structure 2 is relatively easy to produce by a laser interference machining method or the like, and is advantageous as a structure suitable for large-area machining.

[Example 5]
An embodiment of the optical element of the sixth means will be described with reference to FIG. In this example, in addition to the configuration of any one of the optical elements of Examples 1 to 4, the fine structure below the wavelength to be used is divided into a plurality of regions (cells) 3. The structures 2 are configured to have the same pitch and the same height.
In the phase modulation type diffractive optical element, the phase modulation does not need to be individually controlled by the structure, but can be controlled by a collective structure thereof. FIGS. 5A and 5B show an example of the structure. A plurality of structures 2 having the same structure are created in the cell 3, and the height, pitch, direction, and the like of the structure 2 are changed. Phase modulation of transmitted light is caused for each cell 3. As a result, a diffractive optical element having the same function as that of a diffractive optical element having a structure having a wavelength longer than that of the normal wavelength and capable of precisely controlling each phase modulation can be obtained.

[Example 6]
An embodiment of the optical element of the seventh means will be described with reference to FIG. In this example, in addition to the configuration of any one of the optical elements of Examples 1 to 5, the microstructure is formed on both sides of the element (substrate) 1.
As shown in FIG. 6, by creating the fine structure 2 on both surfaces of the substrate 1, it is possible to realize the same effect as the fine structure that is difficult to process only on one surface by using the two-surface structure. it can. At this time, the fine structure of the two surfaces does not need to be the same with respect to the traveling direction of the transmitted light, and it is possible to superimpose different phase modulations with different structures. Thereby, more advanced phase modulation is possible.

[Example 7]
An embodiment of the optical element of the eighth means will be described with reference to FIG. In this example, in addition to the configuration of any one of the optical elements of Examples 1 to 6, the fine structure is formed on a curved surface (for example, on the lens 4).
As shown in FIG. 7, by forming the fine structure 2 on the lens 4, it is possible to add phase modulation to the transmitted light in addition to the power of the lens 4. Further, as shown in FIG. 7, the fine structure 2 does not need to be formed on the entire surface of the lens 4, but can be formed on a part of the lens 4 to change a part of the phase.

Next, an example of a method for manufacturing an optical element having a structure as shown in FIG. 7 will be described with reference to FIGS.
First, a photosensitive resist 5 is spin-coated on the lens 4 (FIG. 8 (1)), and then laser interference light 6 is irradiated (FIG. 8 (2)). At this time, the irradiation range is adjusted so that the irradiation unit becomes a coherent region of the laser. If necessary, the fine structure can be formed at an arbitrary position by repeating the operation while moving the position.
After the laser interference exposure, the fine structure is obtained by developing the resist 5 (FIG. 8 (3)), and this fine structure can be used as an optical element as it is. It is also possible to form the microstructure 2 as a concave structure on the lens side by using a dry etching method or the like as an etching mask (FIG. 8 (4)).

[Example 8]
An embodiment of the optical element of the ninth means will be described with reference to FIG. In this embodiment, in addition to the configuration of any one of the optical elements of Embodiments 1 to 7, the phase of incident light is modulated by the fine structure 2 having a wavelength equal to or less than the wavelength, and at least a part of the incident light is condensed. It is a configuration.
That is, the optical element shown in FIG. 9A realizes a condensing optical element using phase modulation by a fine structure as a condensing function. This is due to the phase modulation by the fine structure, so that the amount of phase change varies depending on the position on the element as shown in FIG. 9B, and the transmitted light is converted into a spherical wave that becomes one point or line. Can be realized. Further, in the example of the optical element shown in FIG. 9, a phase modulation type sub-wavelength element whose phase is greatly delayed at the center of the element for such light collection is shown.

[Example 9]
An embodiment of the optical element of the tenth means will be described with reference to FIG. In this example, in addition to the configuration of any one of the optical elements in Examples 1 to 7, the beam of transmitted light is shaped by modulating the phase of incident light by a structure having a wavelength or less. Is.
Elements called diffractive optical elements and holographic elements can perform functions such as laser shape shaping and separation by modulating the wavefront of transmitted light. For example, in the Fraunhofer diffraction region (far field), the phase modulation calculated by the iterative Fourier transform method (see Non-Patent Document 6) as shown in FIG. It has been confirmed that the structure as shown in (b) is reproduced. By thus modulating the phase of transmitted light, a diffractive optical element capable of creating an arbitrary shape can be realized.

[Example 10]
An embodiment of the optical element of the eleventh means will be described with reference to FIG. In this example, in addition to the configuration of the optical element of any one of Examples 1 to 8, the phase of incident light is modulated by a structure having a wavelength equal to or shorter than the wavelength provided on at least one surface, thereby reducing the aberration of transmitted light. It is configured to correct.
As an example, in this embodiment, a phase modulation type optical element having a microstructure 2 as shown in FIGS. 11A and 11B is used as an aberration correction element. For example, the aberration generated in a single spherical lens can be reduced by the phase modulation of the fine structure 2, and the phase modulation element provided with the ring-shaped fine structure 2 as shown in the figure is arranged in the optical path. In addition, by making it integrally with the lens, it is possible to provide an element with reduced wavefront aberration at a low cost.

  In the above Examples 1-10, although the structural example of the optical element which concerns on this invention was demonstrated, in the following Examples, about the manufacturing method of the optical element which concerns on this invention, and the manufacturing method of the shape transfer type | mold for optical elements explain. In addition, an optical element and a shape transfer mold manufactured by these manufacturing methods, and an optical element duplication method using the shape transfer mold will be described.

[Example 11]
An embodiment of a microstructure manufacturing method according to a twelfth optical element manufacturing method and a twenty-sixth optical element shape transfer mold manufacturing method will be described with reference to FIG.
In this manufacturing method, a laser interference exposure method in which a structure is formed by laser interference is used, and the height of the structure is spatially modulated by modulating the intensity of the interference light by the interference light intensity modulation means. It forms the structure.
FIG. 12 shows an example of an apparatus used for laser interference exposure. This laser interference exposure apparatus includes a laser device (for example, an ultraviolet laser) 11 as a light source, a spatial filter 12, a half-wave plate (λ / 2). A phase plate 13, a non-polarizing beam splitter 14, mirrors 15 a and 15 b, a controller 16, a rotary stage 17 that rotates the half-wave plate 13, and the like.

  In the laser interference exposure method using this apparatus, laser light having high coherence from a laser apparatus (for example, an ultraviolet laser) 11 is shaped by a spatial filter 12 or the like, and is passed through a half-wave plate 13 by a non-polarizing beam splitter 14. The beam is split to an intensity of: 1. Thereafter, the divided laser light is deflected by the mirrors 15a and 15b, irradiated to the resist 5 on the substrate 1, and the laser light is caused to interfere on the resist, thereby creating interference intensity at the processing position. At this time, for example, by rotating the rotary stage 17 with the controller 16 and adjusting the angle of the half-wave plate 13 held by the rotary stage 17, the interference intensity is modulated from the difference in the S and P polarization components of the interference light. Then, as shown in FIGS. 13A and 13B, the intensity is modulated from a certain center value.

  For the modulation of interference intensity, the means for controlling the polarization direction of the branched laser light, the means for controlling the intensity ratio of the branched laser light, the means for controlling the irradiation delay of the laser light branched within the coherent distance, etc. are used. Can be done. As a result, as shown in FIG. 39, a portion where the laser intensity is modulated by interference and a non-interference portion are added, and the positive resist is exposed with light having such an intensity distribution, and the irradiation position is changed. By changing the interference intensity, it is possible to form a fine structure having a spatially different height.

  Laser interference can use not only two lasers but also interference of multiple laser beams. In that case, not only a lattice shape but also a fine structure having a cylindrical shape or a complicated interference fringe structure is manufactured. It is also possible to do. At this time, it is desirable to perform exposure by controlling and defining the interference area once, and by repeating the exposure so that the areas do not overlap, a fine structure having different spatially selected heights is formed without overlapping the interference areas. It becomes possible.

This method can form a plurality of lattices or cylindrical structures with a single exposure, and can be processed significantly faster than the electron beam exposure method.
In addition, when a positive resist is exposed with such an intensity distribution, it is possible to manufacture structures having different heights by controlling the exposure amount, development time, and the like.
The fine structure thus formed can be used as an optical element as it is, but can be used as a mold by transferring this structure to a metal structure. Further, using such a structure, as shown in FIG. 14, the fine structure of the resist 5 formed on the substrate 1 is used as a mask, or the metal deposited on the resist is patterned by a lift-off method or the like. By using a material as a mask, dry etching is performed by a dry etching method or the like, and the fine structure is transferred to the substrate 1 such as quartz glass, so that it can be used as a shape transfer mold for optical elements.

[Example 12]
Next, an embodiment of a microstructure manufacturing method according to a thirteenth optical element manufacturing method and a twenty-seventh optical element shape transfer mold manufacturing method will be described with reference to FIG.
In this manufacturing method, a laser ablation method that forms a fine structure by a laser ablation method is used, the laser beam for processing is made to interfere, and the interference intensity is modulated by an interference light intensity modulation means, so that the structure of the structure is spatially reduced. The height is modulated to form a fine structure.
FIG. 15 shows an example of an apparatus used for laser ablation processing. This processing apparatus includes a laser device (for example, a pulse laser) 21 as a light source, a half-wave plate (λ / 2 phase plate) 22, It comprises a Glan laser prism 23, a spatial filter 24, a mirror 25, a mask 26, a diffraction grating 27, a lens 28, a controller 29, a rotary stage 30 that rotates a half-wave plate, a moving stage 31 that moves the substrate 1, and the like. Yes.

  In this example, laser ablation is used to produce a fine structure, but the laser ablation method is known as a method that can directly process many materials such as transparent polymers, metals, ceramics, and the like. Yes. As shown in the figure, a laser beam from a laser device (for example, a pulse laser) 21 is shaped by a spatial filter 24 via a half-wave plate (λ / 2 phase plate) 22 and a Glan laser prism 23, and then mirror 25 Then, the optical path is deflected, and the light beam is split into two light beams by the diffraction grating 27 and interfered by the lens 28. At this time, it is desirable to limit the processing region with the mask 26 or the like. The laser irradiation intensity at the time of processing is modulated at high speed by the half-wave plate 22 and the Glan laser prism 23 shown in the drawing. FIG. 16 shows changes in the processing shape depending on the intensity of incident light of the laser. Since the laser ablation method has a threshold strength for processing, there is substantially no change in the substrate 1 below a certain strength. A hole is formed in the substrate 1 by increasing the strength. By performing interference-type laser ablation by spatially modulating the intensity in this way, it is possible to easily and inexpensively manufacture microstructures with different processing pitches and different heights.

Thus, by controlling the intensity or number of irradiation laser beams, the irradiation pulse width, and the like, it is possible to directly form fine structures with different heights on the substrate 1 in a spatially selective manner. It is also possible to form fine structures having different heights by the laser ablation method using the laser interference exposure control method shown in the eleventh embodiment. The laser ablation method allows direct processing of many materials including metals, glass, and transparent organic polymer materials used for optical elements, and direct optical elements without additional processing such as vapor deposition and dry etching. Alternatively, a shape transfer mold can be manufactured. This makes it possible to manufacture a high-speed and inexpensive element and shape transfer mold.
At this time, it is desirable to process the laser irradiation region once, and by repeating the processing so that the regions do not overlap with each other, it is possible to form fine structures having different spatially selected heights.

[Example 13]
Next, an embodiment of a fine structure manufacturing method according to the fourteenth means for manufacturing an optical element and the twenty-eighth means for manufacturing an optical element shape transfer mold will be described with reference to FIG.
In this manufacturing method, a laser ablation method that forms a fine structure by a laser ablation method is used, and a structure in which a thin film that is transmissive to a processing laser beam and a thin film that is absorptive are laminated. A fine structure is formed by irradiating a processing laser beam and spatially removing the thin film.

Specifically, an apparatus similar to that shown in FIG. 15 is used. As shown in FIG. 17, an absorption layer 41 made of a thin film that absorbs laser light for processing and a transmissive layer 42 made of a thin film that transmits light are formed on the substrate 1. Are stacked alternately. By making two-beam interference light incident on such a laminated thin film structure 40 with an irradiation fluence that is equal to or greater than the processing threshold, only one layer of the absorption layer 41 and the transmission layer 42 is selectively processed with a single irradiation. can do. Further processing is performed by moving the processing position on the moving stage 31 or changing the processing region. At this time, the processing height can be controlled by controlling the number of laser irradiations to the same position. Further, since the processing width at this time is almost defined by the laser irradiation width, it is possible to create a fine structure having a wavelength equal to or less than the wavelength of the processing laser light by using interference exposure or the like. At this time, the laser beam for processing and the wavelength used for the optical element do not need to be the same, and a laser capable of processing a fine structure equal to or less than the use wavelength can be used.
The laser beam irradiation is used to form such a fine structure, and in addition to interference, a condensing and projection method can be used.

The absorption layer 41 of the laminated thin film structure 40 may be any material that specifically absorbs a processing laser beam, and polycarbonate, polyester, polyimide, a sol / gel material to which an absorption material is added, or the like can be used. The transmissive layer 42 is a material that has little absorption with respect to the processing laser beam, and silicon oxide, metal oxide, a sol / gel material containing these as a main component, a transparent polymer material such as acrylic, and the like can be used.
As the processing laser, an excimer laser, an Nd: YAG laser, or a high-power laser such as a harmonic thereof can be used.

In addition, when the thin film of the laminated thin film structure 40 is entirely made of a material that transmits laser light, it can be directly used as an optical element as the fine structure 2. Moreover, it is also possible to produce a replica by forming a structure in other materials. FIG. 18 shows an example of a replication method. After using the laminated thin film structure 40 as shown in FIG. 17 (FIG. 18 (1)) and laser processing (FIG. 18 (2)), If necessary, a conductive layer made of a metal film 43 is added to the surface by vapor deposition or sputtering (FIG. 18 (3)). Thereafter, an electroforming process is performed to produce a mold 44 having an inverted shape 44 of the element (FIG. 18 (4)). The mold 44 having the inverted shape of the element is used as a shape transfer mold for an optical element (FIG. 18 (5)), and injection molding using an optical material such as a transparent polymer material (for example, a transparent resin such as polycarbonate or acrylic). Then, the optical element 45 having a fine structure can be produced (FIG. 18 (7)) by duplicating using a duplication (transfer) technique such as hot pressing or 2P method (FIG. 18 (6)).
A method for producing a shape transfer mold using a fine structure produced by laser processing or the like and replicating an optical element using the shape transfer mold is described in Examples 11 and 12 above. It can be similarly used for a fine structure and a fine structure shown in Examples described later.

[Example 14]
Next, an embodiment of a microstructure manufacturing method according to the fifteenth means for manufacturing an optical element and the twenty-ninth means for manufacturing an optical element shape transfer mold will be described with reference to FIG.
This manufacturing method uses a photo-curing method in which light is collected and the material is cured in the vicinity of the focal point to form a structure, the structure is formed by multiphoton absorption of the irradiated laser light, and the height of the structure The fine structure is formed by modulating.
FIG. 19 shows an example of an apparatus used for the photocuring method. This apparatus includes a laser device (for example, a femtosecond laser) 51 as a light source, a spatial filter 52, galvanometer mirrors 53a and 53b, a lens 54, and a substrate 1. The photo-curing resin 57 is laminated on the substrate 1 on which the fine structure is formed.

  In this embodiment, a fine structure is realized by a photocuring method using multiphoton absorption, and light emitted from a laser device (for example, a femtosecond laser) 51 is shaped by a spatial filter 52, and a galvanomirror 53a, The light-curing resin 57 is irradiated with laser light in a space-selective manner by a light control means such as 53b and a condensing lens 54. At this time, by setting the wavelength of the laser light to be equal to or longer than the photosensitive wavelength of the photocurable resin 57, the light can penetrate into the resin. At this time, by setting the light intensity so that multiphoton absorption is possible in the vicinity of the condensing point by the lens 54, it is possible to form a structure having an irradiation laser wavelength or less near the condensing point. Furthermore, a fine and high aspect structure can be formed by moving the curing point from the substrate surface.

  In such a photocuring method using multiphoton absorption, it is known that a finer structure can be produced than the wavelength of irradiation laser light for curing, and a fine structure is produced by using the method of this embodiment. It is possible. At this time, a structure having an arbitrary height can be further formed at an arbitrary position by scanning with irradiation laser light and curing it while selectively moving the focal point. The movement of the condensing point can be easily realized by moving the substrate 1 by the moving stage 55 and using the galvano mirrors 53a and 53b, and it is easy to form a three-dimensional shape with a controlled height compared to other exposure methods. Become. At this time, an optical element can be directly formed by using a light curable material such as a transparent polymer material or a light curable sol / gel material. Further, for example, by forming a fine structure with a resist material, it is possible to manufacture a shape transfer mold in which the fine structure is formed.

Since the manufacturing method of this embodiment is photocuring utilizing multiphoton absorption, it can be photocured at any position in a material transparent to the curing laser beam, and has a very high aspect structure. Can be created.
Further, the height can be controlled by the exposure amount, the irradiation time, and the like, thereby enabling highly accurate height control.

[Example 15]
Next, an embodiment of a method for manufacturing a fine structure according to a method for manufacturing an optical element of the sixteenth means and a method for manufacturing a shape transfer mold for optical elements of the thirty means will be described.
In this manufacturing method, in the manufacturing method of any one of Examples 12 to 14, the laser beam for processing is an ultrashort pulse laser having a pulse width of 10 picoseconds (ps) or less.
For example, when an ultrashort pulse laser is used for the laser ablation processing described in Examples 12 and 13, the heat conduction width inside the material at the time of light irradiation is an amount represented by the following (Equation 6) on one side.
L = √Dτ (Formula 6)
Here, L is a diffusion distance, D is a thermal diffusivity, and τ is time.
Table 1 below shows typical materials and their thermal diffusivities (D), and Table 2 shows the one-side thermal diffusion distance (thermal diffusion range) L determined by the above (formula 6) of the materials. Indicates.

In this embodiment, when an ultra-short pulse laser is used for manufacturing an optical element or a shape transfer type microstructure, for example, when a metal material such as aluminum (Al) or stainless steel (SUS) is processed, heat conduction is performed. The rate is 10 ⁶ order, and the propagation distance of the material other than metal whose propagation range is about nm at 10 ps is almost less than that. Therefore, the processing with the accuracy of nm order is realized by setting it to 10 ps or less. Is possible. This is a heat influence range that is sufficiently narrow with respect to the visible light wavelength of 400 to 800 nm, and can be said to be effective for processing in the sub-wavelength region. When this is on the order of nanoseconds (ns), the diffusion is large, and the function of the optical element is lowered due to the change in the processing shape.

In the case of photocuring with multiphoton absorption in Example 14, it is desirable that the laser intensity per unit time is high (a laser with a high peak output is desirable). Ti: Sapphire laser and solid laser capable of short pulse output. The typical pulse width of these lasers is about 10 picoseconds or less, and by setting these laser beams to 10 picoseconds or less, it becomes possible to manufacture optical elements and shape transfer molds with a high-precision fine structure. Also in this case, since there is little heat propagation, it becomes possible to form a highly accurate structure.
As described above, in this embodiment, in addition to the advantages of the methods of Embodiments 12 to 14, a more accurate manufacturing method can be obtained.

[Example 16]
Next, an embodiment of a method for manufacturing a fine structure according to a method for manufacturing an optical element of the seventeenth means and a method for manufacturing a shape transfer mold for optical elements of the thirty-first means will be described.
The manufacturing method of the present embodiment is an improvement of the technique of the above-described embodiment 14 so that a microstructure with a desired shape can be formed with higher accuracy. Basically, as shown in FIG. A photoreactive material such as a photo-curing resin is applied on the substrate, the laser beam is condensed in the material, multiphoton absorption is caused only near the condensing point, and the condensing point is scanned on the substrate surface. This is a method of forming a fine structure on the substrate surface, and by changing the distance between the center of the focal point and the substrate surface during scanning, the height of the structure to be formed is changed to increase the spatial height. Structures having different sizes are produced.

An example of a specific manufacturing method will be described with reference to FIGS. As shown in FIG. 22, the laser light is condensed by the objective lens 70 and forms a spot in the photoreactive material 60 applied on the substrate 1. Furthermore, by scanning the spot in the horizontal direction with respect to the substrate 1, a structure is manufactured over the entire surface of the photoreactive material 60 on the substrate. During this scanning, the distance of the spot from the substrate surface is changed so that the structure has a desired height. Accordingly, for example, if the condensing point is moved in the horizontal direction while moving away from the substrate 1 as shown in FIG. 23A, a staircase-shaped structure as shown in FIG. 23B can be produced.
If the maximum height of the structure to be fabricated is H, the distance d between the condensing point and the substrate is
-H / 2 <d <H / 2
Must be in the range. It should be noted that the condensing point may come to a position below the substrate.

  A more specific manufacturing method of this embodiment will be described with reference to FIG. FIG. 24 shows an example of a processing apparatus used in the manufacturing method of this embodiment. This apparatus includes a laser device 61 as a light source, a half-wave plate 62, a Glan-Thompson prism 63, a mirror 64, and a spatial filter 65. , A galvano mirror 66, a relay lens 67, a beam sampler 68, an imaging lens 69, an objective lens 70, a piezo stage 71, a moving stage 72 on which the substrate 1 is placed, a CCD 73 for monitoring, and the like. A photoreactive material 60 is applied on the substrate 1 on which is formed.

The intensity of the laser light emitted from the laser device 61 is optimally adjusted by the half-wave plate 62 and the Glan-Thompson prism 63, and the intensity distribution is made uniform by the spatial filter 65 via the mirror 64, and the beam diameter is adjusted. Is made.
As the laser device 61, a pulse laser having a strong instantaneous peak power is preferable, and an Nd: YAG laser, a Ti: Sapphire laser, or the like can be used. Regarding the wavelength, most of the photoreactive material 60 reacts by ultraviolet rays, and laser light having a wavelength in the near infrared region is suitable. In addition to the laser intensity adjustment, there are a method using a polarizing plate and a method using a variable ND filter. Further, it is preferable to adjust the intensity of the laser beam and to have the spatial filter 65, but this is not always necessary.

  Thereafter, the optical path of the laser light is changed by a scanner including a galvanometer mirror 66, and then condensed into the photoreactive material 60 on the substrate 1 through the relay lens 67, the beam sampler 68, the imaging lens 69, and the objective lens 70. Is done. The condensing point is scanned in the horizontal direction of the substrate by changing the angle of the galvanometer mirror 66 while adjusting the position in the vertical direction of the substrate by the piezo stage 71.

As the objective lens 70, it is desirable to use a lens having a high numerical aperture (NA) in order to increase the horizontal resolution of the structure to be formed.
The relay lens 67 is preferably a so-called fθ lens. By using the fθ lens, when the galvano mirror 66 alone is moved and scanned in the horizontal direction of the substrate, it is possible to prevent a phenomenon that the condensing position shifts in the vertical direction of the substrate. However, the positional deviation in the substrate vertical direction can be corrected by the piezo stage 71 without using the fθ lens.

For the movement in the horizontal and vertical directions, a method of moving the substrate 1 by the moving stage 72 may be used. In particular, as the horizontal movement, a so-called x · θ stage in which a rotary stage and a translation stage are combined can be used as the moving stage 72. By using the x · θ stage, the entire substrate surface can be scanned by a continuous movement, and the manufacturing time can be shortened.
In addition, as shown in FIG. 24, by installing a beam sampler 68 in the optical path, it is possible to capture and monitor the image being produced in the CCD 73.

As described above, the laser beam is condensed into the material, and the focal point is scanned in the horizontal direction of the substrate while changing the distance between the focal point center and the substrate surface.
Accordingly, as shown in FIG. 25A, a diffraction grating in which step-like structures 2 are periodically arranged on the substrate 1, or structures 2 having different heights as shown in FIG. 25B. Are spatially arranged, and a diffractive optical element capable of performing two-dimensional phase modulation is manufactured.

  The height h (x, y) of the diffractive optical element modulates the spatial phase distribution of the target light when used as a diffractive optical element, and corresponds to a desired phase modulation amount φ (x, y). Thus, it is determined by the following relational expression.

(Formula 7)
h (x, y) = [λ / (n−1)] × [φ (x, y) / 2π]
h (x, y): height of diffractive optical element at arbitrary position x, y φ (x, y): phase modulation amount at arbitrary position x, y of light to be controlled n: refractive index of material λ: Wavelength of light used as a diffractive optical element

  The phase modulation amount φ (x, y) can be calculated by using a so-called computer-generated hologram. Examples of the calculation method include an iterative Fourier transform method and a simulated annealing method. These calculation methods are described in detail in Non-Patent Document 6 and Non-Patent Document 7, respectively.

  The iterative Fourier transform method is more preferable because a hologram having a large number of pixels can be calculated in a shorter time than the simulated annealing method. An example of the result calculated by the iterative Fourier transform method is shown in FIG. FIG. 10A shows the two-dimensional data of the height calculated by calculation, and the white portion indicates that the height is higher. By producing such a structure by the manufacturing method of this embodiment, when a laser beam having a predetermined wavelength is incident on this structure, a laser beam pattern as shown in FIG. 10B is obtained in the Fraunhofer diffraction region. Can do.

  The photoreactive material 60 used for manufacturing the structure refers to a photocurable resin, a resist material, a photocurable organic / inorganic hybrid material, and the like. The photoreactive material 60 is desired to be transparent with respect to a predetermined wavelength range. Further, in order to utilize two-photon or multiphoton absorption, it is preferable that the wavelength of the laser beam used for the production is transparent or almost transparent. In addition, a desired structure is obtained by performing a specific post-treatment depending on the type of the photoreactive material after the laser light irradiation. For example, when a photocurable resin is used as a photoreactive material, an uncured portion of the resin is washed away with a solution after laser light irradiation, or when a resist material is used, a process called so-called development is required. . In this embodiment, it can be considered as a method for manufacturing a diffractive optical element including these post-processing steps or a method for manufacturing a shape transfer mold for a diffractive optical element.

  The fabricated structure itself may be used as a diffractive optical element, or the structure may be used as a mold for shape transfer. The following methods (A) to (C) are conceivable as methods for producing a replica using a shape transfer mold.

(A) As in the process example shown in FIG. 26, first, a microstructure is formed on the photoreactive material 60 on the substrate 1 by the method described above. Next, this is used as a shape transfer mold, and the produced mold is etched and cut to transfer the fine structure onto the substrate 1 to obtain an optical element. At this time, the etching can be either wet etching or dry etching, but dry etching is more preferable in order to perform etching more vertically.

(B) As in the process example shown in FIG. 27, a microstructure is first formed on the photoreactive material 60 on the substrate 1 by the method described above. Next, using this as a shape transfer mold, an optical material such as resin 80 is poured into the produced mold, and the mold is released to produce a replica of the optical element having a fine structure.

(C) As in the process example shown in FIG. 28, a microstructure is first formed on the photoreactive material 60 on the substrate 1 by the method described above. Next, using this as a shape transfer mold, a metal film 81 is deposited on the produced mold. Next, a mold on which the metal film 81 is deposited is electroformed, and a metal mold 82 having a fine structure transferred thereon is newly created. Further, the metal mold 82 is used as a new shape transfer mold, and an optical material such as a resin 80 is poured into the mold 82 and molded, and then released to produce a replica of the optical element having a fine structure.

  An optical element to which a fine structure is transferred can be obtained by the methods (A) to (C) described above, but the usage as a shape transfer mold is not limited to these.

[Example 17]
Next, an embodiment of a manufacturing method of a fine structure according to the manufacturing method of the optical element of the eighteenth means and the manufacturing method of the shape transfer mold for optical elements of the thirty-second means will be described.
In the manufacturing method of the present embodiment, in addition to the manufacturing method of the above-described embodiment 16, the power of the laser beam and the scanning speed of the condensing point are made substantially constant during the irradiation with the laser beam.
That is, at the time of manufacturing the structure described in Example 16, it is preferable that the intensity of the laser beam be kept precisely constant, and it is desirable that the intensity of the laser beam be constantly monitored. For this reason, in the processing apparatus used in this embodiment, as shown in FIG. 29, the processing apparatus of FIG. 24 is improved, a part of the laser light is taken out by the half mirror 75 and the light quantity is monitored by the photodiode 76, The result is fed back to the rotary stage controller 74 of the half-wave plate 62 so that the device can be manufactured while adjusting the light amount.

As described above, in this embodiment, in addition to the manufacturing method of Embodiment 16, it is possible to accurately manufacture a structure having the same height by keeping the laser beam intensity and scanning speed constant. As a result, the distance between the focal point and the substrate accurately corresponds to the height of the structure to be fabricated. This correspondence can be expressed as follows.
When the maximum value of the height of the structure manufactured by one scan is H, the distance between the condensing point and the substrate is H / 2. When the distance between the focal point and the substrate is d, the height h of the structure to be formed is
h = H / 2 + d (when -H / 2 <d <H / 2)
It becomes.

Here, since the diffractive optical element affects only the relative height in the plane, the characteristics of the diffractive optical element affect the characteristics. Therefore, when the diffractive optical element is manufactured by the method of this embodiment, only the change due to the location of the distance d between the condensing point and the substrate can be obtained. Affects the properties.
That is, it becomes possible to manufacture a diffractive optical element having desired characteristics regardless of the maximum height H of the structure manufactured by one scan.
The value of H is a value that is difficult to reproduce because it changes depending on environmental factors such as ambient temperature and humidity. However, the method of this embodiment is not affected by the value of H, and is more advantageous for environmental changes. It is.

[Example 18]
Next, an embodiment of a manufacturing method of a fine structure according to the manufacturing method of the optical element of the nineteenth means and the manufacturing method of the shape transfer mold for optical elements of the thirty-third means will be described.
In the manufacturing method of this example, in addition to the manufacturing method of Example 16 or 17 described above, the position of the substrate and the condensing point is constantly monitored during irradiation with the laser beam. The position is adjusted.
As a means for measuring the distance between the substrate 1 and the focal point, a so-called autofocus system that is generally used can be used. For example, as shown in FIG. 30, a method of measuring a distance from the substrate surface by attaching a laser range finder 77 or the like to the objective lens 70 of the processing apparatus of FIG. 29 can be used.
Then, while measuring the distance between the substrate 1 and the condensing point with the laser range finder 77, by feeding back the result to the moving amount of the condensing point in the vertical direction of the substrate, the influence of the warp and undulation of the substrate 1 is obtained. Accordingly, it becomes possible to manufacture a diffractive optical element or a shape transfer mold for an optical element with higher accuracy.

[Example 19]
Next, an embodiment of a method for manufacturing a fine structure according to a method for manufacturing an optical element of the twentieth means and a method for manufacturing a shape transfer mold for optical elements of the thirty-fourth means will be described.
In the manufacturing method of this embodiment, a so-called ultrashort pulse laser having a pulse width of 1 ps or less is used as a light source in addition to the manufacturing method of any of the above-described embodiments 16-18.
That is, a laser beam having a short pulse width is suitable as a laser beam used for manufacturing, and it is desirable to use a so-called femtosecond pulse laser having a pulse width of 1 ps, which is generally relatively easy to obtain. By using such an ultrashort pulse laser as a light source, a structure can be manufactured with lower power. As a result, it is possible to avoid the generation of bubbles and the destruction due to the ablation of the structure caused by condensing high-intensity laser light.

[Example 20]
Next, an embodiment of a method for manufacturing a fine structure according to a method for manufacturing an optical element of the twenty-first means and a method for manufacturing a shape transfer mold for optical elements of the thirty-fifth means will be described.
In the manufacturing method of the present embodiment, an immersion objective lens is used as means for condensing laser light in the photoreactive material, in addition to the manufacturing method of any of the above-described embodiments 16-19. In this way, by using the immersion objective lens as the light condensing means, a structure with a finer horizontal resolution can be produced.

[Example 21]
Next, an embodiment of a method for manufacturing a microstructure according to a method for manufacturing an optical element of the twenty-second and twenty-third means and a method for manufacturing a shape transfer mold for optical elements of the thirty-sixth and thirty-seventh means will be described. .
In the manufacturing method of the present embodiment, in addition to the manufacturing method of any of the above-described embodiments 16 to 20, the pitch of the structure to be manufactured in at least a part of the plane (the minimum distance width between the structure and the structure) In addition, the structure is formed at an equal pitch in a region functioning as an optical element.

In the manufacturing methods of Examples 16 to 20 described above, when the condensing point of the laser beam is scanned in the horizontal direction, the structure formed by one scan with respect to the horizontal movement amount of the condensing point. When the width is small, a groove is formed between the structures, resulting in a structure as shown in FIG. Due to the presence of such grooves, unnecessary diffracted light is generated, resulting in a problem that the diffraction efficiency is lowered.
On the other hand, in the manufacturing method of the present embodiment, the structure to be manufactured by setting the pitch (the minimum distance width between the structure and the structure) of the structure to be manufactured in at least a part of the plane to be equal to or less than the wavelength. The pitch is smaller than the wavelength used.
In such a structure, even if a periodic pitch structure exists, no diffracted light is generated, but the phase distribution of incident light can be changed.
That is, in the manufacturing method of this example, the pitch of the structure to be manufactured is a structure smaller than the wavelength, and thus, even if a groove exists between the structures at the time of manufacturing, unnecessary diffracted light is not generated. A diffractive optical element capable of obtaining a desired function or a shape transfer mold for an optical element can be produced.

In the above manufacturing method, particularly when the intensity of the focused laser beam is the same and the scanning speed is the same, the width of the structure to be manufactured is always constant, and so-called duty ratios with different pitches change. When the duty ratio changes, the effective refractive index changes, so that the height of the structure to be manufactured needs to be corrected.
Therefore, in order to more easily control the function of the diffractive optical element only by the height, in this embodiment, the structure is manufactured at an equal pitch in the region functioning as the optical element.

As an example of the structure to be manufactured, for example, a structure shown in FIG. 33 is used. Here, the structure is formed at an equal pitch in a certain direction in the plane, and the pitch is shorter than the target wavelength, and preferably less than half of the wavelength.
It is known that a structure having a width of 200 nm or less can be produced by two-photon absorption photocuring with a laser beam in the near-infrared region having a wavelength of 800 nm. Such a structure is the manufacturing method of this embodiment. Can be formed.

[Example 22]
Next, an embodiment of a method for manufacturing a fine structure according to a method for manufacturing an optical element of the twenty-fourth means and a method for manufacturing a shape transfer mold for optical elements of the thirty-eighth means will be described.
In the manufacturing method of this embodiment, the structure is formed on a structure having a curved surface at least partially in the manufacturing method of any of the above-described embodiments 16 to 21. is there.

  In the manufacturing methods of Examples 16 to 21, it is possible to produce a structure on a curved surface, which is produced by measuring the curved surface data of the substrate in advance or measuring the distance from the substrate surface. Thus, the information on the substrate surface can be input and corrected when the condensing point is moved in the vertical direction. As a structure on the curved surface, for example, a structure as shown in FIG. 34 is conceivable. More specifically, there is a structure in which the fine structure 2 is formed on the lens 4 as described in the seventh embodiment. This can be realized by using the lens 4 for the substrate and forming the fine structure 2 on the curved surface of the lens 4 by the manufacturing methods of Examples 16-21.

  In this way, in this embodiment, a fine structure is formed on the curved surface, so that the structure is made aspherical on the spherical lens, or a diffraction grating is made to add a lens chromatic aberration correction function. It is possible to produce an optical element having a composite function such as or a shape transfer mold thereof. Moreover, by replicating an optical element using this shape transfer mold, an optical element having a composite function can be provided at a low cost.

It is a principal part perspective view of the optical element which shows one Example of this invention. It is explanatory drawing of the diffraction effect | action by the fine structure of the optical element which concerns on this invention. It is principal part sectional drawing of the optical element which shows another Example of this invention. It is a figure which shows the example of the shape of the microstructure of the optical element which concerns on this invention. It is a structure explanatory drawing of the optical element which shows another Example of this invention. It is principal part sectional drawing of the optical element which shows another Example of this invention. It is principal part sectional drawing of the optical element which shows another Example of this invention. It is process explanatory drawing which shows an example of the manufacturing method of the optical element shown in FIG. It is explanatory drawing of the optical element which shows another Example of this invention. (A) is a figure showing the two-dimensional data of the height of the fine structure calculated by the iterative Fourier transform method, (b) is the structure of (a) produced by the manufacturing method of the present invention, and a predetermined wavelength is given to this structure. It is a figure showing the laser beam pattern obtained in the Fraunhofer diffraction area | region (far field) when the laser beam which has is incident. It is explanatory drawing of the optical element which shows another Example of this invention. It is a schematic block diagram which shows an example of the processing apparatus used for preparation of a fine structure. (A) is a figure which shows the relationship between the wavelength plate rotation angle in the apparatus shown in FIG. 12, and the incident light intensity to a resist, (b) is a figure which shows the relationship between a laser intensity ratio and the incident light intensity to a resist. It is explanatory drawing of the method to transcribe | transfer the fine structure formed with the resist to a board | substrate. It is a schematic block diagram which shows another example of the processing apparatus used for preparation of a fine structure. It is a figure which shows the process shape change by the incident light intensity of a laser. It is a figure which shows an example of the method of producing a fine structure using a laser ablation processing method. It is process explanatory drawing which shows an example of the manufacturing method which produces the shape transfer type | mold of a microstructure and produces the replica of an optical element. It is a schematic block diagram which shows another example of the processing apparatus used for preparation of a fine structure. It is a figure which shows an example of the manufacturing method of the microstructure which concerns on this invention. It is a figure which shows an example of the conventional preparation methods. It is a figure which shows an example of the manufacturing method of the microstructure which concerns on this invention. It is a figure which shows an example of the manufacturing method of the microstructure which concerns on this invention. It is a schematic block diagram which shows another example of the processing apparatus used for preparation of a fine structure. It is a figure which shows an example of the fine structure produced with the manufacturing method which concerns on this invention. It is process explanatory drawing which shows an example of the method of producing a replica using the microstructure produced with the method concerning this invention as a shape transfer type | mold. It is process explanatory drawing which shows another example of the method of producing a replica using the microstructure produced with the method which concerns on this invention as a shape transfer type | mold. It is process explanatory drawing which shows another example of the method of producing a replica using the microstructure produced with the method which concerns on this invention as a shape transfer type | mold. It is a schematic block diagram which shows another example of the processing apparatus used for preparation of a fine structure. It is explanatory drawing of the method of attaching a laser rangefinder to the objective lens of the processing apparatus of FIG. 29, and measuring the distance with a substrate surface. It is explanatory drawing which shows the mode of the diffraction by the diffractive optical element produced with the preparation method of this invention. It is a figure which shows the example of the microstructure of an inappropriate shape. It is a figure which shows an example of the fine structure which is shorter than a wavelength and is equal pitch. It is a figure which shows an example of the fine structure formed in the curved surface. It is a figure which shows an example of the fine structure of the conventional phase modulation type | mold subwavelength element. It is explanatory drawing of the conventional fine structure with the same pitch and equal pitch. It is a figure which shows the relationship between the fill factor and effective refractive index in the conventional fine structure. It is explanatory drawing of the fine structure from which the conventional height is the same and from which width differs. It is a figure which shows the relationship between the position in the case of performing interference exposure, and light intensity.

Explanation of symbols

1: Substrate 2: Fine structure 3: Cell (region)
4: Lens 5: Resist 11, 21, 51, 61: Laser device 12, 24, 52, 65: Spatial filter 13, 22, 62: 1/2 wavelength plate 14: Non-polarizing beam splitter 15a, 15b: Mirror 16, 29, 56: Controller 17, 30: Rotary stage 23: Glan laser prism 25, 64: Mirror 26: Mask 27: Diffraction grating 28, 54: Lens 31, 55, 72: Moving stage 40: Multilayer thin film structure 41: Absorption Layer 42: Transmission layer 43: Metal film 44: Mold (shape transfer mold)
45: Optical element 53, 66: Galvano mirror 56: Photocurable resin 60: Photoreactive material 63: Glan-Thompson prism 67: Relay lens 68: Beam sampler 69: Imaging lens 70: Objective lens 71: Piezo stage 73: CCD
74: Rotary stage controller 75: Half mirror 76: Photo diode 77: Laser range finder 80: Resin 81: Metal film 82: Mold (shape transfer type)

Claims (40)

An optical element having a microstructure,
An optical element characterized in that the phase of transmitted light is changed by spatially modulating the height of at least some of the structures. The optical element according to claim 1, wherein
An optical element having a structure finer than the wavelength of light to be used. The optical element according to claim 2, wherein
When the wavelength of the light used is λ, the incident angle is θ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2, the period of the structure is λ / (n1sinθ + n2) or less. An optical element. The optical element according to claim 2 or 3,
When the wavelength of the light used is λ, the refractive index of the incident medium is n1, and the refractive index of the structure is n2, the difference in height Δh of the structure is
Δh = 2√2λ × √ (n1 ^ 2 + n2 ^ 2) / (n1 + n2) ^ 2
An optical element characterized by being in the vicinity of. In the optical element as described in any one of Claims 1-4,
An optical element characterized in that the fine structure is a substantially rectangular lattice, a columnar structure or a multistage structure having the same period. In the optical element as described in any one of Claims 2-5,
An optical element, wherein a fine structure having a wavelength shorter than a wavelength to be used is divided into a plurality of regions, and the structures in the regions have the same pitch and the same height. In the optical element as described in any one of Claims 1-6,
An optical element, wherein the fine structure is formed on both surfaces of the element. In the optical element as described in any one of Claims 1-7,
An optical element, wherein the fine structure is formed on a curved surface. In the optical element as described in any one of Claims 2-8,
An optical element, wherein the phase of incident light is modulated by a structure having a wavelength equal to or less than a wavelength, and at least a part of the incident light is collected. In the optical element as described in any one of Claims 2-8,
An optical element characterized by shaping a beam of transmitted light by modulating a phase of incident light by a structure having a wavelength or less. The optical element according to any one of claims 2 to 9,
An optical element characterized in that the aberration of transmitted light is corrected by modulating the phase of incident light by a structure having a wavelength shorter than that provided on at least one surface. In the manufacturing method at the time of manufacturing the optical element according to any one of claims 1 to 11,
Using a laser interference exposure method in which a structure is formed by laser interference, the height of the structure is spatially modulated by modulating the intensity of interference light by means of interference light intensity modulation, and a fine structure is formed. A method for manufacturing an optical element. In the manufacturing method at the time of manufacturing the optical element according to any one of claims 1 to 11,
Using the laser ablation method that forms a fine structure by the laser ablation method, the processing laser beam is made to interfere, and the interference intensity is modulated by the interference light intensity modulation means to spatially modulate the height of the structure. A method for producing an optical element, characterized by forming a fine structure. In the manufacturing method at the time of manufacturing the optical element according to any one of claims 1 to 11,
Using a laser ablation method that forms a fine structure by the laser ablation method, a processing laser beam is applied to a structure in which a thin film that shows transparency and a thin film that absorbs laser light are laminated. A method of manufacturing an optical element, wherein a fine structure is formed by irradiation and spatially removing a thin film. In the manufacturing method at the time of manufacturing the optical element according to any one of claims 1 to 11,
By using a photo-curing method that condenses light and cures the material in the vicinity of the focal point to form a structure, forms the structure by multiphoton absorption of the irradiated laser light, and modulates the height of the structure A method for producing an optical element, characterized by forming a fine structure. In the manufacturing method of the optical element according to any one of claims 13 to 15,
The method of manufacturing an optical element, wherein the laser beam for processing is an ultrashort pulse laser having a pulse width of 10 picoseconds or less. In the manufacturing method at the time of manufacturing the optical element according to any one of claims 1 to 11,
A photoreactive material is applied on the substrate, the laser beam is condensed in the material, multi-photon absorption is caused only near the condensing point, and the condensing point is scanned on the substrate surface to thereby form the substrate surface. This is a method of forming a fine structure. By changing the distance between the center of the focal point and the substrate surface during scanning, the height of the structure to be formed is changed, and structures with spatially different heights are created. A method for manufacturing an optical element, characterized by being manufactured. In the manufacturing method of the optical element according to claim 17,
During the irradiation with the laser beam, the power of the laser beam and the scanning speed of the condensing point are substantially constant. The method of manufacturing an optical element according to claim 17 or 18,
During the irradiation with the laser beam, the position between the substrate and the focal point is constantly monitored, and the position of the focal point is adjusted based on the monitoring result. In the manufacturing method of the optical element as described in any one of Claims 17-19,
The method of manufacturing an optical element, wherein the laser beam is an ultrashort pulse laser beam. In the manufacturing method of the optical element as described in any one of Claims 17-20,
An optical element manufacturing method using an immersion objective lens as means for condensing laser light in the photoreactive material. In the manufacturing method of the optical element as described in any one of Claims 17-21,
A method of manufacturing an optical element, wherein a pitch of a structure to be manufactured in at least a part of a plane (a minimum distance width between the structure and the structure) is set to a wavelength or less. In the manufacturing method of the optical element according to claim 22,
A method of manufacturing an optical element, wherein the structure is manufactured at an equal pitch in a region functioning as an optical element. In the manufacturing method of the optical element as described in any one of Claims 17-23,
A method of manufacturing an optical element, wherein the structure is formed on a structure having a curved surface at least partially.   An optical element manufactured by the method for manufacturing an optical element according to any one of claims 12 to 24. In the manufacturing method of the shape transfer mold for optical elements which is used when manufacturing the optical element according to any one of claims 1 to 11 and transfers the fine structure,
Using a laser interference exposure method in which a structure is formed by laser interference, the height of the structure is spatially modulated by modulating the intensity of interference light by means of interference light intensity modulation, and a fine structure is formed. Manufacturing method of shape transfer mold for optical element. In the manufacturing method of the shape transfer mold for optical elements which is used when manufacturing the optical element according to any one of claims 1 to 11 and transfers the fine structure,
Using the laser ablation method that forms a fine structure by the laser ablation method, the processing laser beam is made to interfere, and the interference intensity is modulated by the interference light intensity modulation means to spatially modulate the height of the structure. A method for producing a shape transfer mold for an optical element, wherein a fine structure is formed. In the manufacturing method of the shape transfer mold for optical elements which is used when manufacturing the optical element according to any one of claims 1 to 11 and transfers the fine structure,
Using a laser ablation method that forms a fine structure by the laser ablation method, a processing laser beam is applied to a structure in which a thin film that shows transparency and a thin film that absorbs laser light are laminated. A method for producing a shape transfer mold for an optical element, wherein a fine structure is formed by irradiation and spatially removing a thin film. In the manufacturing method of the shape transfer mold for optical elements which is used when manufacturing the optical element according to any one of claims 1 to 11 and transfers the fine structure,
By using a photo-curing method that condenses light and cures the material in the vicinity of the focal point to form a structure, forms the structure by multiphoton absorption of the irradiated laser light, and modulates the height of the structure A method for producing a shape transfer mold for an optical element, wherein a fine structure is formed. In the manufacturing method of the shape transfer mold for optical elements according to any one of claims 26 to 29,
The method of manufacturing a shape transfer mold for an optical element, wherein the processing laser light is an ultrashort pulse laser having a pulse width of 10 picoseconds or less. In the manufacturing method of the shape transfer mold for optical elements which is used when manufacturing the optical element according to any one of claims 1 to 11 and transfers the fine structure,
A photoreactive material is applied on the substrate, the laser beam is condensed in the material, multi-photon absorption is caused only near the condensing point, and the condensing point is scanned on the substrate surface to thereby form the substrate surface. This is a method of forming a fine structure. By changing the distance between the center of the focal point and the substrate surface during scanning, the height of the structure to be formed is changed, and structures with spatially different heights are created. A method for producing a shape transfer mold for an optical element, characterized by comprising: In the manufacturing method of the shape transfer type for optical elements according to claim 31,
A method of manufacturing a shape transfer mold for an optical element, wherein the power of the laser light and the scanning speed of the condensing point are substantially constant during the irradiation with the laser light. In the manufacturing method of the shape transcription type for optical elements according to claim 31 or 32,
During the irradiation with the laser light, the position of the substrate and the focal point is always monitored, and the position of the focal point is adjusted based on the monitoring result. In the manufacturing method of the shape transfer mold for optical elements according to any one of claims 31 to 33,
A method of manufacturing a shape transfer mold for an optical element, wherein the laser beam is an ultrashort pulse laser beam. In the manufacturing method of the shape transfer mold for optical elements according to any one of claims 31 to 34,
A method of manufacturing a shape transfer mold for an optical element, wherein an immersion objective lens is used as means for condensing laser light in the photoreactive material. In the manufacturing method of the shape transfer mold for optical elements according to any one of claims 31 to 35,
A method for producing a shape transfer mold for an optical element, wherein a pitch of a structure to be fabricated in at least a part of a plane (a minimum distance width between the structure and the structure) is set to a wavelength or less. In the manufacturing method of the shape transcription type for optical elements according to claim 36,
A method for producing a shape transfer mold for an optical element, wherein the structure is produced at an equal pitch in a region functioning as an optical element. In the manufacturing method of the shape transfer mold for optical elements according to any one of claims 31 to 37,
A method for producing a shape transfer mold for an optical element, wherein the structure is formed on a structure having a curved surface at least partially.   An optical element shape transfer mold manufactured by the method for manufacturing an optical element shape transfer mold according to any one of claims 26 to 38.   40. An optical element produced by transferring a fine structure to an optical material using the shape transfer mold for optical elements according to claim 39.

Images