CN110967785A - Method for preparing holographic grating with small aspect ratio by holographic interference recording means - Google Patents
Method for preparing holographic grating with small aspect ratio by holographic interference recording means Download PDFInfo
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- CN110967785A CN110967785A CN201911280940.XA CN201911280940A CN110967785A CN 110967785 A CN110967785 A CN 110967785A CN 201911280940 A CN201911280940 A CN 201911280940A CN 110967785 A CN110967785 A CN 110967785A
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- 238000000034 method Methods 0.000 title claims abstract description 39
- 239000000463 material Substances 0.000 claims abstract description 47
- 230000001427 coherent effect Effects 0.000 claims abstract description 15
- 229920002120 photoresistant polymer Polymers 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 abstract description 18
- 230000008569 process Effects 0.000 abstract description 6
- 238000000992 sputter etching Methods 0.000 abstract 1
- 238000005530 etching Methods 0.000 description 5
- 238000010884 ion-beam technique Methods 0.000 description 4
- 238000001259 photo etching Methods 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 3
- 238000000206 photolithography Methods 0.000 description 3
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
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- 230000007547 defect Effects 0.000 description 1
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- 238000003379 elimination reaction Methods 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1847—Manufacturing methods
- G02B5/1857—Manufacturing methods using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
Abstract
The invention discloses a novel method for preparing a holographic grating with a small aspect ratio by carrying out secondary exposure by adopting a holographic interference recording means. The method comprises the following steps: the recording material is first exposed by two coherent parallel lights, then the position of the recording material is adjusted by a stepping motor under the condition of not changing the recording beam, the second exposure is carried out, and the development is carried out after the second exposure is finished. The method is easier to realize than an ion etching method, only has one more moving and exposure process of the recording material than the preparation process of the common holographic grating, and can prepare the holographic grating with small aspect ratio by secondary exposure by utilizing the original equipment for preparing the common holographic grating. Compared with the existing method, the added exposure process is simpler, and has no special requirements on preparation materials and does not need additional equipment and special elements. The method has the advantages of simple preparation process, high preparation speed and low preparation cost.
Description
Technical Field
The invention relates to a novel method for preparing a holographic grating with a small aspect ratio by carrying out secondary exposure by adopting a holographic interference recording means.
Background
Compared with the grating for etching, the holographic grating has the advantages of ghost line elimination, stray light reduction, high resolution, wide applicable spectrum range, high production efficiency and the like. The aspect ratio (the ratio of the line width to the period) of the holographic grating is an important parameter in the holographic grating, and the aspect ratio of the holographic grating is different, and the properties of the holographic grating, such as diffraction efficiency, are also different. However, the holographic grating prepared by the holographic interference recording method has an aspect ratio generally controlled within a range of 0.2 to 0.6. The reason is that: in the process of preparing the holographic grating by utilizing the holographic interference recording method, along with the increase of exposure time, the duty ratio of the holographic grating is reduced, the groove shape of the grating is continuously changed in the process, because the exposure amount of the center of the dark fringe of the interference fringe and the exposure amount of the two sides of the dark fringe are different, the wave crest of the grating becomes narrower and narrower (namely the line width of the grating is smaller and smaller) along with the increase of the exposure time, and under the condition that the period of the grating is not changed, the duty ratio of the grating is smaller and smaller; when the aspect ratio (the ratio of the line width to the period) is less than 0.2, the holographic grating grooves collapse, and the grating morphology cannot be preserved. Therefore, the holographic grating prepared by the traditional holographic interference recording method is difficult to obtain the holographic grating with the ratio of less than 0.2. At present, in order to obtain a grating with a small aspect ratio, the existing methods include an ion beam etching method, a method utilizing a guided wave coupling angle and the like, but the ion beam etching method needs to add extra equipment, so that the preparation cost is greatly increased; the method for controlling the duty ratio of the photoetching offset grating mask in real time by utilizing the guided wave coupling angle has a complex preparation process and is not easy to realize.
Disclosure of Invention
The invention mainly aims to overcome the defects in the prior art and provides a method for preparing a holographic grating with a small aspect ratio by a holographic interference recording means, which is simpler, quicker, easier to realize and low in cost.
A method for preparing holographic grating with small aspect ratio by holographic interference recording means comprises the following steps:
s1: the recording material is exposed for the first time with two incident coherent parallel rays, the incident angle θ being determined by the following equation: 2sin theta is lambda/d, wherein lambda is the laser wavelength of a recording light source, d is the grating period, the recording material is a recording dry plate capable of forming relief-shaped interference fringes, and the wavelength of the recording light source is the laser wavelength sensitive to the recording dry plate;
s2: on the premise of not changing the recording beam, the position of the recording material is adjusted by using a stepping motor, and the moving distance is determined by the ratio of the occupied width of the holographic grating to be obtained;
s3: carrying out second exposure after the adjustment is finished;
s4: and after the two exposures are finished, developing to obtain the required holographic grating with the small aspect ratio.
The adjusting the position of the recording material by the stepping motor includes moving the position of the recording material horizontally or moving the position of the recording material vertically by the stepping motor, and if the position of the recording material is moved horizontally by the stepping motor, the relation between the aspect ratio and the horizontal moving distance of the recording material is:
where σ 1 is the duty ratio after the first exposure, L1 is the line width after the first exposure, D1 is the grating period after the first exposure, σ 2 is the duty ratio after the second exposure, L2 is the line width after the second exposure, D2 is the grating period after the second exposure, and D is the recording material horizontal movement distance; if the position of the recording material is vertically moved by the stepping motor, the relationship between the aspect ratio and the horizontal moving distance of the recording material is:
where σ 1 is the duty ratio after the first exposure, L1 is the line width after the first exposure, D1 is the grating period after the first exposure, σ 2 is the duty ratio after the second exposure, L2 is the line width after the second exposure, D2 is the grating period after the second exposure, and D is the recording material horizontal movement distance.
The recording dry plate capable of forming the relief-shaped interference fringes can be selected from a photoresist dry plate (referred to as a photoetching offset plate).
The wavelength of the recording light source is the wavelength of the laser sensitive to the recording dry plate, such as the 442nm wavelength of He-Cd laser or Ar for the photolithography offset plate+458nm wavelength of the laser, etc.
After the holographic grating with small aspect ratio is manufactured, if the transmitted light is reduced to increase the diffraction efficiency, a layer of reflecting film can be plated on the surface of the grating.
The invention is easier to realize than the ion beam etching method, only has more one-time movement and secondary exposure of the recording material than the preparation process of the general holographic grating (with sine groove type), and can utilize the original equipment for preparing the general holographic grating to prepare the holographic grating with small occupying ratio. Compared with the existing method, the added exposure process is simpler, and has no special requirement on the preparation material and no need of adding extra preparation equipment and special elements, thereby simplifying the preparation process of the holographic grating with small aspect ratio, improving the preparation speed and reducing the cost.
Drawings
FIG. 1 is a first exposure path for preparing a holographic grating with a small aspect ratio;
FIG. 2 is an exposure route for the second exposure after horizontal movement for preparing a holographic grating with a small aspect ratio;
FIG. 3 is a first exposure path for preparing a holographic grating with a small aspect ratio;
FIG. 4 is an exposure route for the second exposure after vertical movement for the preparation of a holographic grating with a small aspect ratio;
the invention is described in further detail below with reference to the figures and specific examples.
Detailed Description
The invention is further described below by means of specific embodiments.
S1: the recording material is exposed for the first time with two incident coherent parallel rays, the incident angle θ being determined by the following equation: 2sin theta is lambda/d, wherein lambda is the laser wavelength of a recording light source, d is the grating period, the recording material is a recording dry plate capable of forming relief-shaped interference fringes, and the wavelength of the recording light source is the laser wavelength sensitive to the recording dry plate;
s2: on the premise of not changing the recording beam, the position of the recording material is adjusted by using a stepping motor, and the moving distance is determined by the ratio of the occupied width of the holographic grating to be obtained;
s3: carrying out second exposure after the adjustment is finished;
s4: and after the two exposures are finished, developing to obtain the required holographic grating with the small aspect ratio.
The adjusting of the position of the recording material using the stepping motor includes moving the position of the recording material horizontally or moving the position of the recording material vertically using the stepping motor.
The first embodiment is as follows: the step motor is horizontally moved, and the holographic grating with small aspect ratio is prepared by utilizing a holographic interference recording means secondary exposure method. First, a first exposure is performed with two symmetrically incident coherent parallel lights. The exposure light path is as shown in fig. 1, and a photoresist plate 2 is provided on a glass substrate 1. Two coherent parallel lights 4 and 5 having the same angle θ as the normal 3 of the plate 2 are incident on the plate 2 for a first exposure. The value of the included angle θ is determined according to the requirement of the grating period, and can be calculated by the following formula:
2sinθ＝λ/d
where λ is the laser wavelength and d is the grating period. The exposure time is dependent on the recording material used and the intensity of the laser light and should be determined experimentally. After development, a holographic grating having a sinusoidal groove shape is formed on the surface of the plate 2 in the region where the two coherent lights 4 and 5 overlap (the grating shape is shown in fig. 2).
Then, as shown in fig. 2, the recording material is horizontally moved without changing the two coherent parallel lights 7 and 8. Two coherent parallel lights 4 and 5 are made incident on the resist plate 6 on which the holographic grating of the sine groove type has been formed to perform a second exposure. The resulting relationship between the aspect ratio and the horizontal movement distance of the recording material is:
where σ 1 is the duty ratio after the first exposure, L1 is the line width after the first exposure, and d1 is the grating period after the first exposure. σ 2 is the duty ratio after the second exposure, L2 is the line width after the second exposure, D2 is the grating period after the second exposure, and D is the recording material horizontal movement distance.
The recording plate capable of forming the relief-like interference fringes can be selected from a photoresist plate (referred to as a photolithography plate).
The wavelength of the recording light source is the laser wavelength sensitive to the recording dry plate, such as the 442nm wavelength of a He-Cd laser or the 458nm wavelength of an Ar laser and the like can be used for the photoetching offset plate.
The holographic grating with small occupying-width ratio can be obtained by the method, and after the grating is manufactured, if the transmitted light is reduced to increase the diffraction efficiency, a layer of reflecting film can be plated on the surface of the grating; there is no optical path limitation on how the parallel light used in the two exposures is generated, but two beams of light are required to be coherent light; to obtain a high quality interference effect, all beams are preferably spatially filtered.
Example two: the step motor is vertically moved, and the holographic grating with small aspect ratio is prepared by utilizing a holographic interference recording means secondary exposure method. Firstly, in order to control the moving distance and further control the phase difference so as to obtain the desired duty ratio, a vertical incidence parallel light ray 3 and an oblique incidence parallel light ray 4 are adopted, the two light rays are coherent and have an included angle of 2 theta, and the first exposure is carried out. The exposure light path is as shown in fig. 3, and a photoresist 2 is on a glass substrate 1. The value of the included angle 2 θ is determined according to the requirement of the grating period, and can be calculated by the following formula:
2sinθ＝λ/d
where λ is the laser wavelength and d is the grating period. The exposure time is dependent on the recording material used and the intensity of the laser light and should be determined experimentally. After development, a holographic grating having a sinusoidal groove shape is formed on the surface of the plate where the two coherent light beams 3 and 4 overlap (the grating shape is shown in FIG. 4).
Then, as shown in fig. 4, the recording material is vertically moved without changing the two coherent parallel lights 3 and 4. Two coherent parallel lights 3 and 4 are made incident on the photoresist 5 of the holographic grating formed with the sinusoidal groove shape for the second exposure. The relationship between the aspect ratio of two incident rays and the vertical movement distance of the recording material is:
where σ 1 is the duty ratio after the first exposure, L1 is the line width after the first exposure, and d1 is the grating period after the first exposure. σ 2 is the duty ratio after the second exposure, L2 is the line width after the second exposure, D2 is the grating period after the second exposure, and D is the recording material vertical movement distance.
The relationship between the phase difference of two incident light rays and the vertical moving distance of the recording material is:
where δ is the phase difference of two incident parallel lights, Δ is the optical path difference of the two incident parallel lights, and D is the vertical moving distance of the recording material.
The recording dry plate capable of forming the relief-shaped interference fringes can be selected from a photoresist dry plate (referred to as a photoetching offset plate).
The wavelength of the recording light source is the wavelength of the laser sensitive to the recording dry plate, such as the 442nm wavelength of He-Cd laser or Ar for the photolithography offset plate+458nm wavelength of the laser, etc.
The holographic grating with small occupying ratio can be obtained by the method; after the grating is manufactured, if the transmitted light is reduced to increase the diffraction efficiency, a layer of reflecting film can be plated on the surface of the grating; there is no optical path limitation on how the parallel light used in the two exposures is generated, but two beams of light are required to be coherent light; to obtain a high quality interference effect, all beams are preferably spatially filtered.
The invention is easier to realize than the ion beam etching method, only has more one-time movement and secondary exposure of the recording material than the preparation process of the general holographic grating (with sine groove type), and can utilize the original equipment for preparing the general holographic grating to prepare the holographic grating with small occupying ratio. Compared with the existing method, the added exposure process is simpler, and has no special requirement on the preparation material and no need of adding extra preparation equipment and special elements, thereby simplifying the preparation process of the holographic grating with the small aspect ratio, improving the preparation speed and reducing the cost.
The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.
Claims (6)
1. A method for preparing holographic grating with small aspect ratio by holographic interference recording means is characterized by comprising the following steps:
s1: the recording material is exposed for the first time with two incident coherent parallel rays, the incident angle θ being determined by the following equation: 2sin theta is lambda/d, wherein lambda is the laser wavelength of a recording light source, d is the grating period, the recording material is a recording dry plate capable of forming relief-shaped interference fringes, and the wavelength of the recording light source is the laser wavelength sensitive to the recording dry plate;
s2: on the premise of not changing the recording beam, the position of the recording material is adjusted by using a stepping motor, and the moving distance is determined by the ratio of the occupied width of the holographic grating to be obtained;
s3: carrying out second exposure after the adjustment is finished;
s4: and after the two exposures are finished, developing to obtain the required holographic grating with the small aspect ratio.
2. The method of claim 1, wherein the adjusting the position of the recording material with a stepper motor comprises moving the position of the recording material horizontally or vertically with a stepper motor.
3. The method for preparing a holographic grating with a small aspect ratio by the holographic interference recording means as claimed in claim 2, wherein the position of the recording material is moved horizontally by a stepping motor, and the relationship between the aspect ratio and the horizontal moving distance of the recording material is as follows:
where σ 1 is the duty ratio after the first exposure, L1 is the line width after the first exposure, d1 is the grating period after the first exposure, and σ 2 is the duty ratio after the second exposureIn contrast, L2 is the line width after the second exposure, D2 is the grating period after the second exposure, and D is the recording material horizontal movement distance.
4. The method for preparing a holographic grating with a small aspect ratio by the holographic interference recording means as claimed in claim 2, wherein the position of the recording material is vertically moved by a stepping motor, and the relation between the aspect ratio and the horizontal moving distance of the recording material is as follows:
where σ 1 is the duty ratio after the first exposure, L1 is the line width after the first exposure, D1 is the grating period after the first exposure, σ 2 is the duty ratio after the second exposure, L2 is the line width after the second exposure, D2 is the grating period after the second exposure, and D is the recording material horizontal movement distance.
5. The method for preparing a holographic grating with a small aspect ratio by the holographic interference recording means as claimed in any one of claims 1 to 4, wherein the recording plate capable of forming the embossed interference fringes is selected from a photoresist plate.
6. The method for preparing the holographic grating with the small aspect ratio by the holographic interference recording means as claimed in one of claims 1 to 4, wherein the wavelength of the recording light source is selected from the 442nm wavelength of a He-Cd laser or the 458nm wavelength of an Ar + laser.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112596139A (en) * | 2020-12-18 | 2021-04-02 | 中国科学院上海光学精密机械研究所 | Grating structure writing method of short-wave range reflection type volume grating |
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| US5563704A (en) * | 1995-02-23 | 1996-10-08 | Fitzpatrick; Colleen M. | Camera and method for holographic interferometry using an erasable photosensitive photopolymer film |
| CN1544995A (en) * | 2003-11-17 | 2004-11-10 | 厦门大学 | Method for preparing glistening holographic grating |
| CN101382611A (en) * | 2008-10-10 | 2009-03-11 | 苏州大学 | Method for producing large area holographic grating based on second exposure of reference grating |
| CN103226215A (en) * | 2013-04-19 | 2013-07-31 | 中国科学院半导体研究所 | Preparation method of holographic grating provided with surface with periodically graded width |
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Patent Citations (5)
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|---|---|---|---|---|
| US5563704A (en) * | 1995-02-23 | 1996-10-08 | Fitzpatrick; Colleen M. | Camera and method for holographic interferometry using an erasable photosensitive photopolymer film |
| CN1544995A (en) * | 2003-11-17 | 2004-11-10 | 厦门大学 | Method for preparing glistening holographic grating |
| CN101382611A (en) * | 2008-10-10 | 2009-03-11 | 苏州大学 | Method for producing large area holographic grating based on second exposure of reference grating |
| CN103226215A (en) * | 2013-04-19 | 2013-07-31 | 中国科学院半导体研究所 | Preparation method of holographic grating provided with surface with periodically graded width |
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| CN112596139A (en) * | 2020-12-18 | 2021-04-02 | 中国科学院上海光学精密机械研究所 | Grating structure writing method of short-wave range reflection type volume grating |
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