JP4657775B2 - Method and apparatus for measuring photonic band structure of photonic crystal waveguide - Google Patents

Description

  The present invention relates to a method and apparatus for measuring a photonic band structure of a photonic crystal waveguide, and more particularly, a photonic crystal waveguide suitable for use in evaluating optical characteristics of a photonic crystal waveguide. The present invention relates to a method and apparatus for measuring the photonic band structure.

  In this specification, “photonic crystal” includes at least two types of materials having different refractive indexes, and at least two types of materials having different refractive indexes form a structure having a periodic structure. It means what you do. Therefore, as long as at least a part of the structure having the periodic structure includes the structure having the periodic structure, the presence or absence of the structure other than the structure having the periodic structure is not questioned, and all “photos” in this specification are used. Included in “Nick Crystal”. In other words, the “photonic crystal” in the present specification means the structure itself having the above-described periodic structure, and includes the structure having the above-described periodic structure. It shall mean a larger structure.

  Further, in this specification, the “photonic crystal waveguide” means an optical waveguide structure configured using the above-mentioned “photonic crystal”.

  In recent years, a photonic crystal having a structure having a periodic structure in which at least two kinds of substances having different refractive indexes with a period of about the wavelength of light are arranged one-dimensionally, two-dimensionally or three-dimensionally has attracted attention.

  This photonic crystal is an artificial optical nanostructure having a structure in which the refractive index is periodically changed on the scale of the light wavelength, and is extremely slow, a few tenths of the speed of light in vacuum. It is known that a group velocity of light can be realized (see Non-Patent Document 1), and such photonic crystals are expected to be applied to nonlinear fields and the like, and various techniques using photonic crystals are proposed. Is strongly desired.

By the way, a photonic crystal waveguide having an optical waveguide structure formed using this photonic crystal is, for example, an optical waveguide element, an optically coupled demultiplexing element, a laser element, a light emitting element, an element using light dispersion, Super prism element, super collimating element, lens functional element, negative refraction element, polarizing element, wavelength conversion element, harmonic generation element, sum frequency / difference frequency generation element, optical parametric amplification element, stimulated Raman scattering element, four-wave mixing Used in various optical elements such as optical elements, small laser light sources, optical switch elements, optical bistable elements, optical logic operation elements, optical modulation elements, and phase conjugate light generation elements, and the optimal design of these various optical elements In order to achieve this, it is extremely important to accurately know the photonic band structure that is related to the light dispersion formed in the photonic crystal waveguide. It has been recognized.

  That is, the optical band dispersion control by the photonic crystal waveguide has a possibility of remarkably increasing nonlinear optical effects such as phase matching in second harmonic generation and electric field enhancement at the time of optical switching. This is because all the characteristics of crystal waveguides can be summarized in manipulating and controlling this photonic band structure.

  In other words, if the photonic band structure can be accurately detected, it is possible to predict in advance the optical functions of the various optical elements described above. Therefore, to know the photonic band structure accurately, It was a key point for the optimization design of the various optical elements described above.

Conventionally, in order to measure the photonic band structure of a photonic crystal waveguide from the outside, a laser beam or a collimated white light beam is incident on the photonic crystal waveguide from outside and the incident angle is scanned at that time. , Angle dependence and frequency (energy) dependence of the resonance dip (minimum sharp reflectance) due to coupling phenomenon between external light appearing in reflected light from photonic crystal waveguide and mode in photonic crystal waveguide The technique of examining the property is used, and thereby the photonic band structure is determined (see Non-Patent Documents 1 and 2).

  However, in the conventional methods as shown in Non-Patent Documents 1 and 2, the region above the light line (ω = ck (ω is the frequency of light, c is the speed of light, and k is the wave number)), that is, Only the light dispersion relation in the mode (radiation mode) region having the coupling property with the outside (air) of the photonic crystal waveguide can be measured, and the region below the light line, that is, the photonic crystal waveguide It was impossible to measure the light dispersion relationship in the waveguide mode region that is not coupled to the outside of the light.

  Here, the waveguide mode below the light line has a long life because light does not leak to the outside, and can guide light with less optical loss. Therefore, in photonic crystal waveguides, This mode has high applicability.

  Therefore, it is very important to measure the light dispersion relationship of the waveguide mode in order to accurately grasp the operation characteristics of the photonic crystal waveguide. Specifically, information on the group velocity of light, information on momentum, information on cut-off frequency, etc. can be obtained from the light dispersion relationship of the waveguide mode, which is extremely important in the operation of all the above-mentioned various optical elements. Parameter. Also, by comparing the measurement results with the theoretical calculation design, it is possible to provide feedback between the two, and it is possible to design more functional devices and to inspect the fabrication accuracy of various optical elements. is there.

  However, as described above, the conventional methods as shown in Non-Patent Documents 1 and 2 have a major problem in that it is impossible to measure the light dispersion relationship in the essential waveguide mode region, and a new method has been developed. Was desired.

In recent years, as a method for measuring the photonic band structure of a two-dimensional photonic crystal waveguide from the outside, the transmittance of the in-plane waveguide is measured with respect to a defect waveguide in the two-dimensional photonic crystal waveguide. There has been proposed a method for experimentally obtaining a light dispersion relation of a defect band from Fabry-Perot interference fringes appearing in the transmission spectrum (see Non-Patent Document 3).

  The method shown in Non-Patent Document 3 can measure the light dispersion relationship of the waveguide mode in the sense that the light is guided in the plane (in the method shown in Non-Patent Document 3, the radiation mode is used). Cannot be measured due to loss.)

  However, since the method shown in Non-Patent Document 3 described above needs to measure the transmittance by actually coupling light into a very small waveguide of a two-dimensional photonic crystal waveguide, it is extremely accurate. There was a problem of requiring high technology and complicated processes.

  That is, since the method shown in Non-Patent Document 3 described above needs to perform the same work as actually operating the two-dimensional photonic crystal waveguide, the meaning of measuring in advance is completely lost. there were.

In addition, due to the characteristic of using interference on the transmission spectrum, it is difficult to measure with a two-dimensional photonic crystal waveguide having a large size or a relatively large loss of light. There was also a point.
Phys. Rev. B 69, 205109 1-6 (2004) JP 2004-133429 A Phys. Rev. Lett. 87, 253902 (2001)

  The present invention has been made in view of the various problems of the conventional techniques as described above, and an object of the present invention is to provide a photonic crystal waveguide in a radiation mode and a waveguide mode from the outside. Provided is a method and an apparatus for measuring a photonic crystal structure of a photonic crystal waveguide, which enables accurate and simple measurement of the nick band structure and eliminates restrictions on the photonic crystal waveguide to be measured. It is something to try.

In order to achieve the above object, the present invention uses a prism, and by using the prism,
ω = ck / n _p (n _p is the refractive index of the prism)
Since all modes in the upper region can be measured, a photonic band structure in almost all modes including a radiation mode and a waveguide mode can be measured by using a prism having a large refractive index. .

  That is, according to the present invention, it is possible to observe the photonic band structure in the waveguide mode, which is a mode that is not normally coupled to the outside under the light line, which could not be measured in the past. The potential can be expanded dramatically.

That is, according to the first aspect of the present invention, in the method for measuring a photonic band structure of a photonic crystal waveguide, the photonic crystal layer and the predetermined layer are formed on the photonic crystal layer of the photonic crystal waveguide. When the prism is arranged with the bottom facing each other so as to provide a gap, and when the incident beam is incident on the photonic crystal layer of the photonic crystal waveguide through the prism, the incident beam is converted into the prism. Is incident on the bottom of the prism at an angle satisfying a total reflection angle greater than or equal to the total reflection angle, and the incident beam is totally reflected on the bottom of the prism and is photonic based on the outgoing beam emitted from the prism. The band structure is measured.

  According to a second aspect of the present invention, in the first aspect of the present invention, the incident beam includes the wave number and frequency of a waveguide mode in the photonic crystal waveguide, and the The incident angle and optical frequency are set such that the wave number and frequency in the traveling direction of the incident beam in the waveguide plane coincide with each other.

According to a third aspect of the present invention, there is provided a prism fixing mechanism for fixing a prism, a photonic crystal waveguide having a photonic crystal layer formed on a substrate, and the photonic crystal layer. A sample fixing mechanism that is arranged and fixed so as to face the bottom of the prism , a substrate direction fine movement mechanism for pressing the head portion against the substrate of the photonic crystal waveguide, the prism, and the photonic crystal guide A θ rotation mechanism that relatively finely moves the photonic crystal layer of the waveguide in the θ rotation direction, and a light source that incidents an incident beam toward the photonic crystal layer of the photonic crystal waveguide via the prism. A light source that is incident on the bottom of the prism at an angle satisfying a total reflection angle or more after the incident beam enters the prism; A photodetector for detecting an outgoing beam emitted from the prism after the incident beam is totally reflected at the bottom of the prism and an analysis means for analyzing the detection result of the photodetector are provided.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, at least one of the head portion and the photonic crystal waveguide is further orthogonally coordinated. And a fine movement mechanism that finely moves in the XYZ direction of the system.

  According to the present invention, the photonic band structure in the radiation mode and the waveguide mode of the photonic crystal waveguide can be measured accurately and easily from the outside, and the photonic crystal waveguide to be measured is measured. An excellent effect is obtained that the restriction of the waveguide can be eliminated.

  Hereinafter, an example of an embodiment of a method and apparatus for measuring a photonic band structure of a photonic crystal waveguide according to the present invention will be described in detail with reference to the accompanying drawings.

  The method and apparatus for measuring the photonic band structure of a photonic crystal waveguide according to the present invention can accurately measure the in-plane light dispersion relationship of the photonic crystal waveguide. In order to show the effectiveness of the method and apparatus for measuring the photonic band structure of the photonic crystal waveguide according to the present invention, in the following, by the method and apparatus for measuring the photonic band structure of the photonic crystal waveguide according to the present invention, A case where a nonlinear optical polymer two-dimensional photonic crystal waveguide is measured will be described as an example.

First, FIG. 1 is a sectional perspective view illustrating a conceptual configuration of a nonlinear optical polymer two-dimensional photonic crystal waveguide (hereinafter simply referred to as “two-dimensional photonic crystal waveguide” as appropriate) to be measured. ing.

  The two-dimensional photonic crystal waveguide 100 includes a nonlinear optical polymer layer 102 made of DR1 / PMMA as a nonlinear optical material layer, and a two-dimensional photonic crystal layer 104 made of PMMA as a periodic refractive index modulation layer. It has a waveguide core structure that is stacked vertically via an etch stop layer 106 and is structurally separated but coupled in optical mode.

  Such a structure of the two-dimensional photonic crystal waveguide 100 is disclosed in, for example, Non-Patent Document 2, and can reduce or avoid process damage to the non-linear optical polymer layer 102, and can also be used when guided. It is possible to reduce unnecessary scattering loss. Reference numeral 108 denotes a Si substrate, and reference numeral 110 denotes a metal clad layer made of Ag.

Further, in the structure of the two-dimensional photonic crystal waveguide 100, since the nonlinear material is not processed, a material with poor workability such as LiNbO ₃ can be easily used as the nonlinear material.

  The outline of the manufacturing method of such a two-dimensional photonic crystal waveguide 100 will be described. First, a metal clad layer 110 made of Ag is vacuum-deposited on a cleaned Si substrate 108 until the thickness reaches 500 nm, and nonlinear optics is formed thereon. DR1 / PMMA dissolved in a monochlorobenzene solution as the polymer layer 102 is spin-coated to a thickness of 150 to 300 nm by a spin coater and then baked at 120 to 200 ° C.

  Next, SOG as a protective film is spin-coated on the nonlinear optical polymer layer 102 very thinly (thickness 20 to 100 nm) and then baked at 120 to 300 ° C. to form an etch top layer 106. As the two-dimensional photonic crystal layer 104 serving as a refractive index modulation layer, PMMA dissolved in a monochlorobenzene solution is spin-coated to a thickness of 200 to 800 nm and then baked at 120 to 200 ° C.

Further, SOG (mainly SiO ₂ ) is spin-coated to a thickness of 150 to 300 nm as a hard mask for dry etching, and then baked at 120 to 300 ° C.

  Furthermore, an EB resist is spin-coated to a thickness of 50 to 300 nm on a dry etching hard mask, and then baked at 120 to 180 ° C.

  Next, a photonic crystal pattern (with a period of about 600 nm in this embodiment) is processed on the waveguide by EB lithography, and the pattern is transferred to the hard mask by dry etching using a fluorine-based reactive gas.

Next, photonics are applied to PMMA with high accuracy by dry etching using an O ₂ / Ar reaction gas (the concentration of O ₂ is 10 to 50% and the total pressure is 0.15 to 0.5 Pa). The crystal structure is processed.

  Finally, the mask is removed with hydrofluoric acid as necessary to have a two-layer core in which the nonlinear optical polymer layer 102 as the nonlinear optical material layer and the two-dimensional photonic crystal layer 104 as the periodic refractive index modulation layer are separated. A nonlinear optical polymer two-dimensional photonic crystal waveguide 100 is completed.

Next, a detailed description will be given of a case where a photonic band structure in a two-dimensional photonic crystal waveguide 100 is measured with respect to the photonic band structure in the two-dimensional photonic crystal waveguide 100 by the method and apparatus for measuring the photonic band structure of the photonic crystal waveguide according to the present invention. To do.

  Here, FIG. 2 is an explanatory view showing a measurement method of the photonic band structure of the photonic crystal waveguide according to the present invention, and measures the photonic band structure which is a light dispersion relation in the two-dimensional photonic crystal waveguide 100. Shows when to do.

  In other words, the method for measuring the photonic band structure of a photonic crystal waveguide according to the present invention has a predetermined gap between the two-dimensional photonic crystal layer 104 and the two-dimensional photonic crystal layer 104 of the two-dimensional photonic crystal waveguide 100. A prism (in this embodiment, a triangular prism) 10 is arranged so that the bottom 10a is opposed so as to provide g, and the two-dimensional photonic crystal waveguide 100 of the two-dimensional photonic crystal waveguide 100 is interposed via the prism 10. An incident beam is incident on the nick crystal layer 104. It is assumed that air exists as an external medium in the gap g.

  Here, for example, a laser beam or a collimated white light beam may be used as the incident beam. In addition, the polarization is previously controlled by the optical system element to linearly polarized light (TE: Transverse Electric field) or vertical polarization (TM: Transverse Machinary field). Thereby, each light dispersion relation of horizontal polarization and vertical polarization can be determined.

  When the two-dimensional photonic crystal layer 104 of the two-dimensional photonic crystal waveguide 100 is small, the incident beam is condensed by a long focus condensing lens and microscopically measured.

An incident beam is incident on the two-dimensional photonic crystal layer 104 of the two-dimensional photonic crystal waveguide 100 via the prism 10. At this time, the incident beam enters the prism 10 and then enters the prism. The incident angle at the bottom 10a of the prism 10 is equal to or greater than the total reflection angle (if the external medium of the prism 10 is air, “n _p sin θ> 1.0”, where n _p is the refractive index of the prism 10. ) So that it is incident at an angle satisfying.

  That is, the incident beam hits the bottom 10a of the prism 10 after entering the prism 10, and is totally reflected by the bottom 10a of the prism 10 and emitted from the prism 10 if the incident angle is an angle satisfying the total reflection angle or more. Thus, the photonic band structure is measured based on the outgoing beam emitted from the prism 10. More specifically, this outgoing beam is detected by a photodetector (not shown) and monitored as a reflectance, and the photonic band structure is measured by analyzing it with a known technique.

  For example, if the incident beam is a laser beam, a photodetector or a photomultiplier may be used as the photodetector. Further, if the incident beam is white light, it is convenient to form a photodetector with a spectroscope and a CCD detector and detect the outgoing beam collectively. Of course, the incident beam may be preliminarily dispersed by a monochromator and then incident on the prism 10 to detect the emitted beam.

Here, when the incident beam is totally reflected by the bottom surface 10 a of the prism 10, the evanescent wave actually oozes into the gap g. At this time, the gap g is sufficiently narrow (generally, the gap g is preferably about 100 nm to several um), and the waveguide mode in the adjacent two-dimensional photonic crystal waveguide 100 is also present. If the incident angle and optical frequency are such that the frequency and wave number coincide with the wave number and frequency in the direction of travel of the incident beam in the waveguide plane, the external incident light and the waveguide mode in the photonic crystal are coupled and guided. The wave mode is excited and the optical power is transferred into the waveguide plane.

  If the angle is scanned and measured at this time, the resonance angle in which both the frequency and the wave number coincide and are combined can be detected as a sharp drop in reflectance. The reason is that other angles are totally reflected.

  Therefore, the resonance appearing in the spectrum by scanning the incident angle of the incident beam and the in-plane beam traveling angle with respect to the crystal symmetry axis, or changing the frequency of the incident beam or scanning the optical frequency using white light. From the peak frequency and wavenumber shift, the photonic band dispersion curve can be tracked in all frequency and wavenumber regions.

Normally, the wave number of the incident beam in the traveling direction in the photonic crystal waveguide plane cannot exceed the light line and reach the region below the light line, but use the total reflection of the prism 10. Thus, the effective light line ω = ck / n _p n _p is the refractive index of the prism.

By pushing down until it reaches the area below the light line (ω = ck), it becomes possible to measure.

  For this reason, it is preferable to use a prism 10 having a high refractive index because the measurable region is widened. More specifically, the prism 10 is preferably an optical crystal such as a high refractive index glass or rutile, a semiconductor material prism, or the like, because it has high transparency and a high refractive index, but a prism of any material can be used. Of course.

  The prism 10 is preferably determined each time depending on the refractive index of the two-dimensional photonic crystal waveguide to be measured and the transparency of the measurement wavelength.

Here, an apparatus for carrying out the above-described method for measuring a photonic band structure of a photonic crystal waveguide according to the present invention, that is, a device for measuring a photonic band structure of a photonic crystal waveguide according to the present invention (hereinafter simply referred to as “photonic band structure”). This will be referred to as “the device of the present invention” as appropriate.

  In the device 20 of the present invention, the adjustment of the size of the gap g between the prism 10 and the two-dimensional photonic crystal layer 104 of the two-dimensional photonic crystal waveguide 100 is important for obtaining good coupling. As shown in the conceptual configuration explanatory diagram of FIG. 3, the inventive device 20 includes a mechanism for fine adjustment.

  Hereinafter, the inventive device 20 will be described with reference to FIG. 3. The inventive device 20 includes a prism fixing mechanism 22 for fixing the prism 10 and a two-dimensional photonic crystal layer 104 facing the prism 10. A two-dimensional photonic crystal is obtained by finely moving the sample fixing mechanism 24 for fixing the nick crystal waveguide 100 and the sample fixing mechanism 24 in the XYZ directions of the orthogonal coordinate system by a fine movement mechanism using a micrometer or a pressure adjustment mechanism using a gas pressure. The first XYZ fine movement mechanism 26 for finely adjusting the position of the waveguide 100 and the rounded head portion 28 are finely moved by a fine movement mechanism using a micrometer or a pressure adjustment mechanism using a gas pressure to thereby move the head portion 28 in a two-dimensional photo. Substrate direction fine movement mechanism 30 for pressing the nic crystal waveguide 100 against the Si substrate 108, A second XYZ fine movement mechanism 32 for finely adjusting the position of the head unit 28 by finely moving the direction fine movement mechanism 30 in the XYZ directions of the orthogonal coordinate system by a fine movement mechanism using a micrometer or a pressure adjustment mechanism using gas pressure; A θ rotation mechanism 34 that finely moves the two-dimensional photonic crystal layer 104 of the two-dimensional photonic crystal waveguide 100 relative to the θ rotation direction, and the θ rotation mechanism 34, the entire system of the device 20 of the present invention is a micrometer. And a third XYZ fine movement mechanism 36 that finely moves in the XYZ directions of the Cartesian coordinate system by a fine adjustment mechanism or a pressure adjustment mechanism using gas pressure.

  Note that the light source that makes the incident beam incident on the prism 10 and the light detection means that detects the outgoing beam from the prism 10 may be integrally configured as an accessory device of the inventive device 20 or the inventive device. 20 may be configured as an independent device.

In the above configuration, the rounded head portion 28 is moved by the substrate direction fine movement mechanism 30 and the second XYZ fine movement mechanism 32 to press the head portion 28 against the Si substrate 108 of the two-dimensional photonic crystal waveguide 100.

  At this time, it is important to keep the prism 10 and the surface of the two-dimensional photonic crystal layer 104 of the photonic crystal waveguide 100 sufficiently flat and clean. Although coarse adjustment can be performed by visual recognition, the optimum gap g is finally adjusted by observing the spectrum.

  Also, if the head portion 28 is pressed too strongly and strongly against the Si substrate 108 of the two-dimensional photonic crystal waveguide 100, the mode position will be altered by over-coupling, so care must be taken.

  According to the device 20 of the present invention, the incident angle of the incident beam can be scanned by providing the θ rotation mechanism 34. Also, by providing the θ rotation mechanism 34, it is possible to scan the traveling angle of the incident beam with respect to the photonic crystal lattice in the traveling direction in the waveguide plane.

  Further, according to the apparatus 20 of the present invention, since the substrate direction fine movement mechanism 30, the first XYZ fine movement mechanism 26, the second XYZ fine movement mechanism 32, and the third XYZ fine movement mechanism 36 are provided, the position of the head unit 28 and the two-dimensional photonics are provided. The position of the crystal waveguide 100 can be finely adjusted, the optical coupling point and the photonic crystal pattern position can be finely adjusted, and measurement can be performed even if the photonic crystal region is small. Become.

Using the method for measuring a photonic band structure of a photonic crystal waveguide according to the present invention and the apparatus 20 of the present invention, the incident angle dependence of the measured reflection spectrum is shown for the two-dimensional photonic crystal waveguide 100 described above. 4.

  In this embodiment, a semiconductor laser diode having a wavelength of 838 nm and a wavelength of 1549 nm is used as the light source of the incident beam.

  FIG. 4 shows that a very sharp drop in reflectance occurs in a specific incident angle region. This means that the in-plane two-dimensional photonic band mode and the incident beam are coupled at this resonance angle, and the photonic band structure of the element can be experimentally determined from this resonance peak position.

  An experimental photonic band structure obtained from the spectrum of FIG. 4 is shown in FIG. The points A, B, and C in the photonic band structure of FIG. 5 correspond to the resonance points A, B, and C of FIG.

  Although the theoretical photonic band structure calculated by the three-dimensional FDTD method is also plotted in the photonic band structure diagram of FIG. 5, it can be seen that the obtained experimental values are extremely accurate. This confirms the accuracy of measurement according to the present invention and the high accuracy of manufacturing the two-dimensional photonic crystal waveguide 100.

  In this embodiment, since an example in which semiconductor laser light having a wavelength of 838 nm and 1549 nm is used as an incident beam has been shown, the energy direction on the vertical axis has a jump value, but if white light is used as the incident light, more It is possible to obtain continuous band dispersion in exactly the same manner. Further, point C in the photonic band structure diagram of FIG. 5 is a complete waveguide mode.

  Therefore, by using the method according to the present invention, it was possible to accurately detect and measure the band dispersion characteristics of the waveguide mode in the two-dimensional photonic crystal waveguide structure, that is, the photonic band structure.

The method according to the present invention can also measure the dispersion relationship of defect band modes formed when defects are introduced into a photonic crystal waveguide. This is significant because it is applied to various optical functional elements.

  In addition, the ability to accurately detect the dispersion relation of the waveguide mode from the outside has a very important meaning even in an optical nonlinear element. The guided mode has the longest life, does not leak light to the outside, and can guide light with little optical loss. Therefore, of course, it is most useful for nonlinear elements that require a long interaction length. . If the dispersion relation of the waveguide mode can be accurately known, it becomes possible to design the phase matching conditions in the wavelength conversion process accurately in advance, which is extremely useful in the element development process. In addition, in an optical nonlinear element using a photonic crystal waveguide, it is important to effectively increase the electric field strength by utilizing the decrease in the group velocity. It becomes possible to detect accurately.

  As described above, the present invention provides a technique for directly observing the photonic band structure, which is a light dispersion relation with respect to the waveguide mode of the two-dimensional photonic crystal waveguide, from the outside by a relatively simple method. This is extremely important, and thereby the applicability and controllability of various optical devices using photonic crystal waveguides can be dramatically improved.

The embodiment described above can be modified as shown in the following (1) to (3).

  (1) In the above-described embodiment, a case where a two-dimensional photonic crystal waveguide, more specifically, a nonlinear optical polymer two-dimensional photonic crystal waveguide is measured as a photonic crystal waveguide has been described. Of course, the measurement target is not limited to this, and for example, a photonic crystal waveguide including a one-dimensional photonic crystal waveguide or a three-dimensional photonic crystal waveguide can have any structure. Or what was produced with what kind of production methods can be measured.

  (2) In the above embodiment, the external medium existing in the gap g is air. However, the present invention is not limited to this, and various gases can be used as the external medium.

  (3) You may make it combine the above-mentioned embodiment and the modification shown in above-mentioned (1) thru | or (2) suitably.

  The present invention includes, for example, an optical waveguide element, an optical coupling / demultiplexing element, a laser element, a light emitting element, an element utilizing light dispersion, a super prism element, a super collimating element, a lens functional element, a negative refraction element, a polarizing element, a wavelength Conversion element, harmonic generation element, sum frequency / difference frequency generation element, optical parametric amplification element, stimulated Raman scattering element, four-wave mixing element, small laser light source, optical switch element, optical bistable element, optical logic operation element, light It can be used for optimization design of all optical elements using photonic crystal waveguides such as modulation elements or phase conjugate light generation elements.

FIG. 1 is a cross-sectional perspective view of a conceptual configuration of a nonlinear optical polymer two-dimensional photonic crystal waveguide to be measured. FIG. 2 is an explanatory view showing a method for measuring a photonic band structure of a photonic crystal waveguide according to the present invention. FIG. 3 is an explanatory diagram of a conceptual configuration of a photonic band structure measuring apparatus for a photonic crystal waveguide according to the present invention. FIG. 4 illustrates a method for measuring a photonic band structure of a photonic crystal waveguide according to the present invention and a photonic band structure measuring apparatus for a photonic crystal waveguide according to the present invention. It is a graph which shows the incident angle dependence of the reflection spectrum measured in this way.

Is shown in FIG.
FIG. 5 is a graph showing an experimental photonic band structure obtained from the spectrum of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Prism 10a Bottom part 20 Measurement apparatus of photonic band structure of photonic crystal waveguide 22 Prism fixing mechanism 24 Sample fixing mechanism 26 First XYZ fine movement mechanism 28 Head part 30 Substrate direction fine movement mechanism 32 2nd XYZ fine movement mechanism 34 θ rotation mechanism 36 First 3XYZ fine movement mechanism 100 Two-dimensional photonic crystal waveguide 102 Non-linear optical polymer layer 104 Two-dimensional photonic crystal layer 106 Etch stop layer 108 Si substrate 110 Metal clad layer

Claims (4)

In the measurement method of the photonic band structure of the photonic crystal waveguide,
On the photonic crystal layer of the photonic crystal waveguide, a prism is arranged with the bottom facing the photonic crystal layer so as to provide a predetermined gap,
When an incident beam is incident on the photonic crystal layer of the photonic crystal waveguide through the prism, the incident angle is greater than or equal to the total reflection angle at the bottom of the prism after the incident beam enters the prism. Incident at an angle satisfying
A method for measuring a photonic band structure of a photonic crystal waveguide, wherein the incident beam is totally reflected at a bottom of the prism and is measured based on an outgoing beam emitted from the prism. In the measuring method of the photonic band structure of the photonic crystal waveguide of Claim 1,
The incident beam has an incident angle and an optical frequency such that the wave number and frequency of the guided mode in the photonic crystal waveguide coincide with the wave number and frequency of the incident beam in the traveling direction in the waveguide plane. A method for measuring a photonic band structure of a photonic crystal waveguide. A prism fixing mechanism for fixing the prism;
A sample fixing mechanism for fixing a photonic crystal waveguide having a photonic crystal layer formed on a substrate so that the photonic crystal layer and the bottom of the prism face each other; and
A substrate direction fine movement mechanism for pressing a head portion against the substrate of the photonic crystal waveguide;
A θ rotation mechanism that finely moves the prism and the photonic crystal layer of the photonic crystal waveguide relatively in the θ rotation direction ;
A light source that makes an incident beam incident on the photonic crystal layer of the photonic crystal waveguide through the prism, and the incident angle is fully incident on the bottom of the prism after the incident beam enters the prism. A light source incident at an angle satisfying the reflection angle or more;
A photodetector that detects an outgoing beam that is totally reflected at the bottom of the prism and emitted from the prism;
An apparatus for analyzing a photonic band structure of a photonic crystal waveguide, comprising: an analyzing means for analyzing a detection result of the photodetector . 4. The measuring device for photonic band structure of photonic crystal waveguide according to claim 3, further comprising:
A measuring device for a photonic band structure of a photonic crystal waveguide, comprising: a fine movement mechanism for finely moving at least one of the head portion and the photonic crystal waveguide in an XYZ direction of an orthogonal coordinate system .