JP2005274843A - Light control element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light control element consisting of slab type photonic crystal having defects, capable of increasing light utilization efficiency by reducing the propagation loss of a defective waveguide and capable of improving a dispersion control effect and a group speed delay effect on the basis of the defective waveguide. <P>SOLUTION: When fine substances 8, 10 consisting of a material having refractive index contrast against a material constituting the slab type photonic crystal are arranged on positions other than a slab layer in a defect (3) area, a light confinement effect to the defective waveguide is increased by controlling the the refractive index of the defect (3) part, so that the propagation loss of the defective waveguide can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light control element composed of a slab photonic crystal having defects, and more specifically, a light dispersion control element and a light delay element that perform light control on propagating light propagating through a defect waveguide of the photonic crystal. The present invention relates to light control elements such as optical switches and optical frequency filters.

  A photonic crystal called a photonic crystal has a periodic structure with a small period of about a wavelength to form a photonic band gap that is a forbidden band of light, and a phenomenon peculiar to a photonic crystal that exhibits a unique effect due to strong dispersibility. By using it, there is a possibility that it is possible to realize a light control element having a function different from the conventional one, or a light control element having a very small size compared to the light control element having the same function as the conventional one. Light control elements have been studied. More specifically, there are a polarization separation element using a photonic band gap, an optical waveguide capable of deflecting and bending in the propagation direction in a minute region into which a line defect is introduced, a low threshold laser, and the like.

  Photonic crystals include three-dimensional photonic crystals in which light is completely confined in the three-dimensional direction and two-dimensional photonic crystals in which light is completely confined only in the two-dimensional direction. There is a configuration called a slab type photonic crystal in which light is completely confined in the two-dimensional direction by the two-dimensional photonic crystal and at the same time the light is confined in the vertical direction by the waveguide structure. This requires extremely advanced technology to stably manufacture a three-dimensional photonic crystal in a large area, whereas forming a two-dimensional photonic crystal in a plane diverts an ordinary semiconductor process technology. By utilizing the fact that it is relatively easy, a light confinement structure in a two-dimensional direction that can be easily formed is realized.

  The slab type photonic crystal is obtained by providing a core layer made of a high refractive index material to be a two-dimensional photonic crystal on an under cladding layer made of a low refractive index material provided on a substrate. As a specific semiconductor process for forming a two-dimensional photonic crystal, a hole or pillar having a vertical wall surface is formed by dry etching according to the mask by forming a mask pattern on the thin film layer serving as the core layer by two-dimensional lithography. There are methods of forming the structure. For the core layer, a higher refractive index may be preferable. In most cases, a semiconductor material for LSI as an electronic device currently mass-produced such as silicon or GaAs is used as it is. For the formation of the two-dimensional photonic crystal, a semiconductor process device for LSI can be used as it is.

  Since the slab type two-dimensional photonic crystal has a waveguide structure in the vertical direction as described above, the upper and lower optical confinement effect by the waveguide structure is the ratio of the refractive index of the cladding layer to the refractive index of the core layer. Mainly determined by. This corresponds to the fact that very large leakage occurs with respect to the propagating light propagating through the core layer when the total reflection condition for the interface between the core layer and the cladding layer is not satisfied. For this reason, the photonic crystal is configured such that the band in which the propagating light propagates is below the boundary line called the light line indicating the total reflection condition in the band diagram of the two-dimensional photonic crystal, that is, on the low frequency side. The

  This light line exists for both the under-cladding layer and the over-cladding layer. However, in the air bridge structure in which the upper and lower cladding layers are both air cladding layers, the light line is moved upward most in the band diagram, and the inclination is 1. It has been studied as a structure that can expand the range in which propagation modes exist. That is, in this case, it has one light line determined from the refractive index of the core layer and the refractive index 1 of air.

  However, in the air bridge structure, since the undercladding layer is air, the core layer floats in the air and is weak in strength, so it is easy to break, post-processing is impossible, or due to mechanical resonance of the core layer There are many problems in practical use, such as the optical characteristics easily changing. On the other hand, a structure using a layer made of a material having a low refractive index by an undercladding layer without having an air bridge structure has been studied.

For example, there is a waveguide configuration using an SOI substrate, in which a thermally oxidized SiO ₂ layer is an under cladding layer, a silicon layer is a core layer, and an air layer is an over cladding layer. In this waveguide configuration, when a two-dimensional photonic crystal is formed in a silicon layer as a core layer with a hole structure, unlike the air bridge structure, it is strong in strength and can be processed later. Thus, a slab type two-dimensional photonic crystal that does not cause any resonance can be formed.

With regard to such a structure, Patent Document 1 describes a configuration in which GaAs is used as a semiconductor. In Patent Document 1, a semiconductor substrate made of GaAs is in contact with a low refractive index medium such as SiO ₂ . A hole layer having a photonic crystal arrangement is formed in the core layer made of GaAs, the SiO ₂ layer is an under cladding layer, and the mechanical strength is stronger than the air bridge structure in which the under cladding layer is air. It has become a thing.

However, since the light line in these configurations is determined by the refractive index of the SiO ₂ layer having the higher refractive index as the cladding layer, unlike the case of the air bridge structure, the refractive index of the SiO ₂ layer is about 1.46. The area where the propagation mode can exist is reduced by an amount corresponding to the change in the slope of /1.46. For this reason, there are restrictions on the hole or pillar diameter that can be used in the defect waveguide as an optical control element, the optical frequency that can be used as propagating light, and its propagation mode. The range of the light control effect such as the control range of the delay amount is limited.

Furthermore, when an ordinary optical material having a lower refractive index than that of a semiconductor such as LiNb ₂ O ₃ optical crystal or TiO ₂ is used for the core layer, the refractive index of the core layer itself becomes smaller than that of the semiconductor. The photonic band gap in the figure is shifted upward or its width is reduced. In addition, since the band of the line defect waveguide is also shifted upward in response to the refractive index change, the band is shifted relatively upward with respect to the light line, so that the line defect having a band below the light line exists. The region where the waveguide can be configured becomes smaller. As a result, the range of the light control effect is very limited. In the worst case, since the core layer is an optical material having a low refractive index, the photonic band gap itself cannot be expressed as a two-dimensional photonic crystal, and light in a two-dimensional direction with respect to the slab waveguide is obtained. It may also become impossible to confine. Inorganic and organic optical crystals, ceramics, and organic dye composites made of electro-optic materials or nonlinear optical materials are expected to be able to realize a high degree of light control using their electro-optic effects and nonlinear optical effects. Many of these materials have a refractive index of about 2.5 even if they have a high refractive index. For this reason, a band tends to exist on the light line corresponding to SiO ₂ , and in this case, propagation light leaks to SiO ₂ , so that the light utilization efficiency becomes very small. For this reason, a light control element that can be used normally has a very small range of optical characteristics such as frequency, group velocity, and dispersion of propagating light that can be used in the light control element. For this reason, it is necessary to improve the light utilization efficiency by setting the band below the light line corresponding to SiO ₂ .

  Even when an air bridge structure using air is used for the under-cladding layer, the slab type photonic crystal by the core layer made of such a low refractive material has a core layer made of a high refractive index material such as a semiconductor material. Compared with the case where it is used, the range of the light control effect is originally limited by the change of the photonic band gap. Therefore, there is a demand for a structure that further improves the light confinement effect and improves the light utilization efficiency.

  On the other hand, a coupling defect waveguide has been invented in which a hole structure or pillar structure that is an integral multiple of the period of the hole structure or pillar structure of the photonic crystal is provided in the defect structure of the photonic crystal. This is a fiber type dispersion compensation that required a length of the order of km because a relatively large dispersion and a relatively wide usable frequency were obtained, and these dispersion values were about six orders of magnitude higher than those of optical fibers. There is a possibility that the device can be downsized to the order of mm. An optical control element using this coupling defect waveguide is described in Patent Document 2, for example. A dispersion compensator as a light control element using a coupling defect waveguide described in Patent Document 2 is generally composed of a waveguide and a dispersion compensation waveguide having coupling defects, and the dispersion compensation waveguide depends on its configuration. It has a large dispersion compensation effect calculated as 20 ps / nm / mm, and the dispersion compensator can be miniaturized correspondingly.

  However, since the coupling defect waveguide described in Patent Document 2 is realized by providing a hole structure in the defect waveguide portion, the effective refractive index of the defect waveguide portion is greatly reduced. Since shifting upward, the propagation range that satisfies the total reflection condition corresponding to the light line is reduced. In addition, the coupling defect waveguide itself also shifts the light line greatly downward due to the longer period of the light traveling direction, so that the light confinement effect itself is lost. For these reasons, there is a demand for a structure that improves the light confinement effect and improves the light utilization efficiency even in the coupled defect waveguide.

JP 2000-232258 A JP 2002-333536 A

  An object of the present invention is to solve the above problems.

  The problem to be solved by the invention according to claim 1 is that the range of dispersion control, group velocity delay control, and light transmittance control is improved by improving the light confinement effect of a light control element made of a slab photonic crystal having defects. An object of the present invention is to provide a light control element whose light control effect is increased by enlarging.

  The problem to be solved by the invention according to claim 2 is that the light confinement effect of the light control element made of a slab type photonic crystal having a defect is improved and the light control effect is achieved by enabling high-precision control. Is to provide a light control element with high accuracy.

  The problem to be solved by the invention according to claim 3 is that the range of dispersion control, group velocity delay control, and light transmittance control is improved by improving the light confinement effect of a light control element made of a slab type photonic crystal having a line defect. It is an object of the present invention to provide a light control element whose light control effect increases by enlarging.

  The problem to be solved by the invention according to claim 4 is to improve the light confinement effect of the light control element made of a slab type photonic crystal having a line defect, and to control the light more accurately. An object of the present invention is to provide a light control element having a higher control effect.

  The problem to be solved by the invention according to claim 5 is to provide a structure capable of easily producing the light control element according to claims 1 to 4.

  The problem to be solved by the invention according to claim 6 is that the range of dispersion control, group velocity delay control, and light transmittance control is improved by further improving the light confinement effect of the light control element made of a slab photonic crystal having defects. It is to provide a light control element that further increases the light control effect.

  The problems to be solved by the inventions according to claims 7 and 8 include a lateral light confinement state in the slab direction in addition to the improvement of the light confinement effect in the vertical direction of the light control element made of a slab type photonic crystal having a defect. It is an object of the present invention to provide a light control element in which the light control effect is increased by controlling the light intensity.

The problem to be solved by the invention according to claim 9 is to expand the range of dispersion control and group velocity delay control by improving the light confinement effect of a light control element made of a slab type photonic crystal having a coupling defect. An object to be solved by the invention according to claim 10 is to provide a light control element comprising a slab type photonic crystal having a bonding defect without processing a core layer. It is an object of the present invention to provide a light control element that increases the light control effect without degrading the strength of the core layer.

  The problem to be solved by the invention according to claim 11 is that the range of dispersion control and group velocity delay control is further improved by further improving the light confinement effect of the light control element comprising a slab photonic crystal having a coupling defect. An object of the present invention is to provide a light control element whose light control effect is further increased by enlarging.

  The problem to be solved by the invention according to claim 12 is that dispersion control, group velocity delay control, and light transmission are further improved by further improving the vertical light confinement effect of the light control element made of a slab-type photonic crystal having defects. An object of the present invention is to provide a light control element that further increases the light control effect by further expanding the range of rate control.

  The problem to be solved by the invention according to claim 1 is a light control element comprising a slab type photonic crystal having a defect in claim 1 except for the slab layer of the slab type photonic crystal in the defect region. The light control element is characterized in that a minute object made of a material having a refractive index contrast with respect to the material constituting the slab photonic crystal is provided at a position.

  The problem to be solved by the invention according to claim 2 is based on “a light control element according to claim 1, wherein the minute object is provided periodically”. Solved.

  The problem to be solved by the invention according to claim 3 is based on “a light control element according to claim 1, wherein the defect is a line defect”. Solved.

  The problem to be solved by the invention according to claim 4 is the light control element according to any one of claims 1 to 3, wherein the minute object is a slab layer of the slab type photonic crystal. The light control element is provided on the surface opposite to the substrate. ”

  The problem to be solved by the invention according to claim 5 is the light control element according to any one of claims 1 to 3, wherein the minute object is a slab layer of the slab type photonic crystal. The light control element is provided on both sides. ”

  A problem to be solved by the invention according to claim 6 is that, in the light control element according to claim 6, the line defects are composed of two or more rows of line defects. This is solved by the light control element.

  The problem to be solved by the invention according to claims 7 to 8 is that, in the light control element according to any one of claims 1 to 6, the minute object is located near the center of the defect. The light control element according to claim 3, wherein the micro object is disposed in the vicinity of both sides of the line defect. It is solved by the light control element.

  A problem to be solved by the invention according to claim 9 is the light control according to claim 9, wherein in the light control element according to claim 3, 6 or 8, the line defect is provided with a coupling defect. It is solved by the element.

  The problem to be solved by the invention according to claim 10 is that, in the light control element according to any one of claims 1 to 9, the period of the minute object is an integer of the period of the photonic crystal. This is solved by a light control element characterized by being doubled. "

  The problem to be solved by the invention according to claim 11 is characterized in that in the light control element according to claim 11, the minute object is provided in a coupling defect portion provided in the line defect. The light control element. "

  The problem to be solved by the invention according to claim 12 is that, in the light control element according to any one of claims 1 to 11, the light control element according to claim 12 is provided at a position other than the slab layer of the slab type photonic crystal. , A light control element having a light reflection confinement structure having a periodic structure.

  According to the present invention, the light confinement effect of the defect portion of the photonic crystal is improved with respect to the light control element made of a slab type photonic crystal having defects, and dispersion control, group velocity delay control, and light transmittance control are improved. By expanding the range, it is possible to provide a light control element whose light control effect is increased.

  The best mode for carrying out the present invention will be described with reference to the drawings.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 1, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 3 is a line defect waveguide composed of linear defects, and 4 is incident on the line defect waveguide 3. Incident light 5 is emitted light from the line defect waveguide 3 of the slab type photonic crystal, and 8 and 10 are provided in the lower part of the region of the line defect waveguide 3 and have a higher refractive index than the thin film 1. Three linear objects made of materials. In FIG. 1, a two-dimensional photonic crystal is constituted by holes 2 provided in a thin film 1 arranged periodically.

  FIG. 2 is a schematic diagram showing an example of a cross-sectional structure of a side surface of the light control element made of the slab type two-dimensional photonic crystal shown in FIG. In FIG. 2, 1 is a thin film which becomes a core layer having a uniform background refractive index, 2 is a hole, 3 is a defect waveguide made of a linear defect, and 8 and 10 are lower layers in the region of the defect waveguide 3 on the line. Are linear minute objects made of a material having a higher refractive index than that of the thin film 1.

Hereinafter, it will be described that the light control element made of the photonic crystal of the present embodiment has an action capable of controlling light. First, the light control action of a conventional / general photonic crystal will be described. Photonic crystals are generally known to have a region called photonic band gap where photons do not exist in a material that has a periodicity with a refractive index that is constant in the wavelength order of light. ing. FIG. 3 illustrates a periodic arrangement of general photonic crystals without defects. FIG. 3A is a diagram schematically showing the hole period and hole diameter in the real space characterizing the configuration of the photonic crystal, and FIG. 3B is a graph showing the period in the real space in FIG. It is the figure which showed the relationship of the corresponding wave number space. In FIG. 3B, the hole period of the photonic crystal is a shown in FIG. 3A, and the hole radius is shown by a radius r. At this time, the array having periodicity in the real space of FIG. 3A is three-fold rotationally symmetric, and the Brillouin zone 13 having a hexagonal structure of three-fold rotational symmetry also in the wave number space of FIG. Form. In the Brillouin zone 13, the direction in which the holes are close to each other to form a straight line is denoted as the Γ-K direction, and the middle direction of the Γ-K direction is denoted as the Γ-M direction. Further, in the light control element made of the conventional photonic crystal in FIG. 3, silicon is used as the core layer and SiO ₂ is used as the under cladding layer.

  FIG. 4 shows an example of a cross-sectional structure of the side surface of the photonic crystal having the arrangement of FIG. In FIG. 4, 1 is a thin film that becomes a core layer having a background refractive index, 2 is a hole, 11 is a substrate, and 12 is a thin film that becomes an under cladding layer made of a material having a lower refractive index than that of the thin film 1. In the photonic crystal having the cross-sectional structure as shown in FIG. 4, the thickness of the core layer 1 and the under cladding layer 12a in FIG. 4 is about 0.5 to 1.0 μm, and the conventional fine processing technique is used. It is relatively easy to form.

  FIG. 5 is a band diagram of a photonic crystal showing a band of light that can propagate in a photonic crystal having no defect as shown in FIG. In FIG. 5, the horizontal axis is a normalized wave vector k corresponding to the Γ-K direction and the Γ-M direction. In FIG. 5, the triangular arrangement of FIG. 3A is used as the two-dimensional photonic crystal, the refractive index of the thin film is 3.0, the refractive index of the hole is 1.0, and the r / a value = 0.30. It was calculated by the plane wave expansion method. The vertical axis represents the normalized frequency ωN obtained by normalizing the light frequency ω. The wave vector corresponds to the propagation characteristics of light in the periodic structure, and the normalized frequency is a normalized frequency of light to be propagated. At this normalized frequency ωN = ωa / 2πc (c is the speed of light). This unit is dimensionless. This is the same as a / λ and may be considered as the ratio of wavelength to period. At this time, as shown in FIG. 5, there is a region where the normalized frequency ωN is in the vicinity of 0.25 to 0.3 and no band exists at any wave number, and this region is referred to as a “photonic band gap”. .

  Even if light having a frequency corresponding to the photonic band gap is incident in a predetermined direction, the light is only reflected and cannot be used as a light control element other than a reflection application. However, by providing a defect structure in the periodicity in the photonic crystal having the photonic band gap, a band that becomes a propagation mode corresponding to the defect is generated in the photonic band gap, and a frequency corresponding to the band is generated. By making light appropriately incident on a predetermined defect, it can be used as a light control element. A case where the defect is a hole defect is called a point defect, and a case where the defect is a plurality of continuous one-dimensional defects is called a line defect. When a line defect is provided in the photonic crystal, a defect waveguide in which light of a specific frequency is guided or a waveguide called a line defect waveguide may be formed in the line defect. This defect waveguide has a band in the original photonic band gap, and has a light propagation characteristic peculiar to a photonic crystal that is very different from a waveguide based on normal total reflection.

FIG. 6 is a diagram for explaining a band generated by a photonic crystal having a defect waveguide, and a part of the band diagram of the photonic crystal having a defect waveguide is enlarged for explanation. As the photonic crystal, a band diagram of a defect waveguide due to a single line defect in the same configuration as that in FIG. 3 is calculated by a two-dimensional plane wave expansion method. Others are exactly the same as in FIG. In FIG. 6, the region where the normalized frequency is about 0.24 to about 0.31 is the photonic band gap, the two curves are the bands in the photonic band gap caused by the defect waveguide, the two lines are the light lines, The left straight line of these two straight lines is a light line corresponding to the air layer serving as the over cladding layer, and the right straight line of these two straight lines is the light line corresponding to the SiO ₂ layer serving as the under cladding layer. It is. The horizontal axis uses the normalized wave number obtained by normalizing the wave vector only in the Γ-M direction, and its unit is [2π / a]. Further, a is the hole period of the photonic crystal, and r is the hole radius of the photonic crystal. Due to Brillouin zone folding, the maximum value for a given wave vector direction is normalized to 0.5, half of 1. In FIG. 6, two bands appear in the photonic band gap where the normalized frequency ωN is around 0.25 to 0.3. Both of these bands are bands that can propagate light only in the photonic crystal along the defect waveguide. A normalized frequency ωN is obtained for light of a predetermined frequency, and a horizontal line is drawn from this ωN. In the case of having an intersection with the two bands, a predetermined frequency can be guided in the defect waveguide.

At this time, the light guided through the defect waveguide exhibits a very different waveguide behavior from that in a normal waveguide or vacuum. For example, the propagation velocity is indicated as a group velocity Vg of propagating light, and this group velocity Vg substantially corresponds to a first-order differential value with respect to the normalized wave number of the band (hereinafter simply referred to as “wave number”). Therefore, it can be seen that the group velocity differs greatly with respect to the frequency of light, and the value is small. In FIG. 6, the slope called the SiO ₂ light line is indicated by a line having an inclination of 1 / n (where n is the refractive index of the defect waveguide portion), and corresponds to the propagation speed in SiO _2. A slope of 1 corresponds to the propagation speed of light in air, that is, in a vacuum. At this time, in the light control element having the configuration shown in FIG. 3, since the SiO ₂ light line is below the light line in the air, the propagation light in the region above the lower SiO ₂ light line is , even if confined by a photonic bandgap in a plane two-dimensionally in the core layer, by propagation light leaks onto the air in addition to SiO ₂ to or below this SiO ₂ below, large Loss occurs and light utilization efficiency is reduced. For this reason, the frequency of light that can be used for the light control element is limited to the propagation light in the region below the SiO ₂ light line in FIG.

As shown in FIG. 6, there are two bands which can be propagated in the lower part of the SiO ₂ light line. The lower band is a band which is generally used because its mode is the TE mode. is there. In this band, when the wave number is about 0.4, the absolute value of the slope, which is the first derivative thereof, is 0.1. On the contrary, the propagation speed of light can be made about 10 times slower than in the air. Since the refractive index of the original constituent material is 3.5 and the light propagation speed of the original material in the bulk state is three times that in vacuum, the light propagation speed can be reduced by about three times. Therefore, it can be used as a light control element for group velocity delay and dispersion compensation. Since the inclination of this band changes greatly corresponding to the frequency of light, dispersion with respect to the frequency of light, that is, chromatic dispersion is very large, and very large dispersion compensation can be performed.

However, such a conventional light control element using a photonic crystal is usually used in a band in a region with high light utilization efficiency that does not leak into the upper and lower cladding layers. For this reason, the optical characteristics range such as the frequency, group velocity, dispersion, etc. of the propagating light that can be used in the light control element is very small in order to use the band in the lower region with respect to the air or SiO ₂ light line End up. In addition, when using propagating light of a plurality of wavelengths or using propagating light having a wide range of wavelengths of the light source, since the influence of dispersion due to the wavelength is greatly affected, the usable wavelength width is narrowed. In some cases, it is necessary to perform wavelength matching with very high accuracy by controlling the temperature of the light source or the light control element.

  The present embodiment shown in FIG. 1 increases the effective refractive index of the defect waveguide, thereby shifting the band to the low frequency side, thereby expanding the range of the band existing in the region below the light line. A light control element having a novel structure capable of propagating propagating light in a propagation mode corresponding to a band having a large loss and low light utilization efficiency to a defect waveguide. It is. More specifically, the light control element made of the slab type photonic crystal used in this embodiment is a core layer constituting the slab at a position other than the slab layer in the defect region of the slab type photonic crystal. By providing a micro object made of a material having a refractive index contrast, the refractive index at which the defect waveguide acts on propagating light is increased.

In FIG. 1, incident light 4 incident on the line defect waveguide 3 propagates through the line defect waveguide 3. At this time, the effective refractive index of the line defect waveguide 3 is increased by the minute objects 8 and 10. For this reason, the band of the line defect waveguide 3 can be lowered, and the band region in the region below the light line is enlarged. For this reason, the light control element which implement | achieves the light control which expanded control ranges, such as the light transmittance of the emitted light 5 by the line defect waveguide 3, dispersion | distribution control, and group velocity control, can be provided.
To do.

  By utilizing the dispersion control effect and group velocity control effect of the line defect waveguide 3, it is possible to provide a light control element that performs dispersion control of the outgoing light 5 of the line defect waveguide 3. Further, since the band of the line defect structure can be partially changed in the line defect waveguide 3 by these minute objects 8 and 10, the resonance frequency of the line defect structure is controlled and the same as in the case of the point defect. In addition, only light having a specific frequency can be taken out of the photonic crystal as outgoing light. As a result, the light transmittance of the propagating light to the line defect structure 3 can be controlled. At this time, the defect structure waveguide 3 in FIGS. 1 and 2 includes the minute objects 8 and 10 having a refractive index contrast. Each can be a composite defect structure.

  The minute objects 8 and 10 made of a material having a refractive index contrast used in the present embodiment are required to have a material refractive index different from that of the core layer. When controlling the dispersion characteristics and the group velocity characteristics by controlling the band of the line defect waveguide 3, the refractive index of the micro objects 8 and 10 may be larger than the material refractive index of the core layer. Either small or effective. However, in order to increase the effective refractive index of the line defect waveguide 3, it is effective to increase the refractive index of the minute objects 8 and 10 with respect to the material refractive index of the core layer.

  In the present embodiment, the minute objects 8 and 10 are more preferably thinner than the core layer. If it is thick, the effective refractive index can be greatly increased, but since the refractive index contrast suddenly occurs around the minute object, scattering and reflection at that part may become large, In some cases, light utilization efficiency is reduced. Further, in the minute objects 8 and 10 of the present embodiment, the side surface shape that is perpendicular to the surface of the core layer is not limited to the columnar column shape as shown in FIGS. By providing a taper structure in the peripheral portion to gently generate a refractive index contrast, scattering and reflection near the interface can be reduced, and the light utilization efficiency can be improved.

  The minute objects 8 and 10 of the present embodiment are not limited to the strip shape as shown in FIG. 1 with respect to the surface of the core layer. It is preferable to optimize various shapes such as an elliptical shape, a polygonal shape, a teardrop shape, a streamline shape, a simple hollow shape, a plurality of hollow shapes, and a composite shape thereof according to each light control. Further, in the minute objects 8 and 10 according to the present embodiment, the position with respect to the line defect waveguide 3 with respect to the surface of the core layer is not limited to being arranged at the center of the defect structure as shown in FIG. However, it is equally effective to decenter from the center. Furthermore, the minute objects 8 and 10 do not have to be included in the same region with respect to the core layer surface of the defect waveguide 3, and the electromagnetic field distribution of the propagating light based on the defect structure is influenced in the vicinity of the defect structure. If it is within the range, even if a part or all of the minute object is outside the same region with respect to the surface of the core layer of the defect structure, it is effective as well. In this case, even if the defect structure is not provided in the arrangement of the core layers of the photonic crystal, the defect structure can be formed by changing a part of the effective refractive index. Further, the minute objects 8 and 10 are not limited to the case where the minute objects 8 and 10 are in direct contact with the core layer. It is effective.

  In addition, the minute objects 8 and 10 of the present embodiment are not limited to the minute object made of a material having a uniform material refractive index, and the minute objects 8 and 10 so that the refractive index contrast changes gently. The material may be made of a material that changes in the direction in which the refractive index increases or decreases from the center to the center, and the material is refracted as the propagation direction of propagating light or the distance from the line defect waveguide increases. You may comprise from the material from which a rate changes. These changes in the refractive index of the material may be realized by a change in the composition of the material, or even the same material may be realized by using a change in the refractive index due to temperature, electro-optic effect, or nonlinear effect. At this time, if a means for detecting the wavelength or dispersion of the propagation light or a change in the refractive index of the material is provided and controlled, the light can be controlled with higher accuracy. Further, it is very effective to perform dynamic light control by dynamically changing the refractive index, including the case where the refractive index of the material is made of a uniform material.

  Further, the micro object of the present embodiment is not limited to the configuration embedded in the under cladding layer as shown in FIG. 1, and in the case of the air bridge structure, the micro object protrudes into the air in close contact with the core layer. A minute object may be provided so as to have an uneven structure. In addition, for the defect waveguide portion, a micro object is provided in a layer different from the core layer, and at the same time, the micro object is in the in-slab plane direction of the slab type photonic crystal other than the defect waveguide. With respect to any one or more configurations of the core layer structure or the core layer material and the clad layer structure or the clad layer material, the light confinement effect in the in-slab plane direction can be obtained by being embedded or coplanar. It can be increased by its refractive index contrast, which is very effective.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 7, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 3 is a line defect waveguide, 4 is incident light incident on the line defect waveguide 3, and 5 is The outgoing light 15 emitted from the line defect waveguide 3 is a minute object having a linear shape made of a material having a higher refractive index than that of the thin film 1 provided in the upper layer in the region of the line defect waveguide 3. In FIG. 7, a two-dimensional photonic crystal is constituted by holes 2 that are periodically arranged and provided in the thin film 1.

  In FIG. 7, incident light 4 incident on the line defect waveguide 3 propagates through the line defect waveguide 3. At this time, the effective refractive index of the line defect waveguide 3 is increased by the minute object 15. For this reason, the band of the line defect waveguide 3 can be lowered, and the band region in the region below the light line is enlarged. For this reason, the light control element which implement | achieves the light control which expanded control ranges, such as the light transmittance of the emitted light 5 by the line defect waveguide 3, dispersion | distribution control, and group velocity control, can be provided. Furthermore, since the minute object 15 is provided uniformly on a straight line from the end portion to the end portion of the line defect waveguide 3, light can be propagated with a low loss as one uniform defect waveguide.

  In the present embodiment, the shape of the minute object 15 is not limited to the illustrated linear shape as in the case of the first embodiment, but the thickness, the in-plane shape with respect to the surface of the core layer, the core Controlling the cross-sectional shape, material refractive index distribution, and position with respect to the surface of the layer is very effective in controlling light. In particular, since the minute object 15 having the refractive index contrast is provided in the defect waveguide 3 portion where light propagates, when the electric field distribution of the propagation light is strongly distributed in the minute object 15, the propagation light is transmitted from this portion to the core layer. Therefore, the shape of the micro object and the defect waveguide 3 of the original photonic crystal should be optimally designed so that the leaked light is smaller than the required value. Is preferred.

  In this embodiment, when an optical crystal is used for the core layer and the electro-optic effect or nonlinear optical effect of the optical crystal is used for the propagation light of the core layer, the optical layer is provided on the defect waveguide 3. Since the electric field distribution exists in the minute object 10, the electric field distribution in the defective waveguide 3 portion of the core layer becomes small, so that the electric field distribution in the core layer portion becomes larger than the required value. It is preferable to optimally design the shape of the minute object 15 and the defect waveguide 3 of the original photonic crystal.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. Basically, it is the same as in the second embodiment, but in this embodiment, instead of the micro object 15, an upper layer in the region of the line defect waveguide 3 is made of a material having a higher refractive index than the thin film 1. A plurality of minute objects 16 having a circular shape having a periodic arrangement structure are provided.

  In FIG. 8, incident light 4 incident on the line defect waveguide 3 propagates through the line defect waveguide 3. At this time, since the effective refractive index of the line defect waveguide 3 is increased by the minute object 16, the band of the line defect waveguide 3 can be lowered, and the line defect waveguide 3 can be lowered in the region below the light line. The area of a certain band is expanded. For this reason, the light control element which implement | achieves the light control which expanded control ranges, such as the light transmittance of the emitted light 5 by the line defect waveguide 3, dispersion | distribution control, and group velocity control, can be provided.

  Further, in the present embodiment, the micro object 16 increases the effective refractive index of the line defect waveguide 9 and at the same time has a large control effect on the band of the photonic crystal due to the periodic arrangement it has. Therefore, it becomes possible to control the band of the line defect waveguide 3 with higher accuracy, and thereby to perform light control such as light transmittance, dispersion control and group velocity control of the outgoing light 5 with higher accuracy. A light control element that can be realized can be provided. In the photonic crystal in FIG. 8, the band of propagating light is determined by the action of both periodic structures due to the line defect waveguide 3 itself and the arrangement of the minute objects 16 on the line defect waveguide 3 itself. This is one of the configurations that can easily realize a composite defect waveguide that can utilize both features of a defect waveguide having a pillar structure. For this reason, the line defect waveguide 3 provided in the core layer is not limited to a simple line defect waveguide, and a hole structure further periodically arranged in the line defect waveguide of the core layer is provided. It is also effective to make a structure in which the structure and the pillar structure arranged periodically on the core layer act strongly.

  In the present embodiment, the individual shape of the minute object 16 is not limited to the illustrated cylindrical shape, but the thickness, the in-plane shape with respect to the core layer surface, the cross-sectional shape with respect to the core layer surface, and the material Controlling the refractive index distribution and position is very effective in performing light control. Further, the arrangement is not limited to the linear arrangement, and may be a triangular arrangement or a square arrangement, or the arrangement itself may further have a nested defect structure. It is also effective to exhibit a light control effect by providing a hetero-defect structure in the core layer and providing a composite structure formed by this hetero-defect structure and a periodic arrangement of high refractive index material micro objects. . It is also effective to combine these with the heterocrystalline structure of the core layer itself. Also, as in the case of the first embodiment, it is very effective to change the refractive index of the core layer.

[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. Basically, it is the same as that of the third embodiment, but in this embodiment, instead of the minute object 16, an upper layer in the region of the line defect waveguide 3 is made of a material having a higher refractive index than the thin film 1. A plurality of circular micro objects 17 having a periodic arrangement structure are provided, and the circular shape constituting the micro objects 17 is made larger than the diameter of the circular shape as compared with the case of FIG. It is a small one. By changing the diameter, the transmission refractive index of the line defect waveguide 3 can be optimally controlled even when the same material refractive index is used and the period is the same.

In the present embodiment, as in the case of the third embodiment, the individual shape of the minute object 17 is not limited to the circular shape shown in the figure, but the thickness, in-plane with respect to the surface of the core layer Controlling the shape, the cross-sectional shape with respect to the surface of the core layer, the material refractive index distribution, and the position is very effective in controlling light [Fifth Embodiment]
A fifth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a schematic diagram showing an example of a side surface of a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment, and corresponds to a side view having the same configuration as that of the embodiment shown in FIG. doing.

  In FIG. 10, 1 is a thin film which becomes a core layer having a uniform background refractive index, 2 is a hole, 18 is provided in the upper layer in the region of a line defect waveguide (not shown), and has a higher refractive index than the thin film 1. A linear minute object made of a material, 11 is a substrate, and 12 is a thin film made of a material having a refractive index lower than that of the thin film 1.

  In FIG. 10, the micro object 18 is provided only on the upper part of the core layer. For this reason, after forming the core layer of the photonic crystal, after forming a coating layer made of a thin film of a material having a higher refractive index than the core layer, a mask is formed on the flat portion of the region corresponding to the defect waveguide After that, by etching this coat layer, the micro object 19 having a linear shape can be produced. At this time, since the minute object 18 is formed only on the defect waveguide, that is, only on the side opposite to the substrate 11, the hole formation in the core layer is the same as in the case of producing a normal slab type photonic crystal. A process sequence can be used. In addition, since the high refractive index material is formed on the flat part of the defect structure and the mask is formed thereon, the uniformity of film formation, the film thickness, and the mask accuracy can be made extremely high. it can. Thereby, it is possible to realize a slab type photonic crystal in which the waveguide loss is reduced by the positional deviation and the shape error and the light utilization efficiency is improved.

[Sixth Embodiment]
A sixth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a schematic diagram showing an example of a side surface of a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment, and corresponds to a side view having the same configuration as that of the embodiment shown in FIG. doing.

  In FIG. 11, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a hole, 19 is provided in an upper layer in the region of a line defect waveguide (not shown), and has a higher refractive index than the thin film 1. A linear minute object made of a material, 11 is a substrate, and 12 is a thin film made of a material having a refractive index lower than that of the thin film 1.

  As shown in FIG. 11, when the minute object 19 has a periodic structure, the waveguide loss due to the positional deviation or shape error of the periodic structure tends to increase, but the defect structure is flat as in the case of FIG. Since the high refractive index material is formed on the portion and the mask is formed thereon, the uniformity of the film formation, the film thickness, and the mask accuracy can be made extremely high. Thereby, it is possible to realize a slab type photonic crystal in which the waveguide loss is reduced by the positional deviation and the shape error and the light utilization efficiency is improved. On the other hand, unlike the present embodiment shown in FIG. 11, when a minute object is formed below the defect waveguide, that is, on the substrate 11 side, CMP is performed to improve the flatness of the core layer portion. And a process such as smoothing etching is required, which complicates the manufacturing method and increases the cost.

[Seventh Embodiment]
A seventh embodiment of the present invention will be described with reference to FIG. FIG. 12 is a schematic diagram showing an example of a side surface of a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment, and corresponds to a side view having the same configuration as that of the embodiment of FIG. Yes.

  In FIG. 12, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a hole, 20 and 21 are thin films provided on both upper and lower layers in a line defect waveguide (not shown) region. A linear micro object made of a material having a refractive index higher than 1, 11 is a substrate, and 12 is a thin film made of a material having a lower refractive index than that of the thin film 1.

  In FIG. 12, the minute objects 20 and 21 are provided on both upper and lower sides of the line defect waveguide of the core layer. As a result, the effective refractive index of the core layer can be increased more greatly, so that the refractive index of the line defect waveguide can be increased more greatly, and the band of the line defect waveguide is shifted further downward. Will be able to. Thereby, the dispersion control effect and the group velocity control effect of the line defect waveguide can be increased, and the light that realizes the light control such as the light transmittance, dispersion control, and group velocity control of the outgoing light 5 of the line defect waveguide. A control element can be provided.

[Eighth Embodiment]
An eighth embodiment of the present invention will be described with reference to FIG. FIG. 13 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 13, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 22 is a line defect waveguide composed of two rows of defects, and 4 is incident on the line defect waveguide 22. Incident light 5, outgoing light emitted from the line defect waveguide 22, and 23 a plurality of circular shapes provided on the line defect waveguide 22 and having a periodic arrangement structure made of a material having a higher refractive index than the thin film 1. It is a minute object consisting of a shape.

  In FIG. 13, incident light 4 incident on the line defect waveguide 22 propagates through the line defect waveguide 22. At this time, as in the case of the embodiment shown in FIG. 8, the effective refractive index of the line defect waveguide 22 is increased by the minute object 23. For this reason, the band of the line defect waveguide 22 can be lowered, and the band region in the region below the light line can be enlarged.

  In the present embodiment, since the line defect waveguide 22 is composed of two rows of line defect waveguides, the area of the defect waveguide 22 in the slab plane direction is increased. Since the region where the minute object 23 having the refractive index contrast can be provided is increased, the effective refractive index of the defect waveguide by the minute object 23 is increased, and at the same time, the band profile of the defect waveguide of the photonic crystal is increased. Since it becomes easy to change, it is possible to provide a light control element that realizes light control in which the control range such as the light transmittance, dispersion control, and group velocity control of the outgoing light 5 by the line defect waveguide 22 is further expanded. it can.

[Ninth Embodiment]
A ninth embodiment of the present invention will be described with reference to FIG. FIG. 14 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 14, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 22 is a line defect waveguide composed of two rows of defects, and 4 is incident on the line defect waveguide 22. Incident light 5 is emitted light from the line defect waveguide 22, and 24 is provided in the upper layer in the region of the line defect waveguide 22 and has a periodic arrangement structure made of a material having a higher refractive index than the thin film 1. It is a minute object composed of a plurality of circular shapes.

  In FIG. 16, incident light 4 incident on the line defect waveguide 22 propagates through the line defect waveguide 22. At this time, as in the case of the embodiment shown in FIG. 6, the effective refractive index of the line defect waveguide 22 is increased by the minute object 26. For this reason, the band of the line defect waveguide 22 can be lowered, and the band region in the region below the light line can be enlarged.

  In the present embodiment, as shown in FIG. 16, the minute object 24 is configured near the center of the line defect waveguide 22, so that the closer to the center of the line defect waveguide 22 while having symmetry, the more gently. Since the effective refractive index can be increased, scattering and reflection associated with a change in the refractive index in the direction perpendicular to the propagation direction can be reduced, and the light utilization efficiency of the light control element can be further improved. It is possible to provide a light control element that realizes light control in which a control range such as control and group velocity control is further expanded.

[Tenth embodiment]
A tenth embodiment of the present invention will be described with reference to FIG. FIG. 15 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 15, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 25 is a line defect waveguide composed of three rows of defects, and 4 is incident on the line defect waveguide 25. Incident light 5 is emitted light from the line defect waveguide 25, and 26 is provided in an upper layer in the region of the line defect waveguide 25 and has a periodic arrangement structure made of a material having a higher refractive index than the thin film 1. It is a minute object composed of a plurality of circular shapes.

  In FIG. 15, incident light 4 incident on the line defect waveguide 25 propagates through the line defect waveguide 25. At this time, the effective refractive index of the line defect waveguide 25 is increased by the minute object 26 as in the case of the embodiment shown in FIG. For this reason, the band of the line defect waveguide 25 can be lowered, and the band region in the region below the light line can be enlarged.

  In the present embodiment, since the line defect waveguide 25 is composed of three rows of line defect waveguides, the area of the defect waveguide portion in the slab plane direction becomes larger, so that the line defect waveguide 25 is increased. Since the area where the minute object 26 having the refractive index contrast can be provided is increased, the effective refractive index of the defect waveguide by the minute object 26 is increased, and the band profile of the defect waveguide of the photonic crystal is also increased. Since it becomes easy to change, it is possible to provide a light control element that realizes light control in which the control range such as the light transmittance, dispersion control, and group velocity control of the outgoing light 5 by the line defect waveguide 25 is further expanded. it can.

[Eleventh embodiment]
An eleventh embodiment of the present invention will be described with reference to FIG. FIG. 16 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 16, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 22 is a line defect waveguide composed of two rows of defects, and 4 is incident on the line defect waveguide 22. Incident light 5, outgoing light emitted from the line defect waveguide 22, and 27 a and 27 b provided in an upper layer in the region of the line defect waveguide 22, and a periodic arrangement structure made of a material having a higher refractive index than the thin film 1. It is a micro object consisting of a plurality of circular shapes having

  In FIG. 16, incident light 4 incident on the line defect waveguide 22 propagates through the line defect waveguide 22. At this time, as in the case of the embodiment shown in FIG. 14, the effective refractive index of the line defect waveguide 22 is increased by the minute objects 27a and 27b. For this reason, the band of the line defect waveguide 22 can be lowered, and the band region in the region below the light line can be enlarged.

  In the present embodiment, as shown in FIG. 16, the minute objects 27 a and 27 b are formed in two rows near both ends of the line defect waveguide 22, so that the effective refractive index of the defect waveguide 22 is increased. The effect can be doubled. As a result, the light use efficiency of the light control element can be further improved, and a light control element that realizes light control with a wider control range such as dispersion control and group velocity control can be provided.

[Twelfth embodiment]
A twelfth embodiment of the present invention will be described with reference to FIG. FIG. 17 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 17, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically arranged hole, 25 is a line defect waveguide composed of three rows of defects, and 4 is incident on the line defect waveguide 25. Incident light 5, outgoing light emitted from the line defect waveguide 25, and 28 a and 28 b provided in an upper layer in the region of the line defect waveguide 25, and a periodic arrangement structure made of a material having a higher refractive index than the thin film 1. It is a micro object consisting of a plurality of circular shapes having

  In FIG. 17, incident light 4 incident on the line defect waveguide 25 propagates through the line defect waveguide 25. At this time, as in the case of the embodiment shown in FIG. 16, the effective refractive index of the line defect waveguide 25 is increased by the minute objects 28a and 28b. For this reason, the band of the line defect waveguide 25 can be lowered, and the band region in the region below the light line can be enlarged.

  In the present embodiment, since the line defect waveguide 25 is composed of three rows of line defect waveguides, the area of the defect waveguide portion in the slab plane direction becomes larger, so that the line defect waveguide 25 is increased. Since the area where the minute objects 28a and 28b having the refractive index contrast can be provided is increased, the effective refractive index of the defect waveguide by the minute objects 28a and 28b is increased, and at the same time, the defect introduction of the photonic crystal is improved. Since the band profile of the waveguide can be easily changed greatly, the light control that realizes the light control in which the control range such as the light transmittance, the dispersion control and the group velocity control of the outgoing light 5 by the line defect waveguide 25 is further expanded. An element can be provided.

[Thirteenth embodiment]
A thirteenth embodiment of the present invention will be described with reference to FIGS. FIG. 18 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 18, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically two-dimensionally arranged hole, 29 is a line defect waveguide, and 4 is incident light incident on the line defect waveguide 29. 5 is emitted light from the line defect waveguide 29, 30 is a hole provided in a one-dimensional arrangement in the line defect waveguide 29, and 31 is provided on the hole 30 and has a higher refractive index than the thin film 1. It is a linear micro object made of material. In FIG. 18, a two-dimensional photonic crystal is formed by holes 2 periodically arranged on the thin film 1, and the coupling defect waveguide is formed by holes 30 arranged on the line defect waveguide 29. Is configured.

  FIG. 19 is a schematic diagram showing an example of a side surface of the light control element made of the slab type two-dimensional photonic crystal shown in FIG. In FIG. 19, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a two-dimensionally arranged hole, 4 is incident light incident on the line defect waveguide 29, and 5 is emitted from the line defect waveguide 29. Emitted light 30, a hole provided one-dimensionally in the line defect waveguide 29, and 31 a linear shape made of a material having a higher refractive index than the thin film 1 provided on the dotted hole 30. A minute object, 11 is a substrate, and 12 is a thin film made of a material having a lower refractive index than that of the thin film 1.

  In FIGS. 18 and 19, incident light 4 incident on the line defect waveguide 29 propagates through the line defect waveguide 29. At this time, the line defect waveguide 29 increases the effective refractive index by the minute object 31 and reduces the change in the band characteristics due to the decrease in the refractive index. For this reason, the light control element which implement | achieves the light control which expanded the control range of the light transmittance of the emitted light 5 by the line defect waveguide 29, dispersion | distribution control, group velocity control, etc. can be provided.

  In the present embodiment, the line defect waveguide 29 is a coupling defect waveguide because the line defect has holes 30 having a one-dimensional arrangement with a period larger than the period of the photonic crystal in the line defect. It has a greater dispersion control effect and group velocity control effect for the line defect waveguide of the present invention. However, since a hole structure is conventionally provided in the defect waveguide, its effective refractive index is greatly reduced. For this reason, the band of this coupling defect waveguide is shifted upward, and the band characteristics are different. In this respect, in the present embodiment, the line defect waveguide 29 has an effective refractive index increased by the minute object 31, so that the band of the line defect waveguide 29 can be lowered. Can be shifted downward. For this reason, the light control element which implement | achieves the light control which expanded the control range of the light transmittance of the emitted light 5 by the line defect waveguide 29, dispersion | distribution control, group velocity control, etc. can be provided.

[Fourteenth embodiment]
A fourteenth embodiment of the present invention will be described with reference to FIGS. FIG. 20 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 20, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically two-dimensionally arranged hole, 32 is a line defect waveguide, and 4 is incident light incident on the line defect waveguide 32. Reference numeral 5 denotes outgoing light emitted from the line defect waveguide 32, and reference numeral 33 denotes one-dimensionally arranged micro objects made of a material having a higher refractive index than the thin film 1 provided on the line defect waveguide 32. In FIG. 20, a two-dimensional photonic crystal is constituted by periodically arranged holes 1 provided in the thin film 1.

  FIG. 21 is a schematic diagram showing an example of a side surface of the light control element made of the slab type two-dimensional photonic crystal shown in FIG. In FIG. 21, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a two-dimensionally arranged hole, 4 is incident light incident on the line defect waveguide 32, and 5 is emitted from the line defect waveguide 32. Emitted light 33, which is provided on the line defect waveguide 32, is a linear minute object made of a material having a higher refractive index than the thin film 1, 11 is a substrate, and 12 is made of a material having a lower refractive index than the thin film 1. It is a thin film.

  In FIG. 20 and FIG. 21, the incident light 4 incident on the line defect waveguide 32 propagates through the line defect waveguide 32. At this time, the band defect can be changed by changing the effective refractive index of the line defect waveguide 32 by the minute object 33 and changing the effective refractive index of the line defect waveguide 32. For this reason, the light control element which implement | achieves the light control which expanded the control range, such as the light transmittance of the emitted light 5 by the line defect waveguide 32, dispersion | distribution control, and group velocity control, can be provided.

  Further, in the present embodiment, the line defect waveguide 32 has a one-dimensional array having a period larger than the period of the photonic crystal in the line defect and has a minute object 33 having a refractive index contrast. Therefore, by setting the refractive index contrast to an optimum value, it is possible to connect adjacent minute objects. For this reason, since it is not necessary to provide a hole structure in the defect waveguide portion while realizing the coupling defect waveguide, the intensity of the core layer is improved and the output light 5 from the line defect waveguide 32 is not deteriorated. It becomes possible to provide a light control element having an expanded control range such as light transmittance, dispersion control, and group velocity control.

[Fifteenth embodiment]
A fifteenth embodiment of the present invention will be described with reference to FIGS. FIG. 22 is a schematic diagram showing a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 22, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a periodically two-dimensionally arranged hole, 34 is a line defect waveguide, and 4 is incident light incident on the line defect waveguide 34. Reference numeral 5 denotes outgoing light emitted from the line defect waveguide 34, reference numeral 35 denotes holes provided in a one-dimensional arrangement in the line defect waveguide 34, and reference numeral 36 denotes a hole provided on the line defect waveguide 34 and higher than the thin film 1. It is a one-dimensionally arranged micro object made of a material having a refractive index. In FIG. 22, a two-dimensional photonic crystal is constituted by the periodically arranged holes 2 provided in the thin film 1, and a coupling defect waveguide is constituted by the holes 30 arranged on the line defect waveguide 34. Yes.

  FIG. 23 is a schematic diagram showing an example of a side surface of the light control element made of the slab type two-dimensional photonic crystal shown in FIG. In FIG. 23, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a two-dimensionally arranged hole, 4 is incident light incident on the line defect waveguide 34, and 5 is emitted from the line defect waveguide 34 Emitted light 35, holes provided one-dimensionally in the line defect waveguide 34, and 36 one-dimensionally arranged on the line defect waveguide 34 and made of a material having a higher refractive index than the thin film 1. Further, 11 is a substrate, and 12 is a thin film made of a material having a lower refractive index than that of the thin film 1.

  22 and FIG. 23, the incident light 4 incident on the line defect waveguide 34 propagates through the line defect waveguide 34. At this time, the line defect waveguide 34 increases the effective refractive index by the minute object 36 and reduces the change in the band characteristics due to the decrease in the refractive index. Therefore, it is possible to provide a light control element that realizes light control in which the control range such as the light transmittance, dispersion control, and group velocity control of the outgoing light 5 by the line defect waveguide 34 is expanded.

  In the present embodiment, the line defect waveguide 34 is a coupling defect waveguide because the line defect has holes 35 having a one-dimensional arrangement with a period larger than the period of the photonic crystal in the line defect. It has a greater dispersion control effect and group velocity control effect for the line defect waveguide of the present invention. However, since a hole structure is conventionally provided in the defect waveguide, its effective refractive index is greatly reduced. For this reason, the band of this coupling defect waveguide is shifted upward, and the band characteristics are different. In this embodiment, since the effective refractive index of the line defect waveguide 34 is increased by the minute object 36, the band of the line defect waveguide 34 can be lowered, and the height of the band is increased. Can be shifted downward. Therefore, it is possible to provide a light control element that realizes light control in which the control range such as the light transmittance, dispersion control, and group velocity control of the outgoing light 5 by the line defect waveguide 34 is expanded.

  Further, in the present embodiment, the line defect waveguide 34 has a minute object 36 having a one-dimensional array with a period larger than the period of the photonic crystal and having a refractive index contrast in the line defect. Thus, the refractive index contrast that can be used for the coupling defect in the line defect waveguide 34 can be greatly increased as a difference between the refractive index of the hole 35 due to air and the refractive index due to the minute object. For this reason, by optimizing the period of the minute object 36 and the period and refractive index difference of the coupling defect due to the hole 35, the light transmittance of the outgoing light 5 by the line defect waveguide 34, dispersion control, group velocity control, etc. A light control element with an expanded control range can be provided.

  In the present embodiment, as shown in FIGS. 22 and 23, the line defect waveguide 34 is not limited to a configuration in which the period of the minute object 36 and the coupling defect due to the hole 35 are alternately arranged. It is also effective to realize long-period coupling defects by making the two periods different by an integral multiple, or by reducing the difference between the two periods.

  In addition to providing a minute object having a refractive index contrast in a portion other than the core layer of the defect waveguide or the coupling defect waveguide, it is provided in an embedded shape inside the hole of the defect waveguide or the coupling defect waveguide portion of the photonic crystal. Thus, a bond defect structure can be realized. Further, in a photonic crystal portion having no defect waveguide or coupling defect, a coupling defect structure can be realized by embedding a minute object having a refractive index contrast in a straight line in the hole.

[Sixteenth embodiment]
A sixteenth embodiment of the present invention will be described with reference to FIG. FIG. 24 is a schematic diagram illustrating an example of a side surface of a light control element made of a slab type two-dimensional photonic crystal according to the present embodiment. In FIG. 24, 1 is a thin film that becomes a core layer having a uniform background refractive index, 2 is a two-dimensionally arranged hole, 4 is incident light incident on a line defect waveguide (not shown), and 5 is a line defect guide. Light emitted from the waveguide, 35 is a hole provided in a one-dimensional array in the line defect waveguide portion, and 36 is a one-dimensional array made of a material having a higher refractive index than the thin film 1 provided on the line defect waveguide. 11 is a substrate, 37 is an overclad layer made of a multilayer film, and 38 is an underclad layer made of a multilayer film.

  In FIG. 24, the core layer of the slab type photonic crystal is sandwiched between upper and lower multilayer films 37 and 38, and these multilayer films 37 and 38 are configured to confine the propagation light in the defect waveguide of the photonic crystal. ing. For this reason, it is possible to greatly reduce the light leaked up and down the photonic crystal from the line defect waveguide that becomes a coupling defect structure, and a light control element that greatly improves the light transmittance of the line defect waveguide. Can be provided.

  In the present embodiment, the light reflection confinement structure provided above and below the slab type photonic crystal in order to increase the light confinement effect of the line defect waveguide is not limited to the multilayer film structure as shown in FIG. It is also effective to provide a three-dimensional photonic crystal composed of a woodpile structure or diamond-arranged spherical particles. It is also effective to provide sheets having a two-dimensional photonic crystal arrangement like a holey fiber on the upper and lower sides. The multilayer film is not limited to a simple multilayer film structure, and is composed of a multilayer film having a photonic crystal structure and a multilayer film having a plurality of different characteristics in the in-plane direction and the vertical direction of the core layer. Doing it is equally effective.

It is a schematic diagram which shows the light control element which consists of a slab type photonic crystal which is the 1st Embodiment of this invention. It is a schematic diagram which shows an example of the side surface of the light control element which consists of a general slab type photonic crystal. It is a figure which shows the relationship of the wave number space corresponding to the period in these real spaces, and the arrangement | sequence of the hole period and hole diameter in the real space which characterize the structure of a general photonic crystal. It is a schematic diagram which shows the side surface of the photonic crystal which has the arrangement | sequence of FIG. It is the band figure of the photonic crystal which showed the band of the light which can be propagated in the photonic crystal without a defect. It is a figure which expands and shows a part of band figure of the photonic crystal which has a defect waveguide. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 2nd Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 3rd Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 4th Embodiment of this invention. It is a schematic diagram which shows an example of the side surface of the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 5th Embodiment of this invention. It is a schematic diagram which shows an example of the side surface of the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 6th Embodiment of this invention. It is a schematic diagram which shows an example of the side surface of the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 7th Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 8th Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 9th Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 10th Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 11th Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 12th Embodiment of this invention. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 13th Embodiment of this invention. It is a schematic diagram which shows an example of the side surface of the light control element. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 14th Embodiment of this invention. It is the block diagram which showed typically an example of the side surface of the light control element. It is a schematic diagram which shows the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 15th Embodiment of this invention. It is a schematic diagram which shows an example of the side surface of the light control element. It is a schematic diagram which shows an example of the side surface of the light control element which consists of a slab type | mold two-dimensional photonic crystal which is the 16th Embodiment of this invention.

Explanation of symbols

3, 22, 25 Defect structure 8, 10, 15-18, 20, 23, 24, 26-28 Minute object 11 Substrate

Claims (12)

In the light control element composed of a slab type photonic crystal having defects,
A light having a minute object made of a material having a refractive index contrast with respect to a material constituting the slab photonic crystal in a position other than the slab layer of the slab photonic crystal in the defect region. Control element. The light control element according to claim 1,
A light control element, wherein the minute object is provided periodically. The light control element according to claim 1 or 2,
The light control element, wherein the defect is a line defect. The light control element according to any one of claims 1 to 3,
The light control element, wherein the minute object is provided on a surface opposite to the substrate of the slab layer of the slab photonic crystal. The light control element according to any one of claims 1 to 3,
The light control element, wherein the minute object is provided on both surfaces of a slab layer of the slab type photonic crystal. The light control element according to claim 3,
The light control element, wherein the line defect is composed of two or more rows of line defects. The light control element according to any one of claims 1 to 6,
The light control element, wherein the minute object is disposed near the center of the defect. The light control element according to claim 3,
The light control element, wherein the minute object is arranged in the vicinity of both sides of the line defect. The light control element according to claim 3, 6 or 8,
A light control element, wherein a bond defect is provided in the line defect. The light control element according to any one of claims 1 to 9,
The light control element, wherein the period of the minute object is an integral multiple of the period of the photonic crystal. The light control element according to claim 9, wherein
A light control element, wherein the minute object is provided in a coupling defect portion provided in the line defect. The light control element according to any one of claims 1 to 11,
A light control element having a light reflection confinement structure having a periodic structure at a position other than the slab layer of the slab type photonic crystal.

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