JP2012159792A - Wavelength selective element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength selective element capable of adjusting wavelength selective characteristics for every polarization component.SOLUTION: A wavelength selective element 10 is configured by superposing a metal film 14 on a substrate 12 that is defined as a dielectric body having translucency. The metal film 14 includes a plurality of through-holes 14A penetrating in the direction orthogonal to the surface direction of the metal film 14. The through-holes 14A are disposed on a flat surface of the metal film 14 in two directions of the X direction and the Y direction orthogonal to the X direction into a grid shape. The cross-sectional shape of the through-hole 14A in the surface direction of the metal film 14 according to one embodiment is defined as a rectangular shape formed of four sides of two sides extending in the X direction and two sides of extending in the Y direction. The array period in the X direction and the array period in the Y direction of the through-hole 14A provided in the metal film 14 are defined as different array periods.

Description

  The present invention relates to a wavelength selection element.

  As an element exhibiting a wavelength selection characteristic that selectively transmits light of a specific wavelength band component, an element using a polymer material is known and applied to an image projection apparatus such as a liquid crystal projector. As an element using this polymer material, an element using a resin material (color resist) in which a pigment having light absorption properties is dispersed is known.

  An element exhibiting wavelength selection characteristics using such a polymer material is advantageous in that the material cost is relatively low and a process suitable for mass production can be applied. However, an element having a wavelength selection characteristic using a polymer material needs to prepare a color resist for each wavelength band to be transmitted and repeatedly perform photolithography and development patterning steps. For this reason, the same number of patterning steps as the set number of wavelength bands of light to be transmitted are required, and it is difficult to easily obtain an element exhibiting a specific wavelength selection characteristic.

  In addition, in an element using a polymer material, the wavelength selection characteristic is determined by the characteristic of the dye pigment contained in the color resist. For this reason, there has been a problem that the degree of freedom in selecting the wavelength band to be transmitted is limited by the characteristics of the pigment. Further, the material used for the color resist has a problem that the light resistance to ultraviolet rays is low and the characteristics are deteriorated and the transparency is lowered by long-term use.

On the other hand, an element using a multilayer film of an inorganic material is also known as an element exhibiting wavelength selection characteristics (see Non-Patent Document 1).
Non-Patent Document 1 discloses an element having a configuration in which a resonance layer is disposed at the center in the thickness direction and the resonance layer is sandwiched between reflection layers. In Non-Patent Document 1, the reflection layer sandwiching the resonance layer is a laminate in which high-refractive index materials and low-refractive index materials are alternately stacked with a period of an optical thickness of ¼ wavelength, so that a broadband non-transmission band is obtained. The layer to be created. In Non-Patent Document 1, the thickness of the resonant layer is adjusted by performing photolithography and etching pattern forming processes a number of times corresponding to the set number of transmission target wavelength bands. By patterning the resonance layer, an element that transmits a specific wavelength band in the non-transmission band is obtained.

  An element using such a multilayer film of an inorganic material can improve the wavelength selectivity and the degree of freedom in designing a wavelength band component to be transmitted, as compared with an element using a polymer material. In addition, since an element using a multilayer film of an inorganic material is superior in light resistance and temperature resistance characteristics compared to an element using a polymer material, the applicable range of the element can be expanded.

  However, even in an element using a multilayer film of an inorganic material, it is necessary to repeatedly execute the photolithography and etching pattern steps a number of times corresponding to the set number of transmission target wavelength bands. For this reason, it has been difficult to easily obtain an element exhibiting a specific wavelength selection characteristic.

  On the other hand, an element using a single layer inorganic material has been proposed as an element exhibiting wavelength control characteristics using an inorganic material (see Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3).

  In Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3, a single-layer metal thin film having fine holes arranged at a period similar to the transmitted light wavelength is provided on a support layer or a glass substrate. A configuration is disclosed. In these documents, the surface plasmon at the interface between the metal thin film and the support layer or the glass substrate is adjusted by adjusting the arrangement period of the holes provided in the single inorganic material layer, that is, the single metal thin film. Coupling mode is adjusted to enable selective control of transmitted light wavelength. For this reason, according to the techniques disclosed in these documents, the degree of freedom in wavelength selection and the degree of freedom in designing the wavelength band component to be transmitted are improved. In addition, according to the techniques disclosed in these documents, since the selective control of the transmitted light wavelength is realized by the arrangement period of the holes provided in the metal thin film which is a single inorganic material layer, the wavelength selection characteristic can be easily obtained. The element shown is obtained.

  Here, in recent years, there has been an increasing demand for realizing an element capable of adjusting the wavelength selection characteristic for each polarization component, mainly for optical sensing applications. However, in the elements disclosed in Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3, the wavelength selection characteristics cannot be adjusted for each polarization component.

  This invention is made | formed in view of said point, and makes it a subject to provide the wavelength selection element which can adjust a wavelength selection characteristic for every polarization component.

  In order to solve the above-described problems and achieve the object, the present invention is a wavelength selection element that selectively transmits light of a specific wavelength band component included in incident light, and is a translucent dielectric. And a metal film having a plurality of through-holes stacked on the first substrate and penetrating in the thickness direction, the through-holes being orthogonal to each other on the surface of the metal film Two cross-sectional shapes along the plane direction of the metal film in the through hole are arranged in a lattice shape along two directions of the first direction and the second direction, and extend in the first direction. A rectangular shape comprising four sides of a first side and two second sides extended in the second direction, and the length of the first side in the through hole in the extending direction and the second side The length of the two sides in the extending direction is shorter than the wavelength of the light of the specific wavelength band component, and That the arrangement period of the first direction and said arrangement pitch in the second direction is a wavelength selective element being different from each other.

  According to the present invention, there is an effect that it is possible to provide a wavelength selection element capable of adjusting a wavelength selection characteristic for each polarization component.

FIG. 1 is a schematic diagram illustrating a wavelength selection element according to the first embodiment. FIG. 1A is a plan view schematically illustrating the wavelength selection element according to the first embodiment. FIG. 2A is a cross-sectional view taken along the line AA ′ of (A) schematically illustrating the wavelength selection element according to the first embodiment. FIG. 2 is a diagram showing the measurement results of the wavelength selection characteristics at the polarization angle of 0 ° and the polarization angle of 90 ° of the wavelength selection element according to the first embodiment. FIG. 3 is a diagram showing a change in light transmittance peak in a component having a polarization angle of 90 ° when the arrangement period Px / the arrangement period Py is changed in the wavelength selection element according to the first embodiment. . FIG. 4 shows the light transmittance of the component with the polarization angle of 90 ° when the length Dx / arrangement period Px of the side in the X direction of the through-hole 14A is changed in the wavelength selection element of the first embodiment. It is a diagram which shows the change of a peak. FIG. 5 is a diagram illustrating a transmission wavelength peak for each polarization component in the wavelength selection element according to the first embodiment. FIG. 6 is a schematic view showing a wavelength selection element according to the second embodiment. FIG. 6A is a plan view schematically showing the wavelength selection element according to the second embodiment. These are AA 'sectional views of (A) showing a wavelength selective element of a 2nd embodiment typically. FIG. 7 is a diagram illustrating a transmission wavelength peak for each polarization component in the wavelength selection element according to the second embodiment. FIG. 8 is a schematic diagram illustrating a wavelength selection element according to the third embodiment. FIG. 8A is a plan view schematically illustrating the wavelength selection element according to the third embodiment. These are AA 'sectional views of (A) showing a wavelength selection element of a 3rd embodiment typically. FIG. 9 is an enlarged schematic diagram showing a partial region Q of the wavelength selection element shown in FIG. FIG. 10 is an enlarged schematic view showing a part of the metal film and the lattice region.

  Hereinafter, an embodiment of a wavelength selection element according to the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
A wavelength selection element 10 according to the present embodiment shown in FIG. 1 is an element that selectively transmits a specific wavelength band component included in incident light. The wavelength selection element 10 has a configuration in which a metal film 14 is laminated on a substrate 12. The metal film 14 includes a plurality of through holes 14 </ b> A penetrating in the thickness direction of the metal film 14.

  In FIG. 1, arrows indicated by arrows X, Y, and Z indicate an orthogonal coordinate system. The XY plane in the orthogonal coordinate system is a plane orthogonal to the stacking direction of the substrate 12 and the metal film 14 and a plane parallel to the respective surfaces of the substrate 12 and the metal film 14. Further, the arrow Z direction in the orthogonal coordinate system indicates the incident direction of light to the wavelength selection element 10. This arrow Z direction is the same direction as the through direction of the through hole 14A (the thickness direction of the metal film 14).

  Hereinafter, the light incident on the wavelength selection element 10 will be described as incident light. Further, in the wavelength selection element 10 of the present embodiment, the wavelength selection element 10 has a polarization angle of 0 ° (in the direction of an arrow 0 ° in FIG. 1) and a polarization angle of 90 ° (in the arrow 90 in FIG. 1) as incident light. In the following description, it is assumed that polarized light including both vibration components in the direction (°) is incident.

  The substrate 12 is a dielectric having translucency. In the present embodiment, “having translucency” means that the transmittance with respect to incident light is 80% or more.

The substrate 12 may be made of any known material as long as it is a light-transmitting dielectric. Examples of the constituent material of the substrate 12 include SiO ₂ glass, quartz glass, borosilicate glass such as BK7 and Pyrex (registered trademark), optical crystal materials such as CaF ₂ , Si, ZnSe, and AlO _2. .

  The thickness of the substrate 12 may be any thickness as long as it is physically stable and does not lose translucency.

The metal film 14 is composed of a metal thin film or a metal plate. The metal used for the metal film 14 may be any metal and is appropriately selected according to the application field of the wavelength selection element 10 and design requirements. Specific examples of the metal used for the metal film 14 include gold (Au), silver (Ag), aluminum (Al), and chromium (Cr).
In the present embodiment, as an example, a case where aluminum (Al) is used for the metal film 14 is described; however, the present invention is not limited to such a constituent material.

  The thickness of the metal film 14 may be any thickness that allows the light of the wavelength band component that passes through the wavelength selection element 10 to propagate through the through hole 14A.

  A plurality of through-holes 14A provided on the metal film 14 are arranged in a lattice shape along two directions of the X direction and the Y direction perpendicular to each other on the XY plane of the metal film 14 (details will be described later). ). The cross-sectional shape along the plane direction (XY plane) of the metal film 14 in the plurality of through holes 14A is two sides (first side) extending in the X direction and two sides (first side) extending in the Y direction ( The second side) and the four sides. That is, the cross-sectional shape of the through-hole 14A has four sides: two sides extending in one of the two arrangement directions of the through-hole 14A and two sides extending in the other arrangement direction. A rectangular shape is formed. Further, the sizes (namely, the lengths of the four sides) and shapes of the plurality of through holes 14A provided on the metal film 14 are the same size and shape.

  A length Dx (see FIG. 1) of two long sides along the arrangement direction in the X direction, and four long sides along the arrangement direction in the Y direction, which constitute the four sides of the rectangular shape of the through hole 14A. The length Dy (see FIG. 1) is shorter than the wavelength of the light of the wavelength band component that passes through the wavelength selection element 10.

  In the present embodiment, the length Dx of two long sides along the arrangement direction in the X direction and long along the arrangement direction in the Y direction among the four sides of the rectangular shape of the through holes 14A. The length Dy is different from the length Dy of the two sides, and a mode showing a relationship of length Dx <length Dy will be described. However, the lengths of these sides may be the same (length Dx = Dy), or the length Dy may be longer than the length Dx (length Dx> length Dy). .

  As described above, the plurality of through holes 14A provided on the metal film 14 are arranged in a lattice pattern along two directions (the X direction and the Y direction) perpendicular to each other on the XY plane of the metal film 14. ing. Furthermore, in the wavelength selection element 10 of the present embodiment, the arrangement period of the through holes 14A in the X direction and the arrangement period in the Y direction are different arrangement periods.

  Specifically, the “arrangement period in the X direction” of the through-holes 14 </ b> A is 2 extending from the one side of the two sides extending in the Y direction in the through-hole 14 </ b> A in the Y direction in the through-hole 14 </ b> A adjacent in the X direction. A length up to one side arranged at a position corresponding to the one side among the sides is shown (refer to Px in FIG. 1, hereinafter referred to as an arrangement period Px). Further, the “arrangement period in the Y direction” of the through-holes 14A means that one of the two sides extending in the X direction in the through-hole 14A and the two sides extending in the X direction in the through-hole 14A adjacent in the Y direction. The length to one side arranged at a position corresponding to the one side is shown (refer to Py in FIG. 2, hereinafter referred to as arrangement period Py).

  In the present embodiment, as shown in FIG. 1, the case where the arrangement period Px of the through holes 14A is longer than the arrangement period Py will be described. However, in the wavelength selection element 10, the arrangement period in these two directions is It may be different, and the arrangement period Py may be longer than the arrangement period Px.

  As a method of forming these through holes 14A on the metal film 14, a known method is used. For example, an etching method, an adhesion baking method using a holographic stamping technique, or the like can be given.

  FIG. 1 schematically shows a part of the wavelength selection element 10 in an enlarged manner. For this reason, FIG. 1 shows a form in which the metal film 14 is provided with only nine through holes 14A. However, the metal film 14 may be provided with a larger number of through holes 14A corresponding to the application target of the wavelength selection element 10.

  In the wavelength selection element 10 configured as described above, when incident light is incident on the metal film 14, a specific wavelength band component included in the incident light is generated at the interface of the metal film 14 (interface between the metal film 14 and the substrate 12. , And the interface between the metal film 14 and the air). That is, only a specific wavelength band component to be coupled as surface plasmon contained in incident light propagates through the wavelength selection element 10 via the through hole 14A as a transmitted light component.

  Here, the wavelength band component selectively transmitted through the wavelength selection element 10 is determined by the arrangement period of the through holes 14A.

  In the wavelength selection element 10 of the present embodiment, as described above, the cross-sectional shape of the through hole 14A provided in the metal film 14 is the length Dx extended in one arrangement direction (X direction) of the through hole 14A. And two sides of the length Dy extended in the other arrangement direction of the through holes 14A (Y direction orthogonal to the X direction). Further, in the through-hole 14A, the arrangement direction Px in the X direction and the arrangement period Py in the Y direction, which are the two arrangement directions, are different from each other.

  For this reason, the interface of the metal film 14 for each polarization component having a polarization angle of 0 ° and a polarization angle of 90 ° of incident light incident on the wavelength selection element 10 by the arrangement period Px in the X direction and the arrangement period Py in the Y direction. The wavelength band component coupled as surface plasmon can be adjusted. That is, in the wavelength selection element 10 of the present embodiment, the wavelength band component to be coupled extracted from the incident light as transmitted light can be adjusted for each polarization component.

  Therefore, in the wavelength selection element 10 of the present embodiment, the wavelength selection characteristics can be adjusted for each polarization component.

  In the wavelength selection element 10 of the present embodiment, it is essential that the arrangement period Px in the X direction of the through-holes 14A is different from the arrangement period Py in the Y direction, but the following relationship may be exhibited. preferable.

  Specifically, the longer period of the array period Px in the X direction and the array period Py in the Y direction in the through hole 14A with respect to one of the longer array periods (the array period Py in the present embodiment). The ratio of the other short arrangement period (the arrangement period Px in this embodiment) is preferably in the range of 0.5 to 0.9, and more preferably in the range of 0.6 to 0.8. preferable.

  By adjusting the relationship between the arrangement period Px in the X direction and the arrangement period Py in the Y direction in the through hole 14A so as to be within the above range, the wavelength band component can be efficiently and selectively transmitted.

As an example, the substrate 12 is made of SiO ₂ glass, the metal film 14 is made of Al, the arrangement period Px of the through holes 14A in the X direction, the arrangement period Py of the through holes 14A in the Y direction, and the X direction of the through holes 14A. A wavelength selection element 10 was prepared in which the length Dx of the side, the length Dy of the side in the Y direction of the through hole 14A, and the thickness H of the metal film 14 were as follows.

  Arrangement period Px: 0.4 μm, arrangement period Py: 0.6 μm, side length Dx in the X direction of the through hole 14A: 0.2 μm, side length Dy in the Y direction of the through hole 14A: 0.3 μm, Thickness H of metal film 14: 0.2 μm

  And the wavelength selection characteristic in each polarization component of the polarization angle 0 ° and the polarization angle 90 ° of the wavelength selection element 10 having the above configuration was measured, and the measurement result is shown in FIG. The value of the array period Px / the array period Py was 0.66 (Px / Py = 0.4 / 0.6). As shown in FIG. 2, in the wavelength selection element 10 of the present embodiment, it can be seen that the wavelength band of the transmitted light is different for each polarization component. For this reason, the wavelength selection element 10 can adjust the wavelength selection characteristic for each polarization component.

  Further, in the wavelength selection element 10 having the above configuration, the polarization angle when only the arrangement period Px in the X direction of the through-holes 14A is changed to change the arrangement period Px / the arrangement period Py that is the ratio of the arrangement periods. The change of the peak of light transmittance in the 90 ° component is shown in FIG.

  As shown in FIG. 3, the range in which the peak of the light transmittance appears was a range in which the values of the arrangement period Px / the arrangement period Py were 0.5 or more and 0.9 or less. For this reason, in the wavelength selection element 10, the wavelength band component for every polarization | polarized-light component was able to be selectively permeate | transmitted efficiently by making the relationship between the arrangement period Px and the arrangement period Py into the said range.

  As described above, in the wavelength selection element 10 of the present embodiment, the arrangement period Px in the X direction of the through holes 14A and the arrangement period Py in the Y direction need only be different. In 14A, the length Dx of two sides that is long along the arrangement direction in the X direction is preferably shorter than the arrangement period Px in the X direction that is the extending direction of the two sides. Similarly, in each of the plurality of through-holes 14A, the length Dy of two sides that is long along the Y direction is preferably shorter than the arrangement period Py in the Y direction, which is the extending direction of the two sides.

  Specifically, the value of the length Dx (Dx / Px) of the side in the X direction of the through hole 14A with respect to the arrangement period Px in the X direction of the through hole 14A is in a range of 0.5 ± 10% or less. Is preferred. The value of the length Dy (Dy / Py) of the side of the through hole 14A in the Y direction with respect to the arrangement period Py of the through hole 14A in the Y direction is preferably in the range of 0.5 ± 10% or less.

  When the Dx / Px and the Dy / Py are in the above ranges, the wavelength band component extracted as the transmitted light of the wavelength selection element 10 can be selectively transmitted with higher transmittance for each polarization component.

  FIG. 4 shows the above-described values (arrangement period Px: 0.4 μm, arrangement period Py: 0.6 μm, the length Dx of the side in the X direction of the through hole 14A: 0.2 μm, and the side in the Y direction of the through hole 14A. In the wavelength selection element 10 having a length Dy of 0.3 μm and a thickness H of the metal film 14 of 0.2 μm, only the length Dx of the side in the X direction of the through hole 14A is changed to change the Dx / Px. The change of the peak of the light transmittance in the component with the polarization angle of 90 ° when the value of was changed was shown.

  As shown in FIG. 4, it is confirmed that the peak of the light transmittance shows the maximum when the length Dx of the side in the X direction of the through-hole 14A / the arrangement period Px (Dx / Px) value is 0.5. It was.

  As described above, in the wavelength selection element 10 of the present embodiment, the wavelength selection characteristics can be adjusted for each polarization component. For this reason, in this Embodiment, the wavelength selection element 10 with a high wavelength selection freedom degree of the light to permeate | transmit can be provided.

  Moreover, the wavelength selection element 10 of this Embodiment is a simple structure which has the single layer metal film 14 as a metal film. For this reason, even in the case where the wavelength selection element 10 is applied to an element that selectively transmits light in a plurality of wavelength bands of three or more wavelength bands (three colors), such as an image sensor, in the manufacturing process. An increase in cost is suppressed, and the wavelength selection element 10 can be manufactured by a simple manufacturing process.

  In addition, the wavelength selection element 10 of the present embodiment configured as described above receives light of a specific wavelength band component such as an image sensor, a light beam condensing, a scanning optical microscope, photolithography, and an image projection device. The present invention is applied to various devices that require a selectively transparent function.

(Second Embodiment)
In the first embodiment, the wavelength selection element 10 having the configuration in which the metal film 14 provided with the through holes 14A is laminated on the substrate 12 has been described.
In the present embodiment, a description will be given of a wavelength selection element 10A having a configuration in which a substrate 16 is further provided in addition to the configuration of the wavelength selection element 10 and the through hole 14A is filled with a material having translucency and dielectric properties (FIG. 6).

  As shown in FIGS. 6A and 6B, the wavelength selection element 10A of the present embodiment has a configuration in which a metal film 14 and a substrate 16 are sequentially stacked on a substrate 12. The metal film 14 includes a plurality of through holes 14A. In the present embodiment, each through-hole 14A is filled with a filling portion 18 (first member) having the same refractive index (first refractive index) as that of the substrate 12 and having translucency. .

  The wavelength selection element 10A of the present embodiment is described in the first embodiment except that the substrate 16 is further provided on the metal film 14 and the through hole 14A of the metal film 14 is filled with the filling portion 18. The same configuration as that of the wavelength selection element 10 is used. For this reason, the same reference numerals are given to the parts having the same function and the same configuration as those of the wavelength selection element 10, and detailed description thereof is omitted.

  Similar to the substrate 12, the substrate 16 is a light-transmitting dielectric. The substrate 16 may be made of any material as long as it has the same refractive index as the substrate 12 (first refractive index) and has a light transmitting property. As the substrate 16, for example, the materials mentioned as the material constituting the substrate 12 are used.

The filling portion 18 is a dielectric having translucency, like the substrate 12. The filling portion 18 is filled in the through hole 14 </ b> A of the metal film 14, so that one end side in the thickness direction of the metal film 14 is joined to the substrate 12 and the other end side is joined to the substrate 16.
The filling portion 18 may be made of any material as long as it is a dielectric having the same refractive index (first refractive index) as that of the substrate 12 and translucency. For the filling portion 18, for example, the materials mentioned as the material constituting the substrate 12 are used.

  Here, the specific wavelength band component included in the incident light incident on the wavelength selection element 10 described in the first embodiment includes the interface between the metal film 14 and the substrate 12, and the interface between the metal film 14 and air, Both are coupled as surface plasmons. The wavelength band for coupling differs between the interface between the metal film 14 and the substrate 12 and the interface between the metal film 14 and air. For this reason, in the wavelength selection element 10 described in the first embodiment, light of two types of specific wavelength band components corresponding to these two types of interfaces is transmitted through the wavelength selection element 10 for each polarization component. . Therefore, in the wavelength selection element 10 described in the first embodiment, specifically, as shown in FIG. 5, two types of transmission wavelength peaks (in FIG. 5) corresponding to these two types of interfaces. , Peak 21a and peak 21b) are obtained for each polarization component.

  On the other hand, in the wavelength selection element 10A of the present embodiment, as shown in FIG. 6, the substrate 16 is further provided on the metal film 14 on the substrate 12, and the through hole 14A of the metal film 14 is filled with the filling portion 18. ing.

  As described above, in the wavelength selection element 10A according to the present embodiment, the polarization component is formed by covering the interface of the metal film 14 with the air with the substrate 16 and filling the through hole 14A with the filling portion 18. Each transmission wavelength peak can be one (one type) (see peak 21a in FIG. 7).

  Further, in the wavelength selection element 10A of the present embodiment, since the transmission wavelength peak for each polarization component can be one place, the wavelength selection element can be used as compared with the case where there are a plurality of transmission wavelength peaks for each polarization component. The wavelength band component extracted as ten transmitted lights can be transmitted with higher transmittance for each polarization component (see FIGS. 5 and 7).

(Third embodiment)
In the second embodiment, the wavelength selection element 10 </ b> A in which the substrate 16 is disposed facing the substrate 12 with the metal film 14 interposed therebetween and the through hole 14 </ b> A is filled with the light-transmitting and dielectric filling portion 18. (See FIG. 6).

  In the present embodiment, a case will be described in which a substrate 13 and a substrate 17 described later are used in place of the substrate 12 and the substrate 16 of the wavelength selection element 10A described in the second embodiment (see FIG. 8).

  As shown in FIGS. 8A and 8B, the wavelength selection element 10B of the present embodiment has a configuration in which a metal film 14 and a substrate 17 are sequentially stacked on a substrate 13. The metal film 14 includes a plurality of through holes 14A. The through hole 14A is filled with a filling portion 18 (first member).

  The wavelength selection element 10B of the present embodiment is the same as the wavelength selection element 10A described in the second embodiment except that the substrate 13 is used instead of the substrate 12, and the substrate 17 is used instead of the substrate 16. It is the same configuration. For this reason, parts having the same function and the same configuration as those of the wavelength selection element 10A are given the same reference numerals and detailed description thereof is omitted.

  The substrate 13 has a configuration in which a lattice region 13A is stacked on a substrate region 13B. These regions are continuous phases. This lattice-shaped region 13A is a layered region along the interface with the metal film 14. Therefore, the substrate 13 has a substrate region 13B disposed on the side far from the metal film 14, and a lattice region 13A is disposed on the side in contact with the metal film 14 so as to be continuous with the substrate region 13B.

  The substrate 17 has a configuration in which a lattice region 17A is stacked on the substrate region 17B. These regions are continuous phases. The lattice-like region 17A is a layered region along the interface with the metal film 14. Therefore, the substrate 17 has a substrate region 17B disposed on the side far from the metal film 14, and a lattice region 17A is disposed on the side in contact with the metal film 14 continuously from the substrate region 17B.

  The substrate region 13B and the substrate region 17B are light-transmitting dielectrics, like the substrate 12 described in the first embodiment. The substrate region 13B and the substrate region 17B have the same refractive index. The substrate region 13B and the substrate region 17B may be made of any material as long as they are light-transmitting dielectrics and have the same refractive index. As the substrate region 13B and the substrate region 17B, for example, the materials mentioned as the materials constituting the substrate 12 are used.

  In the wavelength selection element 10B of the present embodiment, the filling portion 18 has the same refractive index as those of the substrate region 13B and the substrate region 17B.

  As shown in FIG. 9, the lattice region 17 </ b> A and the lattice region 13 </ b> A have a plurality of plate-like members 22 in the dielectric layer 20. The plurality of plate-like members 22 are periodically arranged along the interface with the metal film 14. The dielectric layer 20 is a light-transmitting dielectric, and has the same refractive index as the substrate region 13B and the substrate region 17B. As the dielectric layer 20, for example, the materials mentioned as the materials constituting the substrate 12 are used.

  8 to 10 show a case in which the plate-like member 22 has a configuration in which the metal film 14 is periodically arranged (one-dimensional arrangement) along the X direction of the XY plane. However, the arrangement direction of the plate-like members 22 may be a direction along the Y direction of the XY plane of the metal film 14, or a direction (two-dimensional arrangement) along two directions of the X direction and the Y direction. There may be.

The plate-like members 22 are periodically arranged with a period smaller than ½ of the transmission center wavelength. The transmission center wavelength indicates the wavelength of the wavelength of the light of the wavelength band component that passes through the wavelength selection element 10 (the center between the maximum wavelength and the minimum wavelength of the wavelength band).
The plate-like member 22 may be made of any material as long as it has a higher refractive index than the dielectric layer 20. For example, the constituent material of the plate-like member 22 includes TiO ₂ .

  Since the wavelength selection element 10B has such a configuration of the lattice region 13A and the lattice region 17A, the pitch of the plate member 22 in the lattice region 13A and the lattice region 17A (of the plate member 22). 9 and 10 corresponds to the arrangement period, and the width of the plate member 22 (corresponding to the length of the plate member 22 in the arrangement direction, see width W in FIGS. 9 and 10). By adjustment, the refractive index of the region in contact with the metal film 14 in the substrate 13 and the substrate 17 can be adjusted. Hereinafter, the refractive index of the regions in contact with the metal film 14 in the substrate 13 and the substrate 17 (that is, the lattice region 13A and the lattice region 17A) may be referred to as an effective refractive index.

  Below, the formula which shows the relationship between the pitch P of the plate-like member 22 arranged periodically and the width W of the plate-like member 22, and the effective refractive index n is shown.

Wherein each of (1) to _{(3), n TE, n} TM, n 1, n 2, f, w, and p represents the following meaning.

n _TE : Effective refractive index of polarized light having a polarization angle of 90 ° (see arrow TE in FIG. 10).
n _TM : Effective refractive index of polarized light having a polarization angle of 0 ° (see arrow TM in FIG. 10).
n ₁ : Refractive index of the grating member 22.
n ₂ : Refractive index of a region (medium) between adjacent lattice members 22.
w: width W of the plate-like member 22.
p: Pitch P of the plate-like member 22
f: Fill factor indicated by the ratio (w / p) between pitch p and lattice width w.

As shown in the above formulas (1) to (3), by changing the fill factor f, which is the ratio between the pitch p of the plate-like member 22 and the width w of the plate-like member 22, the lattice-like region 17A and the lattice The effective refractive index of the region 13 </ b> A can be adjusted to be an intermediate refractive index between the plate-like member 22 and the dielectric layer 20.
Further, as shown in the equations (1) to (3), by changing the fill factor f, which is the ratio of the pitch p of the plate-like member 22 and the width w of the plate-like member 22, the lattice region 17A and the lattice The effective refractive index of the region 13A varies depending on the polarization component of the incident light.

  For this reason, the wavelength selective element 10B has such a lattice region 13A and the lattice region 17A, so that the effective refractive index of the substrate 13 and the region in contact with the metal film 14 on the substrate 17 can be easily obtained. Can be adjusted. Specifically, the wavelength of light transmitted through the substrate 13 and the substrate 17 can be shifted (shifted) to the longer wavelength side as the effective refractive index of the lattice region 13A and the lattice region 17A is increased. it can.

Therefore, in the wavelength selection element 10B of the present embodiment, adjustment of the arrangement period of the through holes 14A in the metal film 14 and the arrangement period of the plate-like members 22 in the lattice region 17A of the substrate 17 and the lattice region 13A of the substrate 13 are performed. By adjusting both of the above, the coupling condition, that is, the transmission wavelength band of the incident light transmitted through the wavelength selection element 10B can be finely adjusted for each polarization component.
Further, in the wavelength selection element 10B of the present embodiment, it is possible to greatly improve the degree of freedom in designing the wavelength band to be transmitted by the wavelength selection element 10B.

  In the present embodiment, as shown in FIGS. 8 to 10, the plate-like member 22 has a one-dimensional arrangement configuration in which the metal film 14 is periodically arranged along the X direction of the XY plane. Explained. For this reason, the effective refractive index varies depending on the polarization direction of incident light. However, as in the case of the through-hole 14A provided in the metal film 14, the polarization of the incident light can be obtained by adopting a two-dimensional array configuration in which the plate-like members 22 are periodically arranged along two directions of the X direction and the Y direction. Differences in direction can be avoided.

  Whether the plate-like member 22 is configured as the one-dimensional array or the two-dimensional array is appropriately selected depending on the application target of the wavelength selection element 10B of the present embodiment. Good.

  The height of the plate-like member 22 (the length of the plate-like member 22 in the thickness direction of the wavelength selection element 10B, see height Ha in FIGS. 8 and 10) is not particularly limited, but the metal film 14 and From the viewpoint of effectively adjusting the coupling conditions at the interface, the incident light wavelength is preferably longer than the incident light wavelength.

  Further, in the present embodiment, a description has been given of a form in which both the substrate 13 and the substrate 17 are provided with the lattice regions (the lattice region 13A and the lattice region 17A). However, a lattice-shaped region may be provided only on one of the substrate 13 and the substrate 17.

10, 10A, 10B Wavelength selection elements 12, 13, 16, 17 Substrate 13A, 17A Lattice region 14 Metal film 14A Through hole 18 Filling portion 20 Dielectric layer 22 Plate member

JP 2000-1111851 A

IEEE ELECTRON DEVICE LETTERS, VOL. 27, NO. 6, (2006) Nature 445, 39-46 (2007) IEICE technical report 109 (403), 129-132, (2010)

Claims (6)

A wavelength selection element that selectively transmits light of a specific wavelength band component included in incident light,
A first substrate that is a light-transmitting dielectric;
A metal film laminated on the first substrate and having a plurality of through holes penetrating in the thickness direction;
With
The through holes are arranged in a lattice shape along two directions of a first direction and a second direction orthogonal to each other on the surface of the metal film,
The cross-sectional shape along the surface direction of the metal film in the through hole has two first sides extended in the first direction, and two second sides extended in the second direction, A rectangular shape consisting of four sides of
In the through hole, the length in the extending direction of the first side and the length in the extending direction of the second side are shorter than the wavelength of the light of the specific wavelength band component,
In addition, the wavelength selection element is characterized in that the arrangement period in the first direction and the arrangement period in the second direction in the through hole are different from each other.   Of the array period in the first direction and the array period in the second direction in the through hole, the ratio of the other array period to the one array period having a long array period is 0.1 or more and 0.9 or less. The wavelength selective element according to claim 1, wherein A second substrate disposed opposite to the first substrate through the metal film, and having a translucency and a dielectric having the same first refractive index as the first substrate;
A first member filled in the through-hole and having a light-transmitting property and a dielectric having the same refractive index as the first substrate;
The wavelength selection element according to claim 1 or 2, further comprising: The length in the extending direction of the first side in the through hole is 0.5 times ± 10% or less of the arrangement period of the first direction in the through hole,
The length in the extending direction of the second side in the through-hole is 0.5 times ± 10% or less of the arrangement period of the second direction in the through-hole. 2. The wavelength selection element according to item 1. The first substrate has a first region along a surface in contact with the metal film;
The first region includes a plurality of plate-like bodies having a refractive index higher than the first refractive index in a dielectric layer having the same first refractive index as that of the first substrate. ,
5. The plate according to claim 1, wherein the plate-like body is arranged along the surface of the metal film with an arrangement period smaller than ½ of a transmission center wavelength of light of the specific wavelength band component. The wavelength selection element according to 1.   The wavelength selection element according to claim 3, wherein the second substrate has the first region.

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