JP2010078675A - Optical deflection device and optical deflection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical deflection device which is high in optical coupling efficiency to a two-dimensional photonic crystal, and deflects incident light at a wider deflection angle by a super-prism effect of a two-dimensional photonic crystal, and to provide an optical deflection method. <P>SOLUTION: An upper reflection mirror 18 and are lower reflection mirror 20 are arranged with a spacing so that the reflecting surfaces face each other. The two-dimensional photonic crystal 14 is a plate having a two-dimensional periodic structure, is inserted between the upper reflection mirror 18 and the lower reflection mirror 20, and is disposed approximately parallel to the lower reflection mirror 20. When the incident light L<SB>in</SB>of a predetermined wavelength is made incident at a substantial right angle with respect to the lower reflection mirror 20, the incident angle L<SB>in</SB>is repetitively reflected between the upper reflection mirror 18 and the lower reflection mirror 20, and passes the two-dimensional photonic crystal 14 a plurality of times. As a result, for the optical polarization element as a whole, the propagation direction of the light wave is drastically converted, and the diffracted light L<SB>dif</SB>is emitted in a direction different from the direction of the incident light L<SB>in</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical deflection element and an optical deflection method.

  A photonic crystal is a structure having a periodic refractive index distribution therein. In a photonic crystal, a “photonic band gap” that does not allow the presence of light in a specific wavelength range appears. By utilizing this dispersion at the band edge, a concept of refraction that is completely different from normal refraction at the interface according to Snell's law can be obtained. That is, the refraction effect by the photonic crystal varies greatly depending on various factors such as the incident wavelength and the incident angle. For example, using a three-dimensional photonic crystal, a prism is obtained in which the refraction angle of light rays changes by 50 ° only by changing the incident wavelength by 1% (Non-patent Document 1). This refraction effect is referred to as the “super prism” effect.

  Also, light that changes the direction of the scanning light beam emitted from the photonic crystal by changing the refractive index of the ferroelectric according to the applied voltage using a two-dimensional photonic crystal composed of a ferroelectric material. A scanning device has been proposed (see Patent Document 1). Compared with a mechanical optical deflector using a polygon mirror, a MEMS mirror, or the like, an optical deflector using a photonic crystal does not require precise operation control, does not generate an operation sound, and has a scanning angle (deflection). The angle) can be widened.

Hideo Kosaka et al., Journal of Lightwave Technology, Volume 17, No. 11, p2032-2038, November 1999 JP 2006-178363 A

  However, in the optical scanning device described in Patent Document 1, since the two-dimensional photonic crystal is used as a slab waveguide that propagates light in the in-plane direction, light must be incident from the end face, There was a problem that the optical coupling efficiency was lowered.

  On the other hand, as a photonic crystal applicable to a light polarizing element, there is a three-dimensional photonic crystal having a three-dimensional periodic structure in addition to a two-dimensional photonic crystal having a two-dimensional periodic structure. However, the three-dimensional photonic crystal has a complicated manufacturing process and is expensive. Therefore, the two-dimensional photonic crystal is more suitable for general purpose applications such as a light polarizing element.

  The present invention has been made in view of the above problems, and an object of the present invention is to have high optical coupling efficiency with a two-dimensional photonic crystal and to allow incident light to be incident with a wide polarization angle by the super prism effect of the two-dimensional photonic crystal. An object of the present invention is to provide an optical deflection element and an optical polarization method capable of deflecting.

  In order to achieve the above object, an optical polarizing element of the present invention includes a first reflecting plate having a first reflecting surface that reflects incident light, and a second reflecting surface that reflects incident light, and the second reflecting surface. Is disposed between the first reflector and the second reflector, in parallel with the first reflector, and is disposed between the first reflector and the second reflector. And a two-dimensional photonic crystal in which columnar second media having a refractive index different from that of the first medium are two-dimensionally arranged.

  The light polarization method of the present invention is a light deflection method using the light deflection element of the present invention, wherein incident light incident on one of the first reflector and the second reflector is the first. The incident light is reflected several times between the reflecting plate and the second reflecting plate, passes through the two-dimensional photonic crystal a plurality of times, and is diffracted by the two-dimensional photonic crystal and emitted. The incident light is incident at an incident angle.

  The above-mentioned light polarizing element can be configured such that a ferroelectric layer whose refractive index changes due to an electro-optic effect is further inserted between the first reflecting plate and the two-dimensional photonic crystal. In this case, as described above, the incident light is incident at an incident angle of several degrees, and an electric field is applied to the ferroelectric layer to change a refractive index by an electro-optic effect, so that the two-dimensional photonic crystal is formed. The direction in which the diffracted light is emitted is changed by changing the angle of the incident light.

  Further, the light polarizing element may be configured such that the second reflecting plate is rotatably arranged so that an inclination of the second reflecting surface with respect to the first reflecting surface is changed. In this case, as described above, the incident light is incident at an incident angle of several degrees, the second reflecting plate is rotated, and the inclination of the second reflecting surface with respect to the first reflecting surface is changed, The direction in which the diffracted light is emitted is changed.

  In addition, the above-described light polarizing element may be configured such that a piezoelectric element that deforms the two-dimensional photonic crystal is further disposed adjacent to the two-dimensional photonic crystal. In this case, as described above, the incident light is incident at an incident angle of several degrees, and the two-dimensional photonic crystal is deformed by the piezoelectric element to change the direction in which the diffracted light is emitted.

  Further, the light polarizing element includes the first reflector and the second reflector so that a distance between the first reflecting surface and the second reflecting surface is a distance at which a standing wave is generated with respect to a wavelength of incident light. It is preferable that the two reflectors are spaced apart.

  The optical deflection element and the optical polarization method of the present invention have high optical coupling efficiency with a two-dimensional photonic crystal, and can deflect incident light with a wide polarization angle by the super prism effect of the two-dimensional photonic crystal. Play.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

(Basic operating principle)
FIG. 1 is an explanatory diagram for explaining the basic operation principle of the light polarizing element of the present invention.
The light polarizing element of the present invention includes at least a two-dimensional photonic crystal 14, an upper reflection mirror 18, and a lower reflection mirror 20. The two-dimensional photonic crystal 14 is a plate-like body having a two-dimensional periodic structure. The upper reflection mirror 18 and the lower reflection mirror 20 are spaced apart so that the reflection surfaces face each other. The two-dimensional photonic crystal 14 is inserted between the upper reflection mirror 18 and the lower reflection mirror 20, and is disposed substantially parallel to the lower reflection mirror 20.

In the light polarizing element of the present invention, it is incident at an angle nearly perpendicular to the lower reflecting mirror 20 to the incident light L _in a predetermined wavelength. That is, as the angle of incidence is several ° ~ dozen °, is incident to the incident light L _in the lower reflecting mirror 20. Incident incident light L _in is reflected by the lower reflecting mirror 20. The reflected light is incident on the two-dimensional photonic crystal 14, passes through the two-dimensional photonic crystal 14, and reaches the upper reflection mirror 18. The light applied to the upper reflecting mirror 18 is reflected by the upper reflecting mirror 18. The reflected light again passes through the two-dimensional photonic crystal 14 and reaches the lower reflecting mirror 20.

The incident light L _in is between the upper reflecting mirror 18 and the lower reflecting mirror 20, as described above, are repeatedly reflected. While being repeatedly reflected, the incident light L _in the multiple passes through the two-dimensional photonic crystal 14. The incident light L _in the relative two-dimensional photonic crystal 14, at all times operate to bind to the surface direction. That is, the two-dimensional photonic crystal 14 diffracts the incident light by the two-dimensional periodic structure.

However, the effect of changing the propagation direction of the light wave (diffraction effect) is small by passing through the two-dimensional photonic crystal 14 only once. By passing through the two-dimensional photonic crystal 14 a plurality of times, the propagation direction (energy direction) of the light wave is drastically converted when viewed as the entire optical polarizing element. Thus the diffracted light L _dif is, the direction of the incident light L _in is incident (or the incident light L _in the direction to be reflected) is emitted in a direction different from the.

As described above, between the upper reflection mirror 18 and the lower reflecting mirror 20, again the incident light L _in also is reflected, configured such that the incident light L _in the multiple passes through the two-dimensional photonic crystal 14 By doing so, the optical coupling efficiency to the two-dimensional photonic crystal 14 can be increased as compared with the case where the light is incident from the end face like a slab type optical waveguide.

(First embodiment)
<Schematic configuration of light polarizing element>
First, a schematic configuration of the light polarizing element according to the first embodiment of the present invention will be described.
FIG. 2 is a perspective view of the light polarizing element according to the first embodiment. 3 is a cross-sectional view taken along the line AA in FIG. The light polarizing element according to the first embodiment includes a substrate 10 having a substantially rectangular shape in plan view. On the substrate 10, the lower spacer layer 12, the two-dimensional photonic crystal 14, the upper spacer layer 16, and the upper reflection mirror 18 are stacked in this order from the substrate side to form a prismatic mesa. The cross-sectional shape of the mesa is a rectangular shape that is slightly smaller than the substrate 10. Further, a lower reflection mirror 20 is formed on the back surface side of the substrate 10 so as to cover the back surface. Except the upper reflection mirror 18 and the lower reflecting mirror 20 is composed of a transparent material to the incident light L _in.

  Each of the upper reflecting mirror 18 and the lower reflecting mirror 20 is a multilayer film reflecting mirror composed of dielectric multilayer films in which dielectrics having different refractive indexes are alternately stacked. The upper reflecting mirror 18 and the lower reflecting mirror 20 are arranged in parallel so that the reflecting surfaces face each other. The lower spacer layer 12 and the upper spacer layer 16 are formed in a frame shape around the mesa. At the center of the mesa, cavities (cavities) are formed above and below the two-dimensional photonic crystal 14. The structure of the two-dimensional photonic crystal 14 will be described later.

In the present embodiment, the substrate 10 is a silicon (Si) substrate, and the lower spacer layer 12 and the upper spacer layer 16 are formed of silicon oxide (SiO ₂ ). The two-dimensional photonic crystal 14 also includes a silicon (Si) substrate. Each of the upper reflection mirror 18 and the lower reflecting mirror 20 is composed of a dielectric multilayer film formed by alternately laminating silicon oxide (SiO ₂₎ and titanium oxide (TiO _2). As the dielectric multilayer film, for example, a film obtained by alternately stacking three sets of 263 nm thick SiO ₂ layers and 154 nm thick TiO ₂ layers can be used.

The upper reflecting mirror 18 and the lower reflecting mirror 20, the distance between the reflecting surface, it is preferable to spaced such that the distance that the standing wave with respect to the wavelength of the incident light L _in may occur. That is, when the wavelength of the incident light L _in the lambda (e.g., 1550 nm) is the thickness of the substrate 10 L _sub, the thickness of the two-dimensional photonic crystal 14 L _pc, the upper and lower of the two-dimensional photonic crystal 14 The upper reflection mirror satisfies the following relational expression, where L _{air is} the thickness of the air layer present in the substrate 10, n _{sub is} the refractive index of the substrate 10, and n _{pc is} the refractive index of the two-dimensional photonic crystal 14. A separation distance (L _pc + L _air ) between 18 and the lower reflecting mirror 20 can be determined.
n _pc L _pc + n _sub L _sub + L _air = m (λ / 2) (m is an integer of 1 or more)

Note that the air layer thickness L _air exists between the two-dimensional photonic crystal 14 and the lower reflecting mirror 20 and the thickness of the air layer existing between the two-dimensional photonic crystal 14 and the upper reflecting mirror 18. The sum of the thickness of the air layer to be added. Further, the thickness of each layer can be appropriately designed so as to satisfy the above relational expression according to the wavelength and the refractive index of the material.

  Next, the structure of the two-dimensional photonic crystal will be described. The two-dimensional photonic crystal is a photonic crystal in which a columnar second medium having a refractive index different from that of the first medium is two-dimensionally arranged in a substrate composed of the first medium. The columnar second medium may be cylindrical or may be a prism having a hexagonal cross section. The two-dimensional periodic array may be a square lattice array or a triangular lattice array.

  4A is a plan view of the two-dimensional photonic crystal 14, and FIG. 4B is a cross-sectional view taken along the line BB in FIG. 4A. In the present embodiment, as the two-dimensional photonic crystal 14, a silicon substrate 14b having a plurality of air rods (through holes) 14a arranged in a triangular lattice shape is used. Such a two-dimensional photonic crystal 14 can be obtained by forming a through hole 14a having a predetermined diameter in a silicon substrate 14b.

  In the present embodiment, the first medium is silicon and the second medium is air. In addition, 16 air rods 14a are arranged in a triangular lattice pattern on a silicon substrate 14b about 0.5 mm square. The thickness of the silicon substrate 14b can be 0.1 μm to 0.2 μm.

<Method for producing light polarizing element>
Next, a method for manufacturing the light polarizing element shown in FIG. 2 will be described. First, the Si substrate 10 is prepared. Next, a SiO ₂ film to be the lower spacer layer 12 is deposited on the Si substrate 10 by sputtering. On this lower spacer layer 12, a Si film that becomes the two-dimensional photonic crystal 14 is deposited by sputtering. A photonic crystal pattern is drawn on the Si film to be the two-dimensional photonic crystal 14 by a radiation drawing apparatus. At this time, an alignment mark is also attached to the two-dimensional photonic crystal 14. The Si film that becomes the two-dimensional photonic crystal 14 is dry-etched with CF ₄ or the like to form the through hole 14a.

Next, a SiO ₂ film to be the upper spacer layer 16 is deposited on the two-dimensional photonic crystal 14 by sputtering. Thereafter, the substrate is immersed in buffered hydrofluoric acid to leave the frame-like lower spacer layer 12 and the frame-like upper spacer layer 16, and the other SiO ₂ film is dissolved and washed with water. Thereby, spaces are formed above and below the two-dimensional photonic crystal 14. Next, a lower reflection mirror 20 that is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering is formed on the back surface of the Si substrate 10.

On the other hand, on another Si substrate, by depositing a SiO ₂ film and a TiO ₂ film alternately by sputtering to form an upper reflection mirror 18 is a dielectric multilayer film. The upper reflection mirror 18 is overlapped on the upper spacer layer 16 with the mirror side down, and the outer peripheral side is bonded. Finally, a thick resist is applied, and unnecessary SiO ₂ film, Si film, and dielectric multilayer film on the substrate 10 are removed by etching to form mesas, thereby completing the light polarizing element shown in FIG. .

<Polarization operation of the light polarizing element>
Next, the polarization operation of the light polarizing element according to the first embodiment will be described.
FIG. 5 is an explanatory diagram for explaining the operating principle of the deflection action of the optical polarization element. The light polarizing element according to the first embodiment, as described as the basic operating principles, is incident at an angle nearly perpendicular incident light L _in respect to the lower reflecting mirror 20. The incident light L _in is between the upper reflecting mirror 18 and the lower reflecting mirror 20 is repeatedly reflected.

While being repeatedly reflected, the incident light L _in the multiple passes through the two-dimensional photonic crystal 14. The two-dimensional photonic crystal 14 diffracts incident (crossed) light by its two-dimensional periodic structure. By passing through the two-dimensional photonic crystal 14 a plurality of times, the propagation direction of the light wave is significantly changed. Thus the diffracted light L _dif is, the direction of the incident light L _in is incident (or the incident light L _in the direction to be reflected) is emitted in a direction different from the.

As shown in FIG. 5, to change the angle of incidence with respect to the lower reflecting mirror 20 of the incident light L _in. The next incident light L _in (2) is incident at a smaller incident angle than the previous incident light L _in (1). Diffracted light L _dif in accordance with the incident light L _in (1) (1) is injected, the diffracted light L _dif (2) is injected in accordance with the incident light L _in (2). By thus varying the angle of incidence with respect to the lower reflecting mirror 20 of the incident light L _in, the emission direction of the diffracted light L _dif changes.

6A and 6B are wave vector diagrams showing the relationship between wave vectors. From the law of conservation of photon momentum, in the state of phase matching, the wave vector diagram obtained by synthesizing the wave vector of the related light wave is a closed triangle. Therefore, when the wave number of the incident light L _in is varied, also varied wave number of the diffracted light L _dif emitted. Let K be the wave vector of the two-dimensional photonic crystal. Photonic crystals exhibit a “super prism effect” in which the group velocity changes significantly. Therefore, the "direction" and "magnitude" of the wave vector K varies greatly according to the incident angle of the incident light L _in.

As shown in FIGS. 6A and 6B, the wave number vector of the incident light L _in (1) is k _i , the wave number vector of the incident light L _in (2) is k _in ^′ , and the diffracted light L _dif (1 the wave vector of the) k _out, the wave vector of the diffracted light L _dif (2) and k _out ^'. When the wave number vector of the incident light L _in changes from k _i to k _in ^′ , the wave number vector of the diffracted light L _dif becomes k _out according to the change of the wave vector K of the two-dimensional photonic crystal from the law of conservation of photon momentum. To k _out ^' .

As described above, in this embodiment, alone incident angle of the incident light L _in is slightly changed, the super prism effect of the two-dimensional photonic crystal, the emission direction (deflection direction) of the diffracted light L _dif significantly To change. Thereby, an optical deflecting element capable of deflecting with a wide deflection angle can be obtained.

(Second Embodiment)
<Schematic configuration of light polarizing element>
FIG. 7 is a perspective view of a light polarizing element according to the second embodiment of the present invention. 8 is a cross-sectional view taken along the line CC of FIG. The light polarizing element according to the second embodiment is the same as that of the first embodiment except that a ferroelectric layer 22 is laminated instead of the upper spacer layer 16 between the two-dimensional photonic crystal 14 and the upper reflecting mirror 18. The configuration is the same as that of the embodiment. Accordingly, the same components are denoted by the same reference numerals and description thereof is omitted.

The ferroelectric layer 22 is transparent to the incident light L _in, is composed of a ferroelectric material whose refractive index changes by means of an electro-optical effect. As such a ferroelectric material, lithium niobate (LiNbO ₃ ) or PLZT can be used. PLZT is a ferroelectric polycrystal obtained by substituting a part of Pb (lead) of lead zirconate titanate (PZT: PbZrO ₃ —PbTiO ₃ ) with La (lanthanum). Its composition is represented by (Pb _1-x La _x ) (Zr _1-y Ti _y ). In general, a composition having x = 0.07 to 0.12 and y = 0.35 is widely used.

  In the present embodiment, the material, size, and thickness of each member other than the ferroelectric layer 22 are the same as those in the first embodiment. The thickness of the ferroelectric layer 22 is about 0.1 μm. The light polarizing element according to the second embodiment is provided with a pair of electrodes (not shown). By applying a voltage between the pair of electrodes, an electric field is generated, and the electric field is applied to the ferroelectric layer 22, and the refractive index of the ferroelectric layer 22 varies due to the electro-optic effect. It is preferable to generate an electric field so that the two-dimensional photonic crystal 14 and the ferroelectric layer 22 are disposed in a region where the electric field strength is high.

<Method for producing light polarizing element>
Next, a method for manufacturing the light polarizing element shown in FIG. 7 will be described. Until the step of forming the two-dimensional photonic crystal 14, the two-dimensional photonic crystal 14 including the through hole 14a is formed in the same manner as in the first embodiment. Then immersed in buffered hydrofluoric acid, leaving the lower spacer layer 12 of the frame-shaped, and washed with water to dissolve the other of the SiO ₂ film. Thereby, a space is formed below the two-dimensional photonic crystal 14. Next, a lower reflection mirror 20 that is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering is formed on the back surface of the Si substrate 10.

Next, another substrate in which the upper reflection mirror 18 is formed on the ferroelectric layer 22 is prepared. First, a ferroelectric thin film to be the ferroelectric layer 22 is formed. Ferroelectric thin film deposition methods include solution coating methods such as a sol-gel method, physical deposition methods such as sputtering, and chemical deposition methods such as CVD. In either method, an amorphous ferroelectric thin film is first deposited, and then crystallization is performed by heat treatment. Next, the upper reflection mirror 18 that is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering is formed on the ferroelectric layer 22. Next, an electrode (not shown) for applying an electric field is formed.

A separately prepared substrate is laminated on the two-dimensional photonic crystal 14 with the ferroelectric layer 22 side down, and the outer peripheral side is bonded. Finally, resist is applied thickly to form a mesa unnecessary SiO ₂ film on the substrate 10, Si film, a ferroelectric thin film, and a dielectric multilayer film is removed by etching, the light shown in FIG. 7 A polarizing element is completed.

<Polarization operation of the light polarizing element>
Next, the polarization operation of the light polarizing element according to the second embodiment will be described.
FIG. 9 is an explanatory diagram for explaining the operating principle of the deflection action of the optical polarization element. The light polarizing element according to the second embodiment, as described as the basic operating principles, is incident at an angle nearly perpendicular incident light L _in respect to the lower reflecting mirror 20. The incident light L _in is between the upper reflecting mirror 18 and the lower reflecting mirror 20 is repeatedly reflected.

While being repeatedly reflected, the incident light L _in the multiple passes through the two-dimensional photonic crystal 14 and the ferroelectric layer 22. The two-dimensional photonic crystal 14 diffracts incident (crossed) light by its two-dimensional periodic structure. The ferroelectric layer 22 changes the propagation direction of the incident light wave with the refractive index at the time of passage. Therefore, the light wave propagation direction is significantly changed by passing through the two-dimensional photonic crystal 14 and the ferroelectric layer 22 a plurality of times. Thus the diffracted light L _dif is, the direction of the incident light L _in is incident (or the incident light L _in the direction to be reflected) is emitted in a direction different from the.

As shown in FIG. 9, the angle of incidence of the incident light L _in it is constant. As shown in FIG. 10, the refractive index of the ferroelectric layer 22 is changed by applying an electric field. Before the refractive index of the ferroelectric layer 22 changes, the incident light L _in (1) passes through the two-dimensional photonic crystal 14 and the ferroelectric layer 22 as shown by a solid line. On the other hand, after the refractive index of the ferroelectric layer 22 changes, the incident light L _in (2) passes through the two-dimensional photonic crystal 14 and the ferroelectric layer 22 as indicated by the dotted line.

And the refractive index of the ferroelectric layer 22 by the application of an electric field is increased, when incident on the ferroelectric layer 22, the optical path of the incident light L _in (2), from the optical path of the incident light L _in (1) Can also be folded. Diffracted light L _dif in accordance with the incident light L _in (1) (1) is injected, the diffracted light L _dif (2) is injected in accordance with the incident light L _in (2). Thus strong By changing the refractive index of the dielectric layer 22, it is changed optical path of the incident light L _in passing through the ferroelectric layer 22, the emission direction of the diffracted light L _dif changes.

FIGS. 11A and 11B are wave vector diagrams showing the relationship between wave vectors. From the law of conservation of photon momentum, in the state of phase matching, the wave vector diagram obtained by synthesizing the wave vector of the related light wave is a closed triangle. Wave vector K of the two-dimensional photonic crystal, the super prism effect will vary considerably depending on the optical path of the incident light L _in.

The wave vector of the incident light L _in (1) k _i, the wave vector of the incident light L _in (2) and k _in ^', the wave vector k _out of the diffracted light L _dif (1), the diffracted light L _dif (2 ) Is k _out ^' . When the wave number vector of the incident light L _in changes from k _i to k _in ^′ , the wave number vector of the diffracted light L _dif becomes k _out according to the change of the wave vector K of the two-dimensional photonic crystal from the law of conservation of photon momentum. To k _out ^' .

As described above, in the present embodiment, the refractive index of the ferroelectric layer 22 changes due to the external electric field. The change in refractive index of the ferroelectric layer 22, the optical path of the incident light L _in passing through the ferroelectric layer 22 is changed. Alone optical path of the incident light L _in is slightly changed, the super prism effect of the two-dimensional photonic crystal, the emission direction (deflection direction) of the diffracted light L _dif varies greatly. Thereby, an optical deflecting element capable of deflecting with a wide deflection angle can be obtained.

(Third embodiment)
<Schematic configuration of light polarizing element>
FIG. 12 is a perspective view of a light polarizing element according to the third embodiment of the present invention. 13 is a cross-sectional view taken along the line DD of FIG. In the light polarizing element according to the third embodiment, instead of the fixedly arranged upper reflecting mirror 18, an upper rotating reflecting mirror 18R is rotatably arranged, and the two-dimensional photonic crystal 14 and the upper rotating reflecting mirror 18R are arranged. The configuration is the same as that of the first embodiment except that the upper spacer layer 16 is removed. Accordingly, the same components are denoted by the same reference numerals and description thereof is omitted.

  The upper rotary reflection mirror 18R is a plate-like body having a substantially rectangular shape in plan view having the same size as the mesa cross section. A pair of rotating shafts 24 is attached to each of a pair of opposing side surfaces of the upper rotary reflecting mirror 18R by an attachment member (not shown). On the other hand, two (a pair) columnar holding members 26 having bearings are erected on the substrate 10. The pair of holding members 26 are arranged to face each other with the mesa interposed therebetween. The rotating shaft 24 and the holding member 26 are disposed so as to avoid the optical path.

  Each of the pair of rotating shafts 24 is fitted into the bearing portion of the corresponding holding member 26. Thus, the upper rotary reflection mirror 18R is held by the pair of holding members 26 so as to be rotatable around the rotation shaft 24 (in the direction of arrow E). A motor 28 is attached to the rotating shaft 24 to rotate the rotating shaft by a slight angle. As such a motor 28, it is preferable to use a small motor using MEMS (Micro Electro Mechanical Systems) technology.

In the present embodiment, the upper rotary reflection mirror 18R is composed of a dielectric multilayer film in which silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ) are alternately stacked. The material, size, and thickness of each member other than the upper rotary reflection mirror 18R are the same as those in the first embodiment. The rotating shaft 24 and the holding member 26 may be made of any material, but when formed by applying a semiconductor manufacturing technique, the rotating shaft 24 and the holding member 26 are formed of silicon oxide (SiO ₂ ) in the same manner as the lower spacer layer 12. It is preferable to do.

<Method for producing light polarizing element>
Next, a method for manufacturing the light polarizing element shown in FIG. 12 will be described. Until the step of forming the two-dimensional photonic crystal 14, the two-dimensional photonic crystal 14 including the through hole 14a is formed in the same manner as in the first embodiment. Thereafter, the substrate is immersed in buffered hydrofluoric acid to leave the frame-like lower spacer layer 12, and the other SiO ₂ film is dissolved and washed with water. Thereby, a space is formed below the two-dimensional photonic crystal 14. Next, a lower reflection mirror 20 that is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering is formed on the back surface of the Si substrate 10.

Next, a thick resist is applied, and unnecessary SiO ₂ films and Si films on the substrate 10 are removed by etching to form mesas. A columnar holding member 26 having a bearing portion is erected on the substrate 10 exposed by etching. On the other hand, an upper rotary reflection mirror 18R, which is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering, is formed on another substrate. A rotating shaft 24 is attached to the upper rotating reflecting mirror 18R.

  The upper rotary reflection mirror 18R having the rotation shaft 24 is rotatably attached to a columnar holding member 26 having a bearing portion. Then, the motor 28 is attached to the rotating shaft 24. Thereby, the light polarizing element shown in FIG. 12 is completed. A commercially available MEMS mirror device such as “Ecoscan (trade name)” manufactured by Nippon Signal Co., Ltd. can also be used as the upper rotary reflection mirror 18R.

<Polarization operation of the light polarizing element>
Next, the polarization operation of the light polarizing element according to the third embodiment will be described.
FIG. 14 is an explanatory diagram for explaining the operating principle of the deflection action of the optical polarization element. The light polarizing element according to the third embodiment, as described as the basic operating principles, is incident at an angle nearly perpendicular incident light L _in respect to the lower reflecting mirror 20. The incident light L _in is between the upper rotary reflecting mirror 18R and the lower reflecting mirror 20 is repeatedly reflected.

While being repeatedly reflected, the incident light L _in the multiple passes through the two-dimensional photonic crystal 14. The two-dimensional photonic crystal 14 diffracts incident (crossed) light by its two-dimensional periodic structure. Further, the propagation direction (reflection direction) of the incident light wave is changed according to the position of the upper rotary reflection mirror 18R. Therefore, the propagation direction of the light wave is greatly changed by passing through the two-dimensional photonic crystal 14 a plurality of times. Thus the diffracted light L _dif is, the direction of the incident light L _in is incident (or the incident light L _in the direction to be reflected) is emitted in a direction different from the.

As shown in FIG. 14, the angle of incidence of the incident light L _in it is constant. As shown in FIG. 15, the upper rotary reflection mirror 18R is rotated around the rotation shaft 24 by a mechanical mechanism such as a motor to change the inclination of the upper rotary reflection mirror 18R. Before the tilt of the upper rotary reflection mirror 18R changes, the incident light L _in (1) passes through the two-dimensional photonic crystal 14 as shown by a solid line. On the other hand, after the inclination of the upper rotary reflection mirror 18R is changed, the incident light L _in (2) passes through the two-dimensional photonic crystal 14 as indicated by a dotted line.

The upper rotary reflection mirror 18R rotates around the rotation axis 24 in the direction of arrow E (counterclockwise in FIG. 15), and the inclination of the upper rotary reflection mirror 18R changes. Accordingly, the incident angle to the upper rotation reflector 18R of the incident light L _in (= reflection angle) increases. The angle at which the incident light L _in (2) intersects the two-dimensional photonic crystal 14 is larger than the angle at which the incident light L _in (1) intersects the two-dimensional photonic crystal 14. Diffracted light L _dif in accordance with the incident light L _in (1) (1) is injected, the diffracted light L _dif (2) is injected in accordance with the incident light L _in (2). Thus by rotating the upper rotation reflector 18R by changing its position, it is changed optical path of the incident light L _in passing through the two-dimensional photonic crystal 14, the emission direction of the diffracted light L _dif changes.

FIGS. 16A and 16B are wave vector diagrams showing the relationship between wave vectors. From the law of conservation of photon momentum, in the state of phase matching, the wave vector diagram obtained by synthesizing the wave vector of the related light wave is a closed triangle. Wave vector K of the two-dimensional photonic crystal, the super prism effect will vary considerably depending on the optical path of the incident light L _in.

The wave vector of the incident light L _in (1) is k _i , the wave vector of the incident light L _in (2) is k _in ^′ , the wave vector of the diffracted light L _dif (1) is k _out , and the diffracted light L _dif (2 ) Is k _out ^' . When the wave number vector of the incident light L _in changes from k _i to k _in ^′ , the wave number vector of the diffracted light L _dif becomes k _out according to the change of the wave vector K of the two-dimensional photonic crystal from the law of conservation of photon momentum. To k _out ^' .

As described above, in the present embodiment, the tilt of the upper rotary reflection mirror 18R is changed by applying a mechanical variation such as the rotation of the upper rotary reflection mirror 18R. By the slope of the change of the upper rotary reflecting mirror 18R, the optical path of the incident light L _in it is changed to pass through the two-dimensional photonic crystal 14. Alone optical path of the incident light L _in is slightly changed, the super prism effect of the two-dimensional photonic crystal, the emission direction (deflection direction) of the diffracted light L _dif varies greatly. Thereby, an optical deflecting element capable of deflecting with a wide deflection angle can be obtained.

(Fourth embodiment)
<Schematic configuration of light polarizing element>
FIG. 17 is a perspective view of a light polarizing element according to the fourth embodiment of the present invention. 18 is a cross-sectional view taken along line FF in FIG. In the optical polarizing element according to the fourth embodiment, the upper spacer layer 16 between the two-dimensional photonic crystal 14 and the upper reflecting mirror 18 is removed, and the piezoelectric element 30 is placed on the upper reflecting mirror 18. These are the same configurations as those in the first embodiment. Accordingly, the same components are denoted by the same reference numerals and description thereof is omitted.

  The piezoelectric element 30 is a plate-like body having a substantially rectangular shape in plan view having the same size as the mesa cross section. A piezoelectric element is generally a passive element that utilizes a “piezoelectric effect” that converts an applied force into a voltage or converts an applied voltage into a force, and is commonly called a piezoelectric element. In the present embodiment, an electrostrictive element that expands and contracts slightly when a voltage is applied is used as the piezoelectric element 30. The piezoelectric element 30 is provided with a pair of electrodes (not shown). By applying a voltage between the pair of electrodes, the piezoelectric element 30 expands and contracts in the stacking direction and deforms the two-dimensional photonic crystal 14 disposed below.

Examples of the piezoelectric element 30 described above include piezoelectric ceramics such as PZT and PLZT, and piezoelectric polymers such as PVDF (polyvinylidene fluoride), PVC (polyvinyl chloride), nylon 11 (polyamide), and vinylidene cyanide copolymers. A piezoelectric element using a piezoelectric material such as PZT is an abbreviation for lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ).

  In the present embodiment, the material, size, and thickness of each member other than the piezoelectric element 30 are the same as those in the first embodiment.

<Method for producing light polarizing element>
Next, a method for manufacturing the light polarizing element shown in FIG. 17 will be described. Until the step of forming the two-dimensional photonic crystal 14, the two-dimensional photonic crystal 14 including the through hole 14a is formed in the same manner as in the first embodiment. Thereafter, the substrate is immersed in buffered hydrofluoric acid to leave the frame-like lower spacer layer 12, and the other SiO ₂ film is dissolved and washed with water. Thereby, a space is formed below the two-dimensional photonic crystal 14. Next, a lower reflection mirror 20 that is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering is formed on the back surface of the Si substrate 10.

Next, another substrate having the upper reflection mirror 18 formed on the piezoelectric element 30 is prepared. A piezoelectric element 30 is prepared, and an upper reflection mirror 18 that is a dielectric multilayer film in which SiO ₂ films and TiO ₂ films are alternately deposited by sputtering is formed on the piezoelectric element 30. Next, an electrode (not shown) for applying a voltage is formed.

A separately prepared substrate is placed on the two-dimensional photonic crystal 14 with the upper reflection mirror 18 side down, and the outer peripheral side is bonded. Finally, resist is applied to the thick, unnecessary SiO ₂ film on the substrate 10, Si film, and a dielectric multilayer film or the like is removed by etching to form a mesa, light polarizing element was completed as shown in FIG. 17 To do. Note that the light polarizing element shown in FIG. 17 is fitted into a highly rigid metallic frame or the like so that when the piezoelectric element 30 expands and contracts in the stacking direction, the two-dimensional photonic crystal 14 disposed below is efficiently used. Can be deformed well.

<Polarization operation of the light polarizing element>
Next, the polarization operation of the light polarizing element according to the fourth embodiment will be described.
FIG. 19 is an explanatory diagram for explaining the operating principle of the deflection action of the optical polarization element. The light polarizing element according to the fourth embodiment, as described as the basic operating principles, is incident at an angle nearly perpendicular incident light L _in respect to the lower reflecting mirror 20. The incident light L _in is between the upper reflecting mirror 18 and the lower reflecting mirror 20 is repeatedly reflected.

While being repeatedly reflected, the incident light L _in the multiple passes through the two-dimensional photonic crystal 14. The two-dimensional photonic crystal 14 diffracts incident (crossed) light by its two-dimensional periodic structure. The two-dimensional photonic crystal 14 changes the propagation direction (reflection direction) of the incident light wave according to the strain applied by the piezoelectric element 30. Therefore, the propagation direction of the light wave is greatly changed by passing through the two-dimensional photonic crystal 14 a plurality of times. Thus the diffracted light L _dif is, the direction of the incident light L _in is incident (or the incident light L _in the direction to be reflected) is emitted in a direction different from the.

As shown in FIG. 19, the angle of incidence of the incident light L _in it is constant. As shown in FIG. 20, before the two-dimensional photonic crystal 14 is deformed, diffracted light L _dif (1) is emitted from the two-dimensional photonic crystal 14 as shown by a solid line. Meanwhile, after the two-dimensional photonic crystal 14 is deformed, as shown by the dotted line, from the two-dimensional photonic crystal 14, the diffracted light L _dif (2) is emitted.

When distortion is applied by the piezoelectric element 30 to slightly deform the two-dimensional photonic crystal 14, a large group velocity change occurs due to the super prism effect, and the wave vector K of the two-dimensional photonic crystal changes greatly. Therefore, the angle of incidence of the incident light L _in is be constant, and the diffracted light L _dif (1) and the diffracted light L _dif (2), is injected into entirely different directions. By deforming the two-dimensional photonic crystal 14 in this way, the emission direction of the diffracted light L _dif emitted from the two-dimensional photonic crystal 14 changes.

FIGS. 21A and 21B are wave vector diagrams showing the relationship between wave vectors. From the law of conservation of photon momentum, in the state of phase matching, the wave vector diagram obtained by synthesizing the wave vector of the related light wave is a closed triangle. The wave vector of the incident light L _in is k _i , the wave vector of the diffracted light L _dif (1) is k _out , and the wave vector of the diffracted light L _dif (2) is k _out ^′ . Although the wave vector k _i of the incident light L _in is constant, when the wave vector K of the two-dimensional photonic crystal is changed, the photon momentum conservation law, the wave vector of the diffracted light L _dif is the k _out ^'from k _out It changes a lot.

As described above, in the present embodiment, the two-dimensional photonic crystal 14 is slightly deformed, so that the diffracted light L emitted from the two-dimensional photonic crystal 14 due to the super prism effect of the two-dimensional photonic crystal. The exit direction (deflection direction) of _dif changes significantly. Thereby, an optical deflecting element capable of deflecting with a wide deflection angle can be obtained.

  In the first to fourth embodiments described above, the optical deflecting element that changes the direction (deflection angle) in which the incident light having a predetermined wavelength is incident and the diffracted light is emitted has been described. Since the polarization angle changes according to the wavelength of incident light, the basic configuration can be applied to an optical spectrometer. In this case, as the upper reflection mirror and the lower reflection mirror, it is preferable to use a reflection plate in which a metal having a high light reflectance such as gold or silver is deposited on the reflection surface, rather than a multilayer film reflection mirror.

  For example, when incident light in which a plurality of light waves having different wavelengths are multiplexed is used, diffracted light is separated for each wavelength, and the separated light waves are emitted in different directions as shown in FIG. . In the example shown in FIG. 22, the diffracted light is separated into a light wave having a wavelength λ1, a light wave having a wavelength λ2, and a light wave having a wavelength λ3. Three types of light waves λ1, λ2, and λ3 having different wavelengths are emitted in different directions.

It is explanatory drawing for demonstrating the basic operation | movement principle of the light polarizing element of this invention. It is a perspective view of the light polarizing element concerning a 1st embodiment. It is AA sectional drawing of FIG. (A) is a top view of the two-dimensional photonic crystal 14, (B) is BB sectional drawing of (A). It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. (A) And (B) is a wave vector diagram showing the relationship between wave vectors. It is a perspective view of the light polarizing element which concerns on the 2nd Embodiment of this invention. It is CC sectional drawing of FIG. It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. (A) And (B) is a wave vector diagram showing the relationship between wave vectors. It is a perspective view of the light polarizing element which concerns on the 3rd Embodiment of this invention. It is DD sectional drawing of FIG. It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. (A) And (B) is a wave vector diagram showing the relationship between wave vectors. It is a perspective view of the light polarizing element which concerns on the 4th Embodiment of this invention. It is FF sectional drawing of FIG. It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. It is explanatory drawing for demonstrating the principle of operation of the deflection | deviation effect | action of a light-polarizing element. (A) And (B) is a wave vector diagram showing the relationship between wave vectors. It is a figure which shows the modification which applied the structure of the light polarizing element of this invention to the optical spectrometer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 12 Lower spacer layer 14 Two-dimensional photonic crystal 14b Silicon substrate 14a Through hole 16 Upper spacer layer 18 Upper reflection mirror 18R Upper rotation reflection mirror 20 Lower reflection mirror 22 Ferroelectric layer 24 Rotating shaft 26 Holding member 28 Motor 30 Piezoelectric element

Claims (9)

A first reflector having a first reflecting surface for reflecting incident light;
A second reflecting plate provided with a second reflecting surface for reflecting incident light, the second reflecting surface disposed so as to face the first reflecting surface;
Between the first reflector and the second reflector, the first reflector is disposed in parallel with the first reflector, and a columnar second having a refractive index different from that of the first medium is formed in a substrate made of the first medium. A two-dimensional photonic crystal in which two media are arranged two-dimensionally;
An optical deflection element comprising:   2. The optical deflection element according to claim 1, wherein a ferroelectric layer whose refractive index changes due to an electro-optic effect is further inserted between the first reflector and the two-dimensional photonic crystal.   The light deflecting element according to claim 1, wherein the second reflecting plate is rotatably arranged so that an inclination of the second reflecting surface with respect to the first reflecting surface is changed.   2. The optical deflection element according to claim 1, further comprising a piezoelectric element that deforms the two-dimensional photonic crystal adjacent to the two-dimensional photonic crystal.   The first reflecting plate and the second reflecting plate are spaced apart so that a distance between the first reflecting surface and the second reflecting surface is a distance at which a standing wave is generated with respect to a wavelength of incident light. The light deflection element according to claim 1. An optical deflection method using the optical deflection element according to any one of claims 1 to 5,
Incident light that is incident on one of the first reflector and the second reflector is reflected between the first reflector and the second reflector to pass through the two-dimensional photonic crystal a plurality of times. An optical deflection method in which the incident light is incident at an incident angle of several degrees so as to pass through and be diffracted and emitted by the two-dimensional photonic crystal. An optical deflection method using the optical deflection element according to claim 2,
Incident light that is incident on one of the first reflector and the second reflector is reflected between the first reflector and the second reflector to pass through the two-dimensional photonic crystal a plurality of times. The incident light is incident at an incident angle of several degrees so as to pass through and be diffracted and emitted by the two-dimensional photonic crystal;
An electric field is applied to the ferroelectric layer, the refractive index is changed by an electro-optic effect, the angle of incident light incident on the two-dimensional photonic crystal is changed, and the direction in which the diffracted light is emitted is changed. Light deflection method. An optical deflection method using the optical deflection element according to claim 3,
Incident light that is incident on one of the first reflector and the second reflector is reflected between the first reflector and the second reflector to pass through the two-dimensional photonic crystal a plurality of times. The incident light is incident at an incident angle of several degrees so as to pass through and be diffracted and emitted by the two-dimensional photonic crystal;
An optical deflection method in which the direction in which the diffracted light is emitted is changed by rotating the second reflecting plate and changing an inclination of the second reflecting surface with respect to the first reflecting surface. An optical deflection method using the optical deflection element according to claim 4,
Incident light that is incident on one of the first reflector and the second reflector is reflected between the first reflector and the second reflector to pass through the two-dimensional photonic crystal a plurality of times. The incident light is incident at an incident angle of several degrees so as to pass through and be diffracted and emitted by the two-dimensional photonic crystal;
An optical deflection method in which the two-dimensional photonic crystal is deformed by the piezoelectric element to change a direction in which the diffracted light is emitted.

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