WO2018155535A1

WO2018155535A1 - Light deflection device

Info

Publication number: WO2018155535A1
Application number: PCT/JP2018/006385
Authority: WO
Inventors: 馬場　俊彦; 萌江竹内
Original assignee: 国立大学法人横浜国立大学
Priority date: 2017-02-24
Filing date: 2018-02-22
Publication date: 2018-08-30
Also published as: JPWO2018155535A1; JP6883828B2

Abstract

Provided is a light deflection device having a diffraction mechanism for diffracting light beams emitted from a waveguide core to an external direction, the mechanism being configured to sequentially change waveguide modes in a transverse direction, with the length direction of the waveguide core being a longitudinal direction. The degrees of confining light in the transverse direction are sequentially decreased to change the state of leak from the waveguide core, whereby transverse spread of beam intensity distribution of emitted light beams is suppressed, and the radiation from electromagnetic fields having the same sign in the transverse distribution of waveguide modes is promoted, whereby interference at a distant place is suppressed, in order to form a unimodal beam. As a result of the feature, in the transverse distribution of emitted light beams, the transverse spread of beam intensity distribution of emitted light beams is suppressed such that the beam intensity distribution of emitted light beams has unimodality.

Description

Optical deflection device

The present invention relates to an optical deflection device that controls the traveling direction of light.

Laser radar or lidar equipment (LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging)) that uses laser measurement to acquire the distance to surrounding objects as a two-dimensional image It is used for making maps, and its basic technology can be applied to laser printers and laser displays.

In this technical field, a light beam is applied to an object, reflected light that is reflected back from the object is detected, distance information is obtained from the time difference or frequency difference, and the light beam is scanned two-dimensionally. To obtain wide-angle three-dimensional information.

An optical deflection device is essential for optical beam scanning. Conventionally, mechanical mechanisms such as rotating the entire device, mechanical mirrors such as polygonal mirrors (polygon mirrors) and galvano mirrors, and small integrated mirrors using micromachine technology (MEMS technology) have been used. However, the instability of a moving body that is expensive and vibrates is a problem. In recent years, research on non-mechanical optical deflection devices has been actively conducted.

As a non-mechanical optical deflection device, a phased array type or a diffraction grating type that realizes optical deflection by changing the wavelength of light or the refractive index of the device has been proposed. However, the phased array type optical deflection device has a problem that it is very difficult to adjust the phase of a large number of light emitters arranged in an array, and a high-quality sharp light beam cannot be formed. Although the diffraction grating type optical deflection device can easily form a sharp beam, there is a problem that the optical deflection angle is small.

In response to the problem of the light deflection angle, the inventors of the present invention have proposed a technique for increasing the light deflection angle by coupling the slow light waveguide to a diffraction mechanism such as a diffraction grating (Patent Document 1). Slow light is generated in a photonic nanostructure such as a photonic crystal waveguide and has a low group velocity. Slow light has a characteristic that the propagation constant is greatly changed by a slight change in wavelength or refractive index of the waveguide. When a diffractive mechanism is installed in or near the slow light waveguide, the slow light waveguide is coupled to the diffractive mechanism to form a leaky waveguide, and emits light into free space. At this time, a large change in the propagation constant is reflected in the deflection angle of the emitted light, and as a result, a large deflection angle is realized.

The slow light propagating light is non-radiating in a periodic structure in which a circular hole of one kind of diameter is repeated along the waveguide in the plane of the photonic crystal. In addition, in a double periodic structure in which two types of holes having different diameters are repeated, the slow light propagating light is converted into radiation conditions and emitted into space.

Therefore, a photonic crystal waveguide having a periodic structure formed by repeating circular holes of one type of diameter emits propagating light by a diffraction mechanism such as a diffraction grating. On the other hand, the double periodic structure in which two types of holes having different diameters are repeated in the plane of the photonic crystal is composed of one component in which a diffraction mechanism is incorporated in the photonic crystal waveguide.

7A to 7D show an outline of a device structure in which a diffraction mechanism is introduced into a photonic crystal waveguide that propagates light (slow light) having a low group velocity and a radiation beam emitted therefrom.

(First device structure)
7A and 7B show the device structure of the first optical deflection device. The optical deflection device 101A includes a photonic crystal waveguide 102 having a double periodic structure in which

circular holes

111a and 111b having two different diameters are repeated.

In the optical deflection device 101A, a photonic crystal waveguide 102 in which a low refractive index portion 111 is arranged on a high refractive index member 101 is provided on a clad 106 made of a low refractive index material such as SiO ₂ . The lattice arrangement 112 of the low refractive index portion 111 is, for example, a double periodic structure of a periodic structure in which large-diameter circular holes are repeated and a periodic structure in which small-diameter circular holes are repeated. The large and small diameters of the circular holes forming the double periodic structure indicate a large or small relationship with respect to the diameter of the reference circular hole or in comparison of the diameters of the reference circular holes. When the diameter is 2r and the difference width of diameter is 2Δr, the diameter 2r1 of the large-diameter circular hole 111a is 2 (r + Δr), and the diameter 2r2 of the small-diameter circular hole 111b is 2 (r−Δr). In the lattice arrangement 112 of the photonic crystal waveguide 102, a portion where the circular holes 111 are not provided constitutes a waveguide core 105 that propagates incident light.

(Second device structure)
7C and 7D show the device structure of the second optical deflection device. In the optical deflection device 101B, a surface diffraction grating 103 is disposed on a photonic crystal waveguide 102 having a periodic structure formed by repeating circular holes 111c having one type of diameter.

In the lattice arrangement 112, circular holes 111c at low refractive index portions are periodically arranged in the high refractive index member 101, and the photonic crystal waveguide 102 is formed. A surface diffraction grating 103 is disposed on the photonic crystal waveguide 102 and constitutes a diffraction mechanism for emitting propagating light.

Japanese Patent Application No. 2016-10844

In a conventionally proposed optical deflection device, propagating light propagating through a waveguide core is emitted little by little along the waveguide by a diffraction mechanism, and a radiated light beam is formed. The emitted light beam is deflected by changing the refractive index and incident wavelength of the waveguide of the optical deflection device. The emitted light beam is a sharp beam having a uniform beam intensity distribution in the direction along the waveguide (here, the longitudinal direction).

On the other hand, the slow light is confined in the narrow waveguide core 105 and propagates in the direction orthogonal to the waveguide (here, the lateral direction). Since the light is radiated from there, the light beam generally spreads. In addition, since the light emitted from the periodic waveguide mode distribution interferes with each other due to the periodicity of the photonic crystal, a complicated lateral distribution may be formed.

8A and 8B are diagrams for explaining the beam intensity distribution of the emitted light beam, FIG. 8A shows the beam intensity distribution in the vertical direction, and FIG. 8B shows the beam intensity distribution in the horizontal direction. In FIG. 8A, the radiated light beam gradually leaks along the waveguide, so that the beam intensity distribution in the vertical direction becomes a sharp beam. In FIG. 8B, the lateral beam intensity distribution has a wide angular distribution.

The emitted light beam from the optical deflection device is required to be uniform in beam intensity in the vertical direction, to suppress the spread of the beam intensity distribution in the horizontal direction, and to be unimodal. .

In particular, in the lateral distribution of the synchrotron radiation beam, when there is a spread in the lateral direction and there is a complex beam intensity distribution shape having a plurality of peaks, it becomes a factor of reducing the conversion efficiency to a parallel beam. .

In order to suppress the spread of the radiated light beam in the lateral direction, a configuration is often used in which a collimating lens is installed above the light deflection device and the radiated light beam from the waveguide is converted into a parallel beam. However, the conversion to a parallel beam by the collimating lens does not suppress the occurrence of the lateral distribution of the light beam itself, although it suppresses the lateral divergence angle, and the beam has a plurality of lateral peaks. The intensity distribution is maintained as it is even after conversion to a parallel beam.

That is, in order to increase the conversion efficiency to the parallel beam, it is required that the generation of a complex lateral distribution is suppressed in the synchrotron radiation beam and the peak of the beam intensity distribution is a single peak.

The present invention is directed to an optical deflection device that suppresses the spread of the beam intensity distribution of the radiated light beam in the lateral direction and makes the beam intensity distribution of the radiated light beam unimodal.

The optical deflection device of the present invention is a diffraction mechanism that diffracts the light beam emitted from the waveguide core in the outward direction, and when the length direction of the waveguide core is the vertical direction, the waveguide mode changes in the horizontal direction in order. By gradually reducing the degree of light confinement in the lateral direction and changing the leaching state from the waveguide core, the lateral spread of the beam intensity distribution of the radiated light beam is suppressed. By accelerating the radiation from the electromagnetic field having the same sign of the transverse distribution of the waveguide mode, interference at a distant place is suppressed and a unimodal beam is formed.

The optical deflection device of the present invention deflects the propagation light of a photonic crystal waveguide in which low refractive index portions are periodically arranged in a plane of a high refractive index member and a waveguide core of the photonic crystal waveguide. A diffraction mechanism that emits a radiation light beam to the outside, and the diffraction mechanism includes a plurality of periodic portions arranged along the length direction of the waveguide core, and each periodic portion extends in the length direction of the waveguide core. On the other hand, it is arranged at an acute angle or an obtuse angle.

The optical deflecting device of the present invention has a double period in which a photonic crystal waveguide repeats two types of low-refractive-index portions in a lattice arrangement formed by arranging low-refractive-index portions on a high-refractive-index member. A first form having a structure and a second form having a periodic structure in which the photonic crystal waveguide repeats one kind of low refractive index portion having the same size are included.

(First form)
In the first embodiment of the optical deflecting device, the photonic crystal waveguide and the diffraction mechanism include two types of low refractive index portions having different sizes along the length direction of the waveguide core in the plane of the high refractive index member. A lattice arrangement of a double periodic structure arranged periodically is provided.

The diffraction mechanism includes two types of periodic parts in which a low-refractive index part of the same size is periodically arranged in a lattice arrangement of a double periodic structure. The two types of periodic portions are alternately arranged along the length direction of the waveguide core, and are arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core.

The periodic portions are alternately arranged along the length direction of the waveguide core according to a plurality of arrangement forms, and can be arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core.

(a) First arrangement form:
In the first arrangement form of each periodic part of the diffraction mechanism, each periodic part is arranged in a V shape or an inverted V shape with respect to the length direction of the waveguide core.

In the arrangement form in which the double periodic structure is V-shaped or inverted V-shaped, the waveguide mode oozes out from the waveguide core in the lateral direction, thereby gradually reducing the confinement of light in the waveguide core, and the radiation angle. For example, the distribution is narrowed to about ± 25 °.

In addition, this V-shaped periodic part pattern promotes radiation from an electromagnetic field having the same sign in the transverse distribution of the waveguide mode, thereby suppressing interference at a distance and forming a unimodal beam. Play.

(b) Second arrangement form:
The second arrangement form of each periodic part of the diffraction mechanism is an arrangement called a grating shift in which a linear arrangement of a part of the low refractive index part of the grating arrangement is displaced with respect to the length direction of the waveguide core. In the double periodic structure, in the linear arrangement of the low refractive index regions arranged in the length direction of the waveguide core, two linear arrangements at positions symmetrical to the waveguide core are different from the other linear arrangements. Thus, the waveguide cores are arranged so as to be displaced in the length direction. The V-shaped arrangement with lattice shift according to the second arrangement form has an effect of uniforming the deflection angle characteristics of the photonic crystal waveguide that is not lattice-shifted.

(c) Third arrangement:
The third arrangement form of each periodic part of the diffraction mechanism is a lattice arrangement, the grating arrangement in the vicinity of the waveguide core has a double periodic structure, and the first arrangement form for two kinds of periodic parts of the double periodic structure. Are arranged in a V-shape or inverted V-shape, and the other lattice arrangement is a periodic structure. In the lattice arrangement of the photonic crystal waveguide, in the length direction of the waveguide core Among the two types of lattice arrangements arranged along the low-refractive-index regions arranged along the periodic array, the multiple rows of lattice arrangements near the waveguide core have a double periodic structure, and the remaining lattice arrangements are the same. A periodic structure in which low-refractive-index portions having a size are periodically arranged is used.

By making a part of the lattice arrangement into the V shape of the first arrangement form, a double periodic structure can be provided only in the vicinity of the waveguide core where the waveguide modes are mainly concentrated. The effect is made simpler and unimodal.

(d) Fourth arrangement form:
The fourth arrangement form of each periodic part of the diffraction mechanism is arranged in a V shape or an inverted V shape similarly to the first arrangement form, and for two types of periodic parts of the double periodic structure of the lattice arrangement, The sizes of the low refractive index portions are arranged in gradation, and the low refractive index portions are arranged so that the size of the low refractive index portions increases or decreases in order along the arrangement direction of the low refractive index portions.

4th arrangement form is the form which combined V shape or reverse V shape and gradation arrangement. The combination of the V shape and the gradation arrangement has the effect of making the lateral distribution of the emitted light beam smoother by making the double periodic structure gradually uniform as the distance from the waveguide core increases. Play. On the other hand, the form in which the inverted V shape and the gradation arrangement are combined has an effect of effectively widening the width in which the waveguide mode is radiated and narrowing the lateral distribution.

(e) Fifth arrangement form:
The fifth arrangement form of each periodic part of the diffraction mechanism is an arrangement form in which two kinds of periodic parts of the double periodic structure intersect with the waveguide core at an acute angle or an obtuse angle. The periodic part on the side is arranged at an acute angle with respect to the length direction of the waveguide core, and the periodic part on the other side is arranged at an obtuse angle with respect to the length direction of the waveguide core.

In the photonic crystal, in the configuration in which the low refractive index portion provided in the high refractive index member is a circular hole, the lattice arrangement of the double periodic structure has a circular pattern of the photonic crystal having a large diameter hole and a small diameter circular hole. It is composed by repeating. With this double periodic structure composed of large and small circular holes, in addition to fewer processing steps, changing the amount of change in the size of the circular hole in the plane can change the amount of radiation without changing the radiation angle. Therefore, the longitudinal distribution of the radiated light beam is gradually changed to a Gaussian distribution in the waveguide propagation direction, so that a high-quality beam with little side loop in the longitudinal direction can be formed.

(Second form)
In the second embodiment of the optical deflection device, a photonic crystal waveguide having a periodic structure in which low-refractive index portions of one kind are repeated and a diffraction mechanism are arranged on the photonic crystal waveguide. A surface diffraction grating.

The photonic crystal waveguide includes a grating structure having a periodic structure in which low refractive index portions having the same size are periodically arranged along the length direction of the waveguide core in the plane of the high refractive index member. On the other hand, the diffraction mechanism is a surface diffraction grating arranged on a grating array of photonic crystal waveguides. The periodic parts included in the surface diffraction grating are concavo-convex arrays, and each periodic part is arranged at an acute angle or an obtuse angle with respect to the waveguide core.

The periodic part can be arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core depending on a plurality of forms.

(a) First arrangement form:
In the first arrangement form of each periodic part of the surface diffraction grating, each periodic part is arranged in a V shape or an inverted V shape with respect to the length direction of the waveguide core. Also in the first arrangement form of the periodic parts of the surface diffraction grating, the same effect as that of the form in which the V-shaped or inverted V-shaped periodic parts are arranged in the double periodic structure.

(b) Second arrangement form:
The second arrangement form of each periodic part of the surface diffraction grating is an arrangement form in which the periodic part of the periodic structure intersects the waveguide core at an acute angle or an obtuse angle, and the periodic part on one side with respect to the waveguide core. Are arranged at an acute angle with respect to the length direction of the waveguide core, and the periodic part on the other side is arranged at an obtuse angle with respect to the length direction of the waveguide core.

As described above, the optical deflection device of the present invention suppresses the lateral spread of the beam intensity distribution of the radiated light beam in the lateral distribution of the radiated light beam, and the beam intensity distribution of the radiated light beam is unimodal. It can be.

It is a figure for demonstrating schematic structure of the optical deflection | deviation device of this invention. It is a figure for demonstrating the 1st schematic structure of this invention. It is a figure for demonstrating the 1st schematic structure of this invention. It is a figure for demonstrating the breadth of the horizontal direction of a radiation light beam. It is a figure for demonstrating the breadth of the horizontal direction of a radiation light beam. It is a figure for demonstrating the structural example of the double periodic structure of the 1st form of this invention, and is the 1st arrangement | positioning form of each periodic region which comprises a diffraction mechanism. It is the 1st arrangement form of each periodic part which constitutes a diffraction mechanism. It is the 2nd arrangement form of each periodic part which constitutes a diffraction mechanism. It is the 3rd arrangement form of each periodic part which constitutes a diffraction mechanism. It is the 4th arrangement form of each periodic part which constitutes a diffraction mechanism. It is the 4th arrangement form of each periodic part which constitutes a diffraction mechanism. It is a figure for demonstrating the structural example of the double periodic structure of the 1st form of this invention, and is the 5th arrangement | positioning form of each periodic region which comprises a diffraction mechanism. It is the 5th arrangement form of each periodic part which constitutes a diffraction mechanism. It is a figure for demonstrating the structural example of the double periodic structure of the 2nd form of this invention. It is a figure for demonstrating the structural example of the double periodic structure of the 2nd form of this invention. It is a figure for demonstrating the structural example of the double periodic structure of the 2nd form of this invention, and is the 1st arrangement | positioning form which comprises a diffraction mechanism with a surface diffraction grating. It is the 1st arrangement form which constitutes a diffraction mechanism by a surface diffraction grating. It is the 1st arrangement form which constitutes a diffraction mechanism by a surface diffraction grating. It is the 2nd arrangement | positioning form which comprises a diffraction mechanism with a surface diffraction grating. It is the 2nd arrangement | positioning form which comprises a diffraction mechanism with a surface diffraction grating. It is a figure for demonstrating the device structure which introduce | transduced the diffraction mechanism into the photonic crystal waveguide which propagates the light (slow light) with a low group velocity, and is a device structure of the 1st optical deflection | deviation device. It is a device structure of the 1st optical deflection device. It is a device structure of the 2nd optical deflection device. It is a device structure of the 2nd optical deflection device. It is a figure for demonstrating the beam intensity distribution of a synchrotron radiation beam, and is a beam intensity distribution of the vertical direction. It is a figure for demonstrating the beam intensity distribution of a synchrotron radiation beam, and is a beam intensity distribution of a horizontal direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a schematic configuration example of the optical deflection device of the present invention will be described with reference to FIG. 1, and a first example of the optical deflection device of the present invention will be described with reference to FIGS. 2A to 2D, 3A to 3F, 4A, and 4B. The second embodiment of the present invention will be described with reference to FIGS. 5A, 5B, and 6A to 6E.

(Outline of optical deflection device)
FIG. 1 is a diagram for explaining an outline of an optical deflection device of the present invention.

The optical deflection device 1 includes a photonic crystal waveguide 2 in which low refractive index regions 11 are periodically arranged in a plane of a high refractive index member 10, and light propagating through a waveguide core 5 of the photonic crystal waveguide 2. And a diffraction mechanism 3 that emits a radiation beam to the outside.

The photonic crystal waveguide 2 and the diffraction mechanism 3 are provided on a clad 6 made of a semiconductor material such as Si.

Incident light incident on the waveguide core 5 is radiated from the waveguide core 5 to the outside by the diffraction mechanism 3 while propagating in the length direction in the waveguide core 5. The arrows in FIG. 1 schematically indicate incident light and emitted light beams.

The photonic crystal waveguide 2 is formed by a lattice arrangement in which low refractive index portions 11 are periodically arranged on a high refractive index member 10 made of a semiconductor such as Si. The low refractive index region 11 can be, for example, a circular hole provided in the high refractive index member 10.

In the photonic crystal waveguide 2, a waveguide core 5 for propagating light is formed by providing a portion where the low refractive index portion 11 is not provided in a part of the lattice arrangement. In the configuration in which the low refractive index portion 11 is a circular hole, the waveguide core 5 is formed by providing a part where the circular hole is not disposed in a part of the lattice arrangement.

The diffraction mechanism 3 is a mechanism that deflects the propagation light of the waveguide core 5 and emits a radiated light beam to the outside, and includes a plurality of periodic portions 4 arranged along the length direction of the waveguide core 5, Each periodic part 4 is arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core 5. As one form of disposing the periodic part 4, it is disposed in a V shape or an inverted V shape with respect to the length direction of the waveguide core 5.

The periodic part 4 included in the diffraction mechanism 3 is arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core 5 when the longitudinal direction of the waveguide core 5 is the longitudinal direction. The degree of lateral action on the wave mode is reduced, the light confinement of the waveguide core 5 is weakened and the waveguide mode is oozed out, thereby narrowing the radiation angle distribution in the transverse direction of the radiation light beam. The effect of narrowing the radiation angle distribution can be about ± 25 °, for example.

Further, in the configuration in which the periodic portion 4 is arranged in a V shape or an inverted V shape with respect to the length direction of the waveguide core 5, the V-shaped periodic portion has the same sign in the lateral distribution of the waveguide mode. The radiation from the electromagnetic field is promoted, the interference of the radiation light beam is suppressed at a distance far from the optical deflection device, and the formation of a plurality of peaks is suppressed to form a unimodal beam.

The diffraction mechanism 3 of the optical deflection device 1 of the present invention is a first form formed together with the lattice arrangement of the photonic crystal waveguide 2 or a photonic crystal waveguide as a separate component from the photonic crystal waveguide 2 It can be set as the 2nd form which overlaps and comprises.

In the first embodiment, the photonic crystal waveguide 2 has a double periodic structure in which two types of low refractive index portions having different sizes are periodically arranged, and the diffraction mechanism 3 has the double structure. The periodic part of each periodic structure constituting the periodic structure is arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core 5.

In the second embodiment, the photonic crystal waveguide 2 has a periodic structure in which one kind of low refractive index portion having the same size is periodically arranged, and the diffraction mechanism 3 is a surface diffraction grating. The photonic crystal waveguides 2 are arranged on the lattice arrangement of the photonic crystal waveguides 2.

In FIG. 1, the periodic part 4 of the diffraction mechanism 3 is schematically shown to represent both the first form and the second form.

(First form)
A first embodiment of the optical deflection device of the present invention will be described with reference to FIGS. 2A to 2D, FIGS. 3A to 3F, FIGS. 4A and 4B. FIG. 2 is a diagram for explaining the first schematic configuration and the lateral spread of the emitted light beam, and FIGS. 3A to 3F, 4A, and 4B show the configuration of the double periodic structure of the first embodiment. It is a figure for demonstrating an example.

In the first embodiment of the optical deflecting device, two types of low

refractive index portions

11a and 11b having different sizes are periodically arranged along the length direction of the waveguide core 5 in the plane of the high refractive index member 10. A lattice array 12 having a double periodic structure is formed. In the first form, the photonic crystal waveguide 2 and the diffraction mechanism 3 are formed on the same grating array 12.

The low

refractive index portions

11a and 11b can be formed by circular holes formed in the high refractive index member 10 and having different diameters. In the case of using a circular hole as a low-refractive index part in a lattice arrangement with a double periodic structure, in addition to the small number of processing steps, by changing the amount of change of the circular hole in the plane, the radiation angle The amount of radiation can be changed without changing. As a result, the longitudinal distribution of the radiated light beam is gradually changed to a Gaussian distribution in the propagation direction of the waveguide, and a high-quality beam with little side loop in the longitudinal direction can be formed.

In the double periodic structure, the conventionally proposed double periodic structure of the lattice array 12 is such that the

circular holes

111a and 111b of the triangular lattice pattern are periodically formed in the high refractive index material 110 such as Si as shown in FIG. 7B. An optical waveguide core 105 is formed by providing a region where the circular holes (111a, 111b) are not formed in the central portion. In this double periodic structure, circular holes (111a, 111b) having large and small diameters are arranged along the length direction of the waveguide core 5, which is the traveling direction of light propagating in the waveguide core 5. Thus, a double periodic structure is formed, and the light propagating through the waveguide core 5 is emitted out of the plane by the double periodic structure.

The angular distribution in the lateral direction of the radiation light beam formed by this double periodic structure has a wide angular distribution range of about ± 80 ° as shown in FIG. 2D, and the light intensity peak is split into three. . Such a wide angular distribution is attributed to the fact that the propagation light of the waveguide core 5 is radiated out of the plane from the state where it is strongly confined, and the three splits of the light intensity peak are in the transverse direction of the waveguide mode. The distribution oscillates in the positive and negative directions, and it is assumed that radiation from electromagnetic fields having different signs interfere with each other to form a belly and a node.

In contrast to this conventionally proposed double periodic structure, the double periodic structure 3A provided in the optical deflection device 1 according to the first embodiment of the present invention has a length of the waveguide core 5 in the plane of the high refractive index member 10. Two types of periodic parts in which low refractive index parts of the same size are periodically arranged in the grating array 12 formed by periodically arranging two kinds of low

refractive index parts

11a and 11b along the direction. 4Aa, 4Ab.

The configuration shown in FIG. 2B shows an example in which two types of low refractive index portions of the lattice arrangement are configured by a large diameter circular hole 11a and a small diameter circular hole 11b. Here, the arrangement in which the large-diameter circular holes 11a extend in the horizontal oblique direction from the waveguide core 5 constitutes the periodic part 4Aa, and the arrangement in which the small-diameter circular holes 11b extend in the horizontal oblique direction from the waveguide core 5 is the periodic part 4Ab. Configure.

In the double periodic structure of the present invention, the two types of periodic portions 4Aa and 4Ab are alternately arranged along the length direction of the waveguide core 5 (the traveling direction of the light propagating through the waveguide core 5). It is arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core 5. In this arrangement, when the periodic parts 4Aa and 4Ab are acute with respect to the traveling direction of the light propagating through the waveguide core 5, the arrangement of the periodic parts 4Aa and 4Ab is V-shaped or inverted V-shaped. .

The lattice arrangement of the first form constitutes the photonic crystal waveguide 2 and the diffraction mechanism 3.

FIG. 2C shows the angular distribution in the lateral direction of the emitted light beam by the lattice arrangement having a V-shaped periodic portion in the double periodic structure of the present invention.

Since the V-shaped periodic part causes the waveguide mode to ooze out from the waveguide core in the lateral direction to moderately weaken light confinement, the radiation angle distribution is narrowed to about ± 25 °. Further, the V-shaped periodic part promotes radiation from the electromagnetic field having the same sign in the transverse distribution of the waveguide mode, so that interference at a distant place is suppressed and a unimodal beam is formed. The

In FIG. 2C, the wavelength is 1.55 μm, the lattice constant of the photonic crystal is 400 nm, the diameter 2r1 of the large-diameter hole 11a is 215 nm, the diameter of the small-diameter hole 11b is 2r2 is 295 nm, The refractive index of the refractive index member 10 is 3.5, the thickness is 210 nm, and the refractive index of the upper cladding and the lower cladding 6 is 1.45.

In the first embodiment, the periodic portions 4Aa and 4Ab are alternately arranged along the length direction of the waveguide core according to a plurality of arrangement forms, and arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core. Can do. Hereinafter, the arrangement of the periodic parts will be described with reference to FIGS. 3A to 3F, FIG. 4A, and FIG. 4B.

(a) First arrangement form:
In the first arrangement form, each periodic portion 4A (4Aa, 4Ab) is arranged in a V shape or an inverted V shape with respect to the length direction of the waveguide core 5. 3A and 3B show a first arrangement form of each periodic portion constituting the diffraction mechanism, FIG. 3A shows a V-shaped arrangement, and FIG. 3B shows an inverted V-shaped arrangement.

In the arrangement form in which the double periodic structure is V-shaped or inverted V-shaped, the waveguide mode oozes out from the waveguide core 5 in the lateral direction, thereby gradually reducing light confinement in the waveguide core 5. For example, the radiation angle distribution is narrowed to about ± 25 °.

(b) Second arrangement form:
FIG. 3C shows a second arrangement form of each periodic part constituting the diffraction mechanism. In the second arrangement form of each periodic part of the diffraction mechanism 3, the linear array 13 of the low

refractive index parts

11 a and 11 b of the periodic parts 4 Aa and 4 Ab in the grating array 12 is arranged in the length direction of the waveguide core 5. The arrangement is shifted from the arrangement, which is an arrangement form called a lattice shift.

In the double periodic structure, in the linear array 13 of the low

refractive index portions

11a and 11b arranged in the length direction of the waveguide core 5, two

linear arrays

13A and 13B that are symmetrical with respect to the waveguide core 5 are: The waveguide core 5 is arranged so as to be displaced in the length direction with respect to the other linear arrangement. This second arrangement form uniformizes the deflection angle characteristics of the photonic crystal waveguide 2 that is not misaligned.

(c) Third arrangement:
FIG. 3D shows a third arrangement form of each periodic part constituting the diffraction mechanism. The third arrangement form of the periodic parts constituting the diffraction mechanism 3 is that in the grating array 12, the

grating arrays

14A and 14B in the vicinity of the waveguide core 5 have a double periodic structure, and two kinds of periods of the double periodic structure are used. The parts 4Aa and 4Ab are arranged in a V shape or an inverted V shape similarly to the first arrangement form, and the

other lattice arrangements

15A and 15B have the same periodic structure.

In the lattice arrangement of the photonic crystal waveguide, the waveguide is one of the lattice arrangements 12 in which two types of low

refractive index portions

11a and 11b having different sizes arranged along the length direction of the waveguide core are periodically arranged. A plurality of

lattice arrays

14A and 14B in the vicinity of the core have a double periodic structure, and the remaining

lattice arrays

15A and 15B have a periodic structure in which low refractive index portions 11 of the same size are periodically arrayed.

By making a part of the lattice arrangement 12 into the V shape of the first arrangement form, it is possible to adopt a configuration in which a double periodic structure is provided only in the vicinity of the waveguide core where the waveguide modes are mainly concentrated. This has the effect of simplifying the pattern.

(d) Fourth arrangement form:
3E and 3F show a fourth arrangement form of each periodic part constituting the diffraction mechanism. The fourth arrangement form of each periodic part of the diffraction mechanism is arranged in a V shape or an inverted V shape similarly to the first arrangement form, and two kinds of periods of the double periodic structure of the grating array 12 are arranged. For the portion, the size of the low refractive index portion is arranged in gradation. In FIG. 3E, the low refractive index portions 11b are arranged so that the size of the low refractive index portions 11b sequentially increases along the arrangement direction of the low refractive index portions.
In FIG. 3F, the low refractive index portions 11a are arranged so that the size of the low refractive index portions 11a sequentially increases along the arrangement direction of the low refractive index portions.

4th arrangement form is the form which combined V shape or reverse V shape and gradation arrangement. FIG. 3E shows a combination of a V shape and a gradation array. In this arrangement, the structure in which the double periodic structure is gradually uniformed as the distance from the waveguide core is increased, so that the lateral distribution of the emitted light beam is more smoothly smoothed. On the other hand, FIG. 3F shows a combination of an inverted V shape and a gradation array. In this arrangement form, the width in which the guided mode is radiated is effectively widened, and the lateral distribution is further narrowed.

(e) Fifth arrangement form:
4A and 4B show a fifth arrangement form of each periodic part constituting the diffraction mechanism. The fifth arrangement form of each periodic part of the diffraction mechanism is an arrangement form in which two kinds of periodic parts of the double periodic structure intersect the waveguide core at an acute angle or an obtuse angle. 4A, with the waveguide core 5 as the center, the periodic part 16A on one side is arranged at an acute angle with respect to the length direction of the waveguide core 5, and the periodic part 16B on the other side is disposed on the waveguide core 5. It is arranged at an obtuse angle with respect to the length direction. The arrangement shown in FIG. 4B shows a configuration in which the arrangement shown in FIG. 4A is symmetric with respect to the waveguide core 5.

(Second form)
A second embodiment of the optical deflection device of the present invention will be described with reference to FIGS. 5A, 5B, and 6A to 6E. 5A and 5B are diagrams for explaining the second schematic configuration, and FIGS. 6A to 6E are diagrams for explaining a configuration example of the surface diffraction grating of the second embodiment.

The second embodiment of the optical deflection device is a photonic crystal waveguide 2 having a grating structure 12 having a periodic structure in which low-refractive index portions 11 having one size are repeated, and the photonic crystal waveguide as a diffraction mechanism 3. 2 is provided with a surface diffraction grating 3B.

The photonic crystal waveguide 2 includes a grating structure 12 having a periodic structure in which low refractive index portions 11 having the same size are periodically arranged along the length direction of the waveguide core 5 in the plane of the high refractive index member 10. . The diffraction mechanism 3 is configured by disposing a surface diffraction grating 3 </ b> B on the grating array 12 of the photonic crystal waveguide 2. The periodic part 4B (convex part 4Ba, concave part 4Bb) provided in the surface diffraction grating 3B is an uneven arrangement, and each periodic part 4B (4Ba, 4Bb) is arranged at an acute angle or an obtuse angle with respect to the waveguide core 5. In FIG. 5A, the convex portion 4Ba of the surface diffraction grating 3B and the 4Bb concave portion of the surface diffraction grating 3B are used as the periodic portion 4B. In FIG. 5B, the periodic portion of the convex portion 4Ba of the surface diffraction grating 3B is a dark ground pattern. The periodic part of the concave portion 4Bb of the surface diffraction grating 3B is indicated by a thin ground pattern.

The form in which the periodic parts (projections 4Ba, recesses 4Bb) of the surface diffraction grating 3B are arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core 5 can be a plurality of forms.

(a) First arrangement form:
The first arrangement form of the periodic parts (convex part 4Ba, concave part 4Bb) of the surface diffraction grating 3B is a V-shaped or convex part 4Ba and concave part 4Bb of each periodic part 4B with respect to the length direction of the waveguide core 5. Arranged in an inverted V-shape. Even in the first arrangement form of the periodic parts by the surface diffraction grating, the same effect as that of the form in which the periodic parts are arranged in a V-shaped or inverted V-shaped shape in the double periodic structure is obtained.

FIG. 6A, FIG. 6B, and FIG. 6C show a first arrangement form in which a diffraction mechanism is constituted by a surface diffraction grating. FIG. 6A shows a V-shaped configuration in which the angle of the convex portions 4Ba and the concave portions 4Bb, which are each periodic part of the surface diffraction grating 3B, is 60 ° in a triangular arrangement of circular holes. In the grating arrangement in which the holes are arranged in a triangular pattern, an inverted V-shaped configuration is shown in which the angles of the convex portions 4Ba and the concave portions 4Bb that are each periodic portion of the surface diffraction grating 3B are 120 °.

FIG. 6C shows a V-shaped configuration in which the angle of the convex portions 4Ba and the concave portions 4Bb, which are each periodic portion of the surface diffraction grating 3B, is 30 ° in a lattice arrangement in which circular holes are arranged in a triangle.

FIG. 6D and FIG. 6E show a second arrangement form in which the diffraction mechanism is constituted by the surface diffraction grating. FIG. 6D shows a convex arrangement on one side with respect to the waveguide core 5 by inclining the convex portions 4Ba and the concave portions 4Bb, which are each periodic portion of the surface diffraction grating 3B, in one direction in a triangular arrangement of circular holes. The portion 4Ba and the concave portion 4Bb are arranged at 60 ° with respect to the length direction of the waveguide core 5, and the convex portion 4Ba and the concave portion 4Bb on the other side are arranged at 120 ° with respect to the length direction of the waveguide core 5. .

A normal surface diffraction grating has a simple linear diffraction grating having a period twice that of a photonic crystal. On the other hand, according to the second embodiment using the surface diffraction grating, the configuration using this diffraction grating has a wide lateral angle distribution as in the conventional double periodic structure shown in FIG. 2D. The light intensity peak is a radiation light beam divided into a plurality. On the other hand, the diffraction grating of the surface diffraction grating is arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core, similarly to the first embodiment of the optical deflection device having the double periodic structure of the present invention. As a result, a unidirectional radiation light beam with a narrow divergence angle can be obtained.

The present invention is not limited to the above embodiments. Various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

The optical deflection device and the lidar apparatus (laser radar) of the present invention can be mounted on automobiles, drones, robots, etc., and can be mounted on a personal computer or a smartphone to easily capture the surrounding environment, a monitoring system, optical exchange, It can be applied to a space matrix optical switch for a data center.

In the above-described embodiments, Si is used as the high refractive index member constituting the photonic crystal waveguide of the optical deflection device, and light in the near infrared wavelength range is used. By applying it to a visible light material as a refractive index member, further application to a projector, a laser display, a retina display, a 2D / 3D printer, a POS, a card reading, and the like is expected.

This application claims priority based on Japanese Patent Application No. 2017-033640 filed on Feb. 24, 2017, the entire disclosure of which is incorporated herein.

DESCRIPTION OF SYMBOLS 1 Optical deflection device 2 Photonic crystal waveguide 3 Diffraction mechanism 3A Double periodic structure 3B Surface diffraction grating 4A, 4B, 4Aa, 4Ab Periodic part 4Ba Convex part 4Bb Concave part 5 Waveguide core 6 Cladding 10 High refractive index member 11 Low refraction Index part 11a Low refractive index part (circular hole)
11b Low refractive index region (circular hole)
12 grating

array

13, 13A, 13B

linear array

14A,

14B grating array

15A,

15B grating array

16A, 16B periodic part 101 high

refractive index member

101A, 101B optical deflection device 102 photonic crystal waveguide 103 surface diffraction grating 105 waveguide core 106 Cladding 110 High refractive index material 111 Low refractive index region (circular hole)
111a, 111b, 111c circular holes 112 lattice arrangement

Claims

A photonic crystal waveguide in which low refractive index sites are periodically arranged in a plane of a high refractive index member;
A diffraction mechanism for deflecting the propagation light of the waveguide core of the photonic crystal waveguide and radiating a radiation beam to the outside,
The diffraction mechanism includes a plurality of periodic portions arranged along the length direction of the waveguide core, and each periodic portion is arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core. Deflection device.
The photonic crystal waveguide and the diffraction mechanism have a double periodic structure in which two different types of low refractive index portions are periodically arranged along the length direction of the waveguide core in the plane of the high refractive index member. With a grid array of
The diffraction mechanism includes two types of periodic parts in which the low refractive index parts of the same size are periodically arranged in the lattice arrangement of the double periodic structure,
2. The optical deflection according to claim 1, wherein the two types of periodic portions are alternately arranged along a length direction of the waveguide core, and are arranged at an acute angle or an obtuse angle with respect to the length direction of the waveguide core. device.
3. The optical deflection device according to claim 2, wherein the arrangement of each periodic part of the diffraction mechanism is V-shaped or inverted V-shaped with respect to the length direction of the waveguide core.
In the lattice arrangement of the photonic crystal waveguide,
Of the two types of lattice arrays arranged along the length direction of the waveguide core, the low-refractive-index portions of different sizes are periodically arrayed. 4. The optical deflection device according to claim 3, wherein the optical deflection device has a periodic structure, and the remaining grating array is a periodic structure in which low refractive index portions having the same size are periodically arrayed.
In each periodic part of the diffraction mechanism,
Centering on the waveguide core, the periodic part on one side is arranged at an acute angle with respect to the length direction of the waveguide core, and the periodic part on the other side is arranged with respect to the length direction of the waveguide core. The optical deflection device according to claim 2, which is arranged at an obtuse angle.
In the double periodic structure, in the linear arrangement of the low refractive index regions arranged in the length direction of the waveguide core, two linear arrangements that are symmetrical with respect to the waveguide core are different from the other linear arrangement. The optical deflection device according to any one of claims 2 to 4, wherein the optical deflection device is an array shifted in a length direction of the waveguide core.
5. The each periodic part according to claim 2, wherein the size of the low refractive index part increases or decreases in order along the arrangement direction of the low refractive index part in each periodic part. Optical deflection device.
The photonic crystal waveguide includes a grating structure having a periodic structure in which low refractive index portions having the same size are periodically arranged in the length direction of the waveguide core in the plane of the high refractive index member,
The diffraction mechanism is
A surface diffraction grating disposed on a grating array of the photonic crystal waveguide;
2. The optical deflection device according to claim 1, wherein the periodic parts included in the surface diffraction grating are concave and convex arrays, and each periodic part is disposed at an acute angle or an obtuse angle with respect to the waveguide core.
The optical deflection device according to claim 8, wherein the arrangement of each periodic part of the diffraction mechanism is V-shaped or inverted V-shaped with respect to the length direction of the waveguide core.
Each periodic part of the diffraction mechanism is arranged at an acute angle with respect to the length direction of the waveguide core, with the periodic part on one side centered on the waveguide core, and the periodic part on the other side The optical deflection device according to claim 8, wherein the optical deflection device is arranged at an obtuse angle with respect to the length direction of the waveguide core.