WO2018110284A1 - Light deflection device and lidar apparatus - Google Patents

Abstract

A light deflection device and a LIDAR apparatus, configured from one constituent element, adjustment of the intensity distribution (amplitude distribution) being possible due to the simple formation of the configuration. The light deflection device is provided with a double periodic structure in which two types of circular holes having different diameters are repeated along a waveguide within the plane of a photonic crystal. Due to the double periodic structure in which the two types of circular holes having different diameters are repeated, slow-light propagation light is converted into a radiation condition and radiated into a space. The double periodic structure has a configuration in which the diameter of the circular holes is increased and decreased in alternating fashion so as to complement each other along the waveguide, and due to this configuration, the intensity distribution (amplitude distribution) of the radiation beam is adjusted. The amount of increase in area of the circular holes provided to one of the periodic structures of the double periodic structure is made equal to the amount of decrease in area of the circular holes provided to the other periodic structure, and changes in the photonic band are suppressed.

Description

Optical deflection device and rider apparatus

The present invention relates to an optical deflection device that controls the traveling direction of light, and a rider apparatus that includes the optical deflection device.

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 addition, the scanned light beam requires controllability of intensity distribution (amplitude distribution) in addition to the sharpness described above.

For example, Patent Documents 1 to 5 have been proposed as optical deflection devices having controllability of the beam intensity of a radiation beam.

Patent Document 1 discloses a configuration in which the height, width, or depth of an element constituting a grating is monotonously changed in the waveguide direction of guided light, and Patent Document 2 describes a grating thickness with respect to the light propagation direction. Is disclosed as a Gaussian distribution, and Patent Document 3 discloses a structure in which the grating height of the diffraction grating is gradually increased substantially linearly. Patent Document 4 describes the depth of the grating or the thickness of the gap layer. A configuration for changing the width of the groove formed in the surface layer of the grating with respect to the longitudinal direction of the waveguide is shown in Patent Document 5.

JP 62-296102 A JP-A-4-195003 JP-A-6-94939 Japanese Patent Laid-Open No. 7-169088 JP2015-161829 Japanese Patent Application No. 2016-10844 (Fig. 10)

The above-described conventionally known optical deflection device has a configuration in which two components, a waveguide portion and a light emission mechanism such as a grating, are combined, and is configured from a single component in terms of manufacturability, size, cost, and the like. There is a need for an optical deflection device.

Further, the above-described prior art uses a grating (diffraction grating) as an optical deflection device, and adjusts the intensity distribution (amplitude distribution) according to the shape such as the height, width, or depth of the grating. Since the surface shape of these gratings requires fine processing, there are problems such as processing accuracy and variation in shape. Therefore, there is a demand for an optical deflection device that can control intensity distribution (amplitude distribution) with a configuration that can be easily formed.

An object of the optical deflection device and the rider apparatus of the present invention is to solve the above-described problems and to be configured by a single component. It is another object of the present invention to make it possible to adjust the intensity distribution (amplitude distribution) with a configuration that can be easily formed.

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 6). 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 optical deflection device according to the present invention is based on a device having a double periodic structure in which circular holes of two different diameters are repeated along a waveguide in the plane of a photonic crystal.

Slow light propagating light is non-radiated in a periodic structure in which one kind of diameter hole is repeated along the waveguide in the plane of the photonic crystal, but a double period in which two kinds of holes having different diameters are repeated. By adopting a structure, the slow light propagating light is converted into radiation conditions and emitted into space. Since the double periodic structure has a structure in which two types of circular holes having different diameters are repeatedly provided in the surface of the photonic crystal, it can be configured by one component (Patent Document 6).

Such a double periodic structure includes a periodic structure in which a large-diameter circular hole is repeated and a periodic structure in which a small-diameter circular hole is repeated. The diameter of the reference circular hole is 2r, and the difference width of the diameter is 2Δr. The diameter of the large-diameter circular hole is 2 (r + Δr), and the diameter of the small-diameter circular hole is 2 (r−Δr). Here, the large diameter and the small diameter indicate a large or small relationship with respect to the diameter of the reference circular hole or in the comparison of the diameters of each other. The inventors have found that when Δr is changed in such a configuration, the emissivity changes greatly, but other properties such as a radiation angle and a propagation constant in the propagation direction do not change so much.

(Optical deflection device configuration)
The form of the optical deflection device of the present invention is as follows:
(A) As a waveguide, a photonic waveguide made of a photonic crystal is used instead of a conventional glass material or a bulk material of a semiconductor material.
(B) As a diffraction mechanism, a photonic crystal configuration is used instead of the conventionally proposed grating.
(C) As a diffraction mechanism by a photonic crystal, a structure of a plurality of circular holes formed in the plane of the photonic crystal is provided, and a plurality of circular holes whose diameters change along the waveguide in the plane of the photonic crystal. It has a periodic structure.

The plurality of circular holes provided in the optical deflection device of the present invention not only form a waveguide in the plane of the photonic crystal, but also radiate by a periodic structure in which the diameters of the plurality of circular holes change along the waveguide. The beam intensity distribution (amplitude distribution) is adjusted.

According to the optical deflection device of the present invention, since the circular hole in the surface of the photonic crystal can be easily adjusted in diameter and position by the semiconductor film forming technique, the optical deflection device has an intensity distribution (amplitude distribution). ) Can be obtained with an easy configuration.

(Double-period structure of circular holes)
The periodic structure of a plurality of circular holes in which the waveguide of the optical deflection device according to the present invention also has a photonic crystal formed in the plane has a double structure in which the diameters of the circular holes increase or decrease in a complementary manner along the waveguide. It is a periodic structure.

The double periodic structure includes a first periodic structure in which the diameter of the circular hole increases and a second periodic structure in which the diameter of the circular hole decreases. When the diameter of the reference circular hole is 2r, and the increase / decrease width of the diameter to be complementarily increased / decreased is 2Δr ₁ , 2Δr ₂ ,
(D) The diameter 2r _{1 of the} circular hole provided in the first periodic structure is 2 (r + Δr ₁ ).
(E) The diameter 2r _{2 of the} circular hole provided in the second periodic structure is 2 (r−Δr ₂ ).
The diameter 2r ₁ of circular hole first periodic structure comprises a respective diameters of 2r ₂ of the second periodic structure comprises a circular hole, said the diameter 2r of the reference circular hole (d), (e) With this relationship, the diameter of the circular hole can be a double periodic structure that increases or decreases complementarily along the waveguide. Here, the reference circular hole can be arbitrarily set from a plurality of circular holes provided in the periodic structure.

(Increase / decrease width of diameter Δr ₁ , Δr ₂ )
The increase / decrease widths Δr ₁ and Δr ₂ of the diameter can be set in a plurality of setting forms.

[First setting form]
In the first setting mode, the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ are the same increase / decrease width Δr. According to this setting mode, the diameter 2r ₁ of the circular hole of the first periodic structure increases by 2 (r + Δr), and the diameter 2r ₂ of the circular hole of the second periodic structure decreases by 2 (r−Δr). .

[Second setting form]
In the second setting mode, the amount of increase in the area of the circular hole provided in the first periodic structure is equal to the amount of decrease in the area of the circular hole provided in the second periodic structure.

The form which makes the area of the increasing / decreasing circular hole the same amount can be configured by the following relationship between the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ .
The relationship between the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ can be expressed in the following two modes.

1st aspect which makes the increase / decrease area the same amount:
The increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ are relative to the reference diameter r.
(R + Δr ₁ ) ² −r ² = r ² − (r−Δr ₂ ) ²
With the relationship.

Second aspect with the same amount of increase / decrease area:
The ratio k (= Δr ₁ / Δr ₂ ) between the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ is determined with respect to the reference diameter r.
k ² + (2r / Δr ₂ ) · k = (2r / Δr ₂ ) −1
Or (1 + 2r / Δr ₁ ) k ² − (2r / Δr ₁ ) · k = −1
With the relationship.

(Radiation coefficient and light radiation distribution of light deflection device)
The light radiation distribution with respect to the propagation direction of the radiation emitted from the waveguide out of plane depends on the intensity of the propagation light in the waveguide of the optical deflection device and the radiation coefficient of the optical deflection device. In the optical deflection device of the present invention, the radiation coefficient can be set according to the increase / decrease state of the diameter of the circular hole of the periodic structure constituting the diffraction mechanism, and further, the light radiation distribution can be set.

In the optical deflection device of the present invention, the propagation light intensity distribution P with respect to the propagation direction of the propagation light in the waveguide, the radiation coefficient B with respect to the propagation direction of the radiation emitted from the waveguide out of plane, the light intensity emitted from the waveguide The light radiation distribution X is expressed by the product (B × P) of the propagation light intensity distribution P and the radiation coefficient B.

From this relationship, the radiation coefficient B of the light deflection device is represented by B = X / P obtained by dividing the light radiation distribution X by the propagation light intensity distribution P. In the optical deflection device, since the propagation light intensity distribution along the light propagation direction is determined by the characteristics of the waveguide, the light radiation distribution X can be set by the radiation coefficient B of the light deflection device. Therefore, the desired light radiation distribution X can be obtained by optimally setting the radiation coefficient B.

Here, by using the relationship between the radiation coefficient B and the increase / decrease width Δr of the diameter that changes along the waveguide, the increase / decrease width Δr of the circular hole that gives the optimum radiation coefficient B is determined. Therefore, a desired light radiation distribution X can be obtained by setting Δr optimally.

The light radiation distribution X can be an arbitrary distribution shape. For example, when the light radiation distribution X is a Gaussian distribution, the radiation beam distribution Y with respect to the variation Δθ of the radiation angle θ of the radiation light is also a Gaussian distribution, and unnecessary side lobes can be removed.

In the present invention, according to the form of the radiation coefficient set corresponding to the light radiation distribution X, the radiation coefficient B is optimized to reduce the side lobes and tails and form a higher quality light beam. The spatial resolution of a lidar apparatus (LiDAR) using an optical deflection device can be increased. Further, by adjusting the radiation coefficient, a design that minimizes the total loss when the light is restored according to the loss of the slow light waveguide can be realized.

The optical deflecting device according to the present invention has a feature in that the radiation coefficient can be optimized by using a photonic crystal, and the optimization of the radiation coefficient is based on a conventionally used grating (diffraction grating). Such a diffraction mechanism is difficult. In general, the amount of radiation of the grating varies depending on the depth (height) of the grating. Therefore, in order to change the amount of radiation in the plane, it is necessary to change the depth (height) of the grating depending on the location. In this way, processing to adjust the depth (height) of the grating according to the location is not possible. It requires a complicated process and it is difficult to obtain high processing accuracy. Further, since the diffraction condition of light changes when the grating grating depth (height) is changed, when the distribution is given to the depth depending on the location, the radiation angle also has a distribution. As a result, the beam formed by the emitted light also has an excessive spread. That is, when a grating is used as a diffraction mechanism, the radiation coefficient cannot be optimized while keeping the radiation angle uniform.

On the other hand, according to the configuration of the optical deflection device of the present invention, optimization of the radiation coefficient and fixation of the radiation angle can be achieved at the same time by simply changing the in-plane design such as adjusting the diameter of the circular hole. . In addition, the optimization of the radiation coefficient can be realized by an easy process of increasing or decreasing the diameter of the in-plane circular hole along the optical transport path, and has the advantage that high performance can be realized. Yes.

(Rider equipment)
The lidar apparatus of the present invention includes the optical deflection device of the present invention, a laser light source that emits a plurality of laser beams having different wavelengths, and a light detection unit that individually detects the laser beams. The optical deflection device arrives from the outside, which emits a plurality of wavelengths of laser light emitted from a laser light source in parallel in the direction of each deflection angle determined by the wavelength of each laser light and the refractive index of the beam deflector. Of the laser beams having a plurality of wavelengths, an injector that selectively and simultaneously enters laser beams having an incident angle equal to the deflection angle is configured by the same element. The light detector individually detects laser light of each wavelength incident at an incident angle having the same deflection angle as that of the laser light emitted from the emitter at the injector. By making the deflection angle of the emitter coincide with the deflection angle of the injector, the reflected light emitted from the emitter and reflected by the object is detected. The rider apparatus of the present invention can make the light radiation distribution of the laser light irradiated to the irradiation object a desired distribution shape by using the light deflection device of the present invention.

As described above, the optical deflection device and the rider apparatus of the present invention can realize parallel operation with a simple configuration, and can avoid an increase in size or complexity of the system.

It is a figure for demonstrating the formation of the radiation light beam by a leaky waveguide, and the periodic structure which generates a slow light. It is a figure which shows the characteristic of distribution of loss, propagation light intensity distribution, light radiation distribution, and a radiation beam. It is a figure for demonstrating the structure of the optical deflection | deviation device of this invention. It is a figure which shows a photonic band, group refractive index _ng spectrum, radiation angle (theta) with respect to wavelength (lambda), and radiation coefficient _BdB with respect to wavelength (lambda). It is a figure for demonstrating the structure of the optical deflection | deviation device of this invention. It is a figure for demonstrating increase / decrease in the diameter of the circular hole of a 1st periodic structure and a 2nd periodic structure. FIG. 5 is a diagram for explaining the relationship among a propagation light intensity distribution P (y), a radiation coefficient B (y), a light radiation distribution X (y), and a radiation light beam distribution Y (Δθ) in an optical deflection device. It is a figure which shows propagation light intensity distribution P (y), radiation coefficient B (y), light radiation distribution X (y), and radiation light beam distribution Y ((DELTA) (theta)). It is a figure which shows the example of the optical deflection | deviation device in case a radiated light beam is used as a Gaussian beam. It is a figure for demonstrating the form of a structure of a rider apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the light deflection device using the slow light structure, the light emission mechanism using the leakage waveguide will be described with reference to FIG. 1, the configuration of the light deflection device of the present invention will be described with reference to FIGS. 10 is used to explain the configuration of the rider apparatus of the present invention.

(Radiated light beam by leaky waveguide)
FIG. 1 is a diagram for explaining the formation of a radiated light beam by a leaky waveguide and a periodic structure for generating slow light. FIG. 1A shows an outline in which light is emitted from a leaky waveguide, and FIG. 1B shows an example in which a grating (circuit grating) is used as a diffraction mechanism.

In FIG. 1A, incident light incident on the leaky waveguide 10 is radiated as a radiation beam from the leaky waveguide 10 at a deflection angle θ. At this time, the deflection angle θ of the radiation beam changes depending on the wavelength λ of the incident light and the refractive index n of the leakage waveguide.

FIG. 1B shows a configuration example in which a light guide device having a slow light structure and a light emission mechanism are separate mechanisms in an optical deflection device using a leaky waveguide.

The waveguide unit 11 of the optical deflection device 1 is a slow light waveguide configured by arranging a second refractive index medium with a period a between an upper clad 11b and a lower clad 11c of the first refractive index medium. 11a. The slow light waveguide 11a forms a periodic structure (periodic structure of the waveguide) by periodically arranging the second refractive index medium with a period a with respect to the cladding having the refractive index of the first refractive index medium. As the first refractive index medium, a medium having a higher refractive index than that of the second refractive index medium can be selected. When light is incident on a periodic structure formed by deep etching of a material having a large refractive index into the periodic structure, light having a small group velocity (slow light) is generated. The slow light waveguide 11a propagates incident light incident from one end in a slow light mode with a low group velocity.

The emission part 12 of the optical deflection device 1 includes a light emission mechanism 12a such as a surface diffraction grating at a position adjacent to the upper clad 11b. The light emitting mechanism 12a has, for example, an uneven shape with a period Λ. The concavo-convex shape having the period Λ constitutes a periodic structure having a period Λ (periodic structure of the light emitting mechanism) between the refractive index n of the refractive index medium and the refractive index n _out of the external medium such as air.

In the slow light of the slow light waveguide 11a having the periodic structure of the waveguide, the propagation constant β greatly changes due to a slight change in the propagation state such as the wavelength λ of light and the refractive index n of the waveguide. Such light propagates while having an electromagnetic field spread (a oozing component) around it. When the emitting portion 12 having a periodic structure (periodic structure of a light emitting mechanism) having a small step formed by a material having a small refractive index, shallow etching, or the like is disposed at a distance slightly touching the oozing component, The slow light is combined with this to be scattered and diffracted and gradually emitted upward and obliquely. Radiation occurs in a wide range along the traveling direction of the waveguide and is in phase. Therefore, when the optical deflection device is viewed from the lateral direction along the propagation direction, the outgoing beam becomes a high-quality sharp light beam.

When the light wavelength λ or the refractive index n of the refractive index medium constituting the periodic structure of the waveguide is changed, the propagation constant β of the waveguide section 11 is changed, and the coupling condition with the periodic structure of the light emitting mechanism of the emitting section 12 is changed. change. As a result, the outgoing angle θ of the outgoing beam changes.

(Slow light structure with photonic crystal)
An example of a two-dimensional photonic crystal in the slow light waveguide will be described with reference to FIG.

In the two-dimensional photonic crystal waveguide 11d of FIG. 1C, the same circular holes are two-dimensionally arranged in a semiconductor slab of the same thickness (such as Si) in a two-dimensional periodic manner, for example, in a single row of the array. It is the structure which removed the circular hole. In the structure of the two-dimensional photonic crystal waveguide 11d, a photonic band gap is generated in the vicinity of the Bragg wavelength, the group refractive index _ng is increased, and slow light is generated.

In an optical deflection device using a leaky waveguide, in a configuration in which a slow light structure waveguide and a light emission mechanism are separate mechanisms, a surface diffraction grating having a periodic structure is provided on the surface of the two-dimensional photonic crystal waveguide 11d. Form the light emission mechanism. By adjusting the thickness of the clad between the two-dimensional photonic crystal waveguide and the surface diffraction grating, the degree of coupling between the two is changed, and light emission at an appropriate speed is obtained.

(Radiation coefficient of light deflection device, light radiation distribution, radiation beam distribution)
The optical deflection device described above comprises a waveguide and a light emission mechanism as separate components, whereas the optical deflection device of the present invention has a waveguide and a light emission mechanism due to the periodic structure of the circular holes. This is a configuration with one mechanism. Hereinafter, the outline of the radiation coefficient, light radiation distribution, and radiation beam distribution of the optical deflection device in the periodic structure of the circular holes will be described.

In the waveguide having the slow light structure described above, the slow light gradually leaks to form a radiation light beam. At this time, if the structure of the waveguide is uniform with respect to the direction in which light propagates, the radiation coefficient is constant. Therefore, the stronger the slow light, the greater the radiation intensity. Slow light initially has a strong intensity, and the intensity of the slow light becomes exponentially weak as it propagates over a long distance due to the influence of radiation and the loss of the waveguide itself. For this reason, the radiated light beam has a biased intensity distribution that is strong on the near side of the same wavefront and weakens in the depth direction. When such a radiation light beam reaches a distant object, the near-field intensity distribution becomes a distribution obtained by Fourier transform. Since the Fourier transform of the exponential function distribution is a sinc function, the distribution has many side lobes that attenuate while oscillating from the intensity peak. This degrades the quality of the synchrotron radiation beam and thus reduces the spatial resolution of the lidar device (LiDAR).

The intensity distribution of the above-described radiation light beam will be described. The unnecessary loss coefficient of the waveguide is A [cm ⁻¹ ], the light emission coefficient by the light emission mechanism is B [cm ⁻¹ ], and the propagation light intensity distribution in the waveguide with respect to the light travel distance y is P (y). Then, the following differential equation holds.
dP (y) / dy =-(A + B) P (y) (1)

When this equation (1) is solved, the propagation light intensity distribution P (y) and the light emission distribution X (y) are expressed by the following equations (2) and (3), respectively.
P (y) = P ₀ e- ^{(A + B) y} (2)
X (y) = B · P (y) (3)

Here, assuming that the propagation constant of the waveguide is β, the in-plane wavenumber _k∥ converted into the optical diffraction mechanism having the period Λ is expressed by the following equation (4).
k _∥ = β− (2π / Λ) N (4)
Here, N is a natural number. In high-order diffraction where Λ also has a large value N, a plurality of radiation beams are generated. Therefore, normally, first-order diffraction with N = 1 is used.

The wave number _k∥ is stored at the boundary between the device surface and free space to form a radiation beam, and the following equation (5) is established with respect to the radiation angle θ.
_k∥ = β− (2π / Λ) = k ₀ sinθ (5)

If the amount of deviation of the emitted light beam emitted in the θ direction from θ is Δθ, the emitted light beam distribution Y (Δθ) in the distance is expressed by the following equation (6).

In the above formula (6), y ′ is a projection component of y with respect to the direction along the wavefront of the radiation light beam.

FIG. 2 shows the characteristics calculated using the above equations (2), (3), and (6). A _dB and B _{dB in} FIG. 2A are values obtained by converting the loss factor A of the waveguide and the light emission coefficient B of the light emission mechanism into dB / cm, respectively. Here, both the loss coefficient A and the radiation coefficient B are constant values with respect to the traveling direction of light.

The propagation light intensity distribution P (y) shown in FIG. 2B is an exponentially decaying function, and the light emission distribution X (y) shown in FIG. 2C also reflects the propagation light intensity distribution P (y). And decay exponentially.

The synchrotron radiation beam distribution Y (Δθ) shown in FIG. 2D is a single peak beam, but the full width at half maximum of Δθ is about 0.04 [deg] °, and side lobes and tailing appear.
FIG. 2 shows an example in which the radiation coefficient B _dB [dB / cm] is 20 dB / cm, 50 dB / cm, and 80 dB / cm.

(Double periodic structure of optical deflection device)
The optical deflecting device of the present invention comprises a diffraction mechanism that combines a waveguide and a light emitting mechanism with a single mechanism, and combines a plurality of circular hole arrays with a propagating light of a slow light by forming a double periodic structure. The emission coefficient B is gradually changed with respect to the light traveling direction.

Since this double periodic structure does not change the radiation angle of the radiated light, it is possible to obtain a high quality radiated light beam by adjusting the radiant coefficient B as compared with the case where the radiant coefficient B is constant.

The optical deflection device of the present invention uses a photonic crystal waveguide as a slow light waveguide, and the waveguide and the light emission mechanism are configured by one mechanism. The photonic crystal waveguide forms a waveguide by reflecting and propagating light by sandwiching the left and right sides of the waveguide with photonic crystals arranged in a circular hole.

The optical deflection device according to the present invention is based on the provision of a double periodic structure in which two types of circular holes having different diameters are repeated along the waveguide forming the waveguide in the plane of the photonic crystal.

FIG. 3 is a diagram for explaining the basic principle of the optical deflection device according to the present invention (Patent Document 6).
The optical deflecting device 1 has circular holes 3a and 3b of a low refractive index medium such as SiO ₂ arranged two-dimensionally in a slab made of a high refractive index medium such as a semiconductor such as Si in a triangular lattice arrangement, for example. The circular holes in the arrangement of the parts are removed, and the part from which the circular holes are removed constitutes a waveguide part made of a two-dimensional photonic crystal and constitutes an emission part that emits a radiated light beam.

Optical deflection device 1 comprises two different diameters 2r ₁ and 2r ₂ of the circular hole 3a with respect to the light propagation direction, the double periodic structure 4 repeating 3b. By this double periodic structure 4, the slow light propagation light which is non-radiated in the periodic structure in which circular holes of the same diameter are arranged is converted into radiation conditions and is emitted into space.

The double periodic structure included in the optical deflection device according to the present invention includes a periodic structure in which large-diameter circular holes are repeated and a periodic structure in which small-diameter circular holes are repeated. The diameter of the reference circle hole and 2r, when the 2Δr differences width of diameter, the diameter 2r ₁ circular hole having a large diameter is 2 (r + Δr), the diameter 2r ₂ of the small-diameter circular holes 2 (r- Δr). Further, when the distance between the centers of the adjacent large-diameter circular holes 3a and small-diameter circular holes 3b is a, the interval Λ between the circular holes of each periodic structure is 2a.

An example of the size of the optical deflection device 1 is, for example, a = 400 nm, 2r = 210 nm, and the interval s ₃ between the adjacent circular holes 3a and 3b is 84 nm. Note that this size is an example and is not limited to this value.

Further, in the configuration example of the optical deflection device shown in FIG. 3, a device using a third-row shifted silica clad Si-LSPCW or a device using a second-row shifted LSPCW can be used. According to the second-row shift type LSPCW having a large ng, an increase in the light deflection angle Δθ is expected.

4A to 4D show a photonic band, a group refractive index _ng spectrum, a radiation angle θ with respect to a wavelength λ, and a radiation coefficient B _dB with respect to the wavelength λ in the optical deflection device of the present invention. . Note that the radiation angle θ in FIG. 4C is θ = 0 ° in the direction perpendicular to the plane (z direction in FIG. 3).

In FIG. 4A, in the optical deflecting device of the present invention having a double periodic structure, the photonic band representing the light propagation characteristic is the diameter of the circular hole even when the diameter r of the circular hole is changed by 2Δr. Does not change in the same way as when 2 is uniform at 2r. Also, the group refractive index _ng does not change with respect to the diameter change Δr as shown in FIG. 4B, and low-dispersion slow light with _{ng of about} 20 is generated in a wide wavelength band. rapidly n _g is increased toward the wavelength corresponding to the end, it shows that the slow light effect is further increased. The light propagation characteristic indicates that the propagation constant β does not change with respect to the light propagation direction, and the angle θ of the emitted light does not change as shown in FIG.

On the other hand, in FIG. 4D, the light emission coefficient B _dB can be changed by changing the diameter 2r of the circular hole by Δr. FIG. 4D shows an example in which Δr is 5 nm, 10 nm, 15 nm, and 20 nm, and shows that the emission coefficient B _dB increases as Δr increases. The radiation coefficient B represents the rate at which propagating light leaks out of the plane from the optical transport path, and the intensity of the radiation beam emitted out of the plane increases as Δr increases. Also, by adjusting Δr along the light transport path, the intensity of the emitted light beam emitted out of the plane can be controlled, and the light beam distribution can be adjusted to form a high quality light beam distribution. Can do.

In the radiation angle θ with respect to the wavelength λ shown in FIG. 4C, the radiation angle θ reflects the photonic band and therefore has little Δr dependency. Although not shown in FIG. 4C, a light deflection angle Δθ close to 30 ° with respect to the wavelength change Δr = 27 nm is obtained by the slow light effect and refraction at the silica clad / air interface.

In the radiation coefficient B _dB for wavelength λ shown in FIG. 4 (d), Using n _g large second column shift type LSPCW, further B _dB increase is expected. On the other hand, B _dB increases as Δr increases. Therefore, the amount of light radiation can be controlled by controlling Δr, and a light radiation beam with a small spread can be formed.

Thus, the present inventors have found that when Δr is changed, the emissivity changes greatly, but other properties such as the radiation angle and the propagation constant in the propagation direction do not change so much, and this is the purpose of the present application. It has been found that the present invention can be applied to adjust the beam distribution of radiation emitted out of the plane to form a high-quality light beam distribution.

(Optical deflection device configuration)
The form of the optical deflection device of the present invention is a structure of a plurality of circular holes formed in the plane of the photonic crystal as a diffraction mechanism by the photonic crystal, and the diameter changes along the waveguide in the plane of the photonic crystal. A periodic structure of a plurality of circular holes is provided. The plurality of circular holes provided in the optical deflection device of the present invention constitute a waveguide of the carrier light and a light emission mechanism that radiates the radiation light beam out of the plane in the plane of the photonic crystal. The intensity distribution (amplitude distribution) of the radiation beam is adjusted by a periodic structure whose diameter changes along the waveguide.

FIG. 5A shows a schematic configuration of the form of the optical deflection device, and FIG. 5B shows a first periodic structure and a second periodic structure provided in the form of the optical deflection device.

5 (a) and 5 (b), the optical deflection device 1 includes periodic structures 4 of a plurality of circular holes 3a and 3b whose diameters change in the light propagation direction on both sides of the waveguide 5. The periodic structure 4 having a plurality of circular holes is a double periodic structure in which the diameters of the circular holes 3 a and 3 b increase or decrease in a complementary manner along the waveguide 5.

5B, the double periodic structure 4 includes a first periodic structure 4a and a second periodic structure 4b in which the diameter of the circular hole is increased or decreased. The increase and decrease in the diameter of the circular holes of the first periodic structure 4a and the second periodic structure 4b are complementary to each other, and when the diameter of the circular hole increases in one periodic structure, it increases in the other periodic structure. The diameter of the hole adjacent to the hole to be reduced is reduced. The increase / decrease of the diameter of the circular hole is along the direction of the waveguide 5, but whether the direction in which the propagation light travels in the waveguide 5 or the direction opposite to the direction in which the propagation light travels is used as a reference. Therefore, here, the direction in which the propagation light travels will be referred to as a reference direction, the reference direction as an increasing direction, and the direction opposite to the reference as a decreasing direction.

In the first periodic structure 4a, a plurality of circular holes 3a increases or decreases the diameter 2r ₁ to the direction of the propagation light in the waveguide 5. On the other hand, in the second periodic structure 4b, a plurality of circular holes 3b decreases or increases the diameter 2r ₂ with respect to the direction of the propagation light in the waveguide 5.

FIG. 6 is a diagram for explaining an increase or decrease in the diameter of the circular holes of the first periodic structure and the second periodic structure. In FIG. 6A, when the diameter of the reference circular hole is r, the increase / decrease width of the diameter to be increased / decreased complementarily is Δr ₁ , Δr _2, and the direction from the bottom to the top of the drawing is the reference direction, circular hole 3a diameter 2r ₁ of the periodic structure is 4a of increased 2Derutaaru ₁ minute, turn _{2 (r + Δr 1),} 2 (r + 2Δr 1) becomes .... On the other hand, the diameter 2r ₂ of circular holes 3b constituting the second periodic structure 4b is reduced 2Derutaaru ₂ minutes, turn _{2 (r-Δr 2),} 2 (r-2Δr 2), a ....

The diameters 2r ₁ and 2r ₂ of the circular hole 3a included in the first periodic structure 4a and the circular hole 3b included in the second periodic structure 4b are set to 2Δr ₁ , By increasing or decreasing by 2Δr ₂ , the diameters 2r ₁ and 2r ₂ of the circular holes 3a and 3b have a double periodic structure that increases and decreases complementarily along the waveguide. The reference circular hole can be arbitrarily set from a plurality of circular holes provided in the periodic structure. In addition, when Δr ₁ and Δr ₂ for the increase / decrease are common Δr, the diameter of the circular hole 3a included in the first periodic structure 4a is 2 (r + Δr), 2 (r + 2Δr), and the second periodic structure The diameter of the circular hole 3b included in 4b is 2 (r−Δr) and 2 (r−2Δr).

In the description given above, increasing the diameter 2r ₁ of the circular hole of the first periodic structure 4a, an example has been described for reducing the diameter 2r ₂ of the circular hole of the second periodic structure 4b, a first periodic structure 4a reducing the diameter 2r ₁ of the circular hole, it may increase the diameter 2r ₂ of the second periodic structure 4b.

In the above configuration, it is possible to increase or decrease the amount of radiation of light by increasing or decreasing the [Delta] r ₁ and [Delta] r _2, deviation occurs in the photonic band by increasing or decreasing the [Delta] r ₁ and [Delta] r _2, propagation constant by the position in the optical transport path β and radiation angle θ may also change at the same time. As a result, the radiated light beam is not integrated into one, but becomes a low-quality radiated light beam that diffuses in various directions.

Here, as a configuration for suppressing fluctuations in the propagation constant β and the radiation angle θ due to the increase / decrease in Δr ₁ and Δr ₂ described above, the optical deflection device of the present invention has a circular hole when changing Δr ₁ and Δr ₂ . It has been found that it is preferable to have a configuration in which the increase in area and the decrease in the area of the circular hole are equal.

The relationship in which the increase in the area of the circular hole and the decrease in the area of the circular hole have the same amount is as follows in relation to the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ with respect to the reference diameter r: 7).
(R + Δr ₁ ) ² −r ² = r ² − (r−Δr ₂ ) ² (7)

FIG. 6B shows a configuration in which the increase and decrease of each area of the circular holes of the first periodic structure and the circular holes of the second periodic structure of the optical deflection device are equal to each other.

The area of the circular hole 3a of the first periodic structure increases by ΔS ₁ (= (r + Δr ₁ ) ² −r ² ) as the diameter increases from 2r to 2 (r + Δr ₁ ). On the other hand, the area of the circular hole 3b of the second periodic structure decreases by ΔS ₂ (= r ² − (r−Δr ₂ ) ² ) as the diameter decreases from 2r to 2 (r−Δr ₂ ).

By adjusting the increase width Δr ₁ and the decrease width Δr ₂ , the increase / decrease amount of the areas of ΔS ₁ and ΔS ₂ is made the same amount. As described above, a configuration in which Δr ₁ = Δr ₂ = Δr is achieved by using the same amount of increase / decrease in the areas of the first periodic structure circular hole and the second periodic structure circular hole of the optical deflection device. Compared with, it is possible to further suppress the change of the photonic band, to form a high-quality light beam, and to adjust the beam distribution of the emitted light that is emitted out of plane, which is the purpose of this application. It has been found that it is suitable for forming a high-quality light beam distribution.

The relationship in which the increase in the area of the circular hole and the decrease in the area of the circular hole have the same amount can also be expressed using the ratio k (= Δr ₁ / Δr ₂ ) of the increase / decrease width Δr ₁ and the increase / decrease width Δr _2. . In this case, the ratio k (= Δr ₁ / Δr ₂ ) between the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ can be expressed by the following formula (8) or formula (9) with respect to the reference diameter r. it can.
k ² + (2r / Δr ₂ ) · k = (2r / Δr ₂ ) −1 (8)
(1 + 2r / Δr ₁ ) k ² − (2r / Δr ₁ ) · k = −1 (9)

(Radiation coefficient and light radiation distribution of light deflection device)
FIG. 7A shows the relationship among the propagation light intensity distribution P (y), the radiation coefficient B (y), the light radiation distribution X (y), and the radiation light beam distribution Y (Δθ) in the optical deflection device. 7 (b) shows the relationship between the radiation coefficient B (y) and the increase / decrease Δr of the diameter of the circular hole. Here, y is the distance from the incident end of the incident light in the waveguide of the optical deflection device.

The light deflection device of the present invention can set the radiation coefficient according to the increase / decrease state of the diameter of the circular hole of the periodic structure constituting the diffraction mechanism, and can further set the light radiation distribution.

In the optical deflection device of the present invention, the propagation light intensity distribution P (y) with respect to the propagation direction of the propagation light in the waveguide, the radiation coefficient B (y) with respect to the propagation direction of the radiation emitted from the waveguide out of plane, the waveguide If the light radiation distribution X (y) with respect to the propagation direction of the light intensity emitted from the light, the light radiation distribution X (y) depends on the propagation light intensity distribution P (y) and the radiation coefficient B (y), and the light The radiation distribution X (y) is expressed by the following formula (10) by the product of the propagation light intensity distribution P (y) and the radiation coefficient B (y).
X (y) = B (y) · P (y) (10)

From this relationship, the radiation coefficient B (y) of the optical deflection device is expressed by the following equation (11) obtained by dividing the light radiation distribution X (y) by the propagation light intensity distribution P (y).
B (y) = X (y) / P (y) (11)

In the optical deflection device, since the propagation light intensity distribution along the light propagation direction is determined by the characteristics of the waveguide, the light radiation distribution X (y) can be set by the radiation coefficient B (y) of the light deflection device. Therefore, a desired light radiation distribution X (y) can be obtained by setting the radiation coefficient B (y).

Furthermore, the increase / decrease width Δr of the circular hole of the optical deflection device for realizing the desired light emission distribution X (y) can be obtained based on the relationship between the emission coefficient B (y) and the increase / decrease width Δr of the diameter. .

The relationship between the radiation coefficient B (y) and the increase / decrease width Δr of the diameter can be obtained from the radiation coefficient-diameter change characteristic. The increase / decrease width Δr of the diameter is based on the relationship between the radiation coefficient B and the increase / decrease width Δr. , Obtained as a value corresponding to the radiation coefficient B.

The light radiation distribution X (y) can be an arbitrary distribution shape. For example, when the light radiation distribution X (y) is a Gaussian distribution, the side lobe of the radiation light beam distribution Y (Δθ) with respect to the variation Δθ of the radiation angle θ of the radiation light can be removed.

As shown in FIG. 2, when the radiation coefficient B is constant along the direction of the light transport path, the light radiation distribution X (y) attenuates exponentially, and the side lobe of the radiation light beam distribution Y (Δθ). Is a sinc function. In order to suppress the side lobe of the light beam, it is conceivable to make the radiation light beam distribution Y (Δθ) a Gaussian function. In this case, the light radiation distribution X (y) itself needs to be a Gaussian function. The propagation light intensity distribution P (y) is attenuated by the loss factor A and the radiation coefficient B of the waveguide. In order to make the light radiation distribution X (y) into a Gaussian function having a peak at the center of the length L waveguide, taking into account the attenuation due to the loss coefficient A and the radiation coefficient B, change along y. The radiation coefficient B (y) needs to satisfy the following.
X (y) = B (y) · P (y) = Dexp (−a · (y−L / 2) ² )
(12)

Here, a is a coefficient giving the spread of the Gaussian function, and D is a constant representing the radiation amount at the peak of the Gaussian function. Based on the equation (12), the differential equation regarding propagation is expressed by the following equation (13).
dP (y) / dy = −AP (y) −Dexp (−a · (y−L / 2) ² )
... (13)

When the equation (13) is solved, the radiation coefficient B (y) is expressed by the following equation (14).

FIG. 8 shows the calculation results using the above equations (12) and (14), FIG. 8 (a) shows the propagation light intensity distribution P (y), and FIG. 8 (b) shows the radiation coefficient B (y). 8 (c) shows the light radiation distribution X (y), and FIG. 8 (d) shows the radiation light beam distribution Y (Δθ).

Here, η is a constant depending on the constant D, and represents the amount of light remaining without being emitted at the position of y = L. F is a constant given by f = a · (L / 2) ² . For example, f = 0 corresponds to a = 0, and the radiated light distribution X (y) is a Gaussian function whose change is infinitely small. On the other hand, a large constant f corresponds to a large coefficient a and becomes a Gaussian function having a large change.

FIG. 8 shows (f = 2, η = 0.9), (f = 1, η = 0.95), (f = 1, η = 0.9), (f = 0, η = 0.95). ) And (f = 0, η = 0.9), the case where the loss factor A of the waveguide is 0 dB / cm, 10 dB / cm, and 30 dB / cm is shown.

In FIG. 8, the radiation beam distribution Y (Δθ) obtained when f = 2 and η = 0.9 indicates that a Gaussian beam having almost no side lobe or tailing is formed.

(Configuration example of optical deflection device)
FIG. 9 shows an example of an optical deflection device when the radiated light beam is a Gaussian beam. 9A shows a plan view of the optical deflection device 1, FIGS. 9B and 9C show perspective views of the optical deflection device 1, and FIG. 9C schematically shows the distribution shape of the radiation light beam. Is shown.

The radiation coefficient B (y) for making the radiation light beam a Gaussian beam is obtained by the equation (14), and the diameter of the circular hole forming the distribution shape of the obtained radiation coefficient B (y) is further obtained. In order to obtain the diameter of the circular hole, a correspondence relationship between the radiation coefficient B (y) and the increase / decrease width Δr of the diameter of the circular hole formed in the plane of the optical deflection device 1 is obtained in advance, and based on this correspondence relationship. The increase / decrease width Δr of the diameter corresponding to the radiation coefficient B is obtained according to the position of the optical deflection device 1 in the light propagation direction. In the configuration example shown in FIG. 9, the diameters of the rows of the circular holes 3 included in the periodic structure 4 of the optical deflection device 1 are increased or decreased with respect to the vicinity of the center in the light propagation light direction.

(Rider configuration)
The lidar apparatus of the present invention includes the optical deflection device of the present invention, a laser light source that emits a plurality of laser beams having different wavelengths, and a light detection unit that individually detects the laser beams. The optical deflection device includes a laser that emits a plurality of wavelengths of laser light emitted from a laser light source in parallel in the direction of each deflection angle determined by the wavelength of each laser beam and the refractive index of the waveguide, and a plurality of laser beams that reach from the outside. Among the laser beams having the wavelengths, the injectors that selectively and simultaneously enter the laser beams whose incident angles are the deflection angles are configured by the same element. The light detector individually detects laser light of each wavelength incident at an incident angle having the same deflection angle as that of the laser light emitted from the emitter at the injector. By making the deflection angle of the emitter coincide with the deflection angle of the injector, it is possible to detect the reflected light that is emitted from the emitter and reflected by the object.

Each form of the configuration of the rider device will be described with reference to FIG. The 1st form of a rider apparatus is a form which comprises an injector and an emitter separately. FIG. 10A shows a first embodiment of the rider device. The lidar apparatus 100A according to the first embodiment includes an emitter composed of a laser light source 102, a waveguide 104, and an optical deflection device 101, an optical deflection device 101, a waveguide 104, and a photodetector 103 (photodiode). It is the structure which is equipped with the comprised injector separately, and is juxtaposed. The emitter emits the light from the laser light source 102 to the outside from the optical deflection device 101, and the injector enters the reflected light reflected by the object, passes through a filter (not shown), and then passes through the branch path. Then, it guides to the light detection unit 103 and detects it.

Since the reflected light from the object spreads and diffuses greatly, the angle of the light beam that can be received by the injector should be slightly different from the radiation angle of the emitter even if the injector is placed beside the emitter. By setting, it is possible to receive the reflected light without directly entering the light emitted from the emitter.

FIG. 10B shows a second form of the rider device. The rider device 100B according to the second embodiment has a configuration in which the waveguide 104 is branched and a light detection unit 103 (photodiode) is disposed at one end of the branch path. The light deflection device 101 passes incident reflected light through a filter (not shown), and then guides it to the light detection unit 103 via a branch path to detect it.

FIG. 10C shows a third form. The lidar apparatus 100C according to the third embodiment has an optical switch 105 inserted into the waveguide 104, switches to the photodetection unit 103 (photodiode) side after the laser light from the laser light source 102 passes, and is reflected and returned. Light is guided to the light detection unit 103 (photodiode) with high efficiency.

FIG. 10 (d) shows a fourth embodiment. When a strong reverse bias is applied, a photodiode having a pn junction formed in a Si waveguide causes subband gap absorption via crystal defects, and can detect light in a long wavelength band that cannot be detected originally. . The lidar apparatus 100D of the fourth embodiment inserts a photodiode having a pn junction as the light detection unit 103 in the middle of the waveguide 104, and changes the reverse bias after the laser light from the laser light source 102 passes. Then, the reflected light pulse is detected.

FIG. 10 (e) shows a fifth embodiment. The rider apparatus 100E of the fifth embodiment includes a pulse light source / light detection unit 106 that serves as both a laser light source and a light detection unit. The pulse light source / light detection unit 106 can also operate as a photodiode by applying a reverse bias to a semiconductor laser serving as a pulse light source. According to this configuration, after emitting the laser light, the pulse light source / light detection unit 106 operates as a photodiode by applying a reverse bias, and detects the reflected laser light.

In each form of lidar device using reflected light, the light from the laser light source can be a light pulse or continuous light. The rider apparatus can measure distance by the TOF method when using light pulses, and can measure distance by the FMCW method when using continuous light.

According to the configuration of the rider device of each form, even if light of the same wavelength arrives from different directions, the incident angle is different, so the light does not follow the reverse order, so it is not coupled to the original waveguide and is detected by light. It does not enter the part (photodiode).

In each embodiment shown in FIG. 10, an optical filter of a wavelength filter may be inserted into the waveguide 104. The optical filter is a filter that allows the wavelength of the laser light from the laser light source to pass. When the wavelength of the laser light source is changed, it is more preferable that the optical filter be a variable wavelength filter that can change the passing wavelength in synchronization with the wavelength change.

There are various wavelengths of light in the environment, and light having a wavelength different from the wavelength of the laser light source may arrive at the optical deflection device 1 as a noise component. If the incident angle of light of different wavelengths and the exit angle of the light beam are the same, noise components having different wavelengths cannot be coupled to the waveguide, but arrived at the optical deflection device 1 from different directions. Some noise components can be coupled back into the waveguide. The optical filter can remove noise components coupled to the waveguide in this way. The removal of the noise component contributes to the improvement of the SN ratio when detecting the reflection signal of the rider device.

In addition to the configuration using near infrared light, the technology related to optical deflection devices and lidar devices is based on visible light from projectors, laser displays, retinal displays, 2D / 3D printers, POS and card reading, etc., by forming devices with visible light materials. Application is envisaged.

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 device (laser radar) of the present invention are a laser radar (LiDAR) installed in automobiles, drones, robots, industrial equipment, 3D scanners that can be easily installed in personal computers and smartphones, and monitor the surrounding environment. It can be used for systems. If a similar optical deflection device is used, optical exchange, a space matrix optical switch for a data center, and the like are possible.

1 optical deflection device _2r, 2r _1, 2r ₂ diameter 3, 3a, 3b circular hole 4 double periodic structure 4a periodic structure 4b periodic structure 5 waveguide 10 leakage waveguide 11 waveguide 11a slow light waveguide 11b upper cladding 11c Lower clad 11d Two-dimensional photonic crystal waveguide 12 Emitter 12a Light emission mechanism 100A to 100E Rider device 101 Optical deflection device 102 Laser light source 103 Photodetector 104 Waveguide 105 Optical switch 106 Pulse light source / photodetector A A Waveguide Loss factor B Radiation coefficient D Constant f Constant k Wave number P Propagation intensity distribution r Reference diameter X Light radiation distribution Y Radiation beam distribution

Claims (9)

1. An optical deflection device comprising a waveguide having a periodic structure of two types of circular holes of different diameters formed in the plane of a photonic crystal,
   The optical deflection device according to claim 1, wherein the periodic structure is a double periodic structure in which the diameters of the circular holes increase and decrease in a complementary manner along the waveguide.
2. The double periodic structure includes a first periodic structure in which the diameter increases and a second periodic structure in which the diameter decreases,
   When the diameter of the reference circular hole is 2r, and the increase / decrease width of the diameter to be increased / decreased complementarily is 2Δr ₁ , 2Δr ₂ ,
   The diameter 2r _{1 of the} circular hole provided in the first periodic structure is 2 (r + Δr ₁ ),
   2. The optical deflection device according to claim 1, wherein the diameter 2r _{2 of the} circular hole provided in the second periodic structure is 2 (r−Δr ₂ ).
3. The optical deflection device according to claim 2, wherein the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ are the same increase / decrease width Δr.
4. 3. The optical deflection device according to claim 2, wherein the area increase of the circular hole provided in the first periodic structure and the area decrease of the circular hole provided in the second periodic structure are the same amount.
5. The increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ are relative to the reference diameter r.
   (R + Δr ₁ ) ² −r ² = r ² − (r−Δr ₂ ) ²
   The optical deflection device according to claim 2, comprising the relationship:
6. The ratio k (= Δr ₁ / Δr ₂ ) of the increase / decrease width Δr ₁ and the increase / decrease width Δr ₂ is determined with respect to the reference diameter r.
   k ² + (2r / Δr ₂ ) · k = (2r / Δr ₂ ) −1
   Or (1 + 2r / Δr ₁ ) k ² − (2r / Δr ₁ ) · k = −1
   The optical deflection device according to claim 2, comprising the relationship:
7. Propagation light intensity distribution P with respect to the propagation direction of propagation light in the waveguide,
   A radiation coefficient B with respect to the propagation direction of radiation emitted out of plane from the waveguide;
   And the light radiation distribution X with respect to the propagation direction of the light intensity radiated from the waveguide is:
   B = X / P
   With a relationship
   The increase / decrease width Δr of the diameter changing along the waveguide is a value corresponding to the radiation coefficient B in the relationship between the radiation coefficient B and the increase / decrease width Δr. An optical deflection device according to any one of the above.
8. The light deflection device according to claim 7, wherein the light radiation distribution X is a Gaussian distribution.
9. An optical deflection device according to any one of claims 1 to 8,
   A laser light source that emits a plurality of laser beams having different wavelengths;
   A light detection unit that individually detects the laser light,
   The optical deflection device is
   An emitter that emits a plurality of wavelengths of laser light emitted from the laser light source in parallel in the direction of each deflection angle determined by the wavelength of each laser light and the refractive index of the waveguide;
   And, among the laser beams of a plurality of wavelengths that reach from the outside, an injector that selectively and simultaneously enters laser beams having an incident angle that is the deflection angle is configured by the same element or different elements,
   The photodetector is
   The lidar apparatus characterized in that, in the incident device, laser beams having respective wavelengths incident at an incident angle having the same deflection angle as the laser beam emitted from the emitter are individually detected.

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