KR102494190B1 - Two-dimensional Directional Optical Phased Array Device - Google Patents

Abstract

A two-dimensional directional optical phased array device is disclosed. According to one aspect of the present embodiment, the optical phased array device includes: a light source irradiating laser light of a preset wavelength band; an input waveguide receiving the laser light irradiated from the light source; an optical distribution unit distributing the laser light incident to the input waveguide to a predetermined number of channels to have uniform power; and a channel waveguide dispersing and guiding the laser light distributed from the light distribution unit into M number of channels and irradiating the laser light onto a free space.

Description

Two-dimensional directional optical phased array device {Two-dimensional Directional Optical Phased Array Device}

The present embodiment relates to an optical phased array device capable of two-dimensionally adjusting a path of output light without having a separate active element. More specifically, it relates to an optical phased array device capable of two-dimensionally steering a beam by using a tunable laser and an optical phased array device in the horizontal direction and electrically varying the vertical direction.

The contents described in this part merely provide background information on the present embodiment and do not constitute prior art.

Optical Phased Array (OPA) technology, which utilizes semiconductor integration technology, can be used for Light Detection And Ranging (LiDAR) sensor technology that provides 3D images including distance information. Compared to rotary laser beam scanners, it is advantageous for low price and miniaturization.

LiDAR is a technology that detects the distance to an object by emitting a laser pulse and receiving the reflected light after the emitted laser pulse is reflected on a surrounding object. With the advent of the 4th industrial revolution and the commercialization of autonomous driving technology, LiDAR technology has recently received more attention. In particular, because small lidar can be mounted on small weapon systems such as drones, unmanned robots, and unmanned aerial vehicles, research is being actively conducted in the field of defense.

Initially, a silicon-based optical phased array structure was proposed, but there is a limit to obtaining high output due to non-linearity that occurs when high power is applied to an optical waveguide. As a result, it is difficult to detect an object at a relatively long distance, making it difficult to apply it to fields such as LiDAR. To overcome these limitations, an optical phased array structure based on silicon nitride, which has a relatively low refractive index compared to silicon, was proposed, and its applicability to real systems such as LiDAR and short-range communication was confirmed through years of research. It became.

An optical phased array antenna has the advantage of being able to steer a laser beam up, down, left and right without a mechanical driving unit. Beam steering is possible by adjusting the phase of a laser pulse passing through each channel of an antenna using a thermo-optic phase modulator or an electro-optic phase modulator.

An optical phased array antenna, together with a light source and a receiver, may be integrated on a semiconductor substrate by Si Photonics technology. The optical phase modulator may be implemented in a traveling wave electrode structure having a phase inversion characteristic, and the electrode structure may be designed to be flexible with respect to a target pass bandwidth and center frequency.

Optical phased array antennas based on silicon photonics technology can be integrated, can be miniaturized, and have a small radius of curvature. On the other hand, insertion loss is large in OPA, it is difficult to match the phase, and active control elements such as optical phase modulators There is a problem that is absolutely necessary.

An object of one embodiment of the present invention is to provide an optical phased array device capable of adjusting the path of output light in two dimensions without an active control device.

In addition, in one embodiment of the present invention, the horizontal direction in the x-axis direction is rotated using a wavelength laser and an optical phased array device in the horizontal direction, and in the y-axis direction, a device capable of controlling one axis is additionally placed at the front end. One object is to provide an optical phased array device capable of two-dimensional beam rotation.

According to one aspect of the present embodiment, a light source for irradiating laser light in a predetermined wavelength band, an input waveguide receiving laser light emitted from the light source, and a predetermined number of laser lights incident to the input waveguide to have uniform power. Provided is an optical phased array device comprising a light distribution unit for distributing to channels of the light distribution unit and a channel waveguide for dispersing and guiding the laser light distributed in the light distribution unit to M channels and radiating onto a free space. .

According to one aspect of this embodiment, the optical phased array device further includes an optical path adjustment unit disposed in front of the output terminal of the channel waveguide in a direction in which light is irradiated, and adjusting a path of the irradiated laser light. to be characterized

According to one aspect of this embodiment, the optical path adjustment unit is characterized in that implemented as a variable prism.

According to one aspect of this embodiment, the variable prism is characterized in that it includes a liquid crystal (Liquid Crystal) therein.

According to one aspect of this embodiment, the optical path adjusting unit is characterized in that it is implemented as an acoustic-optical modulator.

According to one aspect of this embodiment, the light path adjustment unit is characterized in that it further comprises a cylindrical lens (Circular Cylindrical Lens).

According to one aspect of this embodiment, the cylindrical lens is characterized in that it is disposed between the output end and the variable prism or between the output end and the acousto-light modulator.

As described above, according to one aspect of the present embodiment, the phase can be manually adjusted even if an active element such as a phase modulator is not included, so the manufacturing cost is low, and the element can be used alone or applied to a lidar sensor. there is

In addition, according to one aspect of the present embodiment, there is an advantage of preventing the dispersion of the irradiated laser light so that the laser light is irradiated to a long distance or the light reflected from the object can be returned.

1 is a diagram showing the configuration of an optical phased array device according to an embodiment of the present invention.
2 is an implementation example of an optical phased array device according to an embodiment of the present invention.
3 is a diagram illustrating an output end of a channel waveguide according to an embodiment of the present invention.
4 is an implementation example of an optical phased array device according to the first embodiment of the present invention.
5 is an implementation example of an optical phased array device according to a second embodiment of the present invention.
6 is an implementation example of an optical phased array device according to a third embodiment of the present invention.
7 is an implementation example of an optical phased array device according to a fourth embodiment of the present invention.
8 is an implementation example of an optical phased array device according to a fifth embodiment of the present invention.
9 is an implementation example of an optical phased array device according to a sixth embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals have been used for like elements throughout the description of each figure.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no intervening element exists.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. It should be understood that terms such as "include" or "having" in this application do not exclude in advance the possibility of existence or addition of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. .

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

In addition, each configuration, process, process or method included in each embodiment of the present invention may be shared within a range that does not contradict each other technically.

1 is a diagram showing the configuration of an optical phased array device according to an embodiment of the present invention, and FIG. 2 is an implementation example of an optical phased array device according to an embodiment of the present invention.

1 and 2, an optical phased array device 100 according to an embodiment of the present invention includes a light source 110, an optical phased array element 200, and an optical path adjuster 150, and The device 200 includes an input waveguide 120 , an optical distribution unit 130 and a channel waveguide 140 .

The optical phased array device 100 is manufactured using a silica optical waveguide having excellent OPA insertion loss and diffraction characteristics while fully utilizing silicon photonics technology. The optical phased array device 100 can adjust the path of output light in two dimensions without including a separate active control element to adjust the light path. Such an optical phased array device 100 may be included in a device that needs to irradiate light in a certain range, such as a LiDAR device, and adjust a path of output light. At this time, since the optical phased array device 100 does not include a separate active control element, it has an advantage in that it can be miniaturized while reducing manufacturing cost.

The light source 110 irradiates the optical phased array device 200 corresponding to a variable laser light source of a preset wavelength band, in particular, the input waveguide 120 . The light source 110 may be implemented as a wavelength tunable laser diode capable of changing an oscillation wavelength within a preset range.

As shown in FIG. 2A, the laser light irradiated from the light source 110 is incident to the input waveguide 120, passes through the slab waveguide 132 along the waveguide 120, and passes the light to each channel waveguide 142. It is distributed and reaches the output stage 141. At this time, the power distribution on the end surface 133 of the slab waveguide can be adjusted by changing the shape of the incident surface 131 of the slab waveguide, and the relationship between the two has a Fourier Transform relationship. If the incident surface 131 of the slab waveguide has a Gaussian distribution, the end surface 133 of the slab waveguide has a Gaussian distribution, and each waveguide 142 has a Gaussian distribution as a whole. At this time, if the incident surface 131 of the slab waveguide has a light distribution in the form of a step function, passing through the slab waveguide 132 and reaching the end surface 133 of the slab waveguide, the distribution of the sync function, which is a Fourier transform relationship of the step function, is obtained. will have On the other hand, if the incident surface 131 of the slab waveguide has a distribution of a sink function, the end surface 133 of the slab waveguide has a distribution in the form of a step function, and the channel waveguide 142 has a power ratio of a uniform distribution. As for the power distribution of each waveguide at the output stage, the beam becomes a far field distribution.

Light from the end 133 of the slab waveguide is incident on the channel waveguide 142 and divided into M channels, and the laser light is transmitted to the output terminal 141 having a certain interval. The laser light guided to the output terminal 141 by the channel waveguide 140 is radiated onto a free space. At this time, M silica optical waveguides (WG ₁ to WG _M ) are arranged in the channel waveguide 140 (described later with reference to FIG. 3 ), and each optical waveguide has a length difference of ΔL from adjacent optical waveguides.

In the case of having an optical distribution unit, a distribution ratio of 50:50 is normally provided, but the optical power distribution of the output terminal 141 can be asymmetrically adjusted to have a Gaussian function.

[Equation 1]

In Equation 1, n _c is the refractive index of the optical waveguide, m is the diffraction order, and λ ₀ represents the center wavelength of the incident light (λ). Equation 1 indicates that light is incident from an input terminal at the center having a central wavelength (λ ₀ ) and proceeds to an output terminal at the center. When the diffraction order (m, m = integer multiple) is determined based on the center wavelength (λ ₀ ) at the output terminal of the channel waveguide 140, ΔL of each optical waveguide of the channel waveguide 140 is determined. At this time, as the number of waveguides increases, more waveguides cause a diffraction phenomenon, resulting in better linearity.

Meanwhile, as shown in FIG. 2B, the laser light irradiated from the light source 110 is incident to the input waveguide 120, and the light distribution unit 130 converts the optical signal incident to the input waveguide 120 to a preset power. It is distributed to M channels to have a ratio. At this time, the optical distribution unit 130 may use at least one optical coupler (135a, 130b, 135c, 135d, etc.) having N input ports and M (M, M>n) output ports. The power of the input laser light is distributed at a predetermined ratio and transmitted to other channels. At this time, the optical couplers 135a, 130b, 135c, 135d, etc. do not uniformly distribute the input laser light with equal power, but distribute it so as to have a smaller power as the distance from the center increases. That is, the optical couplers 135a, 130b, 135c, 135d, etc. of the light distribution unit 130 distribute the laser light transmitted to the output terminal 141 to have a Gaussian distribution. Referring to FIG. 2B , when the light distribution unit 130a receives laser light for the first time, it can distribute the laser light with a power of 1:1 at a corresponding position. However, when the light distribution unit 130a distributes the laser light at a point after the corresponding position, the laser light distributed relatively close to the center (of the output stage) is not distributed so that the power is equal. Distribute to have more power.

The light irradiated from the light source 110 passes through the slab waveguide 132 and is divided into M branches, each having a constant length difference ΔL, passing through the channel waveguide 140 in which curved optical waveguides are arranged, and diffracted at the output terminal 141. . Accordingly, the laser light travels with directivity in a specific direction (on the y-axis shown in FIG. 2). At this time, when the wavelength of the incident light changes, the length difference (ΔL, optical path difference) also changes accordingly, so that the traveling direction of the laser light changes on the corresponding axis. Accordingly, the light source 110 and the optical phased array device 200 can adjust the optical path on one axis using this.

The optical path adjustment unit 150 is disposed in front of the output terminal 141 of the optical phase array device 200 in the direction in which the light is irradiated, and adjusts the path of the irradiated laser light. In particular, the optical path adjusting unit 150 adjusts in a direction (y axis in FIG. 2 ) perpendicular to the axis (x axis in FIG. 2 ) that the optical phased array element 200 adjusts.

Meanwhile, the laser light incident to the input waveguide 120 has Gaussian characteristics at the incident surface 131 of the slab waveguide. In the case of having an optical distribution unit type structure, the Gaussian optical power distribution ratio can be adjusted in the output terminal 141 by adjusting the distribution ratio in each splitter.

When the finally output laser light has a Gaussian characteristic, it may have a characteristic focused on a point to be irradiated, such as an object. When the output laser light is concentrated, the irradiated laser light can be reflected in a smaller area, so that a lidar device or the like (to which the optical phased array device 100 is applied) can secure relatively excellent resolution.

On the other hand, when the laser light incident on the input waveguide 120 has the characteristic of a step function in the slab waveguide 131, it is converted into the characteristic of a sink function at the end surface 133 of the slab waveguide. Then, when outputted through the channel waveguide 142, the laser light has a step function characteristic. However, since the step function is not concentrated to one point, the irradiated laser light is reflected in a relatively wide area, and a lidar device (to which the optical phased array device 100 is applied) can secure a relatively low resolution. there is.

3 is a diagram illustrating an output end of a channel waveguide according to an embodiment of the present invention.

Referring to FIG. 3A , when the center wavelength and the diffraction order are determined, the length of each optical waveguide of the channel waveguide 140 of the optical phased array device 100 is determined.

The channel waveguide 140 has a curved shape in which a straight line having a predetermined length and a curve having a predetermined curvature are combined due to a difference in length (ΔL) between adjacent optical waveguides, and converge at the output end 141.

Accordingly, as shown in FIG. 3A, when the output end 141 of the channel waveguide 140 is formed, the laser light causes a diffraction phenomenon and is directed in each direction according to the wavelength.

Unlike the y-axis direction, diffraction does not occur by the optical phased array element 200 in the x-axis direction, and the far field of the waveguide comes out. In addition, it has a divergence angle according to the size and refractive index of the waveguide and spreads in the vertical direction.

Meanwhile, as shown in FIG. 3B, the output end 141 may have a shape of a surface cut obliquely and polished. When the output surface is processed obliquely, the laser light output from the output end 141 is output in a direction (+y-axis direction) perpendicular thereto, not in the direction in which the waveguide 140 travels as in the prior art. Accordingly, the thickness of the packaging of the optical phased array device 100 can be reduced, so that the device 100 can be mounted and operated in various devices.

4 is an implementation example of an optical phased array device according to the first embodiment of the present invention.

Referring to FIG. 4 , the light path adjuster 150 is implemented as a tunable prism 410 and controls the direction of the laser light incident from the front (in the direction of irradiating light) of the output terminal 141. change the In particular, the angle-changing variable prism 410 adjusts the direction on an axis (x-axis) perpendicular to the incident direction. The angle-changing variable prism 410 can be implemented with two flat glasses and a fluid filled between the two glasses, and the angle of either glass is adjusted, and the angle of the incident laser light or the output laser light is changed and the light propagates. change the direction

5 is an implementation example of an optical phased array device according to a second embodiment of the present invention.

Referring to FIG. 5, the optical path adjuster 150 is implemented as a variable prism 510 including liquid crystal and changes the traveling direction of the laser light incident from the front of the output terminal 141. The liquid crystal is included. The variable prism 510 includes two glasses like the angle-changing variable prism, but liquid crystal is filled between the two glasses.The direction of the liquid crystal changes according to the magnitude of the voltage applied to the two glasses, The traveling direction of the output laser light also changes accordingly.

6 is an implementation example of an optical phased array device according to a third embodiment of the present invention.

Referring to FIG. 6 , the optical path adjuster 150 is implemented as an Acousto-Optic Modulator (AOM) 610 and changes the traveling direction of the laser light incident from the front of the output terminal 141. The acoustic light modulator 610 includes a quartz part through which light passes and a transducer that generates sound waves. The transducer expands or contracts when a voltage is applied, and generates sound waves having a constant frequency by adjusting the applied voltage.

When light is incident at a certain angle toward the quartz where sound waves are formed, it is separated into light that passes through at that angle and light that proceeds at a different angle.

The acoustic light modulator 610 may change the traveling direction of the output laser light according to the magnitude of the voltage applied to the transducer.

7 is an implementation example of an optical phased array device according to a fourth embodiment of the present invention.

Referring to FIG. 7, the optical phased array device according to the fourth embodiment of the present invention is an optical path adjusting unit, and includes a circular cylindrical lens 710 in addition to each component described with reference to FIGS. 4 to 6. can do.

A cylindrical cylindrical lens 710 is disposed between the output end 141 and the variable prism or acousto-light modulator. The cylindrical cylindrical lens 710 is disposed at the corresponding position and serves to send the light output in the x-axis direction from the output end 141 in parallel, and is a cylindrical cylindrical lens at the same distance from the x = 0 plane at the light output end. (710) is arranged in a circular shape, so that light can be incident in a vertical form at the same distance in the y-axis from the exit of the light, so that the light does not spread in the x-axis while rotating 180 ° forward, sending the light far away. can

The cylindrical cylindrical lens 710 is disposed at the above-described position to prevent dispersion of light output from the output terminal 141 . In particular, the cylindrical cylindrical lens 710 prevents light output from the output end 141 from being dispersed in a direction adjusted by the optical path adjuster 150 . The cylindrical cylindrical lens 710 shifts an optical path of light incident thereto into parallel light. Accordingly, the cylindrical lens 710 minimizes distortion of the laser light by allowing most of the light passing through it to travel like light close to the central axis (the angle formed with the central axis is less than a predetermined reference value).

8 is an implementation example of an optical phased array device according to a fifth embodiment of the present invention.

Referring to FIG. 8 , grating patterns 810 and 815 may be respectively formed on the input waveguide 120 and the output terminal 141 of the optical phased array device 200 . As the grating pattern 810 is formed on the input waveguide 120 , light input to the input waveguide 120 may be incident toward the input waveguide 120 in the -y-axis direction. Similarly, as the grating pattern 815 is formed on the output terminal 141, the output terminal 141 output from the output terminal 141 may be irradiated in the +y-axis direction. Accordingly, the grating pattern 810 is applied to the input waveguide 120 and the output terminal 141 in consideration of the position or direction in which the optical phased array device 100 is to be disposed, the thickness of the element in which the optical phased array device 100 is to be disposed, and the like. , 815) may be formed, respectively.

The direction of the laser light output can be adjusted according to the lattice spacing of the grating pattern 815, and the optical path adjuster 150 described with reference to FIGS. 4 to 7 is disposed at a position where the laser light is output from the output end 141, You can adjust the ro.

9 is an implementation example of an optical phased array device according to a sixth embodiment of the present invention.

As shown in FIG. 9 (a), the end 143a of the output end 141 may be implemented in a flat state. However, if the end 143a is implemented flat, the laser light output from the output end 141 is dispersed and proceeds in a direction that the optical phased array element 200 can adjust (even if the degree is relatively less).

On the other hand, as shown in FIG. 9(b) , output directions of each waveguide of the output end 141 may converge toward the end 143b. That is, the waveguide located at the central part of the waveguide is arranged parallel to the optical axis of the output light, and as the waveguide moves away from the central part, the ends 143b of the waveguide are twisted in a direction in which they converge (in the form of having a certain angle with the optical axis of the output light). are placed That is, when extending the waveguide, they are arranged to converge at a distance away from the end 143b of the output end 141 by a distance f. When the waveguide is arranged in this way, the output light has a form of convergence without being dispersed up to point f, and is dispersed and proceeds from that point onwards. As described above, when the waveguide is virtually extended, the output light may be adjusted so that the output light is not dispersed until at least the point 2f as it is arranged to converge at the point f at the end 143b of the output end 141.

Meanwhile, the optical path adjuster 150 described with reference to FIGS. 4 to 7 is disposed at the front end of the optical phased array device 200 having the curved end 143b to adjust the optical path. At this time, even if the cylindrical cylindrical lens 710 described with reference to FIG. 7 is additionally disposed, the cylindrical cylindrical lens 710 is adjusted by the optical path adjusting unit 150, unlike the curvature-implemented end 143b. Since scattering of light in the direction is prevented, a case in which both 143b and 710 are in conflict with each other does not occur.

The above description is merely an example of the technical idea of the present embodiment, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment, but to explain, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of this embodiment should be construed according to the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of this embodiment.

100: optical phased array device
110: light source
120: input waveguide
130: optical distribution unit
132: slab waveguide
135 optical splitter
140: channel waveguide
141: output stage
150: optical path adjustment unit
200: optical phased array element
410, 510: variable prism
610: Acousto-optical modulator
710: cylindrical cylindrical lens
810, 815: grating pattern

Claims (7)

a light source for irradiating laser light of a preset wavelength band;
an input waveguide receiving the laser light irradiated from the light source;
an optical distribution unit distributing the laser light incident to the input waveguide to a predetermined number of channels to have uniform power;
a channel waveguide for dispersing and guiding the laser light distributed from the light distribution unit into M channels and radiating the laser light onto a free space; and
An optical path adjustment unit disposed in front of the output terminal of the channel waveguide in a direction in which light is irradiated and adjusting a path of the irradiated laser light;
The optical phased array device according to claim 1 , wherein the optical path adjustment unit is implemented as an acoustic-optic modulator and further comprises a circular cylindrical lens. delete delete According to claim 1,
The optical path adjusting unit,
An optical phased array device, characterized in that implemented as a variable prism. According to claim 4,
The variable prism,
An optical phased array device comprising a liquid crystal therein. According to claim 1,
The cylindrical cylindrical lens,
An optical phased array device characterized in that it is disposed between the output terminal and the acoustooptic modulator. According to claim 4,
The cylindrical cylindrical lens,
An optical phased array device, characterized in that disposed between the output end and the variable prism.

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