All-solid-state horizontal beam steering device based on blazed grating

Abstract

The application is a kind of full solid state horizontal beam steering device based on multi-slot density blazed grating, wavelength tuning beam is irradiated on a plurality of blazed grating arrays arranged in opposite directions, about central symmetry, with different slot density, after the gating of optical switch and collimation of collimator, the deflection of the beam is realized by the dispersion characteristics of the blazed grating. By controlling the gating and opening of the optical switch, the light can be irradiated on the blazed grating with different slot density, and the combination of different beam deflection angles can be realized. Compared with the traditional scheme of realizing angle scanning by dispersion, the application has higher spectral utilization efficiency, only a relatively short wavelength tuning range is needed to realize a larger beam scanning angle, while reducing the requirements for light source and backend devices, and maintaining the advantage of low control complexity.

Description

Technical Field

[0001] This invention relates to beam steering, and in particular to an all-solid-state horizontal beam steering device based on a blazed grating. Background Technology

[0002] Beam steering devices are key components of lidar and free-space optical communication systems, and have significant applications in 3D imaging, autonomous driving, remote sensing, and many other fields. Traditional beam steering devices based on mechanically rotating mirrors, galvanometers, and gimbals suffer from limited scanning speed, susceptibility to environmental interference such as vibration, large size, and limited lifespan, resulting in poor reliability. All-solid-state beam steering devices, with their robustness and high steering speed, have attracted considerable attention. Therefore, all-solid-state beam steering devices hold promise as a next-generation beam scanning technology, potentially replacing mechanical scanning.

[0003] The following methods have been reported for achieving all-solid-state beam steering:

[0004] (1) The solution based on microelectromechanical systems (MEMS) achieves beam steering by controlling the angle of the reflector. However, MEMS systems still have miniature mechanical parts, which inevitably lead to mechanical fatigue and low service life.

[0005] (2) Liquid crystal phase shifter-based scheme. This scheme changes the phase of the incident light field at different positions of the liquid crystal phase shifter, thereby changing the phase of the incident light field at the corresponding positions and achieving beam deflection. This scheme does not have the problem of mechanical fatigue, but the scanning speed is relatively slow and the optical power it can withstand is very limited.

[0006] (3) Scheme based on integrated optical phased array. This scheme achieves beam steering by changing the phase of the optical signals of different emitting units on the integrated chip, causing constructive interference of the emitted light in a specific direction. This method can achieve continuous adjustment of the beam pointing angle, but it requires modulation of the optical phase of all emitting units on the integrated chip. As the array size increases, the control complexity and power consumption also increase. In addition, this scheme suffers from a relatively low signal-to-noise ratio of the main lobe relative to the background noise.

[0007] (4) A scheme for beam scanning based on the angular dispersion capability of a long grating. This scheme uses a swept-frequency laser source and utilizes the angular dispersion capability of the grating to achieve one-dimensional beam scanning in the vertical dimension of beam wavelength control. This scheme does not require phase modulation of the optical signal and has low control complexity. However, since the typical angular dispersion value of an on-chip integrated grating is only 0.1° / nm, this method requires a scanning laser source with a large wavelength scanning range to achieve a large beam scanning range. Therefore, the requirements for the scanning range of the light source and the response flatness of the back-end receiver detector are relatively high. In order to improve the angular dispersion capability of the grating, a slow-light grating with a larger angular dispersion capability can also be used. However, the slow-light grating has a bandgap, and the tuning range of the swept-frequency laser is limited, so it cannot fundamentally improve the beam scanning range.

[0008] (5) Lens-assisted beam deflection scheme. This scheme switches the beam to different channels via an on-chip switch and uses on-chip or off-chip lenses to achieve beam collimation and deflection. Currently proposed lens-assisted beam deflection schemes include three implementations: integrated planar lenses, off-chip two-dimensional array grating emission combined with off-chip lenses, and on-chip one-dimensional photonic crystal grating combined with off-chip lenses. This scheme has the advantages of low control complexity and low power consumption, but it cannot perform continuous scanning, and the resolution is limited by the minimum spacing between the emitting units, thus resulting in a certain blind zone during beam scanning.

[0009] (6) By combining lens-assisted beam deflection technology with dispersive angle scanning, a beam is emitted from a waveguide array into free space by controlling the light switch. After being collimated by a microlens array, it illuminates a grating, which deflects the beam in one dimension according to the beam wavelength. The deflected beam then illuminates a cylindrical lens, which deflects the beam again according to the incident position. The two deflections are perpendicular, and two-dimensional scanning of the beam can be achieved by changing the wavelength and the waveguide array. This scheme has low control complexity, but low spectral efficiency and a limited range for achieving angle deflection using dispersion.

[0010] In summary, the above-mentioned solutions all have limitations in terms of power capacity, control complexity and power consumption, or two-dimensional scanning capability. Therefore, there is an urgent need for a beam steering device that can overcome the many shortcomings of the above-mentioned solutions, and has the advantages of high power budget, low control complexity, and low power consumption, enabling large-area, blind-zone-free continuous, and fast light-speed scanning within a relatively small wavelength tuning range. Summary of the Invention

[0011] The problem to be solved by the present invention is to overcome the problems and shortcomings of the above-mentioned beam steering devices and to provide an all-solid-state horizontal beam steering device based on a blazed grating. The device uses a multi-segmented blazed grating with different groove densities to achieve continuous and fast scanning. It has the advantages of large power capacity, low control complexity, and low power consumption, and does not require a laser source with a large tuning range.

[0012] To solve the above problems, the technical solution of the present invention is as follows:

[0013] A fully solid-state horizontal beam steering device based on a blazed grating includes an input coupler, a connecting waveguide, a 1×N optical switch, and N output waveguides of the optical switch integrated on a chip, as well as N output couplers, a switching electrical interface, a controller, a 1×N collimator array, and a blazed grating off-chip; its characteristic is that...

[0014] The 1×N collimator array consists of N collimators. The beam is controlled by the 1×N optical switch to pass through the output waveguide of the Nth optical switch and the Nth output coupler in sequence to enter the corresponding Nth collimator and then illuminate the blazed grating.

[0015] The blazed grating has a one-dimensional array of N grooves with the same orientation but different densities, and the groove density changes stepwise. At different times, a light beam tuned to a certain wavelength is emitted from a collimator and shines on a combination of blazed gratings with different groove densities. Through dispersion diffraction, the beam is combined and spliced ​​with N different deflection field angles.

[0016] The input coupler is a tapered optical fiber or a Bragg grating.

[0017] The connecting waveguide, 1×N optical switch, and N output waveguides of the optical switch are made of silicon, III-V semiconductor, silicon nitride, or silicon dioxide.

[0018] The 1×N optical switch is a parallel, series, or a combination of both optical switch networks.

[0019] The output coupler is a tapered optical fiber.

[0020] The 1×N collimator array employs gradient refractive index (GRIN) fiber collimators, self-focusing lens (SELFOC) collimators, microlens arrays, plano-convex lenses, planar biconvex lenses, aspherical plano-convex lenses, or aspherical biconvex lenses to expand and collimate the light emitted from the output coupler.

[0021] The combined structure of the N one-dimensional array of transmissive blazed gratings with different groove densities is as follows: the groove density increases in a stepwise manner from the center to both sides, and the direction of the grooves is symmetrical about the center. The size of the blazed grating with a certain groove density matches the size of the light spot propagating to the blazed grating after beam expansion; that is, the width of the beam in the horizontal direction is equal to the working width of the sub-grating in the horizontal direction, and the width of the beam in the vertical direction is less than the working width of the sub-grating in the vertical direction. The center of the one-dimensional array of the N transmissive blazed gratings with different groove densities is a parallel plate.

[0022] Preferably, the input coupler, connecting waveguide, and switching output waveguide all operate in single-mode transverse electric mode (TE) or single-mode transverse magnetic mode (TM).

[0023] The output coupler expands the diameter of the optical mode in the switch output waveguide to match the mode field of the collimator.

[0024] The one-dimensional collimator expands and collimates the light emitted from the output coupler, making the width of the beam in the horizontal direction equal to the working width of the sub-grating in the horizontal direction, and the width of the beam in the vertical direction less than the working width of the sub-grating in the vertical direction.

[0025] The collimator end faces are all coated with an anti-reflection film that matches the operating wavelength to avoid backscattering.

[0026] The light beam enters a 1×N optical switch network through an input coupler and a connecting waveguide. The controller controls the switch via the switch's electrical interface, guiding the beam through the optical switch path to a specific output waveguide. The beam then enters a collimator via the output waveguide, exits into free space, and is deflected after passing through a transmissive blazed grating with a specific groove density corresponding to that collimator. By controlling the selection and disconnection of the 1×N optical switch, the beam can be emitted through different collimators. Because the groove density and groove direction of the blazed gratings below different collimator array units are different, the diffraction angles for the same wavelength beam are also different. Through the diffraction of N one-dimensionally arranged blazed gratings with discrete groove densities, N different deflection field of view (FOV) angles of the beam can be combined and stitched together.

[0027] The principle of this invention is that the angular dispersion of a grating is inversely proportional to its period; different grating periods result in different angular dispersions. Gratings with different groove densities will diffract light within the same wavelength range in different directions. A 1×N optical switch controls the light beam to enter a collimator from a channel of a specific output coupler. The collimator array is placed directly above an array of blazed gratings with different groove densities, symmetrical grooves from the center outwards, and a step-change groove density. After being expanded and collimated by the collimator, the light beam illuminates a blazed grating with a specific groove density. By tuning the laser wavelength range, the beam can scan through this blazed grating. Furthermore, by adjusting the relative position of the emitting plane and the blazed grating, the size of the blazed grating, its groove density, and the laser wavelength tuning range, a perfect match can be achieved between the beam deflection angles of different blazed gratings. The total deflection angle is equal to the sum of the deflection angles of each blazed grating, i.e. This allows for a larger scanning angle within a limited wavelength tuning range. Since the groove angle of the blazed grating is symmetrical about the center of the blazed grating array, the deflection angle can be doubled further. The beam passes through the collimator and the blazed grating, directly emitted into free space, resulting in very low emission loss.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. This invention has an all-solid structure with no moving mechanical parts, resulting in high reliability, no mechanical fatigue issues, and a long service life.

[0030] 2. Compared to liquid crystal beam scanning schemes, this invention allows the use of non-semiconductor materials, and the selection of insulating materials can withstand higher power. Furthermore, this invention enables rapid beam scanning, with the scanning speed primarily depending on the 1×N optical switch response time and wavelength tuning speed.

[0031] 3. Compared with the optical phased array technology, the present invention allows only one end face to emit light at a time, eliminating the need to control the phase of the light signals of all emitting units simultaneously. The control complexity and power consumption are lower than those of the optical phased array technology.

[0032] 4. Compared to beam scanning schemes based on the angular dispersion ability of long gratings, this invention significantly reduces the wavelength scanning range, making fuller use of the angular dispersion ability of multiple blazed gratings. The total field of view is equal to the sum of the beam deflection angles of each blazed grating, greatly improving the angular deflection range. Because a shorter laser tuning range is required to achieve the same field of view, the requirements for the tuning range of the frequency-modulated laser and the response flatness of the downstream photodetector are lower.

[0033] 5. Compared with the lens-assisted beam steering scheme, the present invention can continuously scan without the problem of blind spots in detection, thus having higher resolution and being suitable for many fields such as lidar and space optical communication.

[0034] 6. Compared to beam scanning schemes based on lens-assisted grating dispersion, this invention offers higher spectral utilization efficiency. Within the same optical wavelength scanning range, the angle that the beam deflection can cover can be increased several times, thus requiring a lower light source tuning range. Furthermore, this invention eliminates the problem of blind spots, enabling blind-spot-free beam scanning across the entire field of view (FOV). Attached Figure Description

[0035] Figure 1 This is a schematic diagram of Embodiment 1 of the all-solid-state beam steering device based on multi-blazed gratings of the present invention.

[0036] Figure 2 This is a schematic diagram illustrating how a central parallel plate and blazed gratings with the same groove density but different groove orientations achieve wavelength-tuned beam angle deflection in this invention.

[0037] Figure 3 This is a schematic diagram illustrating how a blazed grating array with the same groove direction but different groove densities achieves wavelength-tuned beam angle deflection in this invention.

[0038] Figure 4 This is a schematic diagram illustrating the principle of how the scanning range of a beam is multiplied by connecting the scanning angles of multiple blazed grating beams in this invention.

[0039] In the figure: 1-Input coupler, 2-Connecting waveguide, 3-1×N optical switch, 4-N output waveguides of optical switches, 5-N output couplers, 6-Electrical interface of the switch, 7-Controller, 8-N collimators, 9-N one-dimensional array of blazed gratings with different groove densities; 10-Collimated emitted beam incident on the blazed grating, 11-Deflection of the longer wavelength beam after diffraction by the blazed grating, 12-Deflection of the shorter wavelength beam after diffraction by the blazed grating. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention. Embodiments of the present invention include, but are not limited to, the following embodiments.

[0041] Please see Figure 1 , Figure 1This is a schematic diagram of the all-solid-state horizontal beam steering device based on a multi-segmented discrete periodic blazed grating according to the present invention. As shown in the figure, an all-solid-state beam steering device based on a multi-segmented discrete periodic blazed grating includes an input coupler 1, a connecting waveguide 2, a 1×N optical switch 3, N optical switch output waveguides 4, N output couplers 5, a switch electrical interface 6, a controller 7, a 1×N collimator array 8, and a one-dimensional array of N discrete periodic blazed gratings 9. The input coupler 1, connecting waveguide 2, 1×N optical switch 3, N optical switch output waveguides 4, and N output couplers 5 are all fabricated on the same substrate. Along the direction of optical signal propagation, the sequence is as follows: the input coupler 1, connecting waveguide 2, 1×N optical switch 3, N optical switch output waveguides 4, N output couplers 5, N collimators 8, and N one-dimensional arrays of transmissive blazed gratings with different groove densities 9. The collimator 8 is located at the end of the output coupler and has no contact with the one-dimensional array of N blazed gratings with different groove densities 9.

[0042] The input terminal of the 1×N optical switch is connected to the connecting waveguide. The N output terminals of the optical switch are connected to N output waveguides and N output couplers, respectively. The output terminal of the electrical controller is connected to the control terminal of the 1×N optical switch through the switch's electrical interface. The N output couplers extend to the edge of the integrated optical chip, and their other ends are connected to a one-dimensional array of 1×N collimators. The N collimators are positioned directly above N transmissive blazed gratings with different groove densities. The N beams emitted from the 1×N collimator array, after collimation, all illuminate a blazed grating with a specific groove density. The horizontal width of the beam is equal to the horizontal working width of the sub-grating, and the vertical width of the beam is less than the vertical working width of the sub-grating.

[0043] Example

[0044] In this embodiment, N=7, and the input coupler 1, connecting waveguide 2, 1×N optical switch 3, N optical switch output waveguides 4, N output couplers 5, and N one-dimensional arrays of transmission-type blazed gratings with different groove densities 9 all operate near a wavelength of 1550nm.

[0045] The input coupler 1 is a tapered optical fiber or a Bragg grating.

[0046] The connecting waveguide 2, the 1×N optical switch 3, and the N optical switch output waveguides 4 are made of silicon, III-V semiconductor, silicon nitride, or silicon dioxide.

[0047] The 1×N optical switch 3 is an optical switch network with a parallel, series, or combination of both structures.

[0048] The output coupler 5 is a tapered optical fiber.

[0049] The N collimators 8 are gradient refractive index (GRIN) fiber collimators, self-focusing lens (SELFOC) collimators, microlens arrays or plano-convex lenses, planar biconvex lenses, aspherical plano-convex lenses or aspherical biconvex lenses, used to expand and collimate the light emitted from the output coupler.

[0050] The structure of the N one-dimensional array of transmissive blazed gratings with different groove densities is as follows: It is a combination of one-dimensionally arranged blazed gratings with groove density increasing in a stepwise manner from the center to both sides, and with the groove directions symmetrical about the center. Gratings with different groove densities have different diffraction angles for the same wavelength of light. The size of a blazed grating with a certain groove density matches the size of the light spot reaching that blazed grating after beam expansion. A parallel plate is located at the center of the N one-dimensional array of transmissive blazed gratings with different groove densities.

[0051] Preferably, the input coupler 1, the connecting waveguide 2, and the switching output waveguide 4 all operate in single-mode transverse electric mode (TE) or single-mode transverse magnetic mode (TM).

[0052] The output coupler 5 expands the diameter of the optical mode in the switch output waveguide 4 to match the mode field of the collimator 8.

[0053] The collimator 8 further expands and collimates the light emitted from the output coupler, so that the width of the beam in the horizontal direction is equal to the working width of the sub-grating in the horizontal direction, and the width of the beam in the vertical direction is less than the working width of the sub-grating in the vertical direction.

[0054] The end face of the collimator 8 is coated with an anti-reflection film that matches the working wavelength.

[0055] Figure 1 An embodiment of the device of the present invention is shown, in which blazed gratings with different groove densities and orientations correspond one-to-one with the collimator directly above them, and are arranged symmetrically about the center of the parallel plate in the grating array. After beam expansion by the collimator, when the emitted beam reaches the blazed grating, the beam diameter is consistent with the length of the blazed grating of that groove density. The parallel plate is used to achieve output without beam deflection. It should be noted that at any given time, only one collimator in the present invention emits a beam.

[0056] Figure 2 The middle drawing Figure 1A schematic diagram of an optical field on a cross-section. At different times, three wavelength-tuned beams emerge from different collimators 8 and illuminate a central parallel plate, as well as two blazed gratings on either side of the parallel plate with the same groove density, opposite orientation, and symmetrical about the central parallel plate. When the beam wavelength is tuned, the blazed gratings on both sides generate scanning wavelengths with opposite directions and symmetrical about the central parallel plate. The beam angle passing through the parallel plate does not deflect with wavelength tuning. By combining blazed gratings with symmetrical groove orientation, the scanning range can be multiplied.

[0057] Figure 3 shows Figure 1 Another schematic diagram of the light field on the cross section. At different times, two wavelength-tuned beams emerge from two different collimators 8 and illuminate two blazed gratings with the same groove direction but different groove densities. When the beam wavelength is tuned, the blazed gratings on both sides generate a wavelength scan with the same direction. However, due to the different groove densities of the blazed gratings, even for light within the same tuning range, the beam deflection angle is different. By reasonably designing the groove density of the beam and the relative position of the collimator array and the blazed grating array, the angles between the deflected beams of several blazed gratings can be connected to achieve aliasing-free beam scanning. The total angular scanning range is the sum of the deflection angles of the beams of each blazed grating.

[0058] Figure 4 The diagram illustrates the principle of increasing the beam scanning range within a limited wavelength range by connecting the scanning angles of multiple blazed gratings.

Claims

1. A solid-state horizontal beam steering device based on a blazed grating, comprising an input coupler, a connecting waveguide, a 1×N optical switch, and N output waveguides of the optical switch integrated on a chip, and N output couplers, a switching electrical interface, a controller, a 1×N collimator array, and a blazed grating off-chip; characterized in that, The 1×N collimator array consists of N collimators. The beam is controlled by the 1×N optical switch to pass through the output waveguide of the Nth optical switch and the Nth output coupler in sequence to enter the corresponding Nth collimator and then illuminate the blazed grating. The blazed grating has a one-dimensional array of N grooves with the same orientation but different densities, and the groove density changes stepwise. At different times, a light beam tuned to a certain wavelength is emitted from a collimator and shines on a combination of blazed gratings with different groove densities. Through dispersion diffraction, the beam is combined and spliced ​​with N different deflection field angles.

2. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 1, characterized in that, The blazed grating groove density increases in a stepwise manner from the center to both sides, and the direction of the grooves is symmetrical about the center. Gratings with different groove densities have different diffraction angles for the same wavelength of light. The size of the blazed grating with a certain groove density is matched with the size of the light spot that reaches the blazed grating with that groove density after beam expansion.

3. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 2, characterized in that, The one-dimensional array of the blazed grating has a parallel plate at its center.

4. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 1, characterized in that, The input coupler is a tapered optical fiber or a Bragg grating, and the output coupler is a tapered optical fiber. The output coupler expands the diameter of the optical mode in the switch output waveguide to match the mode field of the collimator.

5. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 1, characterized in that, The connecting waveguide, 1×N optical switch, and N output waveguides of the optical switch are made of silicon, III-V semiconductor, silicon nitride, or silicon dioxide.

6. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 1 or 5, characterized in that, The 1×N optical switch is a parallel, series, or a combination of both optical switch networks.

7. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 1, characterized in that, The input coupler, connecting waveguide, and switching output waveguide all operate in single-mode transverse electric mode (TE) or single-mode transverse magnetic mode (TM).

8. The all-solid-state horizontal beam steering device based on a blazed grating according to claim 1, characterized in that, The end faces of the collimators are coated with antireflection films that match the operating wavelength, which are used to expand and collimate the light emitted from the output coupler, so that the width of the beam in the horizontal direction is equal to the working width of the blazed grating sub-region corresponding to the collimator in the horizontal direction, and the width of the beam in the vertical direction is less than the working width of the blazed grating sub-region in the vertical direction.

9. The all-solid-state horizontal beam steering device based on a blazed grating according to any one of claims 1-5, characterized in that, The light beam passes through the input coupler and the connecting waveguide into the 1×N optical switch. The controller controls the 1×N switch through the switch's electrical interface, so that the light beam is guided to a certain output waveguide after passing through the 1×N optical switch. The light beam passes through the output waveguide into the collimator corresponding to the output waveguide, and then exits into free space. After passing through a transmission blazed grating with a groove density corresponding to the collimator, the beam angle is deflected.

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