CN117631155A - All-solid-state horizontal beam steering device based on blazed grating - Google Patents

Abstract

The invention relates to an all-solid-state horizontal beam steering device based on a blazed grating with multiple notch densities, wherein after the wavelength-tuned beam is collimated by a gating and collimator of an optical switch, the beam irradiates on a blazed grating array which is arranged in a plurality of opposite directions, is symmetrical about the center and has different notch densities, and the deflection of the beam is realized by utilizing the dispersion characteristic of the blazed grating. By controlling the gating and switching-off of the optical switch, the light can be controlled to shine on blazed gratings with different notch densities, and further, the combination of different beam deflection angles can be realized. Compared with the traditional scheme of realizing angle scanning by using chromatic dispersion, the invention has higher spectrum utilization efficiency, can realize larger beam scanning angle only by a relatively shorter wavelength tuning range, and has the advantages of reducing the requirements on a light source and a rear-end device and simultaneously keeping low control complexity.

Description

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

Technical Field

The invention relates to beam steering, in particular to an all-solid-state horizontal beam steering device based on blazed gratings.

Background

The beam steering device is a key component of a laser radar and free space optical communication system, and has important application value in the fields of three-dimensional imaging, automatic driving, remote sensing and the like. The traditional beam steering device based on the mechanical rotating reflecting mirror, the vibrating mirror and the universal joint has the problems of limited scanning speed, easy environmental interference such as vibration, large volume, limited service life and the like, and has poor reliability. All-solid-state beam steering devices are of great interest for their robustness, fast steering speed, and the like. Therefore, the all-solid-state beam steering device is expected to replace mechanical scanning to become a new generation of beam scanning technology.

Several methods have been reported to achieve all-solid-state beam steering:

(1) Microelectromechanical Systems (MEMS) based solutions that achieve beam steering by controlling the angle of the mirrors, however MEMS systems still have miniature mechanical components, inevitably suffer from low life due to mechanical fatigue.

(2) A liquid crystal phase shifter based scheme. The scheme changes and controls the phases of different positions of the liquid crystal phase shifter, changes the phases of an incident light field at corresponding positions, and realizes the deflection of light beams. This solution does not have the problem of mechanical fatigue, but the scanning speed is slow and the optical power that can be tolerated is very limited.

(3) An integrated optical phased array based scheme. According to the scheme, the phase of optical signals of different emitting units on the integrated chip is changed, so that emergent light interferes constructively in a specific direction, and the beam steering is realized. The method can realize continuous adjustment of the beam pointing angle, but the optical phases of all the emitting units on the integrated chip need to be modulated, and along with the increase of the array scale, the control complexity and the power consumption become larger. In addition, the scheme has the problem that the signal-to-noise ratio of the main lobe relative to background noise is low.

(4) A solution for realizing beam scanning based on the angular dispersive power of a long grating. The scheme uses a sweep laser source, and utilizes the angular dispersion of a grating to realize one-dimensional beam scanning in the vertical dimension of the control of the beam wavelength. The scheme does not need to regulate and control the phase of an optical signal, and the control complexity is low, but because the typical angular dispersion typical value of an on-chip integrated grating is only 0.1 degrees/nm, the method needs a scanning laser source with a large wavelength scanning range to realize a larger light beam scanning range, so that the requirements on the scanning spectrum range of the light source and the response flatness of a rear-end receiving detector are relatively high. In order to improve the angular dispersion capability of the grating, a slow-light grating with larger angular dispersion capability can be adopted, but the slow-light grating has a forbidden band, and the tuning range of the sweep-frequency laser is limited, so that the scanning range of the light beam cannot be fundamentally improved.

(5) A solution based on lens-assisted beam deflection. The beam scanning of the scheme switches the beam to different channels for emission through an on-chip switch, and the beam collimation and deflection are realized by using an on-chip or off-chip lens. The proposal based on the lens auxiliary beam deflection comprises three implementation modes of realizing the beam deflection by integrating a plane lens, realizing the beam deflection by combining the off-chip two-dimensional array grating emission with the off-chip lens and realizing the beam deflection by combining the on-chip one-dimensional photon crystal grating with the off-chip lens. The scheme has the advantages of low control complexity and low power consumption, but can not scan continuously, and the resolution is limited by the minimum interval between the emitting units, so that a certain blind area exists in the light beam scanning process.

(6) The method comprises the steps of combining a lens auxiliary beam deflection technology with dispersion angle scanning, emitting a beam from a certain emission waveguide array to a free space by controlling light opening, irradiating the beam onto a grating after being collimated by a micro lens array, and deflecting the beam in one dimension by the grating according to the wavelength of the beam; the deflected light beam strikes a cylindrical lens, which deflects the light beam again according to the incident position. The direction of the two deflections is vertical, and two-dimensional scanning of the light beam can be achieved by changing the wavelength and waveguide array of the light beam. The scheme has low control complexity, but low spectral efficiency, and the range of realizing angle deflection by using chromatic dispersion is limited.

In general, the above schemes have limitations in either power capacity, or in control complexity and electrical power consumption, or in two-dimensional scanning capabilities. Therefore, a medium beam steering device is needed to overcome the shortcomings of the above-mentioned scheme, and has the advantages of high power budget, low control complexity and low power consumption, and can perform continuous and rapid light speed scanning with a large range and no blind area in a smaller wavelength tuning range.

Disclosure of Invention

The invention aims to solve the problems and the defects of the light beam steering device and provide an all-solid-state horizontal light beam steering device based on blazed gratings, which adopts the blazed gratings with different groove densities in multiple segments to realize continuous and rapid scanning and has the advantages of large power capacity, low control complexity and low power consumption, and does not need a laser source with a large tuning range.

In order to solve the problems, the technical solution of the present invention is as follows:

an all-solid-state horizontal beam steering device based on blazed gratings comprises an input coupler, a connecting waveguide, a 1 XN optical switch, N optical switch output waveguides, N output couplers outside a chip, a switch electrical interface, a controller, a 1 XN collimator array and blazed gratings, wherein the input coupler, the connecting waveguide, the 1 XN optical switch and the N optical switch output waveguides are integrated on a chip; it is characterized in that the method comprises the steps of,

the 1 XN collimator array consists of N collimators, and the 1 XN optical switch control light beam sequentially enters the corresponding N collimators through the N optical switch output waveguide and the N output coupler to be collimated and then irradiates the blazed grating;

the blazed grating is provided with N one-dimensional arrays with the same notch orientation and different densities, the notch densities are changed in a step change mode, light beams with a certain wavelength tuned are emitted from a collimator at different moments, and then irradiated onto the blazed grating combination with different notch densities, and the combination and the splicing of N different deflection field angles of the light beams are realized through dispersion and diffraction.

The input coupler is a tapered fiber or a Bragg grating.

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

The 1 XN optical switch is an optical switch network with a parallel type, serial type or a combined structure of the two.

The output coupler is a tapered optical fiber.

The 1 XN collimator array adopts a Gradient Refractive Index (GRIN) optical fiber collimator, a self-focusing lens (SELFOC) collimator, a micro lens array or a plano-convex lens, a planar biconvex lens, an aspheric plano-convex lens or an aspheric biconvex lens, and is used for expanding and collimating light emitted by the output coupler.

The one-dimensional array combination structure of the N transmission blazed gratings with different groove densities is as follows: the grating groove density increases stepwise from the center to the two sides, and the groove direction is symmetrical about the center. The size of the blazed grating with certain notch density is matched with the size of the light spot which propagates to the blazed grating after beam expansion, namely the width of the light beam in the horizontal direction is equal to the working width of the sub-grating in the horizontal direction, and the width of the light beam in the vertical direction is smaller than the working width of the sub-grating in the vertical direction. The center of the N transmission type blazed grating one-dimensional arrays with different groove densities is a parallel flat plate.

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

The output coupler expands the diameter of the light wave mode in the switch output waveguide to match with the mode field of the collimator.

The one-dimensional collimator expands and collimates the light emitted from the output coupler, so that the width of the light beam in the horizontal direction is equal to the working width of the sub-grating in the horizontal direction, and the width of the light beam in the vertical direction is smaller than the working width of the sub-grating in the vertical direction.

The end surfaces of the collimators are plated with antireflection films matched with the working wave bands so as to avoid back scattering.

The light beam enters the 1 XN optical switch network through the input coupler and the connecting waveguide, and the controller controls the switch through the switch electrical interface, so that the light beam is guided to a certain output waveguide through the optical switch circuit. The light beam enters a certain path of collimator through the output waveguide, then exits to free space, and deflects through a transmission blazed grating with certain notch density corresponding to the collimator. By controlling the gating and switching off of the 1 xn optical switch, the beam can be made to enter different collimators for emission. The diffraction angles of the light beams with the same wavelength are different because the groove densities and the groove directions of the blazed gratings below different collimator array units are different, and the combination and the splicing of N different deflection field angles (FOVs) of the light beams can be realized through the diffraction of N blazed gratings which are arranged in one dimension and have discrete groove densities.

The principle of the invention is that the angular dispersion of the grating is inversely proportional to the grating period, and the grating period is different, and the angular dispersion is also different. Gratings of different groove densities diffract light of the same wavelength range in different directions. The beam is controlled to enter a collimator from the channel of a certain output coupler by a 1 XN optical switch. The collimator array units are respectively arranged above the blazed grating arrays with different groove densities and symmetrical groove densities from the center to the two sides, and the light beams subjected to beam expansion and collimation by the collimator are irradiated on the blazed gratings with certain groove densities, and the light beams can be scanned by the blazed gratings through tuning the wavelength range of the laser. In addition, by adjusting the relative position of the emission plane and the blazed grating, the size of the blazed grating, the density of the grooves and the wavelength tuning range of the laser, perfect matching of deflection beam angles of different blazed gratings is realized, and the total deflection angle is equal to the sum of the deflection angles of all blazed gratings, namelyThis allows for a larger scan angle over a limited wavelength tuning range. Since the groove angle of the blazed grating is symmetrical about the center of the blazed grating combination array, the deflection angle can be doubled. The light beam passes through the collimator and is transmitted through the blazed gratingThe transmission is carried out into free space, and the transmission loss is very low.

Compared with the prior art, the invention has the following advantages:

1. the invention has the advantages of full solid structure, no mechanical moving parts, high reliability, no mechanical fatigue problem and long service life.

2. The present invention allows the use of non-semiconductor materials, and the choice of insulator materials can withstand higher power than liquid crystal beam scanning schemes. In addition, the invention can realize rapid light beam scanning, and the light beam scanning speed mainly depends on the response time and the wavelength tuning speed of the 1 XN optical switch.

3. Compared with the scheme of the optical phased array technology, only one end face has optical emission at the same time, the phase control of optical signals of all emission units is not needed, and the control complexity and the power consumption are lower than those of the optical phased array technology.

4. Compared with the scheme of realizing light beam scanning based on the angular dispersion of the long grating, the invention can obviously reduce the wavelength scanning range, more fully utilizes the angular dispersion of a plurality of blazed gratings, has the total field angle equal to the sum of the light beam deflection angles of the blazed gratings, and greatly improves the angle deflection range. Because the laser tuning range required to achieve the same angular field angle is shorter, the response flatness requirements for the tuned laser tuning range and the back-end light detector are lower.

5. Compared with the scheme of lens assisted beam steering, the invention can continuously scan without the problem of detection blind areas, thereby having higher resolution and being applicable to various fields such as laser radar, space optical communication and the like.

6. Compared with the optical beam scanning scheme based on the combination of lens assistance and grating dispersion, the optical spectrum scanning method has higher spectrum utilization efficiency, and the angle covered by the optical beam deflection can be improved by a plurality of times in the same optical wavelength scanning range, so that the requirement on the optical source tuning range can be lower. In addition, the invention has no scanning blind area problem, and can realize the scanning of the light beam without blind area in the whole FOV.

Drawings

Fig. 1 is a schematic diagram of an embodiment 1 of an all-solid-state beam steering device based on a multi-blazed grating according to the present invention.

Fig. 2 is a schematic diagram of the central parallel plate of the present invention, and the same groove density, the blazed gratings of different groove sides realizing the angular deflection of the light beam for wavelength tuning.

Fig. 3 is a schematic diagram of a blazed grating array of the present invention with the same groove direction and different groove densities to achieve angular beam deflection for wavelength tuning.

Fig. 4 is a schematic diagram of the principle of the present invention for multiplying the scanning range of the light beam by the engagement of a plurality of blazed grating light beam scanning angles.

In the figure: 1-input coupler, 2-connecting waveguide, 3-1 XN optical switch, 4-N optical switch output waveguide, 5-N output coupler, 6-switch electrical interface, 7-controller, 8-N collimator, 9-N blazed grating one-dimensional array with different groove densities; 10-a collimated emission beam incident on the blazed grating, 11-a deflection of a longer wavelength beam after diffraction by the blazed grating, 12-a deflection of a shorter wavelength beam after diffraction by the blazed grating.

Detailed Description

The invention will be further described with reference to the drawings and examples, which should not be construed as limiting the scope of the invention. Embodiments of the present invention include, but are not limited to, the following examples.

Referring to fig. 1, fig. 1 is a schematic diagram of an all-solid-state horizontal beam steering device based on a multi-segment discrete period blazed grating according to the present invention, and as can be seen from the drawing, an all-solid-state beam steering device based on a multi-segment discrete period blazed grating includes an input coupler 1, a connection 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, N discrete period blazed grating one-dimensional arrays 9, wherein the input coupler 1, the connection waveguide 2, the 1×n optical switch 3, the N optical switch output waveguides 4, and the N output couplers 5 are all fabricated on the same substrate, and the following steps are sequentially performed along the propagation direction of an optical signal: the optical fiber coupler comprises an input coupler 1, a connecting waveguide 2, a 1 XN optical switch 3, N optical switch output waveguides 4, N output couplers 5, N collimators 8 and N transmission type blazed grating one-dimensional arrays 9 with different notch densities, wherein the collimators 8 are positioned at the tail ends of the output couplers and are in non-contact with the N blazed grating one-dimensional arrays 9 with different notch densities.

The input end of the 1 XN optical switch is connected with the connecting waveguide, the N output ends of the optical switch are respectively connected with N output couplers through N output waveguides, the output end of the electrical controller is connected with the 1 XN optical switch control end through the switch electrical interface, the N output couplers extend to the edge of the integrated optical chip, the other end of the N output couplers are correspondingly connected with one-to-one arranged 1 XN collimator array units, the N collimators in one-dimensional arrangement are respectively positioned right above N transmission blazed gratings with different notch densities, and the N light beams emitted by the 1 XN collimator arrays are respectively irradiated on the blazed gratings with certain notch densities after being collimated. The width of the horizontal direction of the light beam is equal to the working width of the horizontal direction of the sub-grating, and the width of the vertical direction of the light beam is smaller than the working width of the vertical direction of the sub-grating.

Examples

In this embodiment, n=7, and the input coupler 1, the connection waveguide 2, the 1×n optical switch 3, the N optical switch output waveguides 4, the N output couplers 5, and the N transmissive blazed grating one-dimensional arrays 9 with different notch densities all operate at a wavelength of about 1550 nm.

The input coupler 1 is a tapered fiber or a bragg grating.

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

The 1 XN optical switch 3 is an optical switch network with parallel connection type, serial connection type or a combination structure of the two.

The output coupler 5 is a tapered optical fiber.

The N collimators 8 are gradient index (GRIN) fiber collimators, self-focusing lens (SELFOC) collimators, microlens arrays or plano-convex lenses, planar biconvex lenses, aspheric plano-convex lenses or aspheric biconvex lenses for expanding and collimating the light emitted by the output coupler.

The structure of the transmission type blazed grating one-dimensional array combination 9 with N different notch densities is as follows: the grating groove density increases from the center to the two sides in a step-like manner, and the directions of grooves are symmetrical about the center. The gratings with different groove densities have different groove densities and different diffraction angles for light with the same wavelength. The size of the blazed grating with certain notch density is matched with the size of the light spot of the blazed grating reaching the notch density after beam expansion. The center of the one-dimensional array 9 of the N transmission blazed gratings with different notch densities is a parallel flat plate.

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

The output coupler 5 expands the optical wave mode diameter in the switched output waveguide 4 to match the mode field of the collimator 8.

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

The end faces of the collimator 8 are plated with antireflection films matched with the working wave bands.

Fig. 1 shows an embodiment of the device of the invention, wherein blazed gratings with different groove densities and orientations are in one-to-one correspondence with collimators directly above the blazed gratings, and are symmetrically arranged about the center of a parallel plate in the center of the grating array. After the beam is expanded by the collimator, when the emergent beam reaches the blazed grating, the beam diameter is consistent with the length of the blazed grating with the notch density. The parallel plates are used to achieve the output without beam deflection, and it is noted that only one collimator of the present invention emits a beam at any time.

A schematic of the light field in the cross-section of fig. 1 is shown in fig. 2. At different moments, the three wavelength-tuned light beams respectively exit from the different collimators 8 and then strike the central parallel plate, and the two blazed gratings which are the same in groove density, opposite in orientation and symmetrical with respect to the central parallel plate are engraved on two sides of the parallel plate. When the wavelength of the light beam is tuned, blazed gratings on two sides generate scanning of the wavelength which is opposite in direction and symmetrical to the central parallel plate, and the angle of the light beam passing through the parallel plate cannot deflect along with the tuning of the wavelength. By combining blazed gratings with symmetric groove directions, multiplication of the scanning range can be achieved.

Another schematic of the light field in the cross-section of fig. 1 is shown in fig. 3. At different moments, after two wavelength-tuned light beams are emitted from two different collimators 8 respectively, the light beams irradiate on blazed gratings with the same orientation of the two grooving directions and different grooving densities. When the wavelength of the light beam is tuned, the blazed gratings on two sides generate scanning with the same wavelength in the same direction, but due to different groove densities of the blazed gratings, even for light in the same tuning range, the beam deflection angles are different, and the connection between the angles of the plurality of blazed gratings for deflecting the light beam can be realized by reasonably designing the groove densities of the light beam and the relative positions of the collimator array and the blazed grating array, so that the non-aliasing light beam scanning is realized, and the total angle scanning range is the sum of the beam deflection angles of all the blazed gratings.

Fig. 4 shows a schematic diagram of the principle of increasing the scanning range of the light beam in the case of a limited wavelength range by linking a plurality of blazed grating light beam scanning angles.

Claims (9)

1. An all-solid-state horizontal beam steering device based on blazed gratings comprises an input coupler, a connecting waveguide, a 1 XN optical switch, N optical switch output waveguides, N output couplers outside a chip, a switch electrical interface, a controller, a 1 XN collimator array and blazed gratings, wherein the input coupler, the connecting waveguide, the 1 XN optical switch and the N optical switch output waveguides are integrated on a chip; it is characterized in that the method comprises the steps of,

the 1 XN collimator array consists of N collimators, and the 1 XN optical switch control light beam sequentially enters the corresponding N collimators through the N optical switch output waveguide and the N output coupler to be collimated and then irradiates the blazed grating;

the blazed grating is provided with N one-dimensional arrays with the same notch orientation and different densities, the notch densities are changed in a step change mode, light beams with a certain wavelength tuned are emitted from a collimator at different moments, and then irradiated onto the blazed grating combination with different notch densities, and the combination and the splicing of N different deflection field angles of the light beams are realized through dispersion and diffraction.

2. The blazed grating-based all-solid-state horizontal beam steering device according to claim 1, wherein the blazed grating notch density increases stepwise from the center to both sides, and the notch directions are symmetrical about the center, the diffraction angles of the same wavelength light are different for the gratings with different notch densities, and the size of the blazed grating with a certain notch density matches the size of the spot of the blazed grating reaching the notch density after beam expansion.

3. The blazed grating-based all-solid-state horizontal beam steering device of claim 2, wherein the one-dimensional array of blazed gratings is centered as a parallel plate.

4. The blazed grating-based all-solid-state horizontal beam steering device of claim 1, wherein the input coupler is a tapered fiber or a bragg grating, the output coupler is a tapered fiber, and the output coupler expands the optical wave mode diameter in the switched output waveguide to match the mode field of the collimator.

5. The blazed grating-based all-solid-state horizontal beam steering device of claim 1, wherein the connecting waveguide, the 1 xn optical switch, and the N optical switch output waveguides are made of silicon, III-V semiconductor, silicon nitride, or silicon dioxide materials.

6. The blazed grating-based all-solid-state horizontal beam steering device of claim 1 or 5, wherein the 1 xn optical switch is a parallel-type, series-type or a combination of both optical switch networks.

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

8. The blazed grating-based all-solid-state horizontal beam steering device according to claim 1, wherein the end surfaces of the collimators are coated with an antireflection film matched with the working wavelength band, and the antireflection film is used for expanding and collimating the light emitted from the output coupler, so that the width of the light beam in the horizontal direction is equal to the working width of the sub-gratings in the horizontal direction, and the width of the light beam in the vertical direction is smaller than the working width of the sub-gratings in the vertical direction.

9. The blazed grating-based all-solid-state horizontal beam steering device of any one of claims 1-8, wherein the beam enters a 1 xn optical switching network via the input coupler and connecting waveguide, and the controller controls the switch via the switch electrical interface such that the beam is directed to one of the output waveguides via the optical switch path. The light beam enters a certain path of collimator through the output waveguide, then exits to free space, and deflects through a transmission blazed grating with certain notch density corresponding to the collimator.