CN114609723A - Light modulator without complex phase correction - Google Patents

Abstract

The invention discloses a light modulator without complex phase correction, which comprises: the integrated temperature-stabilized laser, the low-loss optical beam splitter, the low-phase error phase modulator array, the phase error-free routing waveguide array and the dense optical antenna array. The invention adopts the design of the low-phase error waveguide link, effectively weakens the influence of the waveguide width change on the effective refractive index of the waveguide caused by the processing nonuniformity, can realize the interference and scanning of far-field beams without phase correction, and greatly reduces the complexity of later test and actual batch application. The invention adopts Manhattan or other routing paths, so that the optical paths of all channels are the same, and the change of phase difference between the channels caused by the change of the environmental temperature can be further reduced. All the curved waveguides in the invention adopt the optimized design of gradually changing curvature and width, so that the whole structure is more compact, and simultaneously, the high-order mode crosstalk can be inhibited.

Description

A Light Regulator Without Complex Phase Correction

technical field

The invention belongs to the field of optoelectronic chips, in particular to an optical regulator that does not require complex phase correction.

Background technique

Beam steering technology is widely used in free space optical communication, 3D printing and other fields, especially with the rapid development of artificial intelligence, people's demand for products with small size, light weight, high reliability and low price is increasing. Silicon photonics technology is compatible with mature CMOS, and has obvious advantages in realizing low-cost on-chip integrated all-solid-state beam steering systems, which has attracted widespread attention.

At present, researchers focus on silicon-based integrated beam scanning chips mainly in terms of scanning range, resolution and scanning speed, and have produced a series of high-performance on-chip beam scanning systems. The cladding has a high refractive index difference, and is limited by the precision of processing, so that the existing beam scanning chip needs to use an optimization algorithm to perform phase correction point by point before use, which greatly increases the complexity of the system and The cost of use is not conducive to actual industrial applications in the future. Therefore, how to eliminate the phase noise of the beam scanning chip and realize the beam scanning chip without complex phase correction is of great significance.

SUMMARY OF THE INVENTION

In view of the problems existing in the background art, the purpose of the present invention is to provide a light regulator that does not require complex phase correction.

The technical scheme adopted in the present invention is:

An optical regulator that does not require complex phase correction, comprising: an integrated temperature-stabilized laser (1), a low-loss optical beam splitter (2), a low-phase-error phase modulator array (3), and a phase-error-free routing waveguide array ( 4) and a dense optical antenna array (5);

The integrated temperature-stabilized laser (1) is connected to an input end of a low-loss optical beam splitter (2) via an input optical waveguide, and an output end of the low-loss optical beam splitter (2) is connected to a low-phase error phase modulator The array (3) and the input ends of the phase-error-free routing waveguide array (4) are connected in one-to-one correspondence, and the output end of the phase-error-free routing waveguide array (4) is connected to the dense optical antenna array (5) to complete the output of the optical signal;

The low-loss optical beam splitter (2) is used to equally divide the optical signals generated by the integrated temperature-stabilized laser (1) into 2 ^N paths; the low-phase error phase modulator array (3) is used to pass an applied voltage The control method is to perform continuous phase modulation on each optical signal after beam splitting, so that the adjacent two optical signals generate a specific phase difference; then the modulated optical signal is emitted through the dense optical antenna array (5), The far-field specific angular interference constructively forms a scanning beam.

The specific phase difference generated by the low phase error phase modulator array (3) satisfies the formula:

为相邻两路光信号的相位差，d'为相邻两路天线的间距，λ为工作光波长，θ为扫描光束的偏转角度。in the formula

is the phase difference of two adjacent optical signals, d' is the distance between two adjacent antennas, λ is the wavelength of the working light, and θ is the deflection angle of the scanning beam.

Preferably, the low-loss optical beam splitter (2) is composed of cascaded low-error 3dB beam splitters, and the low-error 3dB beam splitter has an axisymmetric structure, comprising an input straight waveguide (210), a core region (220), first upper curved waveguide (231), first lower curved waveguide (232), upper output straight waveguide (241), lower output straight waveguide (342), second upper curved waveguide (251), second lower curved waveguide (252);

After the optical signal enters the core region (220) through the input straight waveguide (210), the light intensity is equally divided into two paths. An output port of the core region (220) is connected to the first upper curved waveguide (231) and the upper output straight waveguide (241). ) and the second upper curved waveguide (251) are connected in sequence; the other output port of the core region (220) is connected to the first lower curved waveguide (232), the lower output straight waveguide (242), and the second lower curved waveguide (252) in sequence Connection; the output ends of the second upper curved waveguide (251) and the second lower curved waveguide (252) are respectively connected with the input straight waveguide of the next stage 3dB beam splitter (210).

The output ends of the first upper curved waveguide (231) and the first lower curved waveguide (231) are low-phase error waveguides, and the input ends are narrow waveguides, which are used for removing high-order beams generated during beam splitting in the core region (220). mode; the input and output ends of the second upper curved waveguide (251) and the second lower curved waveguide (252) are both low phase error waveguides.

Preferably, the first upper curved waveguide (231), the first lower curved waveguide (231), the second upper curved waveguide (251) and the second lower curved waveguide (252) adopt, but are not limited to, a gradient-width Euler line type Or Bezier line-shaped curved waveguides that reduce excitation of higher-order modes while being compact.

Preferably, the input port of the phase-error-free routing waveguide array (4) is a wide-spacing low-phase-error waveguide array, that is, a wide-spacing waveguide array (the phase modulator is generally implemented by heating, and the spacing of the waveguides is increased here. , it is necessary to ensure that there is no thermal crosstalk between adjacent phase modulators, and the specific interval size needs to be determined according to the design of the phase modulator), to ensure that the adjacent phase modulators in the low phase error phase modulator array (3) There is no crosstalk; the output port is a densely arranged low-phase error waveguide array, that is, an output dense waveguide array (the smaller the array element interval, the larger the scanning range of the far-field scanning beam, and the ideal array element interval is half of the working wavelength. In this way, a scanning range of 180° can be achieved, but at this time, if the array element spacing is too small, strong coupling crosstalk will occur between adjacent array elements. Therefore, the array element spacing of the output dense waveguide array needs to ensure that there is no coupling between the array elements. In the case of , as small as possible), there is no coupling crosstalk between the array elements of the output dense waveguide array; each waveguide in the routing waveguide array without phase error (4) has the same optical path, so that each channel has the same optical path. initial phase.

Optionally, the output port of the waveguide array (4) is in the form of a sparse array or a sparse array, which can effectively suppress the generation of far-field grating lobes, thereby increasing the scanning angle of the light beam.

Preferably, the low-loss optical beam splitter (2), the low-phase-error phase modulator array (3), and the phase-error-free routing waveguide array (4) are connected by a low-phase-error waveguide, which reduces the need for processing and fabrication. phase noise due to errors.

Optionally, the low phase error phase modulator array (3) adopts the principle of thermo-optic or electro-optic, and changes the effective refractive index of the waveguide by applying pressure, so as to control the phase relationship of the light beams between adjacent channels, and change the output near The direction of the wavefront of the field enables the scanning of the far-field beam.

Optionally, the dense optical antenna array (5) adopts a two-dimensional large-aperture waveguide grating structure, and realizes two-dimensional scanning of the light beam by combining wavelength and phase modulation.

The beneficial effects that the present invention has are:

(1) The present invention adopts the design of the low phase error waveguide link, which effectively reduces the influence of the waveguide width change caused by the processing inhomogeneity on the effective refractive index of the waveguide, and can realize the interference and scanning of the far-field beam without the need for phase correction. , which greatly reduces the complexity of post-test and actual batch applications.

(2) In the present invention, "Manhattan" or other routing paths are adopted, so that the optical lengths of all channels are the same, which can further reduce the change of the phase difference between the channels caused by the change of the ambient temperature.

(3) All the curved waveguides in the present invention adopt the optimized design of gradual curvature and width, so that the overall structure is more compact, and the crosstalk of high-order modes can be suppressed at the same time.

Description of drawings

1 is a schematic structural diagram of an embodiment of the present invention;

In the picture: Integrated temperature-stabilized laser (1), low-loss optical beam splitter (2), low-phase-error phase modulator array (3), phase-error-free routing waveguide array (4), and dense optical antenna array (5) .

Fig. 2 is a schematic diagram of two kinds of curved waveguides used in the embodiment of the present invention. The curved waveguides shown in Fig. 2(a) and Fig. 2(b) are obtained by optimizing Bezier curves by using particle swarm algorithm.

Figure 3 is a schematic diagram of a "Manhattan-shaped" phase error-free routing waveguide array employed in an embodiment.

FIG. 4 is a graph showing the relationship between the width of the waveguide and the effective refractive index of the waveguide in a specific embodiment.

FIG. 5 is the transmission loss curve of the two kinds of curved waveguides in FIG. 2 .

Detailed ways

The scheme of the present invention will be further described below in conjunction with the accompanying drawings.

As shown in FIG. 1, an optical regulator without complex phase correction includes the following parts: an integrated temperature-stabilized laser (1), a low-loss optical beam splitter (2), and a low-phase error phase modulator array (3) , a phase error-free routing waveguide array (4) and a dense optical antenna array (5);

The integrated temperature-stabilized laser (1) is connected to an input end of a low-loss optical beam splitter (2) via an input optical waveguide, and an output end of the low-loss optical beam splitter (2) is connected to a low-phase error phase modulator The array (3) and the input ends of the phase-error-free routing waveguide array (4) are connected in one-to-one correspondence, and the output end of the phase-error-free routing waveguide array (4) is connected to the dense optical antenna array (5) to complete the output of optical signals.

The specific working process is as follows: the low-loss optical beam splitter (2) is used to equally divide the optical signal generated by the integrated temperature-stabilized laser (1) into 2 ^N paths (the number can be freely selected, the more the number, the more the far field The smaller the divergence angle of the scanning beam, the higher the detection accuracy, but at the same time it will increase the difficulty of manufacturing and control of the system); the low phase error phase modulator array (3) controls each beam splitting One optical signal is subjected to continuous phase modulation, so that two adjacent optical signals generate a specific phase difference; then the modulated optical signal is emitted through the dense optical antenna array (5), and interferes constructively at a specific angle in the far field. A scanning beam is formed.

The specific phase difference generated by the low phase error phase modulator array (3) satisfies the formula:

为相邻两路光信号的相位差，d'为相邻两路天线的间距，λ为工作光波长，θ为扫描光束的偏转角度。in the formula

is the phase difference of two adjacent optical signals, d' is the distance between two adjacent antennas, λ is the wavelength of the working light, and θ is the deflection angle of the scanning beam.

The low-loss optical beam splitter (2) is composed of cascaded low-loss 3dB beam splitters, and the overall structure of the low-loss 3dB beam splitter is symmetrical about the central axis, including an input straight waveguide (210), a core region (220) , a first upper curved waveguide (231), a first lower curved waveguide (232), an upper output straight waveguide (241), a lower output straight waveguide (342), a second upper curved waveguide (251), a second lower curved waveguide ( 252); after the optical signal enters the core region (220) through the input straight waveguide (210), the light intensity is equally divided into two paths, and one output port of the core region (220) is connected to the first upper curved waveguide (231) and the upper output straight waveguide. The waveguide (241) and the second upper curved waveguide (251) are connected in sequence; the other output port of the core region (220) is connected to the first lower curved waveguide (232), the lower output straight waveguide (242) and the second lower curved waveguide ( 252) are connected in sequence; the output ends of the second upper curved waveguide (251) and the second lower curved waveguide (252) are respectively connected with the input straight waveguide of the next stage 3dB beam splitter (210).

As shown in FIG. 2, the first upper bending waveguide (231), the first lower bending waveguide (231), the second upper bending waveguide (251) and the second lower bending waveguide (252) are based on Bessel lines Type freely optimized curved waveguide that reduces the excitation of higher-order modes while being compact.

As shown in Fig. 3, the "Manhattan-shaped" waveguide path is adopted in the no-phase error routing waveguide array (4) to ensure that each waveguide has the same optical path, so that each channel has the same initial phase, and each part has the same initial phase. The waveguide spacing satisfies the following formula:

where d _in represents the array element spacing of the input wide-spaced waveguide array, d _out represents the array element spacing of the output dense waveguide array, and d represents the array element spacing of the phase-error-free routing waveguide array.

The low-loss optical beam splitter (2), the low-phase-error phase modulator array (3), and the phase-error-free routing waveguide array (4) are all composed of a low-phase-error waveguide and a specially designed low-phase-error bending Route waveguide connections to reduce phase noise due to fabrication errors. The above-mentioned special design requires a more compact overall structure, and at the same time can suppress high-order mode crosstalk, and an optimized design of curvature and width gradient can be adopted.

Specific examples:

A silicon platform on an insulating substrate is used to fabricate the waveguide. The silicon thickness of the core layer is 220 nm and the refractive index is 3.46; The refractive index is 1.45.

The relationship between the effective refractive index of the waveguide and the width of the waveguide is shown in Figure 4. It can be seen that as the width of the waveguide increases, the rate of change of the effective refractive index with the width of the waveguide slows down. Therefore, the selection of a wide waveguide can reduce the random error of the waveguide. Influence of inner beam phase.

The beam splitter is realized by cascaded MMI, which has the characteristics of large processing tolerance.

As shown in Figure 2, the connected curved waveguide is obtained by optimizing the Bessel line shape by using particle swarm algorithm; From the transmittance curve of this kind of curved waveguide, it can be seen that the loss is less than 0.01dB in the wavelength range from 1500nm to 1600nm.

The above-mentioned embodiments are only used to explain the present invention, not to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall be included in the present invention. within the scope of protection.

Claims (9)

1. A light modulator that does not require complex phase correction, comprising: the system comprises an integrated temperature-stabilized laser (1), a low-loss optical beam splitter (2), a low-phase error phase modulator array (3), a phase error-free routing waveguide array (4) and a dense optical antenna array (5);

the integrated temperature-stabilized laser (1) is connected with the input end of a low-loss optical beam splitter (2) through an input optical waveguide, the output end of the low-loss optical beam splitter (2) is connected with the input end of a phase error-free routing waveguide array (4) through a low-phase error phase modulator array (3) in a one-to-one correspondence mode, and the output end of the phase error-free routing waveguide array (4) is connected with a dense optical antenna array (5) to finish the outgoing of optical signals.

2. A light modulator without complex phase correction as claimed in claim 1, characterized in that the low loss beam splitter (2) is used to divide the light signal generated by the integrated temperature stabilized laser (1) into 2 equally^NA way; the low phase error phase modulator array (3) performs continuous phase modulation on each split optical signal in a control mode of external voltage so as to enable two adjacent optical signals to generate a specific phase difference; then the modulated optical signals are emitted through a dense optical antenna array (5) and are subjected to interference constructive at a specific angle of a far field to form a scanning beam;

the specific phase difference generated by the low phase error phase modulator array (3) satisfies the formula:

in the formula

D' is the distance between two adjacent antennas, λ is the wavelength of the working light, and θ is the deflection angle of the scanning beam.

3. A light modulator without complex phase correction according to claim 1 or 2, characterized in that the low loss light splitter (2) is composed of cascaded low-error 3dB splitters, the low-error 3dB splitters are in an axisymmetric structure and include an input straight waveguide (210), a core region (220), a first upper curved waveguide (231), a first lower curved waveguide (232), an upper output straight waveguide (241), a lower output straight waveguide (342), a second upper curved waveguide (251), and a second lower curved waveguide (252);

after an optical signal enters a core region (220) through an input straight waveguide (210), the light intensity is averagely divided into two paths, and one output port of the core region (220) is sequentially connected with a first upper bent waveguide (231), an upper output straight waveguide (241) and a second upper bent waveguide (251); the other output port of the core region (220) is connected with the first lower bent waveguide (232), the lower output straight waveguide (242) and the second lower bent waveguide (252) in sequence; the output ends of the second upper bent waveguide (251) and the second lower bent waveguide (252) are respectively connected with the input straight waveguide of the next-stage 3dB beam splitter (210);

the output ends of the first upper bending waveguide (231) and the first lower bending waveguide (231) are low phase error waveguides, and the input ends of the first upper bending waveguide and the first lower bending waveguide are narrow waveguides, so that a high-order mode generated during beam splitting of the core region (220) is removed; the input end and the output end of the second upper bent waveguide (251) and the second lower bent waveguide (252) are low-phase error waveguides.

4. A light modulator without complex phase correction as claimed in claim 3, wherein the first upper curved waveguide (231), the first lower curved waveguide (231), the second upper curved waveguide (251) and the second lower curved waveguide (252) are curved waveguides with gradually varied widths, such as euler type or bessel type, to reduce the excitation of higher order modes while achieving a compact structure.

5. A light modulator without complex phase correction as claimed in claim 3 or 4, characterized in that the input port of the phase error free routing waveguide array (4) is a wide-pitch low phase error waveguide array, that is, a wide-pitch waveguide array, which ensures that no crosstalk occurs between adjacent phase modulators in the low phase error phase modulator array (3); the output port is a densely arranged low-phase error waveguide array, namely an output dense waveguide array, and no coupling crosstalk exists among array elements of the output dense waveguide array; each waveguide in the phase error free routing waveguide array (4) has the same optical path length such that each channel has the same initial phase.

6. A non-complex phase-correcting light modulator according to claim 5, characterized in that the output ports of the waveguide array (4) are sparse array or sparse array, which can effectively suppress the generation of far-field grating lobes and thus increase the scanning angle of the light beam.

7. A non-complex phase-correcting optical modulator according to claim 3 or 4, characterized in that the low loss optical splitter (2), the low phase error phase modulator array (3) and the non-phase error routing waveguide array (4) are connected by low phase error waveguides, so as to reduce the phase noise caused by manufacturing errors.

8. A light modulator without complex phase correction as claimed in claim 3 or 4, characterized in that said low phase error phase modulator array (3) uses thermo-optic or electro-optic principle to change the effective refractive index of the waveguide by applying pressure, thereby controlling the phase relationship of the light beams between adjacent channels, changing the wave front direction of the output near field, and realizing the scanning of the far field light beam.

9. A light modulator without complex phase correction according to claim 3 or 4, characterized in that the dense optical antenna array (5) uses a two-dimensional large aperture waveguide grating structure, and combines wavelength and phase modulation to realize two-dimensional scanning of light beam.

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