A bidirectional dual-polarization beam deflector

Abstract

The present invention discloses a bidirectional dual-polarization beam deflector. Light with TE polarization enters a polarization selector composed of a Mach-Zehnder interferometer modulator, an adiabatic coupler, and a mode converter through an input port. When the light with TE polarization is output from the upper port of the Mach-Zehnder interferometer modulator, the TE polarization is converted into TM polarization through the adiabatic coupler and the mode converter; when the light with TE polarization is output from the lower port of the Mach-Zehnder interferometer modulator, the polarization state of the TE polarization remains unchanged after passing through the adiabatic coupler and the mode converter; light with TE polarization or TM polarization passes through the Mach-Zehnder interferometer modulator to select the direction of the beam entering the grating emitting antenna; by optimizing the structural parameters of the grating emitting antenna, after the light with two orthogonal polarization states and two transmission directions is emitted by the grating emitting antenna, their far-field viewing fields are arranged adjacent to each other. Compared with the prior art, under the condition of the same working bandwidth of the light source, the present invention significantly improves the continuous scanning range of the beam of the beam deflector.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic devices, and particularly relates to a bidirectional dual-polarization beam deflector. Background Art

[0002] The CMOS process-compatible on-chip optical waveguide technology has promoted the high integration and miniaturization of beam deflectors. The beam deflector based on on-chip optical waveguides has the characteristics of easy large-scale integration, low power consumption, light weight, and low cost. These advantages make it have broad application prospects in lidar, free-space optical communication, optical detection, and ranging.

[0003] The beam scanning range is an important index of the beam deflector. Existing two-dimensional beam deflector schemes based on optical waveguides are divided into two types: One scheme is to use a two-dimensional antenna array to achieve two-dimensional beam deflection by controlling the phase of each element. However, this scheme is limited by the element spacing and it is difficult to achieve large-angle beam deflection; at the same time, as the number of elements increases, the arrangement of elements and waveguides will become more complex. Another commonly used scheme is to combine phase adjustment and wavelength adjustment to achieve two-dimensional beam deflection. This scheme can increase the beam deflection angle in the phase adjustment direction by reducing the waveguide spacing of the arrayed waveguide grating, but in the wavelength adjustment direction, the traditional beam deflector adopts a single-polarization and unidirectional transmission scheme, and is limited by the working bandwidth of the light source and beam splitter, and its beam deflection angle is often limited. Optical communication and optical detection have requirements for the beam deflection angle. Therefore, significantly improving the deflection angle of the beam deflector has important significance and application value. Summary of the Invention

[0004] Aiming at the limitations of the prior art, the purpose of the present invention is to solve the above technical limitations and effectively increase the beam deflection range under the limited bandwidth of the existing light source. The present invention proposes a method of direction multiplexing and polarization multiplexing, which will significantly increase the beam deflection range of the beam deflector.

[0005] The present invention proposes a bidirectional dual-polarization beam deflector, which is composed of the following parts: an input port (1), a first-stage Mach-Zehnder interferometer modulator (2), an adiabatic coupler (3), a mode converter (4), a second-stage Mach-Zehnder interferometer modulator (5), and a grating emission antenna (6).

[0006] Light with TE polarization is input through the input port (1), and after passing through the first-stage Mach-Zehnder interferometer modulator (2), the adiabatic coupler (3), and the mode converter (4) to select the polarization state, it enters the second-stage Mach-Zehnder interferometer modulator (5), and it can select light with TE polarization or TM polarization to enter the direction of the grating emission antenna (6); light with two orthogonal polarization states and two transmission directions is emitted through the grating emission antenna to achieve beam deflection.

[0007] The basic principle is that light with TE polarization enters a polarization selector composed of a Mach-Zehnder interferometer modulator, an adiabatic coupler, and a mode converter through an input port. When the light with TE polarization is output from the upper port of the Mach-Zehnder interferometer modulator, the TE polarization is converted to TM polarization through the adiabatic coupler and the mode converter; when the light with TE polarization is output from the lower port of the Mach-Zehnder interferometer modulator, the polarization state of the TE polarization remains unchanged after passing through the adiabatic coupler and the mode converter, still being TE polarization; the light with TE polarization or TM polarization can select the direction of the light entering the grating emitting antenna through the Mach-Zehnder interferometer modulator; by optimizing the structural parameters of the grating emitting antenna, after the light in two orthogonal polarization states and two transmission directions is emitted by the grating emitting antenna, their far-field views are arranged adjacent to each other; the continuous deflection range of the far-field beam corresponding to the beam deflector is the sum of the far-field beam deflection ranges corresponding to four working states: forward-transmitted TE polarization, forward-transmitted TM polarization, backward-transmitted TE polarization, and backward-transmitted TM polarization. Compared with the prior art, under the condition of the same working bandwidth of the light source, the continuous scanning range of the beam of the beam deflector is significantly improved.

[0008] The input port (1) is connected to a light source, and the light source is light with TE polarization.

[0009] The combination of the first-stage Mach-Zehnder interferometer modulator (2), the adiabatic coupler (3), and the mode converter (4) can achieve the function of polarization selection, and then the second-stage Mach-Zehnder interferometer modulator (5) is connected behind it;

[0010] When the light with TE polarization is output from the upper port of the first-stage Mach-Zehnder interferometer modulator (2), the TE polarization is coupled into the lower waveguide through the adiabatic coupler (3), and then undergoes mode hybridization through the mode converter (4), and the output is TM polarization; when the light with TE polarization is output from the lower port of the first-stage Mach-Zehnder interferometer modulator (2), the polarization state of the TE polarization remains unchanged after passing through the adiabatic coupler (3) and the mode converter (4), still being TE polarization.

[0011] The adiabatic coupler (3) includes two strip waveguides, the upper waveguide of which changes from wide to narrow, and the lower waveguide changes from narrow to wide;

[0012] When the light in TE0 mode is input from the upper port, it is coupled into the lower waveguide through the adiabatic coupler (3), and the output is TE1 mode; when the light in TE0 mode is input from the lower port, it does not undergo coupling through the adiabatic coupler (3), and the output is still TE0 mode.

[0013] The mode converter (4) adopts a double-etched ridge waveguide structure;

[0014] When the light in the TE0 mode is input, no mode conversion occurs through the mode converter (4), and the output remains in the TE0 mode; when the light in the TE1 mode is input, mode hybridization occurs through the mode converter (4), and the output is in the TM0 mode.

[0015] The second-stage Mach-Zehnder interferometer modulator (5) has polarization-insensitive characteristics and includes a 1×2 multimode interference coupler, two equal-optical-path connecting waveguides, a heating wire, and a 2×2 multimode interference coupler; the 1×2 multimode interference coupler can equally divide the input TE-polarized or TM-polarized light by 3 dB; the 2×2 multimode interference coupler can equally divide the TE-polarized or TM-polarized light input from any port on one side by 3 dB on the other side; when the TE-polarized or TM-polarized light is input from the input end of the 1×2 multimode interference coupler and enters the 2×2 multimode interference coupler through the two equal-optical-path connecting waveguides, the heating wire is located above one of the connecting waveguides, and by heating, the optical path difference between the two connecting waveguides can be changed to achieve the function of selecting the output path of the TE-polarized or TM-polarized light.

[0016] The grating emission antenna (6) has a double-layer structure and is realized by shallowly etching a uniform periodic structure on a strip waveguide.

[0017] The method for the beam deflector structure proposed by the present invention to improve the continuous beam deflection range is as follows:

[0018] The effective refractive indices of the TE-polarized and TM-polarized light waves in the on-chip optical waveguide are different. Therefore, after being coupled and output by the grating emission antenna (6), they will deflect at different angles. By adjusting the waveguide parameters and grating parameters of the grating emission antenna (6), the far-field scanning ranges of the TE-polarized and TM-polarized light corresponding to the same transmission direction can be located on both sides of θ = 0 respectively; at the same time, one side of the scanning range of a certain mode is at θ = 0, and its scanning range is equal to the blind area in the middle of the scanning ranges corresponding to the TE-polarized and TM-polarized light in the same transmission direction. At this time, the far-field deflection ranges of the light waves transmitted in two directions in the grating emission antenna (6) can cover each other's blind areas. At this time, the continuous far-field beam deflection range of the beam deflector is the sum of the far-field beam deflection ranges corresponding to the four working states of forward-transmitted TE polarization, forward-transmitted TM polarization, backward-transmitted TE polarization, and backward-transmitted TM polarization. Therefore, compared with the prior art, when the light source spectral width is the same, the continuous beam deflection range is significantly improved.

[0019] The beneficial effects of the present invention are:

[0020] In view of the limitations of the prior art, the present invention proposes a beam deflector based on an on-chip optical waveguide, and a new method for direction multiplexing and polarization multiplexing control. Under the current limited spectral width of the light source, the beam deflection range of the beam deflector is doubled, and the deflection scanning range can be further expanded using this principle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. is a schematic structural diagram of a bidirectional dual-polarization beam deflector according to the present invention.

[0022] In the figure: input port (1), first-stage Mach-Zehnder interferometer modulator (2), adiabatic coupler (3), mode converter (4), second-stage Mach-Zehnder interferometer modulator (5), grating emission antenna (6).

[0023] Figure 2 FIG. is a schematic diagram of two beam deflection angles.

[0024] In the figure: TE0 and TM0 respectively represent the beam deflection ranges corresponding to the two modes of TE0 and TM0; 1 and -1 respectively represent the beam deflection ranges corresponding to different transmission directions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] As Figure 1 shown, a bidirectional dual-polarization beam deflector is composed of the following parts: input port (1), first-stage Mach-Zehnder interferometer modulator (2), adiabatic coupler (3), mode converter (4), second-stage Mach-Zehnder interferometer modulator (5), grating emission antenna (6).

[0027] Light in the TE0 mode enters the polarization selector composed of a Mach-Zehnder interferometer modulator, an adiabatic coupler, and a mode converter through the input port. When the light in the TE0 mode is output from the upper port of the Mach-Zehnder interferometer modulator, the TE0 mode is converted to the TE1 mode through the adiabatic coupler and then converted to the TM0 mode through the mode converter; when the light in the TE0 mode is output from the lower port of the Mach-Zehnder interferometer modulator, the mode of the TE0 mode remains unchanged after passing through the adiabatic coupler and the mode converter and is still the TE0 mode; the light in the TE0 mode or the TM0 mode can select the direction of the light entering the grating emission antenna through the second-stage Mach-Zehnder interferometer modulator (5).

[0028] The adiabatic coupler (3) includes two strip waveguides. The upper waveguide narrows from wide to narrow, and the lower waveguide widens from narrow to wide. The effective refractive index of the TE0 mode at the midpoint of the upper waveguide is equal to the effective refractive index of the TE1 mode at the midpoint of the lower waveguide. When light in the TE0 mode is input from the upper port, it is coupled into the lower waveguide through the adiabatic coupler (3) and the output is in the TE1 mode. There is no mode in the upper waveguide that matches the effective refractive index of the TE0 mode in the lower waveguide. Therefore, when light in the TE0 mode is input from the lower port, no coupling occurs through the adiabatic coupler (3) and the output remains in the TE0 mode.

[0029] The mode converter (4) adopts a double-etched ridge waveguide structure. By double-etching, the up-down symmetry of the waveguide can be destroyed, and mode hybridization occurs when light in the TE1 mode is input, converting to the TM0 mode for output. However, there is no mode hybridization during the transmission of the TE0 mode. Therefore, no mode conversion occurs through the mode converter (4) and the output remains in the TE0 mode.

[0030] The second-stage Mach-Zehnder interferometer modulator (5) has polarization-insensitive characteristics. The one-to-two multimode interference coupler can equally divide the input light in the TE0 mode or TM0 mode by 3 dB for output; the two-to-two multimode interference coupler can equally divide the light in the TE0 mode or TM0 mode input from any port on one side by 3 dB for output on the other side.

[0031] The first-stage Mach-Zehnder interferometer modulator (2) and the second-stage Mach-Zehnder interferometer modulator (5) control the output path by regulating the refractive index generated in one of the connecting waveguides. The expression for the phase change on the connecting waveguide path is as follows:

[0032]

[0033] In Equation (1), is the phase difference generated by the light wave in the connecting waveguide after passing through the two waveguides, λ is the working wavelength, Δn is the waveguide refractive index difference caused by the phase modulator, and L is the modulation length.

[0034] The grating emission antenna (6) has a uniform periodic structure. The deflection angle of the light coupled out from the grating coupler satisfies the following relationship:

[0035]

[0036] In Equation (2), d is the direction coefficient (-1 when the light is input from the right side, 1 when the light is input from the left side), Λ is the grating period, n eff is the effective refractive index of the waveguide, n b is the background refractive index, and λ is the working wavelength.

[0037] The effective refractive indices of the optical waves of two orthogonal polarization modes in the on-chip optical waveguide are different. After being output through the same grating coupling, they will deflect at different angles. By adjusting the waveguide parameters and grating parameters of the grating transmitting antenna (6), the far-field scanning ranges of the TE-polarized and TM-polarized lights corresponding to the same transmission direction can be located on both sides of θ = 0 respectively. At the same time, one side of the scanning range of a certain mode is at θ = 0, and its scanning range is equal to the blind area in the middle of the scanning ranges corresponding to the TE-polarized and TM-polarized lights in the same transmission direction. At this time, the far-field deflection ranges of the optical waves transmitted in two directions in the grating transmitting antenna (6) can cover each other's blind areas, as shown in Figure 2 (a) or 2(b). At this time, the continuous far-field beam deflection range of the beam deflector is the sum of the far-field beam deflection ranges corresponding to the four working states of forward-transmitted TE polarization, forward-transmitted TM polarization, backward-transmitted TE polarization, and backward-transmitted TM polarization. When the spectral width of the light source is the same, the continuous beam deflection range is increased by four times.

[0038] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, they can also make several substitutions or modifications to these described embodiments, and these substitution or modification methods should all be regarded as belonging to the protection scope of the present invention.

[0039] The parts not detailed in the present invention belong to the well-known technologies in the art.

Claims

1. A bidirectional dual-polarization beam deflector, characterized in that, The device consists of the following parts: input port (1), first-stage Mach-Zehnder interferometer modulator (2), adiabatic coupler (3), mode converter (4), second-stage Mach-Zehnder interferometer modulator (5), grating emitting antenna (6); Light with TE polarization is input through the input port (1), passes through the first-stage Mach-Zehnder interferometer modulator (2), the adiabatic coupler (3) and the mode converter (4) to select the polarization state and then enters the second-stage Mach-Zehnder interferometer modulator (5), which can select light with TE polarization or TM polarization to enter the direction of the grating emitting antenna (6); light with two orthogonal polarization states and two transmission directions is emitted through the grating emitting antenna to achieve beam deflection; The second-stage Mach-Zehnder interferometer modulator (5) has polarization-insensitive characteristics and includes a 1×2 multimode interference coupler, two equal optical path connecting waveguides, a heating wire and a 2×2 multimode interference coupler; The 1×2 multimode interference coupler can split the input light with TE polarization or TM polarization into two equal parts with a 3dB splitting ratio; The 2×2 multimode interference coupler can split the input light with TE polarization or TM polarization from any port on one side into two equal parts with a 3dB splitting ratio on the other side; the two output ports of the 2×2 multimode interference coupler are respectively connected to the two branches of the grating emitting antenna (6); When light with TE polarization or TM polarization is input from the input end of the 1×2 multimode interference coupler, passes through the two equal optical path connecting waveguides and enters the 2×2 multimode interference coupler, the heating wire is located above one of the connecting waveguides, and by heating, the optical path difference between the two connecting waveguides can be changed to achieve the function of selecting the output path of light with TE polarization or TM polarization.

2. The dual - polarization beam deflector according to claim 1, wherein, The input port (1) is connected to a light source, and the light source is light with TE polarization; The combination of the first-stage Mach-Zehnder interferometer modulator (2), the adiabatic coupler (3) and the mode converter (4) can achieve the function of polarization selection, and the second-stage Mach-Zehnder interferometer modulator (5) is connected behind it; When light in the TE0 mode is output from the upper port of the first-stage Mach-Zehnder interferometer modulator (2), the TE0 mode is converted to the TE1 mode through the adiabatic coupler (3), and then converted to the TM0 mode through the mode converter (4); when light in the TE0 mode is output from the lower port of the first-stage Mach-Zehnder interferometer modulator (2), the polarization state of the TE0 mode remains unchanged after passing through the adiabatic coupler (3) and the mode converter (4) and is still the TE0 mode.

3. The bidirectional dual-polarization beam deflector according to claim 2, wherein The adiabatic coupler (3) includes two strip waveguides, the upper waveguide of which changes from wide to narrow, and the lower waveguide changes from narrow to wide; When light in the TE0 mode is input from the upper port, it is coupled into the lower waveguide through the adiabatic coupler (3) and the output is the TE1 mode; when light in the TE0 mode is input from the lower port, it does not couple through the adiabatic coupler (3) and the output is still the TE0 mode.

4. A bidirectional dual-polarization beam deflector according to claim 2, characterized in that, The mode converter (4) adopts a double-layer etched ridge waveguide structure; When the light of TE0 mode is input, no mode conversion occurs through the mode converter (4), and the output remains in TE0 mode; when the light of TE1 mode is input, mode hybridization occurs through the mode converter (4), and the output is in TM0 mode.

5. A bidirectional dual-polarization beam deflector according to claim 2, characterized in that, The grating emitting antenna (6) has a double-layer structure, which is realized by shallow etching a uniform periodic structure on a strip waveguide. The method for improving the continuous deflection range of the light beam is as follows: The effective refractive indices of the light waves of TE polarization and TM polarization in the on-chip optical waveguide are different. After being coupled and output through the grating emitting antenna (6), they will deflect at different angles. By adjusting the waveguide parameters and grating parameters of the grating emitting antenna (6), it is ensured that: 1) The far-field beam deflection ranges of the TE-polarized and TM-polarized lights corresponding to the same transmission direction are respectively located on both sides of θ = 0; 2) One boundary of the beam deflection range of a certain polarization mode is at θ = 0; 3) The beam deflection range close to θ = 0 is equal to the blind area in the middle of the beam deflection ranges of the TE-polarized and TM-polarized lights corresponding to the same transmission direction; At this time, the far-field beam deflection ranges of the light waves transmitted in two directions in the grating emitting antenna (6) can cover each other's blind areas. The continuous far-field beam deflection range of the beam deflector is the sum of the far-field beam deflection ranges corresponding to the four working states of forward-transmitted TE polarization, forward-transmitted TM polarization, backward-transmitted TE polarization, and backward-transmitted TM polarization. When the light source spectral width is the same, the continuous deflection range of the light beam is effectively improved.

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