Phased array element, optical phased array and manufacturing method

Abstract

The present invention relates to a phased array element, an optical phased array, and a manufacturing method. The phased array element comprises: a silicon waveguide; an oxide layer located on the upper surface of the silicon waveguide; a silicon nitride grating located on the upper surface of the oxide layer, wherein the width of the grating teeth of the silicon nitride grating is greater than the width of the silicon waveguide, and the width of the grating body of the silicon nitride grating is less than the width of the silicon waveguide; and an upper cladding layer covering the periphery of the silicon nitride grating. The present invention can extend the effective emission length, reduce the divergence angle, improve resolution, and expand the full width at half maximum of the light beam.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based optical phased arrays, and in particular to a phased array element, an optical phased array, and a manufacturing method thereof. Background Art

[0002] Silicon-based optical phased arrays can achieve fast, arbitrary position scanning and are one of the important solutions for realizing all-solid-state lidar. Common silicon-based optical phased arrays transmit light beams through a transmitting unit to achieve beam scanning. How to achieve a large scanning range and high resolution of the phased array is a current research hotspot. In order to achieve a large scanning range, it is necessary to reduce the sidelobe level. Half-wavelength periodic distribution is an effective way to eliminate grating lobes, but due to the close spacing, the crosstalk between channels is large. Therefore, the grating with a half-wavelength periodic distribution must usually radiate light within a very short length to avoid crosstalk between channels. In order to obtain high resolution, it is necessary to expand the effective emission length of the grating to reduce the divergence angle, but this is contrary to the requirements of the traditional short grating half-wavelength periodic distribution. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a phased array element, an optical phased array and a manufacturing method, which can extend the effective emission length, reduce the divergence angle, improve the resolution, and expand the full half-height width of the light beam.

[0004] The technical solution adopted by the present invention to solve the technical problem is to provide a phased array element, including:

[0005] Silicon waveguide;

[0006] an oxide layer located on the upper surface of the silicon waveguide;

[0007] a silicon nitride grating located on the upper surface of the oxide layer, wherein the width of the grating teeth of the silicon nitride grating is greater than the width of the silicon waveguide, and the width of the grating body of the silicon nitride grating is less than the width of the silicon waveguide;

[0008] The upper cladding layer covers the periphery of the silicon nitride grating.

[0009] The silicon waveguide has a thickness of 220 nm and a width of 500 nm.

[0010] The thickness of the oxide layer is 100 nm.

[0011] The thickness of the silicon nitride grating is 400 nm.

[0012] The technical solution adopted by the present invention to solve the technical problem is: to provide an optical phased array having a plurality of the above-mentioned phased array elements arranged in a non-periodic array.

[0013] The spacing of the non-periodic array is obtained as follows:

[0014] The minimum value sll1 and the maximum value sll0 of the sidelobe suppression ratio within the scanning range are used as performance metrics to construct a fitness function, which is solved by the particle swarm optimization algorithm to obtain the spacing of the aperiodic array; where the fitness function is 1 / (sll0*sll1).

[0015] A method for manufacturing a phased array element comprises the following steps:

[0016] Based on SOI substrate, silicon waveguide is formed by photolithography and etching process;

[0017] A layer of silicon dioxide is deposited on the silicon waveguide using the PECVD method as an oxide layer, and the oxide layer is polished flat using CMP;

[0018] Depositing a layer of silicon nitride on the oxide layer by LPCVD or PECVD, and forming a side-etched silicon nitride grating structure by photolithography and etching, wherein the width of the grating teeth of the silicon nitride grating structure is greater than the width of the silicon waveguide, and the width of the grating body of the silicon nitride grating structure is less than the width of the silicon waveguide;

[0019] A layer of silicon dioxide is deposited on the periphery of the silicon nitride grating structure by the PECVD method as the upper cladding layer of the silicon nitride grating structure, and the upper cladding layer is polished flat by CMP.

[0020] The silicon waveguide has a thickness of 220 nm and a width of 500 nm.

[0021] The thickness of the oxide layer is 100 nm.

[0022] The thickness of the silicon nitride grating is 400 nm.

[0023] Beneficial effects

[0024] Due to the adoption of the above-mentioned technical solution, the present invention has the following advantages and positive effects compared with the existing technology: the present invention adopts silicon waveguide to transmit light, which is beneficial to reducing the loss of light per unit length, extending the effective length of the grating, radiating light upward through the silicon nitride grating, expanding the full half-maximum width of the light beam by designing reasonable parameters, and substituting the directional factor of the emitting grating into the optimization algorithm, so that the non-periodic spacing distribution obtained conforms to the actual scanning scenario. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a top view of a phased array element according to an embodiment of the present invention;

[0026] Figure 2 is a side view of a phased array element according to an embodiment of the present invention;

[0027] Figure 3 is a far-field image of a phased array element according to an embodiment of the present invention;

[0028] Figure 4 is a normalized curve diagram of the directional factor of the phased array element according to the embodiment of the present invention;

[0029] Figure 5 1 is a diagram showing the distribution of scanning angle field intensity of the optical phased array according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0031] The embodiment of the present invention relates to a phased array element, such as Figure 1 and Figure 2 As shown, it includes: a silicon waveguide 1; an oxide layer 2, located on the upper surface of the silicon waveguide 1; a silicon nitride grating 3, located on the upper surface of the oxide layer, wherein the width of the grating teeth 31 of the silicon nitride grating is greater than the width of the silicon waveguide 1, and the width of the grating body 32 of the silicon nitride grating is less than the width of the silicon waveguide 1; and an upper cladding layer 4, covering the periphery of the silicon nitride grating 3.

[0032] In this embodiment, the thickness d of the silicon waveguide 1 is Si is 220nm, width W Wg The thickness of the oxide layer 2 is 500 nm. SiO The thickness d of the silicon nitride grating 3 is 150 nm. SiN is 400nm.

[0033] The phased array element of this embodiment utilizes a structure combining a silicon waveguide and a silicon nitride grating, which can extend the effective emission length, reduce the divergence angle, and improve the resolution. Figure 3 and Figure 4 The far-field image and normalized curve of the direction factor of the simulated 50μm-long grating are shown. It can be seen that the full width at half maximum of the emission grating of the structure is 91.82°. It can be seen that in this embodiment, by etching the silicon nitride grating on the side and making the width of the grating teeth larger than the width of the silicon waveguide and the width of the grating body smaller than the width of the silicon waveguide, the width W2 of the grating teeth 31, the width W1 of the grating body 32 and the width W of the silicon waveguide 1 are adjusted. Wg , which makes the directional factor of the phased array element have a larger full width at half maximum, which is beneficial to expanding the beam scanning range of the phased array main beam.

[0034] An embodiment of the present invention further relates to an optical phased array having a plurality of the above-mentioned phased array elements arranged in a non-periodic array.

[0035] The spacing of the non-periodic array can be obtained as follows: using the minimum value sll1 and the maximum value sll0 of the sidelobe suppression ratio within the scanning range as performance measurement criteria, constructing a fitness function, and solving it through the particle swarm optimization algorithm to obtain the spacing of the non-periodic array; wherein the fitness function is 1 / (sll0*sll1).

[0036] like Figure 5 As shown in the figure, it shows the field intensity distribution of the optical phased array at 0°, ±30°, and ±60°, respectively, obtained by optimizing the particle swarm optimization algorithm combined with the grating direction factor within the range of ±60°. The sidelobe suppression ratio is 13.56dB when the main beam is deflected by 0°, 11.93dB when it is deflected by ±30°, and 9.11dB when it is deflected by ±60°. Figure 5 It can be seen that the non-periodic phased array obtained using this method can achieve a beam scanning range of 120°, and the sidelobe level is lower than -9dB in the entire range.

[0037] Accordingly, this embodiment further provides a method for manufacturing a phased array element. The method uses an SOI substrate and is based on a Si waveguide and Si3N4 grating manufacturing process, and includes the following steps:

[0038] Step 1: Based on the SOI substrate, a Si waveguide structure is formed through photolithography and etching processes. The Si waveguide structure has a thickness of 220nm and a width of 500nm.

[0039] Step 2: Use PECVD to deposit a layer of SiO2 on the Si waveguide structure to form an oxide gap between the Si waveguide and the Si3N4 grating, and then use CMP to polish the SiO2 layer flat. The thickness of the oxide gap is 100nm.

[0040] Step 3: Using LPCVD or PECVD, deposit a layer of Si3N4 on the oxide layer gap, and form a side-etched Si3N4 grating structure through photolithography and etching. The thickness of the Si3N4 grating structure is 400nm.

[0041] Step 4: Use the PECVD method to deposit a layer of SiO2 outside the Si3N4 grating structure as the upper cladding layer of the Si3N4 grating structure, and then polish the SiO2 layer flat by CMP.

[0042] It is not difficult to find that the present invention adopts silicon waveguide to transmit light, which is beneficial to reducing the loss of light per unit length, extending the effective length of the grating, radiating light upward through the silicon nitride grating, expanding the full half-width of the light beam by designing reasonable parameters, and substituting the directional factor of the emitting grating into the optimization algorithm. The resulting non-periodic spacing distribution conforms to the actual scanning scenario.

Claims

1. An optical phased array, characterized in that: A phased array element is provided, wherein the phased array element comprises: Silicon waveguide; an oxide layer located on the upper surface of the silicon waveguide; a silicon nitride grating located on the upper surface of the oxide layer, wherein the width of the grating teeth of the silicon nitride grating is greater than the width of the silicon waveguide, and the width of the grating body of the silicon nitride grating is less than the width of the silicon waveguide; an upper cladding layer covering the periphery of the silicon nitride grating; The spacing of the non-periodic array is obtained as follows: The minimum value sll1 and the maximum value sll0 of the sidelobe suppression ratio within the scanning range are used as performance metrics to construct a fitness function, which is solved by the particle swarm optimization algorithm to obtain the spacing of the aperiodic array; where the fitness function is 1 / (sll0*sll1).

2. The optical phased array according to claim 1, wherein: The silicon waveguide has a thickness of 220 nm and a width of 500 nm.

3. The optical phased array according to claim 1, wherein: The thickness of the oxide layer is 150 nm.

4. The optical phased array according to claim 1, wherein: The thickness of the silicon nitride grating is 400 nm.

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