CN115857094A - Phased array element, optical phased array and manufacturing method - Google Patents
Phased array element, optical phased array and manufacturing method Download PDFInfo
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- CN115857094A CN115857094A CN202211463209.2A CN202211463209A CN115857094A CN 115857094 A CN115857094 A CN 115857094A CN 202211463209 A CN202211463209 A CN 202211463209A CN 115857094 A CN115857094 A CN 115857094A
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Abstract
The invention relates to a phased array element, an optical phased array and a manufacturing method, wherein the phased array element comprises: a silicon waveguide; the oxide layer is positioned on the upper surface of the silicon waveguide; the silicon nitride grating is positioned on the upper surface of the oxide layer, the width of the grating teeth of the silicon nitride grating is larger than that of the silicon waveguide, and the width of the grating body of the silicon nitride grating is smaller than that of the silicon waveguide; and the upper cladding layer covers the periphery of the silicon nitride grating. The invention can prolong the effective emission length, reduce the divergence angle, improve the resolution ratio and enlarge the full-width-at-half-height of the light beam.
Description
Technical Field
The invention relates to the technical field of silicon-based optical phased arrays, in particular to a phased array element, an optical phased array and a manufacturing method thereof.
Background
The silicon-based optical phased array can realize rapid scanning at any position, and is one of important schemes for realizing the all-solid-state laser radar. The common silicon-based optical phased array emits light beams through the emission unit to realize beam scanning, and how to realize the large scanning range and high resolution of the phased array is a hotspot of current research. In order to achieve a large scanning range, the side lobe level needs to be reduced, and the half-wavelength periodic distribution is an effective way to eliminate grating lobes, but because the crosstalk between channels is large due to the close spacing, the half-wavelength periodic distribution grating must generally radiate light within a short length to avoid crosstalk between channels. To achieve high resolution, however, the effective emission length of the grating needs to be extended to reduce the divergence angle, which is contrary to the requirement of the conventional half-wavelength periodic distribution of short gratings.
Disclosure of Invention
The invention aims to provide a phased array element, an optical phased array and a manufacturing method thereof, which can prolong the effective emission length, reduce the divergence angle, improve the resolution and enlarge the full-width-at-half-maximum of a light beam.
The technical scheme adopted by the invention for solving the technical problems is as follows: providing a phased array element comprising:
a silicon waveguide;
the oxide layer is positioned on the upper surface of the silicon waveguide;
the silicon nitride grating is positioned on the upper surface of the oxide layer, the width of the grating teeth of the silicon nitride grating is larger than that of the silicon waveguide, and the width of the grating body of the silicon nitride grating is smaller than that of the silicon waveguide;
and the upper cladding layer covers the periphery of the silicon nitride grating.
The thickness of the silicon waveguide is 220nm, and the width of the silicon waveguide is 500nm.
The thickness of the oxide layer is 100nm.
The thickness of the silicon nitride grating is 400nm.
The technical scheme adopted by the invention for solving the technical problems is as follows: an optical phased array is provided having a plurality of the above-described phased array elements arranged in a non-periodic array.
The pitch of the aperiodic array is obtained by:
constructing a fitness function by taking a minimum value sll1 and a maximum value sll0 of a sidelobe suppression ratio in a scanning range as performance measurement standards, and solving through a particle swarm optimization algorithm to obtain the spacing of the aperiodic array; wherein the fitness function is 1/(sll 0 sll 1).
A manufacturing method of a phased array element comprises the following steps:
forming a silicon waveguide by photoetching and etching processes based on the SOI substrate;
depositing a layer of silicon dioxide on the silicon waveguide by adopting a PECVD method as an oxide layer, and polishing the oxide layer flat by CMP;
depositing a layer of silicon nitride on the oxide layer by adopting an LPCVD (low pressure chemical vapor deposition) or PECVD (plasma enhanced chemical vapor deposition) method, and forming a silicon nitride grating structure with etched side edges by photoetching and etching processes, wherein the width of a grating tooth of the silicon nitride grating structure is larger than that of the silicon waveguide, and the width of a grating body of the silicon nitride grating structure is smaller than that of the silicon waveguide;
and depositing a layer of silicon dioxide on the periphery of the silicon nitride grating structure by adopting a PECVD method to be used as an upper cladding of the silicon nitride grating structure, and polishing the upper cladding by CMP.
The thickness of the silicon waveguide is 220nm, and the width of the silicon waveguide is 500nm.
The thickness of the oxide layer is 100nm.
The thickness of the silicon nitride grating is 400nm.
Advantageous effects
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects: the invention adopts the silicon waveguide to transmit light, is beneficial to reducing the loss of light in unit length and prolonging the effective length of the grating, the light is radiated upwards through the silicon nitride grating, the full-width-at-half-height of the light beam is enlarged through reasonable design parameters, the directional factor of the emission grating is substituted into an optimization algorithm, and the obtained aperiodic spacing distribution accords with the actual scanning scene.
Drawings
FIG. 1 is a top view of a phased array element of an embodiment of the present invention;
FIG. 2 is a side view of a phased array element of an embodiment of the present invention;
FIG. 3 is a far field image of a phased array element of an embodiment of the present invention;
FIG. 4 is a graph of the direction factor normalization of a phased array element of an embodiment of the invention;
fig. 5 is a scanning angle field intensity partial graph of the optical phased array according to the embodiment of the present invention.
Detailed Description
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The embodiment of the invention relates to a phased array element, as shown in fig. 1 and fig. 2, comprising: a silicon waveguide 1; the oxide layer 2 is positioned on the upper surface of the silicon waveguide 1; the silicon nitride grating 3 is positioned on the upper surface of the oxide layer, the width of the grating tooth 31 of the silicon nitride grating is greater than that of the silicon waveguide 1, and the width of the grating body 32 of the silicon nitride grating is less than that of the silicon waveguide 1; and the upper cladding 4 covers the periphery of the silicon nitride grating 3.
Thickness d of silicon waveguide 1 in the present embodiment Si Is 220nm and has a width W Wg Is 500nm. Thickness d of oxide layer 2 SiO Is 150nm. Thickness d of silicon nitride grating 3 SiN Is 400nm.
The phased array element of the embodiment can prolong the effective transmitting length, reduce the divergence angle and improve the resolution by utilizing the structure of combining the silicon waveguide and the silicon nitride grating. Fig. 3 and 4 show normalized curves simulating the far-field image and the direction factor of a grating with a length of 50 μm, and the full-half-height width of the emission grating with the structure can be 91.82 °, so that in the embodiment, the silicon nitride grating is etched on the side edge, the width of the grating teeth is larger than that of the silicon waveguide, the width of the grating body is smaller than that of the silicon waveguide, and the width W of the grating teeth 31 is adjusted 2 Width W of grating body 32 1 And the width W of the silicon waveguide 1 Wg Therefore, the directional factor of the phased array element has larger full half-height width, and the beam scanning range of the phased array main beam is favorably expanded.
Embodiments of the present invention also relate to an optical phased array having a number of the above-described phased array elements arranged in a non-periodic array.
Wherein, the pitch of the non-periodic array can be obtained by the following method: constructing a fitness function by taking a minimum value sll1 and a maximum value sll0 of a sidelobe suppression ratio in a scanning range as performance measurement standards, and solving through a particle swarm optimization algorithm to obtain the spacing of the aperiodic array; wherein the fitness function is 1/(sll 0 sll 1).
As shown in fig. 5, it shows the field intensity distributions of the optical phased array obtained by optimizing the particle swarm optimization algorithm combined with the grating direction factor in the range of ± 60 ° at 0 °, ± 30 °, ± 60 °, respectively. The sidelobe suppression ratio is 13.56dB when the main light beam deflects 0 degrees, 11.93dB when the main light beam deflects +/-30 degrees and 9.11dB when the main light beam deflects +/-60 degrees. As can be seen from fig. 5, the aperiodic phased array obtained by using the method can realize a beam scanning range of 120 °, and the side lobe level is lower than-9 dB in the whole range.
Correspondingly, the embodiment also provides a manufacturing method of the phased-array element, which adopts the SOI substrate and is based on the Si waveguide and the Si 3 N 4 The manufacturing process of the grating comprises the following steps:
the method comprises the following steps: and forming a Si waveguide structure by photoetching and etching processes based on the SOI substrate. Wherein the thickness of the Si waveguide structure is 220nm, and the width of the Si waveguide structure is 500nm.
Step two: depositing a layer of SiO on the Si waveguide structure by PECVD method 2 Forming Si waveguide and Si 3 N 4 The oxide layer gap between the gratings and the SiO2 layer is polished flat by CMP. Wherein the thickness of the oxide layer gap is 100nm.
Step three: depositing a layer of Si on the oxide layer gap by LPCVD or PECVD method 3 N 4 And forming a side-etched Si3N4 grating structure by photoetching and etching processes. Si 3 N 4 The thickness of the grating structure was 400nm.
Step four: depositing a layer of SiO outside the Si3N4 grating structure by adopting a PECVD method 2 As Si 3 N 4 Upper cladding of grating structure, and Chemical Mechanical Polishing (CMP) of SiO 2 And (6) polishing the layer.
It is not difficult to find that the invention adopts the silicon waveguide to transmit light, which is beneficial to reducing the loss of light in unit length and prolonging the effective length of the grating, the silicon nitride grating is used for radiating light upwards, the full-width-at-half-maximum of the light beam is enlarged by designing reasonable parameters, the directional factor of the emission grating is substituted into an optimization algorithm, and the obtained non-periodic interval distribution conforms to the actual scanning scene.
Claims (10)
1. A phased array element, comprising:
a silicon waveguide;
the oxide layer is positioned on the upper surface of the silicon waveguide;
the silicon nitride grating is positioned on the upper surface of the oxide layer, the width of the grating teeth of the silicon nitride grating is larger than that of the silicon waveguide, and the width of the grating body of the silicon nitride grating is smaller than that of the silicon waveguide;
and the upper cladding layer covers the periphery of the silicon nitride grating.
2. The phased array element according to claim 1, wherein said silicon waveguide has a thickness of 220nm and a width of 500nm.
3. The phased array element according to claim 1, wherein said oxide layer has a thickness of 150nm.
4. The phased array element according to claim 1, wherein said silicon nitride grating has a thickness of 400nm.
5. An optical phased array having a plurality of phased array elements as claimed in claims 1 to 4 arranged in a non-periodic array.
6. The optical phased array as claimed in claim 5, wherein the pitch of the aperiodic array is obtained by:
constructing a fitness function by taking a minimum value sll1 and a maximum value sll0 of a sidelobe suppression ratio in a scanning range as performance measurement standards, and solving through a particle swarm optimization algorithm to obtain the spacing of the non-periodic array; wherein the fitness function is 1/(sll 0 sll 1).
7. A manufacturing method of a phased array element is characterized by comprising the following steps:
forming a silicon waveguide by photoetching and etching processes based on the SOI substrate;
depositing a layer of silicon dioxide on the silicon waveguide by adopting a PECVD method as an oxide layer, and polishing the oxide layer flat by CMP;
depositing a layer of silicon nitride on the oxide layer by adopting an LPCVD (low pressure chemical vapor deposition) or PECVD (plasma enhanced chemical vapor deposition) method, and forming a silicon nitride grating structure with etched side edges by photoetching and etching processes, wherein the width of a grating tooth of the silicon nitride grating structure is larger than that of the silicon waveguide, and the width of a grating body of the silicon nitride grating structure is smaller than that of the silicon waveguide;
and depositing a layer of silicon dioxide on the periphery of the silicon nitride grating structure by adopting a PECVD method to be used as an upper cladding of the silicon nitride grating structure, and polishing the upper cladding by CMP.
8. The method of claim 7, wherein the silicon waveguide has a thickness of 220nm and a width of 500nm.
9. The method of fabricating phased array elements according to claim 7, wherein said oxide layer has a thickness of 100nm.
10. The method of claim 7, wherein the silicon nitride grating has a thickness of 400nm.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117170020A (en) * | 2023-11-02 | 2023-12-05 | 赛丽科技(苏州)有限公司 | Optical antenna |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117170020A (en) * | 2023-11-02 | 2023-12-05 | 赛丽科技(苏州)有限公司 | Optical antenna |
| CN117170020B (en) * | 2023-11-02 | 2024-02-09 | 赛丽科技(苏州)有限公司 | Optical antenna |
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