A multi-layer waveguide grating antenna based on staggered etching for optical phased array and its preparation method

Abstract

The present invention relates to a multi-layer structure waveguide grating antenna based on staggered etching for use in an optical phased array and a preparation method thereof, comprising, from bottom to top, a substrate (1), a waveguide region and a top oxide layer (5); the waveguide region comprises, from bottom to top, a first waveguide layer (2), an isolation layer (3) and a second waveguide layer (4); wherein the second waveguide layer (4) has staggered deep and shallow grooves. The present invention reduces the leakage of light to the substrate, increases the proportion of light emitted upward, thereby improving the emission efficiency of the grating, and has the advantage of a long effective emission length, which is helpful to improve the detection distance of the phased array and realize high-power output devices.

Description

Technical Field

[0001] The present invention belongs to the field of integrated optoelectronic devices, and in particular relates to a multi-layer structure waveguide grating antenna based on staggered etching applied to an optical phased array and a preparation method thereof. Background Art

[0002] Solid-state LiDAR can significantly reduce system size, weight, power consumption and cost, and is an inevitable trend in the development of LiDAR. Optical phased array based on silicon-based optoelectronics technology has promoted the development of integrated solid-state LiDAR. The high integration, compatibility with CMOS technology, and optoelectronic monolithic integration of silicon-based optoelectronics technology can provide broad prospects for large-scale, low-cost quantitative production of silicon-based LiDAR chips.

[0003] The loss of the optical phased array limits the detection distance. The waveguide grating antenna is an important component of the optical phased array, responsible for coupling light from the waveguide to the free space. The current waveguide grating antenna generally has the problem of low transmission efficiency. Therefore, it is very important to improve the transmission efficiency of the transmitting grating for the optical phased array. The radiation of the grating antenna toward the substrate will affect the transmission efficiency of the transmitting grating. The efficiency of upward diffraction is mainly determined by the directivity of the grating. The directivity of the grating is defined as the ratio of the optical power coupled to the top of the chip to the optical power coupled out of the waveguide. Therefore, a highly directional waveguide grating antenna has far-reaching significance for improving the detection distance of silicon-based optical phased arrays.

[0004] CN112946814A discloses a high-efficiency and large-aperture grating antenna for an optical phased array and a preparation method thereof. The grating antenna has the problems of insufficient directivity and insufficient effective transmission length. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a multi-layer structure waveguide grating antenna based on staggered etching for use in optical phased arrays and a preparation method thereof. By utilizing the staggered etching structure and the multi-layer structure, high directivity and centimeter-level effective transmission length can be achieved, thereby solving the problem of low transmission efficiency of the grating antenna.

[0006] The present invention provides a multi-layer structure waveguide grating antenna based on staggered etching for use in an optical phased array, which comprises, from bottom to top, a substrate, a waveguide region and a top oxide layer; the waveguide region comprises, from bottom to top, a first waveguide layer, an isolation layer and a second waveguide layer; wherein the second waveguide layer has staggered deep and shallow grooves.

[0007] The substrate, the isolation layer and the top oxide layer are all made of silicon dioxide.

[0008] The material of the first waveguide layer is silicon; the material of the second waveguide layer is silicon nitride.

[0009] The depth of the deep groove of the second waveguide layer is 250-300 nm; the depth of the shallow groove is 150-200 nm.

[0010] The thickness of the first waveguide layer is 50-100 nm; the thickness of the second waveguide layer is 500-550 nm.

[0011] The present invention provides a method for preparing a multi-layer structure waveguide grating antenna based on staggered etching for use in an optical phased array, comprising:

[0012] providing a substrate;

[0013] Providing a first waveguide layer located on the surface of the substrate;

[0014] Providing a second waveguide layer, which is arranged above the first waveguide layer in a direction perpendicular to the substrate, and the second waveguide layer has a grating structure formed by alternating deep etching and shallow etching;

[0015] providing an isolation layer disposed between the first waveguide layer and the second waveguide layer;

[0016] A top oxide layer is provided and disposed on the surface of the second waveguide layer.

[0017] The present invention utilizes deep and shallow grooves to control interference conditions, so that the radiation fields of grooves with two different etching depths produce constructive interference in the emission direction and destructive interference in the substrate direction, which can improve the directivity. The separation of the grating structure and the silicon waveguide can control the emission length of the grating and provide a new degree of freedom for optimizing the optical path length. The asymmetric multilayer structure can serve as a bottom reflector, and the radiation in the direction of the substrate is reflected at the interface of each layer. Therefore, by optimizing the grating structure parameters such as etching depth and waveguide layer thickness, the high directivity of the waveguide grating antenna can be achieved.

[0018] Beneficial Effects

[0019] The present invention reduces the leakage of light to the substrate, increases the proportion of light emitted upward, and thus improves the emission efficiency of the grating. At the same time, it has the advantage of a long effective emission length, which is helpful to improve the detection distance of the phased array and realize high-power output devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the cross-section structure of the grating antenna of the present invention;

[0021] Figure 2 A three-dimensional diagram of the structure of the grating antenna of the present invention;

[0022] Figure 3 The curve showing the change of directivity of the grating antenna according to the present invention with wavelength and waveguide thickness;

[0023] Figure 4 is the grating directivity -1dB bandwidth of the grating antenna of the present invention;

[0024] Figure 5 is the near-field electric field strength of the grating antenna of the present invention;

[0025] Figure 6 Fitting the near-field electric field strength of the grating antenna of the present invention;

[0026] Figure 7 Far-field projections of the grating antenna of the present invention at wavelengths of 1500nm and 1600nm;

[0027] Figure 8 is the far field normalization and angle of the grating antenna of the present invention at different wavelengths;

[0028] Component number description:

[0029] 1 substrate;

[0030] 2 First waveguide layer;

[0031] 3. Isolation layer;

[0032] 4 second waveguide layer;

[0033] 5 Top oxide layer. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it 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 within the scope limited by the appended claims of the application equally.

[0035] Example 1

[0036] Depend on Figure 1 and Figure 2 As shown, this embodiment provides a multi-layer structure waveguide grating antenna based on staggered etching for optical phased array, which includes a substrate 1, a waveguide area and a top oxide layer 5 from bottom to top; the waveguide area includes a first waveguide layer 2, an isolation layer 3 and a second waveguide layer 4 from bottom to top; wherein the second waveguide layer 4 has deep and shallow grooves arranged staggered. The materials of the substrate 1, the isolation layer 3 and the top oxide layer 5 are all silicon dioxide. The material of the first waveguide layer 2 is silicon; the material of the second waveguide layer 4 is silicon nitride. In this embodiment, the depth of the deep groove of the second waveguide layer 4 is 260nm; the depth of the shallow groove is 180nm. The thickness of the first waveguide layer 2 is 90nm; the thickness of the second waveguide layer 4 is 540nm.

[0037] This embodiment also provides a method for preparing a multi-layer structure waveguide grating antenna based on staggered etching applied to an optical phased array, comprising:

[0038] Providing a substrate 1;

[0039] Providing a first waveguide layer 2, located on the surface of the substrate 1;

[0040] Providing a second waveguide layer 4, which is arranged above the first waveguide layer 2 in a direction perpendicular to the substrate 1, and the second waveguide layer 4 has a grating structure formed by alternating deep etching and shallow etching;

[0041] Providing an isolation layer 3, located between the first waveguide layer 2 and the second waveguide layer 4;

[0042] A top oxide layer 5 is provided and disposed on the surface of the second waveguide layer 4 .

[0043] In this embodiment, the first waveguide layer can achieve a directivity of more than 94% when the thickness is 90nm ( Figure 3 ), the grating -1dB bandwidth reaches 287nm near the central wavelength of 1550nm ( Figure 4 ), which provides space for increasing the beam deflection angle by expanding the scanning wavelength range. The near-field distribution of the 50μm length grating ( Figure 5 ), the structure of separating the grating and the waveguide provides controllable perturbation intensity, thus achieving centimeter-level emission length ( Figure 6 ), the effective emission length reaches the centimeter level, thus ensuring a very small divergence angle. The far-field diagram of the grating at 1500nm and 1600nm ( Figure 7 ), in the wavelength scanning range of 1500nm to 1600nm, the far-field deflection angle in air is greater than 11° ( Figure 8 ). Therefore, the device has high directivity, long effective emission length, and appropriate far-field deflection angle, and can be well applied in silicon-based optical phased arrays.

Claims

1. A multi-layer waveguide grating antenna based on staggered etching for use in an optical phased array, comprising, from bottom to top, a substrate (1), a waveguide region and a top oxide layer (5); characterized in that: The waveguide region comprises, from bottom to top, a first waveguide layer (2), an isolation layer (3) and a second waveguide layer (4); wherein the second waveguide layer (4) has deep and shallow grooves arranged alternately; the depth of the deep grooves of the second waveguide layer (4) is 260 nm; the depth of the shallow grooves is 180 nm; the thickness of the first waveguide layer (2) is 90 nm; and the thickness of the second waveguide layer (4) is 540 nm.

2. The grating antenna according to claim 1, characterized in that: The materials of the substrate (1), the isolation layer (3) and the top oxide layer (5) are all silicon dioxide.

3. The grating antenna according to claim 1, characterized in that: The material of the first waveguide layer (2) is silicon; the material of the second waveguide layer (4) is silicon nitride.

4. A method for preparing a multi-layer structure waveguide grating antenna based on staggered etching for use in an optical phased array according to claim 1, comprising: Providing a substrate (1); Providing a first waveguide layer (2) located on the surface of the substrate (1); Providing a second waveguide layer (4), which is arranged above the first waveguide layer (2) in a direction perpendicular to the substrate (1), and the second waveguide layer (4) has a grating structure formed by alternating deep etching and shallow etching; Providing an isolation layer (3) located between the first waveguide layer (2) and the second waveguide layer (4); A top oxide layer (5) is provided and arranged on the surface of the second waveguide layer (4).

Images