A novel etching-free optical waveguide and dispersion modulation method based on continuous bound states

Abstract

This invention discloses a novel etch-free optical waveguide based on continuous bound states and a dispersion control method, belonging to the field of integrated optoelectronics. From top to bottom, it comprises a waveguide cladding, a low-emissivity planar layer, an optical waveguide layer, a buried oxide layer, and a substrate. The width and length of the optical waveguide layer, the buried oxide layer, and the substrate are all the same. The waveguide cladding is composed of several strip structures. The etch-free optical waveguide eliminates the need for complex etching processes, reducing manufacturing costs, minimizing process errors and defects, simplifying the manufacturing process, and exhibiting low-loss characteristics, which is beneficial for developing ultra-low-loss waveguide devices. The dispersion control method can achieve dispersion modulation of modes without altering the morphology of the optical waveguide using ion beam etching and photolithography, contributing to the development of high-performance on-chip nonlinear devices.

Description

Technical Field

[0001] This invention belongs to the field of integrated optoelectronics, specifically relating to a method for etching-free optical waveguides and dispersion modulation. Background Technology

[0002] Silicon, with its high refractive index and high nonlinear refractive index, is an ideal material platform for developing high-density integrated nonlinear devices. Dispersion, as one of the core factors affecting the performance of nonlinear devices, directly impacts their bandwidth and energy conversion efficiency. For example, in the development of cutting-edge technology like Kerr optical frequency combs, the range of anomalous dispersion regions is particularly critical, directly limiting the bandwidth achievable by the Kerr frequency comb and thus affecting its application capabilities in fields such as optical communication, spectral analysis, and quantum information processing. By controlling the geometry of waveguides, such as adjusting parameters like width, height, and sidewall tilt angle, the dispersion characteristics of waveguides can be effectively controlled. However, previous dispersion control methods have relied on altering the waveguide morphology through etching or photolithography, resulting in complex processes and introducing scattering losses due to waveguide sidewall roughness, which in turn affects the performance of nonlinear devices.

[0003] Extensive research has been conducted on dispersion modulation through etching to alter waveguide morphology. In terms of publications, in 2010, Zhang et al. from the University of Southern California proposed a silicon slit waveguide that produced flat dispersion of 0±16 ps / nm / km in the 553 nm wavelength range (Optics Express, 18, 19, 20529). In 2016, Hanxiao Liang et al. from the University of Rochester proposed double-clad and multi-clad waveguide structures that can flexibly modulate group velocity dispersion across multiple octaves of the spectrum (Optics Express, 24, 26, 29444). In 2019, Yuhao Guo et al. from Tianjin University proposed a novel dispersion flattening technique that can generate ultraflat group velocity dispersion curves with 5 and 6 zero-dispersion wavelengths (Photonics Research, 7, 11, 1279). However, all of the above studies modulate dispersion by altering the waveguide morphology through ion beam etching or photolithography, which are complex processes and introduce scattering losses.

[0004] Regarding patents, in 2017, Chen Minghua et al. from Tsinghua University applied for a Chinese invention patent (201710525571.0) by adjusting the width spacing between waveguide cores using the mode coupling principle. In 2020, Cheng Zhenzhou et al. from Tianjin University invented a convex multimode waveguide, which made the TE0 and TE1 modes have similar dispersion curves by controlling the geometric morphology of the waveguide, and applied for a Chinese invention patent (202010623165.X). However, in the above patents on waveguide dispersion control, photolithography or ion beam etching is also used to change the waveguide morphology.

[0005] In summary, although dispersion modulation in waveguides has been extensively studied, previous studies have all aimed to modulate dispersion by altering the waveguide morphology through ion beam etching or photolithography. These methods are complex and expensive, and the roughness of the waveguide sidewalls affects the waveguide transmission loss, which to some extent limits the development of high-performance nonlinear waveguide devices. Summary of the Invention

[0006] To address the limitations imposed on the development and application of optical parametric devices by existing dispersion modulation techniques that require ion beam etching or photolithography to alter the waveguide morphology, this invention proposes a novel etching-free optical waveguide and dispersion modulation method based on a novel continuous bound state.

[0007] This invention is achieved through the following technical solution:

[0008] A novel etch-free waveguide based on continuous bound states comprises, from top to bottom, a waveguide cladding 1, a low emissivity planar layer 2, an optical waveguide layer 3, a buried oxide layer 4, and a substrate 5; the optical waveguide layer 3, the buried oxide layer 4, and the substrate 5 have the same width and length; the waveguide cladding 1 is composed of several strip structures.

[0009] Furthermore, the waveguide cladding 1 is made of one or more of the following materials: silicon dioxide, silicon nitride, and polymer, in a layered combination.

[0010] Furthermore, the material of the low emissivity flat plate layer 2 is a layered combination of one or more of the following materials: silicon dioxide, silicon nitride, and polymer.

[0011] Furthermore, the material of the optical waveguide layer 3 is composed of one or more of the following materials: silicon, germanium, silicon-germanium mixture, silicon nitride, indium phosphide, gallium arsenide, lithium niobate, indium gallium arsenide, and aluminum gallium arsenide.

[0012] Furthermore, the waveguide cladding 1 is fabricated by magnetron sputtering, ion beam sputtering, chemical vapor deposition, thermal oxidation, or gel-sol method.

[0013] Furthermore, the low emissivity flat plate layer 2 is fabricated by magnetron sputtering, ion beam sputtering, chemical vapor deposition, thermal oxidation, or gel-sol method.

[0014] On the other hand, the present invention provides a novel dispersion control method for continuous bound state etch-free optical waveguides. By controlling the geometry of the waveguide cladding and low-refractive-index planar layer structure, dispersion control is achieved for the spatial modes inside the continuous bound state etch-free optical waveguide.

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] (1) The dispersion control method involved in this invention can achieve dispersion modulation of the mode without changing the morphology of the optical waveguide using ion beam etching and photolithography, which is helpful for the development of high-performance on-chip nonlinear devices.

[0017] (2) The fabrication process of the device of the present invention is fully compatible with the existing CMOS process, which is conducive to the large-scale mass production of the device.

[0018] (3) The optical waveguide fabrication of the present invention does not require a complex etching process, which reduces manufacturing costs, reduces process errors and defects, and simplifies the manufacturing process.

[0019] (4) The waveguide structure developed in this invention has low loss characteristics, which is beneficial for developing ultra-low loss waveguide devices.

[0020] (5) The waveguide structure of the present invention can be applied to a variety of optical functional materials, providing greater flexibility and selection space for the design of integrated optical chips, and can adapt to the needs of optical devices of different sizes and shapes. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0022] Figure 1 This is a schematic diagram of the continuous bound-state etch-free optical waveguide structure of the present invention;

[0023] Figure 2 Dispersion curves for silicon, silicon dioxide, and silicon nitride;

[0024] Figure 3 The dispersion curves of the TM0 mode are given when the waveguide cladding width is 0.8 μm, the waveguide cladding thickness is 0.1 μm, the low-refractive-index plate layer width is 2.8 μm, and the low-refractive-index plate layer thickness is 0.2 μm.

[0025] Figure 4 The dispersion curves of the TM0 mode are given when the waveguide cladding width is 1.2 μm, the waveguide cladding thickness is 0.1 μm, the low-refractive-index plate layer width is 4.2 μm, and the low-refractive-index plate layer thickness is 0.3 μm. Detailed Implementation

[0026] To clearly and completely describe the technical solution and its specific working process of the present invention, the specific embodiments of the present invention are as follows, in conjunction with the accompanying drawings:

[0027] Example 1

[0028] like Figure 1 As shown, this embodiment provides an etch-free optical waveguide based on continuous bound states, which includes, from top to bottom, a waveguide cladding 1, a low emissivity planar layer 2, an optical waveguide layer 3, a buried oxide layer 4, and a substrate 5. The waveguide cladding 1 is composed of several strip structures.

[0029] The aforementioned continuous-bound, etch-free optical waveguide can modulate the dispersion of spatial modes by changing the shapes of the waveguide cladding and the low-refractive-index slab layer. First, a set of structural dimensional parameters for the waveguide cladding and the low-refractive-index slab layer are designed, including the waveguide cladding width W1, waveguide cladding thickness H1, low-refractive-index slab layer width W2, and low-refractive-index slab layer thickness H2. The dispersion curve of the spatial mode is calculated based on the second derivative of the effective refractive index of the waveguide mode in the continuous-bound, etch-free optical waveguide. Then, by adjusting one or more of these parameters, the dispersion of the spatial mode can be controlled.

[0030] To further illustrate the proposed technique, this invention utilizes the commercial software tool COMSOL Multiphysics, a finite element method mode solver based on the beam propagation method, to simulate the effective refractive index of the optical waveguide, and then calculates the group velocity dispersion curve based on the simulation results.

[0031] like Figure 1As shown, the selected waveguide cladding is a strip structure, and the waveguide cladding material is silicon nitride. The low-refractive-index plate layer has a cuboid shape, and the low-refractive-index plate layer material is silicon nitride. The optical waveguide material is silicon, and the buried oxide layer material is silicon dioxide. The waveguide layer thickness is 220 nm, and the buried oxide layer thickness is 3 μm. The effective refractive index of TM0 is calculated using the commercial software COMSOL Multiphysics, and the dispersion of TM0 is calculated using formula (1) in Matlab software. In this embodiment, the waveguide cladding width is 0.8 μm, the waveguide cladding thickness is 0.1 μm, the low-refractive-index plate layer width is 2.8 μm, and the low-refractive-index plate layer thickness is 0.2 μm. The effective refractive index of the TM0 mode from 1.2 μm to 1.7 μm is calculated, and then the dispersion curve of the TM0 spatial mode is calculated using formula (1). The results are shown below. Figure 3 As shown, the group velocity dispersion of the TM0 mode exhibits multiple peaks and troughs in the range of 1.32 μm to 1.7 μm, providing a variety of wavelength options for the development of nonlinear devices.

[0032] Example 2

[0033] like Figure 1 As shown, the selected waveguide cladding is a strip structure, and the waveguide cladding material is silicon nitride. The low-refractive-index plate layer has a cuboid shape, and the low-refractive-index plate layer material is silicon nitride. The optical waveguide material is silicon, and the buried oxide layer material is silicon dioxide. The waveguide layer thickness is 220 nm, and the buried oxide layer thickness is 3 μm. The effective refractive index of TM0 is calculated using the commercial software COMSOL Multiphysics, and the dispersion of TM0 is calculated using formula (1) in Matlab software. In this embodiment, the waveguide cladding width is 1.2 μm, the waveguide cladding thickness is 0.1 μm, the low-refractive-index plate layer width is 4.2 μm, and the low-refractive-index plate layer thickness is 0.3 μm. The effective refractive index of the TM0 mode from 1.2 μm to 1.7 μm is calculated respectively, and then the dispersion curve of the TM0 spatial mode is calculated using formula (1). The results are shown below. Figure 4 As shown, the group velocity dispersion curve of TM0 varies around -5000 ps / nm / km, thus enabling the control of the space mode.

[0034] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0035] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0036] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A new type of continuous bound state based etchless waveguide, characterized in that, From top to bottom, it includes a waveguide cladding (1), a low emissivity planar layer (2), an optical waveguide layer (3), a buried oxide layer (4), and a substrate (5); the optical waveguide layer (3), the buried oxide layer (4), and the substrate (5) have the same width and length; the waveguide cladding (1) is composed of several strip structures. The waveguide cladding (1) is made of a layered combination of one or more of the following materials: silicon dioxide, silicon nitride, and polymer. The material of the low emissivity flat plate layer (2) is a layered combination of one or more of the following materials: silicon dioxide, silicon nitride, and polymer. The optical waveguide layer (3) is composed of one or more of the following materials: silicon, germanium, silicon-germanium mixture, silicon nitride, indium phosphide, gallium arsenide, lithium niobate, indium gallium arsenide, and aluminum gallium arsenide. The waveguide cladding (1) is fabricated by magnetron sputtering, ion beam sputtering, chemical vapor deposition, thermal oxidation or gel-sol method; The low-refractive-index plate layer (2) is fabricated by magnetron sputtering, ion beam sputtering, chemical vapor deposition, thermal oxidation, or gel-sol method. By controlling the geometry of the waveguide cladding and the low-refractive-index plate layer, dispersion control is achieved for the spatial mode inside the continuous bound state etch-free optical waveguide. First, a set of structural dimensional parameters of the waveguide cladding and the low-refractive-index plate layer are designed, including the waveguide cladding width W1, the waveguide cladding thickness H1, the low-refractive-index plate layer width W2, and the low-refractive-index plate layer thickness H2. The dispersion curve of the spatial mode is calculated based on the second derivative of the effective refractive index of the waveguide mode in the continuous bound state etch-free optical waveguide. Then, by adjusting one or more parameters of the waveguide cladding width W1, the waveguide cladding thickness H1, the low-refractive-index plate layer width W2, and the low-refractive-index plate layer thickness H2, dispersion control of the spatial mode is achieved. The waveguide layer has a thickness of 220 nm, the buried oxide layer has a thickness of 3 μm, the waveguide cladding has a width of 0.8 μm and a thickness of 0.1 μm, the low-refractive-index plate layer has a width of 2.8 μm and a thickness of 0.2 μm.

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