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CN-122018080-A - Three-channel wavelength division multiplexer based on film lithium niobate and wavelength division multiplexing method

CN122018080ACN 122018080 ACN122018080 ACN 122018080ACN-122018080-A

Abstract

The invention discloses a three-channel wavelength division multiplexer based on film lithium niobate and a wavelength division multiplexing method, the device comprises three-level filters which are connected in sequence, each filter comprises a multimode combined waveguide, a bent gradual change waveguide, a multimode waveguide grating and a through waveguide, the multimode waveguide grating adopts a structure of a silicon Bragg grating heterogeneous integrated lithium niobate waveguide, the device receives multi-wavelength fundamental mode optical signals, and realizes the conversion from TE 0 to three high-order modes while finishing filtering to obtain optical signals with different wavelengths in three channels in sequence. The wavelength division multiplexer has the advantages of high extinction ratio, low channel crosstalk and small channel space.

Inventors

  • LI TAO
  • GAO ZIHAN
  • WANG ZHIZHANG
  • ZHU SHINING

Assignees

  • 南京大学

Dates

Publication Date
20260512
Application Date
20260317

Claims (10)

  1. 1. The three-channel wavelength division multiplexer based on the film lithium niobate is characterized by comprising three-stage filters which are sequentially connected, wherein the three-stage filters comprise a first filter, a second filter and a third filter, the input end of the first filter receives a multi-wavelength fundamental mode optical signal, and the first to third filters respectively output three single-wavelength fundamental mode optical signals; The first filter to the third filter comprise multimode combined waveguides (1), bent graded waveguides (2), multimode waveguide Bragg gratings (3) and through waveguides (4); The multimode combined waveguide (1) and the bent graded waveguide (2) form an adiabatic coupling region together, and the adiabatic coupling region is used for carrying out mode spot broadening on a forward fundamental mode optical signal and converting a reflected single-wavelength optical signal into a fundamental mode optical signal and outputting the fundamental mode optical signal; The multimode waveguide Bragg grating (3) is used for converting a fundamental mode optical signal with a phase-matched wavelength into a corresponding TE mode and reflecting the TE mode to the multimode combined waveguide (1) and the bent graded waveguide (2); the through waveguide (4) is used for transmitting the fundamental mode optical signal which is not reflected by the multimode waveguide Bragg grating (3) to a next-stage filter or directly outputting.
  2. 2. The three-channel wavelength division multiplexer based on thin film lithium niobate according to claim 1, wherein the multimode combined waveguide (1) comprises an adiabatic coupling region wide graded waveguide (1-2), the curved graded waveguide (2) comprises an adiabatic coupling region narrow graded waveguide (2-2), and the adiabatic coupling region wide graded waveguide (1-2) and the adiabatic coupling region narrow graded waveguide (2-2) are positioned to correspond to each other to jointly form an adiabatic coupling region.
  3. 3. The three-channel wavelength division multiplexer based on the thin film lithium niobate according to claim 2, wherein the bent graded waveguide (2) further comprises a front 180 ° circular arc bent waveguide (2-1) and a rear 90 ° circular arc bent waveguide (2-3), the front 180 ° circular arc bent waveguide (2-1), the adiabatic coupling region narrow graded waveguide (2-2) and the rear 90 ° circular arc bent waveguide (2-3) are sequentially connected, and a single-wavelength fundamental mode optical signal is output from the lower end of the front 180 ° circular arc bent waveguide (2-1).
  4. 4. The three-channel wavelength division multiplexer based on thin film lithium niobate according to claim 1, wherein the multimode combined waveguide (1), the bent graded waveguide (2) and the through waveguide (4) all adopt lithium niobate ridge waveguide structures.
  5. 5. The three-channel wavelength division multiplexer based on thin film lithium niobate according to claim 1, wherein the multimode waveguide bragg grating (3) is a multimode lithium niobate ridge waveguide structure on which a silicon bragg grating is deposited.
  6. 6. The three-channel wavelength division multiplexer based on the thin film lithium niobate according to claim 5, wherein the silicon bragg gratings are rectangular silicon bragg grating structures, the rectangular arrangement is in antisymmetric distribution, and the first to third filters are respectively matched with different wavelengths by adjusting the number of structures, apodization intensity and grating period of the silicon bragg gratings.
  7. 7. The three-channel wavelength division multiplexer based on thin film lithium niobate according to claim 5, wherein the multimode waveguide bragg grating (3) comprises a silicon dioxide substrate (7), a thin film lithium niobate layer (8) and a silicon loading layer (9), wherein the thin film lithium niobate layer (8) is bonded to the upper surface of the silicon dioxide substrate (7), the thin film lithium niobate layer (8) is etched for the first time to form a lithium niobate ridge waveguide, the silicon loading layer (9) is deposited on the upper surface of the thin film lithium niobate layer (8), and the silicon loading layer (9) is etched for the second time to form a sub-wavelength-sized bragg grating structure.
  8. 8. A three-channel wavelength division multiplexing method based on thin film lithium niobate, characterized in that the three-channel wavelength division multiplexer according to claim 1 is used for performing wavelength division multiplexing, comprising the following steps: inputting a multi-wavelength fundamental mode optical signal into a first filter, converting the fundamental mode optical signal with a first wavelength into a TE 1 mode by a multi-mode waveguide Bragg grating 3 of the first filter, reflecting the optical signal with the TE 1 mode to a multi-mode combined waveguide (1) and a bent graded waveguide (2) of the first filter, converting the optical signal into a fundamental mode optical signal with the first wavelength, and outputting the fundamental mode optical signal; The unreflected fundamental mode optical signal is transmitted to a second filter through a straight-through waveguide (4) of the first filter, the fundamental mode optical signal with a second wavelength is converted into a TE 2 mode through a multimode waveguide Bragg grating (3) of the second filter, and the optical signal with the TE 2 mode is reflected to a multimode combined waveguide (1) and a bent graded waveguide (2) of the second filter and then converted into the fundamental mode optical signal with the second wavelength and output; The unreflected fundamental mode optical signal is transmitted to a third filter through a through waveguide (4) of the second filter, the fundamental mode optical signal with the third wavelength is converted into a TE 3 mode through a multimode waveguide Bragg grating (3) of the third filter, and the optical signal with the TE 3 mode is reflected to a multimode combined waveguide (1) and a bent graded waveguide (2) of the third filter and then converted into the fundamental mode optical signal with the third wavelength and output.
  9. 9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the computer program when loaded into the processor implements the three-channel wavelength division multiplexing method based on thin film lithium niobate according to claim 8.
  10. 10. A computer program product comprising a computer program, characterized in that the computer program, when being executed by a processor, implements the three-channel wavelength division multiplexing method based on thin film lithium niobate according to claim 8.

Description

Three-channel wavelength division multiplexer based on film lithium niobate and wavelength division multiplexing method Technical Field The invention relates to the field of integrated optics, in particular to a three-channel wavelength division multiplexer based on film lithium niobate and a wavelength division multiplexing method. Background With the increase of data traffic, high demands are now placed on the capacity and efficiency of optical communication systems, and integrated photonics is critical to this challenge. Silicon-on-insulator platforms have enjoyed significant success over the last decade due to the high refractive index contrast and mature processing, however, research is increasingly focused on lithium niobate platforms on insulators due to the limitations of silicon materials themselves, such as higher optical losses, lack of intrinsic electro-optic effects, etc., in pursuit of lower loss and higher speed optical communication systems. Lithium niobate has excellent photoelectric characteristics such as strong electro-optic effect, low loss, strong nonlinearity, and the like, and can realize miniaturized and high-integration photonic chip devices by combining a high refractive index difference optical waveguide structure. In the application demands of high speed and large capacity, the Wavelength Division Multiplexing (WDM) technology is one of the most common multiplexing technologies for improving the capacity of a data communication link, and the existing thin film lithium niobate wavelength division multiplexer has two processing modes, namely, the processing mode of directly etching a lithium niobate waveguide has the defect that the processing difficulty of etching lithium niobate is high, and only mode conversion between TE 0 and TE 1 can be realized due to the adoption of side wall etching, and the two processing modes are that a silicon nitride waveguide is heterogeneous integrated on the thin film lithium niobate and the silicon nitride waveguide is etched to realize the functions of wavelength division multiplexing and the like. Disclosure of Invention The invention aims to provide a three-channel wavelength division multiplexer based on film lithium niobate and a wavelength division multiplexing method, which avoid directly etching lithium niobate to form a grating, realize multi-wavelength multiplexing by utilizing different mode conversion, reduce crosstalk among different channels and improve signal to noise ratio. The three-channel wavelength division multiplexer based on the thin film lithium niobate comprises three-stage filters which are sequentially connected, wherein the three-stage filters comprise a first filter, a second filter and a third filter, the input end of the first filter receives a multi-wavelength fundamental mode optical signal, and the first to third filters respectively output three single-wavelength fundamental mode optical signals; The first filter, the second filter and the third filter respectively comprise a multimode combined waveguide, a bent graded waveguide, a multimode waveguide Bragg grating and a straight-through waveguide; The multimode combined waveguide and the bent graded waveguide form an adiabatic coupling region together and are used for carrying out mode spot broadening on a forward fundamental mode optical signal and converting a reflected single-wavelength optical signal into a fundamental mode optical signal and outputting the fundamental mode optical signal; the multimode waveguide Bragg grating is used for converting a fundamental mode optical signal of a wavelength matched with the phase into a corresponding TE mode and reflecting the TE mode to the multimode combined waveguide and the bent graded waveguide; The through waveguide is used for transmitting the fundamental mode optical signal which is not reflected by the multimode waveguide Bragg grating to a next-stage filter or directly outputting the fundamental mode optical signal. Further, the multimode combined waveguide comprises an adiabatic coupling region wide graded waveguide, the bending graded waveguide comprises an adiabatic coupling region narrow graded waveguide, and the adiabatic coupling region wide graded waveguide and the adiabatic coupling region narrow graded waveguide are mutually corresponding in position and jointly form an adiabatic coupling region. Further, the bending gradual change waveguide further comprises a front 180-degree arc-shaped bending waveguide and a rear 90-degree arc-shaped bending waveguide, the front 180-degree arc-shaped bending waveguide and the adiabatic coupling area narrow gradual change waveguide are sequentially connected with the rear 90-degree arc-shaped bending waveguide, and a single-wavelength fundamental mode optical signal is output from the lower end of the front 180-degree arc-shaped bending waveguide. Further, the multi-mode combined waveguide, the bent graded waveguide and the through waveguide all adopt lithium n