Design method of all-optical wavelength converter for segmental QPM (quasi-phase-matched) crystals

Abstract

The invention discloses a design method of an all-optical wavelength converter for segmental QPM (quasi-phase-matched) crystals. The design method includes at the premise that constraint conditions of segmental PPLN (periodic poling LiNbO 3) of an all-optical wavelength conversion plan based on bi-pass configuration cascading SHG (second harmonic generation) and DFG (difference frequency generation) has given, searching structure parameters of the segmental PPLN under different temperatures as the constraint conditions are met; determining a relation between the structure parameters and temperature changes; determining a design parameter of a wavelength converter of the segmental PPLN according to the relation and a working temperature of the all-optical wavelength converter. During the design of the all-optical wavelength converter, influence of the temperature changes to conversion property is fully considered, and a structure parameter of a broadband wavelength converter is designed in the design method, in this way, a high and smooth wavelength conversion efficiency is kept for the wavelength converter at the operating temperature, and wavelength conversion band width is greatly expanded.

Description

technical field [0001] The invention relates to a design method of an all-optical wavelength converter of a segmented quasi-phase-matched crystal, which can maintain a relatively high and flat wavelength conversion efficiency of the all-optical wavelength converter at an operating temperature, and greatly expand the wavelength conversion bandwidth. It belongs to the technical field of optical elements. Background technique [0002] With the rapid growth of network services, the market of various broadband and multimedia services continues to grow, and high-speed and large-capacity integrated service networks have become the development trend of modern communication networks. The all-optical communication network is rapidly developing from the previous point-to-point communication to the multi-wavelength optical fiber network. The use of optical nonlinear effects to realize all-optical processing of high-speed optical signals has become one of the requirements for the develop...

AI Technical Summary

Problems solved by technology

The conversion bandwidth of the wavelength converter based on the uniform period QPM crystal is very small (around 60nm)

Although individual schemes have obtained large conversion bandwidth, the bandwidth size is still unsatisfactory

Previous studies have shown that the use of non-uniform polarization periodic structures, such as linear chirped structures, segmented structures, segmented phase-shift structures, or multi-wavelength phase-matched structures, can effectively expand the conversion bandwidth and improve pump stability. These studies are only for a single SHG effect or DFG effect

[0006] In recent years, Tehranchi et al. proposed a stepped chirped grating (SCG) structure, and used this structure to study the wavelength converter based on the "SFG+DFG" effect, and obtained good flat characteristics, but the conversion bandwidth Small (about 90nm), and does not consider the influence of temperature on structural design

In addition, the polarization period of each section in the SCG structure can only change monotonically rising or falling monotonically compared with the previous section, and the change value is fixed, making the structure inflexible, resulting in the conversion bandwidth in the case of multiple sections. The structure is smaller, and the wavelength tunable is not considered

Zhang Hanyi and Guo Yili's research group at Tsinghua University used segmented structure PPLN crystals to theoretically analyze the wavelength conversion scheme directly based on the DFG effect, and obtained a conversion bandwidth exceeding 130nm, but their research only focused on a single DFG effect

[0007] The feasibility and effectiveness of the wavelength conversion scheme based on QPM technology are beyond doubt, and the technical advantages of the scheme are also obvious, but there are still some shortcomings: For WDM optical communication systems, if you want to obtain flat ultra-wideband wavelength conversion characteristics, you should use For QPM crystals with non-uniform periodic structure, it is difficult to design a non-uniform periodic structure that meets the requirements; for the same structure, the optimal design parameters of the structure should also change when the temperature changes, and the non-uniform periodic QPM crystal that considers temperature changes Structural optimization design and broadband wavelength conversion scheme based on it are rarely reported

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