Design Of Optical Switch And Polarization Beam Splitters Based On Ge₂Sb₂Se₄Te₁

With the development of optical communication technology,the demand for optical communication system capacity is becoming higher and higher.In order to meet with this demand,integrated optical waveguide devices have become a research hotspot due to their advantages of small size,high performance and low cost.Since Dr.S.E.Miller of Bell Labs in the United States proposed the concept of integrated optics in1969,integrated optics has become a discipline integrating laser,microelectronics,communication and other technologies.At present,integrated optical waveguide devices mainly include grating couplers,optical splitters,star couplers,optical switches and so on.As one of the most important devices in the field of on-chip optical communication,optical switch plays an important role in improving the quality of optical communication network.In optical networks,the performance of optical switches directly affects the speed and capacity of the entire optical network.With the increasing integration of optical communication systems,there are more and more unit devices passing through each optical path on the optical network,resulting in increasing optical path loss.Then,low power consumption is also an inevitable requirement of integrated devices,the increase of optical switching ports leads to a great increase in the total power consumption of devices,which affects the normal operation of switches.In addition,silicon-based waveguide devices mostly use silicon-on-insulator（SOI）technology.Therefore,silicon-based optical switches generally only support Transverse Electric（TE）mode or Transverse Magnetic（TM）mode,and the actual optical communication system needs to eliminate the polarization dependence of the optical switch.Starting from the above problems,the realization of on-chip polarization beam splitting is studied,and the realization of spatial polarization beam splitting is also studied.The content of this paper can be summarized as the following two aspects:1.A polarization-independent multifunctional optical switch is realized based on the waveguide coupling theory.Aiming at the problem that the current optical switch only supports single-mode input,a controllable optical switch with a central wavelength of 1550 nm is designed based on the SOI platform.The optical switch can complete the polarization beam splitting in TE/TM mode,and the refractive index of the phase change material can be changed by the amorphous（Am）to crystalline（Cr）and Cr-to-Am phase transitions through high temperature induction,thereby controlling the exit port of the TE mode to achieve controllable requirements,and meeting the requirements of low loss and crosstalk in different ports.When TE mode was input and the wavelength was 1550nm,for a directional coupler loaded with Ge₂Sb₂Se₄Te₁that realizes the optical switch function,the insertion loss（IL）is lower than 0.62dB and the crosstalk（CT）is lower than-9.88dB whether Ge₂Sb₂Se₄Te₁is in amorphous or crystalline state,and the extinction ratio（ER）of the two waveguides of the directional coupler is lower than-11.40dB,simultaneously.When TM₀mode was input and the wavelength was 1550nm,for a directional coupler loaded without Ge₂Sb₂Se₄Te₁,the IL is lower than 0.62dB.The device is more flexible when applied,and its polarization insensitivity can be applied to more scenarios.2.Based on the relationship between the grating period and the incident wavelength,polarization beam splitting in different wavelength ranges is realized.Firstly,aiming at the demand of infrared polarization detection technology,a polarization beam splitter with broadband and large incident angle tolerance in the near-infrared band is designed based on subwavelength gratings.The device realizes TE mode reflection and TM mode transmission.At 1550nm wavelength,the TE mode reflection efficiency and TM mode transmission efficiency are both higher than 96%,and the reflection extinction ratio of the device is more than 17dB,and the transmission extinction ratio is more than 35dB.The device is of great significance to help detect complex environments.Then,based on the requirements of lithography technology,an anomalous polarization beam splitter with high polarization performance in the deep ultraviolet band is designed.The device achieves TE mode transmission and TM mode reflection,the TE mode transmission is as high as 83.4%,and the extinction ratio is as high as 57.0dB.The device has certain application value in improving the resolution of lithography machine.