Ultracompact Polarization Rotator Based on Liquid Crystal Channel on Silicon

Abstract

A novel highly tunable polarization rotator (PR) based on channel waveguide on silicon is introduced and analyzed. The proposed SiO2/Si channel is infiltrated with nematic liquid crystal (NLC) material of type E7. The design parameters of the NLC channel PR have been studied to obtain an efficient polarization conversion with an ultrashort device length. Additionally, a tolerance analysis of the structure geometrical parameters, temperature, and operating wavelength is reported in detail. The modal analysis of the NLC PR is carried out using full-vectorial finite-difference method (FVFDM). Further, the propagation characteristics through the suggested design are obtained using full-vectorial finite-difference beam propagation method (FVFD-BPM). The numerical results reveal that the reported PR of compact device length of 4.02 μ m can achieve nearly 100% polarization conversion ratio with insertion loss of 2.19 dB and good crosstalk of –21.73 dB at a wavelength of 1.55 μ m. Further, the crosstalk would be better than –20 dB within the wavelength range of 1.55 ± 0.04 μ m. Moreover, the polarization conversion ratio can be controlled by applying an external electric field. To the best of the authors’ knowledge, it is the first time to introduce ultracompact highly tunable PR based on a channel on silicon platform with simple design and broadband operation.