RESUMO
A novel ultra-broadband TM-pass polarizer with high polarization extinction ratio (PER) and low reflection has been proposed and demonstrated by utilizing multimode Bragg grating waveguide (MBGW) and two tapered waveguides. By optimizing the period of the MBGW, the injected TE0 mode is coupled into the backward TE2 mode and effectively leaked into the cladding. Meanwhile, the injected TM0 mode propagates through the polarizer without any negative impact. The operation bandwidth can be significantly expanded by cascading multiple MBGW structures, each of which operates at a different central Bragg wavelength. The simulation results indicate that the designed polarizer can achieve an insertion loss (IL) below 0.24â dB and a PER above 39â dB simultaneously across a bandwidth of 300â nm (1400â nmâ¼1700nm), while the reflected signal is below -9.1â dB. The experiment results demonstrate that the fabricated polarizer can realize an IL below 0.56â dB and a PER above 33â dB in a 160â nm bandwidth ranging from 1470â nm to 1630â nm. Due to limitations in the equipment used, measurements for other wavelength ranges are not conducted. With these merits, the proposed device would find significant applications in optical communication systems.