Ultra-Compact and Ultra-Low Insertion Loss Silicon Optical Polarizer Based on Inverse Design

As the key device to realize polarization diversity function, the optical polarizer is a favorable way to solve the polarization sensitivity problem of silicon photonic devices. Nevertheless, on-chip silicon polarizers are still difficult to balance the compact size and superior performance. In order to break the above problems, an inverse design method is exploited to achieve ultra-compact silicon transverse electrical (TE)-pass polarizers. Compared with the reported polarizers (tens of micrometers), the 5.43- $\mu $ m-length of the proposed polarizer is significantly reduced by an order of magnitude. More importantly, the minimum insertion loss is as low as 0.17 dB and the experimental operation bandwidth could realize 100 nm (1500 nm~1600 nm). Furthermore, the maximum value of the extinction ratios could realize up to 32.2 dB. To the best of our knowledge, it is the first time to realize silicon optical polarizers with a record ultra-short length of $5.43~\mu $ m, ultra-low insertion loss of 0.17 dB and wide bandwidth of 100 nm based on the inverse design method. The proposed optical polarizers have great potential applications in on-chip high-performance and high-capacity optical communication systems.