Ultra-compact silicon on-chip polarization controller

On-chip polarization controllers are extremely important for various optical systems. In this paper, a compact and robust silicon-based on-chip polarization controller is proposed and demonstrated by integrating a special polarization converter and phase shifters. The special polarization converter consists of a 1×1 Mach–Zehnder interferometer with two polarization-dependent mode converters at the input/output ends. When light with an arbitrary state of polarization (SOP) is launched into the chip, the TE 0 and TM 0 modes are simultaneously excited. The polarization extinction ratio (PER) and the phase difference for the TE 0 / TM 0 modes are tuned by controlling the first phase shifter, the polarization converter, and the second phase shifter. As a result, one can reconstruct the light SOP at the output port. The fabricated polarization controller, as compact as ∼150 μm ×700 μm , exhibits an excess loss of less than 1 dB and a record PER range of >54 dB for arbitrary input light beams in the wavelength range of 1530–1620 nm.