Patent ID: 9366818
Filing Date: 2016-06-14
CPC Classification: G02B

Claim Text:
1. A polarization beam splitter comprising: a first-stage directional coupler comprising a first waveguide and a second waveguide laid in parallel with a first coupling gap and configured to have a coupling length for TE polarization mode be twice of that for TM polarization mode, the first waveguide being configured with an input port for receiving an optical signal over a predetermined wavelength band and a first through port for outputting a first primary TM mode portion of the optical signal with a first TM extinction ratio, the second waveguide being configured to have a first cross port for outputting a first primary TE mode portion of the optical signal cross coupled from the input port of the first waveguide with a first TE extinction ratio; a couple of second-stage directional couplers each being configured substantially same as the first-stage directional coupler except being complementary designed with a second coupling gap, a first second-stage directional coupler being cascaded to the first through port for further coupling the first primary TM mode portion to a second primary TM mode portion at a second through port with a second TM extinction ratio and a second second-stage directional coupler being cascaded to the first cross port for further cross-coupling the first primary TE mode portion to a second primary TE mode portion at a second cross port with a second TE extinction ratio; wherein the first and second coupling gap are set complementary for maximizing the first and second TE/TM extinction ratio respectively within a shorter and longer wavelength window of the predetermined wavelength band or vise versa.