A short polarization splitter without metal overlays on InGaAsP-InP

A new and very short polarization splitter on InGaAsP-InP is designed and realized for the first time. The component contains a ridge waveguide directional coupler of 0.4 mm length and an output section of 0.7 mm. It uses the large waveguide birefringence of the first-order TE and TM modes to obtain polarization selective directional coupling. In this way, additional metal layers on the waveguides to create birefringence are avoided and fabrication becomes very simple. Components are realized, which show splitting ratios close to -20 dB. Excess losses are below 1 dB. The polarization splitting is investigated in the wavelength region of 1525-1560 nm and found to be better than -9 dB.