Low-loss, polarization-independent spot-size converter manufacturable with a 0.18 µm CMOS process

We developed a spot size converter (SSC) that can be fabricated with a 0.18 µm CMOS process. The SSC has a partial half-height SiN sturucture to reduce polarization dependent loss (PDL). In order to expand the mode field diameter (MFD) and suppress radiation, SiON structures are introduced. As a result of the measurement, the optical losses for mode expansion were 0.5 dB for the transverse electric (TE) mode and 0.7 dB for the transverse magnetic (TM) mode, respectively. PDL was 0.2 dB and the MFD was between 6.0 µmand 8.0 µm.