Silicon Photonic Filters Fabrication and Characterization

The silicon photonic filters were fabricated on an SOI wafer with a top-silicon layer that was 220 nm thick and a buried-dioxide layer that was 2 μm thick. The fabrication process involved electron-beam lithography (EBL) and inductively-coupled plasma dry-etching to create the silicon core regions. A 1.2 μm thick silica thin film was then deposited on top as the upper-cladding using plasma enhanced chemical vapor deposition (PECVD).

Microscope images of the fabricated silicon photonic integrated circuit (PIC) and scanning electron microscopic (SEM) images of the grating sections are shown in Figures 5a–5c. TE-polarization grating couplers were used in the PICs to achieve efficient chip-fiber coupling for measurement purposes. A super-continuum light source was used as the input source and an optical spectrum analyzer (OSA) was used to measure the transmissions at the output ports.

To characterize the spectral responses of the silicon photonic filter, light was launched from the input port and the transmissions at the through/drop ports were monitored. The measured results were normalized with respect to the transmission of a 450 nm wide straight waveguide connected with grating couplers on the same chip.