改下润色下述段落The designed silicon photonic filters were then fabricated on an SOI wafer with a 220-nm-thick top-silicon layer and a 2-μm-thick buried-dioxide layer The processes of electron-beam lithograph

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 form the silicon core regions. A 1.2 μm thick silica thin film was then deposited on top using the plasma enhanced chemical vapor deposition (PECVD) process, serving as the upper-cladding. 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. To facilitate measurement, grating couplers for TE-polarization were used in the PICs to achieve efficient chip-fiber coupling. The measurements were performed using a super-continuum light source as the input and an optical spectrum analyzer (OSA) to readout the transmissions at the output ports. By monitoring the transmissions at the through/drop ports, the spectral responses of the silicon photonic filter were characterized. 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.