Photonic crystal and related devices fabricated by CMOS-compatible process

Silicon CMOS-compatible process enables us to integrate various photonic devices such as passive waveguide components, fibre couplers, heaters, and pn junctions. Technical difficulties in integrating an air-bridge photonic crystal (PC) slab with these devices can be overcome by multi-step masking and etching process. The fibre coupler reduces the fibre-to-fibre insertion loss to <;10 dB even when the PC waveguide is inserted. Slow light in PC waveguides and microring circuits is applied for the delay tuning and nonlinear enhancement. For the delay tuning, the slow light spectrum is controlled by integrated heaters, and the delay of 40 Gbps signals is tuned in the range of 150 ps. Exploiting low-dispersion slow light, the two-photon absorption, self-phase modulation, and four-wave-mixing are efficiently generated in a 400-μm long PCW with a reasonably low power. The PC waveguide with a pn junction is used as a phase shifter in MZI modulators. High-speed modulation of up to 10 Gbps is obtained in a 200-μm-long device. They will also be applicable for the fast delay tuning and dynamic tuning in slow light devices.