Fabrication of Low-Loss Silicon Photonic Wires by Self-Profile Transformation and Applications in 3-D Photonic Integration and Nonlinear Optics

A new technology using self-profile transformation is introduced to make subwavelength silicon photonic wires with very smooth surface. Due to the smooth surface, the propagation loss was measured to be as low as 1.26 dB/cm. Moreover, 2-D beam spot-size converters and 2-D multimode interference couplers were demonstrated to monolithically integrate the photonic wires, showing the possibility of 3-D photonic integration. Owing to the low-insertion loss of the wires, various nonlinear optical processes such as four-wave mixing and spontaneous Raman emission were observed with low-pump power of just tens of milliwatts.