Ultra-Low-Loss Silicon Photonic Waveguides Operating With the Wavelength-Bands of 1.31/1.55/2 μm

Silicon photonics is developing rapidly for the operation at the wavelength-bands of 1.31/1.55 μm as well as 2 μm. One of the most fundamental tasks is to develop low-loss silicon photonic waveguides, which are crucial for various photonic integrated circuits used in optical gyroscopes, tunable delay-line arrays and high-Q resonators, etc. Here silicon photonic waveguides work with ultra-low propagation losses in the wavelength-bands of not only 1.31/1.55 μm but also 2 μm are designed and demonstrated for the first time. Long waveguide spirals are designed optimally according to the comprehensive theoretical analysis, and the measured propagation losses of the fabricated waveguides are about 0.18, 0.13 and 0.07 dB/cm at the wavelength-bands of 1.31, 1.55, and 1.91 μm, respectively, which agrees well with the theoretical prediction. The total propagation loss is reduced greatly by more than a half for achieving the same time delay when using the wavelength of 1.91 μm than the wavelength of 1.31 μm.