TDFA-Band Silicon Optical Variable Attenuator

TDFA-band (2-mu m waveband) has been considered as a promising optical window for the next generation of optical communication and computing. Absorption modulation, one of the fundamental reconfigurable manipulations, is essential for large scale photonic integrated circuits. However, few efforts have been involved in exploring absorption modulation at TDFA-band. In this work, variable optical attenuators (VOAs) for TDFA-band wavelengths were designed and fabricated based on a silicon-on-insulator (SOI) platform. By embedding a short PIN junction length of 200 mu m into the waveguide, the fabricated VOA exhibits a high modulation depth of 40.49 dB at 2.2V and has a fast response time (10 ns) induced by the plasma dispersion effect. Combining the Fabry-Perot cavity effect and plasma dispersion effect of silicon, the attenuator could achieve a maximum attenuation of more than 50 dB. These results promote the 2-mu m waveband silicon photonic integration and are expected to the future use of photonic attenuators in crosstalk suppression, optical modulation, and optical channel equalization.