Silicon-chip mid-infrared frequency comb generation.

Optical frequency combs are a revolutionary light source for high-precision spectroscopy because of their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared spectral region (2-20 μm) is important for molecular gas detection owing to the presence of a large number of absorption lines in this wavelength regime. Microresonator-based frequency comb sources can provide a compact and robust platform for comb generation that can operate with relatively low optical powers.

High RF carrier frequency modulation in silicon resonators by coupling adjacent free-spectral-range modes.

We demonstrate the modulation of silicon ring resonators at RF carrier frequencies higher than the resonance linewidth by coupling adjacent free-spectral-range (FSR) resonance modes. In this modulator scheme, the modulation frequency is matched to the FSR frequency. As an example, we demonstrate a 20 GHz modulation in a silicon ring with a resonance linewidth of only 11.

Deposited low temperature silicon GHz modulator.

We demonstrate gigahertz electro-optic modulator fabricated on low temperature polysilicon using excimer laser annealing technique compatible with CMOS backend integration. Carrier injection modulation at 3 Gbps is achieved. These results open up an array of possibilities for silicon photonics including photonics on DRAM and on flexible substrates.

Waveguide-integrated telecom-wavelength photodiode in deposited silicon.

We demonstrate photodiodes in deposited polycrystalline silicon at 1550 nm wavelength with 0.15 A/W responsivity, 40 nA dark current, and gigahertz time response. Subband absorption is mediated by defects that are naturally present in the polycrystalline material structure.