Laser modelocking and dual wavelength lasing in silicon

Nonlinear optics in silicon has drawn substantial attention in the recent years. In this research, laser mode-locking and dual wavelength lasing are achieved in a fiber-ring-cavity using an Erbium–doped fiber amplifier (EDFA) as a gain medium and a 1.7cm long silicon-on-insular waveguide as pulse compressor, a mode-locker and a Raman gain media. We show that the transient behavior of two photon absorption (TPA) and TPA induced free carrier absorption can be used for pulse compression and laser modelocking in the silicon waveguide inside the laser cavity. The proposed technique takes advantage of spontaneous generation of free carriers and the slow recombination time, >17ns, to attenuate the trailing edge of the time varying signals passing through the waveguide. When a 5μm model area silicon waveguide is placed inside a fiber ring cavity consisting of an EDFA as a gain media and ~50ps modelocked laser pulses are generated at 1540nm. We also observe that the generated short pulses also induce stimulated Raman scattering at 1675nm in the same silicon waveguide. We show that engineering the laser cavity facilitates laser modelocking and dual wavelength laser oscillation at 1540nm and 1675nm. Experimentally we obtain <100ps modelocked pulses at both wavelengths. The average pump threshold power of the Raman laser is measured to be 3.75mW and the Stokes average output power is measured to be 3 μW.