Narrow-linewidth integrated hybrid InP-Si3N4 dual-wavelength laser

Integrated dual-frequency lasers are of interest in a wide range of applications, in particular THz generation, distance and position measurements, and optical remote sensing. Integration in a chip-sized format and direct operation with an electric current requires that such lasers make use of light amplification in semiconductors, such as InP. However, the problem with semiconductor lasers is that they suffer from large optical linewidths, typically a few hundreds of kHz [1], due to the short photon lifetime in the resonator. We address this problem by butt-coupling an InP gain section to a long and low loss Si3N4 feedback circuit. Dual-frequency laser oscillation is achieved by using a Si3N4 circuit with two tunable, frequency-selective feedback mirrors. We present first experimental results, in particular dual-frequency spectra and linewidth measurements.