Hybrid-Integrated Comb Source With 16 Wavelengths

Comb sources and multi-wavelength lasers can be used as central sources of light in many communication systems using high channel count wavelength division multiplexing. Here, we demonstrate a 16 wavelengths comb source built through large scale hybrid integration of 16 active gain chips with a passive silica chip that incorporates a 16 channel arrayed waveguide grating. Optical coupling between the 16 gain chips and the silica chip is achieved through 32 ball lenses (two per channel), that are aligned and attached in place with an automated process that we developed. The 16 channels have 100 GHz spacing and are centered in the C-band. We show monomode lasing, both in single-channel and multi-channel operation, with side mode suppression ratio as high as, respectively, 67 dB and 55 dB. The total output power of our comb source is about 17.9 dBm when all the 16 channels are activated simultaneously. The channels of our multi-wavelength laser have very narrow Lorentzian linewidths, with best value as narrow as 880 Hz and worst value of about 3.6 kHz. Our comb source integrates hybridly a large number of optical components, however thanks to the parallel architecture and the possibility of packaging the lenses with an automated process, our integration approach can be scaled to an even higher number of channels.