Rare-earth-ion-doped lasers integrated on a silicon chip

Future integrated photonic circuits will utilize hybrid integration of optical materials with different functionalities, among them optical gain. We have developed two rare-earth-ion-activated materials which can be directly deposited on any passive material platform, among others on silicon wafers. In a Nd-complex-doped fluorinated polymer, we demonstrated the first-ever continuous-wave solid polymer laser, operating at 1062 nm and 878 nm. In amorphous Al2O3, we demonstrated an Er-doped, widely wavelength-selective microring laser that operates across the telecom C-band. Employing Bragg gratings lithographically inscribed into channel waveguides, we obtained cavities with a Q-factor of >10e6. With such grating reflectors, we achieved a free-running 1542-nm distributed-feedback laser with an ultra-narrow linewidth of 1.7 kHz, equaling a coherence length of 55 km and a Q-factor of 1.14x10e11. With a distributed-Bragg-grating cavity, we obtained an Yb-doped laser at 1021 nm with 47 mW output power and 67% slope efficiency, which may enable linewidths below 100 Hz.