Compact tunable kHz-linewidth semiconductor laser stabilized with a whispering-gallery mode microresonator

We report on the realization of a compact-package (44x27x14mm) narrow linewidth laser based on self-injection locking of a distributed feedback semiconductor diode laser to a high-Q whispering gallery mode resonator fabricated with electro-optic material. The packaged device operates at 1,550 nm and offers instantaneous spectral linewidth performance smaller than 1.8 kHz for 3 mW of output power. We are able to tune the laser frequency by applying voltage to the resonator. This suggest that the technology enables fabrication of ultra narrow linewidth semiconductor lasers in a broad wavelength range of 390 nm to 2,900 nm. The laser source in a compact footprint enables a multitude of sensing, monitoring, and metrology applications where high resolution and precision and absolute accuracy are required.