A 770 nm Narrow Line Width VBG Laser Via Self-Injection Locking to a Fully Packaged High-Q WGM Microresonator

Abstract

Quantum sensors depend on precise manipulation and measurement of the states of microscopic particles, leveraging quantum effects for correlated sensing and detection, achieving sensitivity and accuracy approaching fundamental limits. These advanced capabilities are revolutionizing fields such as biological, physical, and chemical sciences. Among these, the spin-exchange relaxation-free (SERF) atomic comagnetometer emerges as an ultrasensitive inertial measurement device with significant potential for both high precision and compact size. Low-noise light sources are critical components in the pumping and light detection systems, significantly enhancing the accuracy limits of atomic comagnetometers. In this paper, we present a dual-cavity narrow line width laser that integrates a fully packaged high-Q whispering-gallery mode cavity in a volume Bragg grating laser, operating at the SERF comagnetometer pumping wavelength of 770 nm. This laser exhibits over 3 orders of magnitude reduction in frequency noise at 10 Hz–1 MHz compared to the free-running laser and an instantaneous line width about 20 Hz in a nonclean experimental environment, along with a high locking range for weak Rayleigh scattering, thereby improving the accuracy limit of the SERF atomic comagnetometer and facilitating small volume integration.