Semiconductor optical amplifier-based laser system for cold-atom sensors

Abstract

Precise control of atomic systems has led to an array of emerging ‘quantum’ sensor concepts ranging from Rydberg-atom RF-electric probes to cold-atom interferometer gravimeters. Looking forward, the potential impact of these technologies hinges on their capability to be adapted from laboratory-scale experiments to compact and low-power field-deployable instruments. However, existing setups typically require a bulky and power-hungry laser and optics system (LOS) to prepare, control, and interrogate the relevant atomic system using a variety of frequency-referenced and rapidly reconfigurable laser beams. In this work, we investigate the feasibility of using semiconductor optical amplifiers (SOAs) to replace high-power pump lasers and acousto-optic modulators within a simple atom cooling apparatus, looking forward to the ultimate goal of a space-deployable atom interferometer. We find that existing off-the-shelf SOA components operating at relevant wavelengths for Cs and Rb atom cooling (852 and 780 nm, respectively) are able to permit an attractive combination of rapid (sub-microsecond), high extinction ratio (>60-65 dB) switching while acting as power boosters prior to the atom physics package. These attributes enable a radically different, power-efficient approach to LOS design, reducing or eliminating the need for Watt-class laser amplifiers that are unsuitable for flight deployment. Building on these results, we construct a simple and compact all-semiconductor laser/amplifier LOS for atom cooling that is integrated with custom path-to-flight drive electronics. Up to 125 mW of total optical power is delivered to six fiber-coupled channels for magneto-optical-trap-based cooling of a cloud of neutral Cs atoms. The entire LOS, including reference and cooling laser subsystems and control electronics, occupies a volume of 20×20×15 cm and totals DC power consumption of around 13.5 W, and is designed in a modular format so that additional hardware for synthesizing atom interferometry beams may be added through future development efforts. These results indicate the utility of all-semiconductor laser systems for future low-power flyable atom-based sensor instruments.