Narrow Linewidth Distributed Feedback Diode Lasers for Cooling in Cold Atom Systems

Abstract

Distributed feedback (DFB) lasers have been realized emitting at a wavelength of 780.24 nm which demonstrate powers in excess of 60 mW with 612 kHz linewidth for use in rubidium ( 87 Rb) cold atom systems.

Single-mode Distributed Feedback Lasers for 87Rb Two-Photon Quantum Technology Systems

“…The DFB lasers were fabricated on an aluminium-free active area [5,6] four-quantum-well GaAs/AlGaAs wafer material, with an epilayer structure that was designed for narrow-linewidth applications. The epilayer material was optimized over previous designs at 780.24 nm [5,6] to reduce modal propagation losses and far-field emission pattern to decrease the beam divergence in the epilayer direction to 20º, potentially improving the single-mode fibre coupling up to a simulated value of 80%. A third-order Bragg grating was patterned on a 500 nm thick hydrogen silsesquioxane (HSQ) resist mask by electron beam lithography (EBL).…”

“…High accuracy optical clocks require lasers with sufficiently narrow linewidth, in this case significantly less than the 87 Rb 2-photon transition of 300 kHz [1]. Such diode lasers can also be integrated with Si3N4 photonic platforms [2,3] whilst maintaining single mode and narrow linewidth operation [4][5][6] with the potential for future chip-scale quantum technology systems. In this paper we present 3 mm long cavity DFB lasers with over 48 mW power output, side-mode suppression ratios (SMSRs) approaching 40 dB, and linewidths of 3.67 kHz that demonstrated suitable for 87 Rb two-photon transitions at 778.1 nm in free-running conditions.…”