High-Power Narrow Linewidth Distributed Feedback Lasers With an Aluminium-Free Active Region Emitting at 852 nm

Abstract

In this letter, we demonstrate the design, fabrication, and characterization of single-mode distributed feedback (DFB) lasers emitting at 852 nm for atomic clocks and spatial applications. The epitaxial structure comprises an aluminium-free active region with the DFB fabrication technology based on an epitaxial regrowth concept. Initial results carried out on uncoated broad-area devices showed low internal losses (<3 cm-1), a high internal efficiency (95%), and for antireflection/high-reflectivity coated broad-area lasers, an output optical power of 5.5 W was measured at 8.5 A. Ridge waveguide structures were then fabricated with a ridge width of 4 mum showing typical single spatial mode emission with the M2 factor <1.5. Based on these preliminary results, DFB ridge waveguides were then processed and characterized. Single-mode emission was achieved at 852.12 nm corresponding to the D2 cesium transition, with an optical output power of 40 mW at 140 mA. Linewidth measurement was also carried out on these devices with a linewidth of 0.9 MHz measured at 70 mA.