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

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.