Narrow-Strip 670 nm Gain-Coupled Distributed Feedback Laser Based on Periodic Anodes Fabricated by I-Line Lithography

A narrow-strip single-longitudinal-mode gain-coupled distributed feedback semiconductor laser with a central wavelength of approximately 670 nm is demonstrated. We fabricate a novel micro-scale regrowth-free gain-coupled grating with an island-like shape without nanoscale gratings by i-line lithography only. The maximum output power from the fiber of the device with butterfly package is 48.1 mW at 100 mA and its slope efficiency is 0.79 W/A. The laser can be continuously tuned from 670.750 to 670.784 nm with a side-mode suppression ratio of over 40 dB, covering the absorptive peak of lithium atoms. Our easily fabricated devices have great potential as light sources in many applications such as lithium atom detectors.