High Power 780 nm Broad-Area DFB Laser With Narrow Spectral Width

The 7xx nm laser diode is the core pump source for Diode Pumped Alkali Vapor Laser (DPAL). For these applications, high power and narrow spectral width are essential. Traditional Fabry-Pérot (FP) diode lasers can provide high continuous output power, but their spectral width is too broad for many applications. By burying a Bragg grating within the semiconductor, a narrow and temperature-stable spectrum can be achieved. In this paper, we investigate the factors limiting the power enhancement of distributed feedback (DFB) lasers and characterize the grown gratings using transmission electron microscopy. We discuss the effects of grating coupling strength, wavelength detuning, and oxygen contamination in the grating region on performance. Under optimized growth conditions, a high-performance 780 nm DFB laser based on InGaAsP/InGaP gratings has been developed, achieving a continuous output power exceeding 10 W, which is the highest power for a 780 nm DFB laser to date. The spectral linewidth (FWHM) is less than 0.5 nm, and the device maintains locking across the entire operating current and a wide temperature range.