GaN-DFB lasers covering the 400–520nm spectrum

Distributed feedback (DFB) laser diodes based on gallium nitride (GaN) enable narrow-linewidth, single-frequency emission across the 400–520 nm range, offering compact, efficient sources for applications in communications, sensing, and quantum technologies. These devices employ monolithic gratings integrated into single-transverse-mode ridge-waveguide structures, achieving side-mode suppression ratios (SMSR) >40 dB and stable operation over a wide current range. They exhibit low threshold currents, high differential efficiencies (>1 W/A at 450 nm), and wall-plug efficiencies comparable to Fabry–Perot lasers. Wavelength tuning is continuous and mode-hop free, with sensitivities of ~15 pm/K and 4 pm/mA. The intrinsic linewidths are typically below 1 MHz, as measured by delayed self-heterodyne techniques. The monolithic grating design ensures high spectral stability (