Narrow-linewidth 780 nm DFB lasers fabricated using nanoimprint lithography

The paper presents narrow-linewidth 780 nm edgeemitting semiconductor DFB lasers fabricated without regrowth using UV-nanoimprinted surface gratings. The thirdorder laterally-coupled ridge-waveguide surface gratings enable single mode operation, excellent spectral purity (40-55 dB side mode suppression ratio and 10 kHz linewidth) and good lightcurrent- voltage characteristics in continuous wave operation (~112 mA threshold current, ~1.55 V opening voltage and 28.9 mW output power from one facet at 300 mA current for 2.4 mm long devices), which are vital in various applications, such as rubidium spectroscopy and atomic clock pumping. The low fabrication costs, high throughput, structural flexibility and high device yield make the fabrication method fully compatible with large scale mass production, enabling the fabrication of low-cost miniaturized modules.