Narrow-Linewidth 780-nm DFB Lasers Fabricated Using Nanoimprint Lithography

This letter presents narrow-linewidth 780-nm edge-emitting semiconductor DFB lasers fabricated without re-growth using UV-nanoimprinted surface gratings. The third-order 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 light-current-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 cost, 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.