Narrow-linewidth diode laser using a dual-VBG external cavity feedback structure with polarization beam-splitting technology

Abstract

High-power, narrow-linewidth diode lasers with a high side-mode suppression ratio (SMSR) are critical for achieving enhanced pumping efficiency in advanced laser systems. However, conventional volume Bragg grating (VBG)-based external cavity structures are prone to spectral self-excitation, which degrades spectral purity, reduces pump efficiency, and compromises overall system performance. This study aims to improve spectral purity and an SMSR by developing an external cavity feedback structure that integrates dual VBGs with polarization beam-splitting technology. The approach combines beam shaping with external cavity feedback from two VBGs. Experimental implementation produced a narrow-linewidth diode laser with a central wavelength of 780.112 nm, a spectral linewidth of 0.0767 nm, an SMSR exceeding 35 dB, and an output power of 8.56 W, corresponding to an electro-optical conversion efficiency of 46.27%. Results confirm that the proposed dual-VBG external cavity feedback structure simultaneously narrows the linewidth, enhances spectral purity, and improves the SMSR in high-power diode lasers. These improvements make the structure highly suitable for efficient gain media pumping in applications such as disk lasers, high-energy gas lasers, and fiber laser systems.