High-Power Narrow-Linewidth Tunable Blue Laser Diode Array Utilizing a Blazed Grating External Cavity

High-power, narrow-linewidth blue laser sources have been in high demand for applications in laser pumping and spectral beam combining. In this paper, a blue laser source, consisting of 12 transistor-outline (TO) packaged laser diodes (LD), is established through space beam combining. An improved external cavity (EC) utilizing a blazed grating (BG), a beam splitter, and a beam expander is investigated. Through injection feedback and mode competition, a laser output, with 31.2 W power, 445.04 nm central wavelength, 0.18 nm full-width at half maximum (FWHM) linewidth, is achieved at a driving current of 3.0 A. A tunable range of 3.6 nm is observed at 2.0 A driving current. Additionally, the effect of the deformation of the aluminum-coated grating under a high-intensity blue laser is examined. The external cavity requires a moderately efficient blazed grating and prevents potential damage caused by high absorption and thermal stress concentration. The system exhibits excellent temporal stability in both output power and spectrum. Moreover, wavelength-locking experiments using both a volume Bragg grating (VBG) and a surface grating (SG) are conducted to serve as comparative tests for this study. Compared with volume Bragg gratings, blazed gratings offer spectral tunability and are insensitive to temperature perturbations and mechanical stress. Compared with surface gratings, blazed gratings offer a relatively high threshold and stable performance at high driving currents. Furthermore, blazed gratings are more cost-effective than VBGs, providing a competitive advantage. To the best of our knowledge, it’s the first blue laser source with over 30 W output and 0.18 nm FWHM linewidth utilizing a blazed grating external cavity.