Wavelength-locking by a volume holographic grating (VHG) is reported for a diode laser bar with 49 single mode emitters, fitted with a dual-axis collimation phase-plate for smile elimination and excellent beam pointing correction. The much-improved VHG feedback with the ultra-collimated array beam gives 100% wavelength locking at 975 nm over a 17°C temperature range and external cavity lengths up to 110 mm. This enables a folded cavity configuration to provide a fully-locked array with wavelength selection into 200 pm channels over an 8 nm band, suitable for multi-bar dense wavelength-combining.
Trela, N., Baker, H. J., & Hall, D. (2013). Locking and wavelength selection of an ultra-collimated single-mode diode laser bar by a volume holographic grating. Optics Express, 21(4), 4512–4517. https://doi.org/10.1364/OE.21.004512