Spectral stabilization of high efficiency diodes and diode bars by external Bragg resonator

Adjustable spectral and angular selectivity combined with low optical losses and high laser damage thresholds of volume Bragg gratings, which are recorded in photo-thermo-refractive (PTR) glass, enabled the use of those elements as high efficient selective feedback elements for spectral narrowing and stabilization. High efficiency diodes and diode bars developed by AlfaLight and nLight companies for DARPA/SHEDS program were studied in volume Bragg lasers with PTR holographic gratings used as output coupling elements. Reflection coefficients from the front facets of the bars were varied from 0.5 to 5%. Reflection coefficients of PTR Bragg gratings were varied from 3 to 50%. It was found that for any applicable pumping level the optimal parameters of the grating could be found which provide spectral narrowing and stabilization within 0.5 nm for temperature variations within ±10 K. Total power of the locked bar exceeded 97% of that for the unlocked bar.