Spectrally Narrowed Pump Diode Arrays for Diode Pumped Alkali Lasers

Diode-pumped Alkali Lasers (DPAL) have recently gained attention as highly-efficient lasers due to the very small energy differences between the pump and lasing levels (2% for Rb and 5% for Cs). Pump arrays with narrow spectral outputs with linewidths below 0.2 nm and which can be accurately tuned to Rb or Cs absorption lines are required, but conventional arrays have spectral widths as wide as 10 nm. Linewidth narrowing methods using Volume Bragg Gratings provide limited tunability, limited spectral locking, poor manufacturability and high cost but, maybe most importantly, do not provide a realistic path towards power levels and volumes required for tactical operations of HEL. We propose to develop very narrow linewidth, temperature tunable 780 nm pump arrays using novel on-chip wavelength stabilized high brightness diode arrays. This design provides very narrow linewidth, high power output and ease of temperature tunability in a monolithic, easily manufactured low cost diode array that is scalable to hundreds of kW level.