Wavelength Stabilized High-Power Diode Lasers for Alkali Atom Pumping

This Phase II SBIR proposal is submitted to address the need for high-power narrow spectral linewidth diode laser pump sources in alkali vapor lasers. Diode-pumped alkali vapor lasers (DPALs) can be most efficiently pumped with spectrally-stabilized laser diode arrays (LDAs) with very narrow linewidths (a few GHz). This allows DPAL operation at lower pressure and increased efficiency due to optimized absorption of the pump energy. With an efficient pump source, DPALs have the potential for scaling to kilowatt (KW) or megawatt (MW) power levels for industrial and military applications. A major hurdle to achieving this has been the availability of high-power narrow spectral linewidth laser diode sources. In Phase I, Photodigm demonstrated a new method for diode laser stabilization based on emergent Guided-Mode Resonant Filter (GMRF) mirror technology. These mirrors possess both wavelength and angular selectivity with narrowband spectral linewidths approaching 1 GHz. GMRF mirrors are presented as an enabling technology to realize scalable narrow-linewidth wavelength-stabilized laser diode pump sources for DPAL applications. These GMR-stabilized laser array modules are expected to operate at output power levels of approximately 100 Watts per bar. The proposed high-power pump sources have key industrial and medical applications including laser machining and spin-exchange optical pumping.