Abstract: A narrow-band diode pumped alkali laser (DPAL) comprising a diode emitter assembly of broad area diode lasers arranged in a stack or array to emit longitudinally at a power level in a power range of 10-1500 W through a frequency selective element assembly aligned and positioned in an external laser cavity to the diode emitter assembly. The frequency selective element assembly comprising: an optical cell containing alkali vapor positioned between a pair of crossed polarizers; a partially reflective mirror that reflects a portion of light passing through the optical cell back toward the diode emitter assembly; and magnetic field producing components that produce a magnetic field through the optical cell that creates a 90° polarization of light passing through the optical cell at a narrow-band frequency corresponding to the absorption line of alkali atom, attenuating components of the light passing through the optical cell at frequencies outside of the narrow-band frequency.