A diode-pumped Nd:Lanthanum Magnesium Hexaluminate laser was constructed which provides up to 15 mW of single-mode, tunable CW emission at 1083 nm. By appropriately polarizing the narrow-band laser emission (< 10 MHz), the laser can be used to determine the populations of the magnetic substates of the He ( 23S1) atoms. The laser is tuned to one of the absorption peaks of the helium metastable atom by tilting a thin (1 mm) solid, coated etalon placed inside the laser cavity and the absorption is measured. The relative absorption is used to determine the ensemble polarization ; the absolute absorption yields the metastable density.