Tunable diode-laser-pumped solid state LNA laser for helium spectroscopic experiments

We have designed, built, and tested a compact, integrated, single-mode solid state LNA laser pumped by a semiconductor laser array for exciting the He resonance line at lambda = 1.083 microm. The laser's three major components are mounted on a single aluminum base, and the diode laser and its beam shaping optics are mounted on a separate stage. This compact and stable structure provides good frequency stability and nearly pure TEM(00) transverse mode operation. The laser can be tuned around the metastable He resonance transition in a single longitudinal mode with linewidth congruent with 5 MHz using a solid, 60% coated intracavity 0.25-mm thick etalon. Saturated absorption signals on this transition have been used to measure the stability and tuning range. We have measured the properties for several crystals and calculated the expected performance characteristics to compare with the measured ones.