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 λ = 1.083 μm. The laser’s three majorcomponents are mounted on a single aluminum base, and the diode laser and its beam shaping optics aremounted on a separate stage. This compact and stable structure provides good frequency stability and nearlypure TEM₀₀ transverse mode operation. The laser can be tuned around the metastable He resonancetransition in a single longitudinal mode with linewidth ≅ 5 MHz using a solid, 60% coated intracavity 0.25-mmthick etalon. Saturated absorption signals on this transition have been used to measure the stability andtuning range. We have measured the properties for several crystals and calculated the expected performancecharacteristics to compare with the measured ones.