Diode pumped compact single frequency cw ruby laser

Investigations on 405 nm diode-pumped cw ruby lasers operated in less than 3 mm plane-parallel resonators are reported. With 2.5 mm long ruby crystals TEM00 emission with output powers up to 40 mW are achieved. With an uncoated thin etalon of 0.13 mm thickness, single frequency emission on both ruby lines R1 and R2 is possible. With the piezoelectric shifting of one resonator mirror and corresponding tilting of the etalon, single frequency tuning of up to 400 GHz has been achieved. Details of the laser system are presented, and potential applications will be discussed.