Dual-Frequency 780-nm Ti:Sa Laser for High Spectral Purity Tunable CW THz Generation

A two-axis, two-polarization, dual-frequency Ti:Sa laser optimized for high spectral purity CW-THz generation is demonstrated. The laser output power is 50 mW. Its mean emission wavelength is optimized ~780 nm in order to suit the maximum efficiency of low temperature grown GaAs photomixers. Despite the extremely wide gain bandwidth of Ti:Sa, a proper intracavity filtering design, adapted to this particular laser architecture, enables tunable and single-frequency operation of each laser mode. The resulting beatnote is shown to be tunable between dc and 1.5 THz by steps of 82 GHz. Its linewidth is narrower than 30 kHz without any active stabilization or cavity insolation.