Optical noise reduction in a femtosecond Ti:sapphire laser

Abstract

It has been observed that the optical noise of a Ti:sapphire laser is related to the optical noise of the laser used for its optical pumping. Argon ion lasers are largely used as optical pump for solid-state lasers, such as Ti:sapphire lasers. The intensity noise of Argon laser is transferred to the beam (or pulses) emitted by the pumped laser. In this paper, we report on the optical noise reduction of a Ti:sapphire laser, operated in continuous-wave (cw) and mode-locked regimes. This effect is achieved through the optical noise reduction of the pump laser by coupling it to a passive external cavity ended by a dielectric mirror. In the mode-locked regime, the noise reduction of the low-frequency noise components, as averaged over the interval from 100 kHz to 800 kHz, is larger than 20 dB and the maximum noise reduction is larger than 34 dB. We have also compared the noise level of the Ti:sapphire laser to the noise measured when it is pumped by a solid-state laser (diode-pumped, intracavity frequency-doubled, Nd:Vanadate laser).