Optical noise reduction in a femtosecond Ti:sapphire laser pumped by a passively stabilized argon ion laser

Ionic gas lasers are widely used as optical pumps for a broad variety of solid-state and dye lasers. In such applications, the power fluctuations of the ionic gas lasers are contributing to the noise of the pumped lasers. In this paper, we report on the observation that a significant noise reduction can be achieved in a Ti:sapphire laser when it is pumped by a multiline argon ion laser stabilized with a passive external cavity. Under optimal conditions, the average optical noise of the argon ion laser beam was reduced by 20 dB over a spectral band ranging from 100 to 800 kHz. A similar noise reduction was observed in a Ti:sapphire laser when its pumping argon ion laser was stabilized with an external cavity; noise reduction occurred both in the continuous-wave regime and in the femtosecond regime. Our results are consistent with a model considering the response of the laser to pump fluctuations. We also compared the noise level of the Ti:sapphire laser when it was pumped by the stabilized argon ion laser to its noise level when it was pumped by an all-solid-state laser; our results indicate that, for frequencies above 125 kHz, the noise of the Ti:sapphire laser was significantly lower when the stabilized argon ion laser was used.