Carrier-envelope phase stability of a polarization-encoded chirped pulse Ti: Sapphire amplifier

The scheme of polarization-encoded chirped pulse amplification (PE-CPA) reduces the gain narrowing effect in Ti:Sapphire (Ti:Sa) amplifiers by utilizing both crystal axes of Ti:Sa. Hence, the carrier-envelope phase (CEP) of a PE-CPA pulse originates from two othogonal polarization directions. The CEP stability of PE-CPA pulses was investigated for various amplification conditions by varying the pump pulse energy. The CEP stability is directly compared to the conventional CPA scheme under the same laser parameters. A quasi-common-path interferometer was realized inside a four-pass amplifier stage, ensuring exceptional geometrical path length stability and high spectral phase sensitivity. The spectral phase noise of PE-CPA pulses showed a minor increase of 4 mrad compared to the conventional scheme, while at unsaturated amplification of a net gain of 13, it revealed a CEP stability better than 63 mrad.