SANTA CLARA, Calif., Feb. 24, 2010 – Coherent Inc. has launched the Legend Elite CEP (carrier envelope phase)-stabilized Ti:sapphire amplifier. The system amplifies the ultrafast pulses generated by the proprietary Micra CEP oscillator up to the millijoule level of energy required for applications such as high harmonics generation, attosecond physics, coherent x-ray generation and other experiments relying on highly nonlinear optical processes. It delivers a pulse duration of <35 fs with a repetition rate of 1 kHz, and it has up to 4 W of average power and 4 mJ per pulse. The final carrier envelope offset stability depends upon the operating environment, with typical laboratory performance of better than 200 mrad. CEP stabilization refers to fixing the temporal relationship between the overall ultrafast pulse envelope and the underlying electric field oscillations. In the amplifier, the offset is detected by the nonlinear f-2f interferometer method, and this feedback signal is used to actively control the dispersion of the amplifier cavity by changing the relative angle of the dispersion compensation gratings. The system has the low-noise components and a low-noise operating environment required for successful CEP stabilization. The regenerative amplifier includes an active feedback control to lock the phase velocity of the oscillating light field to the group velocity of the phase envelope. For ultrashort pulses consisting of only a few optical cycles, the peak of the oscillating electrical field can be maximized under the phase envelope. At the heart of the system is a nonlinear interferometer. An octave-spanning optical spectrum is generated by focusing a small part of the amplifier beam on a sapphire plate. The red end of this spectrum is frequency-doubled and co-linearly combined with the blue end of the same broad spectrum. The resulting spectral interference fringes are measured by a spectrometer, and custom software uses this signal to measure, stabilize and control the CEP by making adjustments in the amplifier.