Amplified femtosecond pulses from an Er:fiber system: Nonlinear pulse shortening and selfreferencing detection of the carrier-envelope phase evolution

We present an improved design of an amplified Er:fiber laser system for the generation of intense femtosecond pulses. By properly controlling the influence of optical nonlinearities inside a stretched pulse amplifier, the spectrum is broadened to over 100 nm. The pulses are recompressed to 65 fs. A linearly polarized output of 110 mW is obtained at 67 MHz repetition rate. As a first application, we report the generation of an octave-spanning supercontinuum inside a short piece of a highly nonlinear fiber. Self-referencing detection of the carrier-envelope phase evolution with an f-to-2f interferometer is demonstrated.