Generation of sub-4-fs pulses via compression of a white-light continuum using only chirped mirrors

Using noble gases as a nonlinear medium, it has become possible to compress energetic laser pulses into the sub-10-fs regime. Hollow fiber capillaries can serve to increase the effective interaction length of the pulses, and impressive white-light continua have been reported as a result. With demonstrated bandwidths exceeding the optical octave, this method holds the potential for generating single-cycle optical pulses. On the practical side, however, it becomes very difficult to compensate for dispersive effects and to fully exploit the enormous bandwidth. We will discuss chirped mirrors as one means for pulse compression. A further challenge lies on the characterization side. Utilizing advanced characterization schemes, we were able to demonstrate compression of a white-light continuum down to a pulse duration of 3.8 fs, which corresponds to only about 1.6 cycles at the carrier wavelength. These are the shortest pulses in the visible/near-infrared wavelength range that have ever been produced with a non-adaptive approach to dispersion compensation. Moreover, these are the shortest pulses generated using chirped mirrors, which compares favorably to previous results that were achieved with much more elaborate and lossier adaptive compression schemes.