High-quality 3.6-fs pulses by compression of an octave-spanning supercontinuum

Few-cycle pulses offer a wide range of interesting applications, for example in time-resolved studies of ultra-fast phenomena in physics, chemistry and biology. Nonlinear spectral broadening in photonic crystal fibers (PCFs) followed by dispersive compression allows for the generation of extremely short optical pulses. By employing this technique pulse durations of only 5.5 fs (2.4 optical cycles) have been achieved so far. In this contribution we take advantage of SC generation in all-normal dispersion PCF (ANDi PCF), which features only positive group-velocity dispersion across the spectral region of interest. Spectral broadening therefore is dominated by self-phase modulation and optical wave breaking, leading to smooth and highly coherent SC spectra. We show generation of SC spectra covering more than one optical octave around 810 nm central wavelength. Active phase control and spectral shaping were employed to compress the pulses to 3.64 fs (1.3 optical cycles), which is the shortest pulse duration achieved from SC compression in solid core fibers to date. In contrast to other approaches, the presented concept delivers pulses with an excellent temporal pulse quality and can be extended to even larger bandwidths to reach the sub-cycle regime, provided an adequate compressor is employed.