Few-cycle pulse generation in a dispersion-shifted silica fiber with erbium-doped laser system

We report a simple all-fiber erbium-doped laser system that is capable of generating 11-fs pulses at a wavelength of 1.7 micron. The setup consists of standard telecommunication components and does not contain photoni crystal fibers commonly used for few-cycle pulse production in the near infrared. We start with a compact polarization mode-locked femtosecond Er:fiber master oscillator delivering pulses centered at 1.57 μm at 49 MHz repetition rate. The pulses are amplified in a forward and backward diode-pumped Er:fiber amplifier to 110 mW and pre-compressed in a single-mode fiber (SMF28) to the 50-fs duration. Next, a short segment (4.5 cm) of highly nonlinear dispersion-shifted fiber (HNL-DSF) is spliced directly to SMF28. The 50-fs pulses are launched into HNL-DSF in the anomalous dispersion regime and experience higher-order soliton pulse compression down to few-cycle duration. To reconstruct the pulse intensity profile we used second-harmonic-generation frequency-resolved-optical-gating (SHS FROG). Reconstructed intensity is shown in Fig 1a, which corresponds to 11-fs pulse duration at FWHM. Taking into account its central wavelength of 1.7 μm it corresponds to two-cycle optical pulse. The optical spectrum, FROG trace, and dispersion profile are shown in Fig. 1b,c,d, correspondingly.