Spectral phase measurements for broad Raman sidebands by using spectral interferometry

Generation of a phase-locked Raman frequency comb in gas-filled hollow-core photonic crystal fiber

In a relatively simple setup consisting of a microchip laser as pump source and two hydrogen-filled hollow-core photonic crystal fibers, a broad, phase-locked, purely rotational frequency comb is generated. This is achieved by producing a clean first Stokes seed pulse in a narrowband guiding photonic bandgap fiber via stimulated Raman scattering and then driving the same Raman transition resonantly with a pump and Stokes fields in a second broadband guiding kagomé-style fiber. Using a spectral interferometric technique based on sum frequency generation, we show that the comb components are phase locked.

Femtosecond ultrashort pulse generation by addition of positive material dispersion

We demonstrate femtosecond ultrashort pulse generation by adding further positive group velocity dispersion (GVD) to compensate for the presence of positive GVD. The idea is based on the integer temporal Talbot phenomenon. The broad Raman sidebands with a frequency spacing of 10.6 THz are compressed to form a train of Fourier-transform-limited pulses by passing the sidebands through a device made of dispersive material of variable thickness.

Line-by-line control of 10-THz-frequency-spacing Raman sidebands

We report line-by-line control of a coherent discrete spectrum (Raman sidebands) with a frequency spacing of 10.6 THz that is produced by an adiabatic Raman process. We show that the spectral phase of the Raman sidebands is finely controlled to the target (flat relative-spectral-phase). This is achieved by employing a combination of a spatial phase controller and a spectral interferometer, which are specifically designed for a high-power discrete spectrum. We also show that such spectral-phase control produces a train of Fourier transform limited pulses with an ultrahigh repetition rate of 10.6 THz in the time domain.