Phase-locking and pulse generation in multi-frequency brillouin oscillator via four wave mixing.

There is an increasing demand for pulsed all-fibre lasers with gigahertz repetition rates for applications in telecommunications and metrology. The repetition rate of conventional passively mode-locked fibre lasers is fundamentally linked to the laser cavity length and is therefore typically ~10-100 MHz, which is orders of magnitude lower than required. Cascading stimulated Brillouin scattering (SBS) in nonlinear resonators, however, enables the formation of Brillouin frequency combs (BFCs) with GHz line spacing, which is determined by the acoustic properties of the medium and is independent of the resonator length. Phase-locking of such combs therefore holds a promise to achieve gigahertz repetition rate lasers. The interplay of SBS and Kerr-nonlinear four-wave mixing (FWM) in nonlinear resonators has been previously investigated, yet the phase relationship of the waves has not been considered. Here, we present for the first time experimental and numerical results that demonstrate phase-locking of BFCs generated in a nonlinear waveguide cavity. Using real-time measurements we demonstrate stable 40 ps pulse trains with 8 GHz repetition rate based on a chalcogenide fibre cavity, without the aid of any additional phase-locking element. Detailed numerical modelling, which is in agreement with the experimental results, highlight the essential role of FWM in phase-locking of the BFC.

Low Raman-noise correlated photon-pair generation in a dispersion-engineered chalcogenide As2S3 planar waveguide.

We demonstrate low Raman-noise correlated photon-pair generation in a dispersion-engineered 10 mm As2S3 chalcogenide waveguide at room temperature. We show a coincidence-to-accidental ratio (CAR) of 16.8, a 250 times increase compared with previously published results in a chalcogenide waveguide, with a corresponding brightness of 3×10(5) pairs·s(-1)·nm(-1) generated at the chip. Dispersion engineering of our waveguide enables photon passbands to be placed in the low spontaneous Raman scattering (SpRS) window at 7.4 THz detuning from the pump. This Letter shows the potential for As2S3 chalcogenide to be used for nonlinear quantum photonic devices.

Highly-efficient, octave spanning soliton self-frequency shift using a specialized photonic crystal fiber with low OH loss.

We report the first demonstration of efficient, octave spanning soliton self-frequency shift. In order to achieve this we used a photonic crystal fiber with reduced OH absorption and widely spaced zero-dispersion wavelengths. To our knowledge, this is the largest reported frequency span for a tunable, fiber-based source. In addition, we observe the generation of light above 2 µm directly from a Ti:Sapphire laser in the form of Cerenkov emission by the soliton when the red-shift saturates at the edge of the anomalous dispersion region.

Octave spanning supercontinuum in an As2S3 taper using ultralow pump pulse energy.

An octave spanning spectrum is generated in an As2S3 taper via 77 pJ pulses from an ultrafast fiber laser. Using a previously developed tapering method, we construct a 1.3 µm taper that has a zero-dispersion wavelength around 1.4 µm. The low two-photon absorption of sulfide-based chalcogenide fiber allows for higher input powers than previous efforts in selenium-based chalcogenide tapered fibers. This higher power handling capability combined with input pulse chirp compensation allows an octave spanning spectrum to be generated directly from the taper using the unamplified laser output.

Soliton self-frequency shift performance in As(2)S(3) waveguides.

The soliton self-frequency shift in As(2)S(3) is investigated theoretically. Differences in the shapes of the Raman spectra in silica and As(2)S(3) are predicted to lead to variations of less than 25% in the frequency shift rate of a fundamental soliton. Detailed simulation of the propagation of a low peak power pulse in a chalcogenide ridge waveguide shows the concepts of Raman soliton behaviour in silica to be transferrable to As(2)S(3). Thus we predict the effectiveness of the soliton self-frequency shift in contributing to wide bandwidth generation in low-power supercontinua at mid-infrared wavelengths in this highly nonlinear chalcogenide, as well as other nonlinear processing applications such as digital quantization for optical analogue to digital conversion.