Chenji Gu

Microstructure fiber optical parametric oscillator with femtosecond output in the 1200 to 1350 nm wavelength range

We describe an ultrafast fiber optical parametric oscillator operating in the 1210 nm to 1340 nm wavelength range. The system consists of a microstructure fiber placed in a Fabry-Perot cavity which is optically pumped with 1030-nm light from an Ytterbium mode-locked fiber laser. The output wavelength is tunable over a 130-nm span by adjusting the position of one cavity mirror. SHG FROG measurements reveal that the output pulse quality varies as a function of pump power and wavelength. Ultrafast sources operating in this range are particularly instrumental for deep-tissue nonlinear biophotonics applications.

Fiber optical parametric oscillator for sub-50 fs pulse generation: optimization of fiber length

We demonstrate generation of 48fs pulses with linear chirp using a short (27mm) fiber optical parametric oscillator (FOPO), which is synchronously pumped by a mode-locked ytterbium-doped fiber laser. We also study the pulse quality for both the short- and long-wavelength operation where the fiber length inside of the oscillator varies from 17 to 61mm. The optimal pulse duration is observed only in the short-wavelength operation. Furthermore, we model the FOPO system as a single-pass parametric amplifier including dispersive pulse broadening and walk-off between the pump and output. The optimal condition arises from the minimization of the walk-off and dispersion. When walk-off is large, the parametric amplification process is most efficient over some reduced effective fiber length, leading to an upper limit in the amount of the observed pulse broadening.

Cross-phase-modulation-induced spectral effects in high-efficiency picosecond fiber optical parametric oscillators

We explore the spectral effects due to cross-phase modulation and walk-off in picosecond fiber optical parametric oscillators. The output spectrum exhibits pump-power-dependent broadening, which can be quite asymmetric associated with a redshift or a blueshift depending on pump synchronization. By slightly increasing the cavity length, one obtains a blueshifted spectrum and a conversion efficiency as high as 15%.

Full characterization of femtosecond pulses at 1225–1350 nm produced by a high power fiber optical parametric oscillator

We describe a fiber optical parametric oscillator operating at 1225 to 1350 nm in wavelength with 100 mW of average power. Characterization using SHG-FROG reveals linearly-chirped compressible pulses with duration of 250 fs.

Parabolic pulse generation in gain-guided optical fibers with nonlinearity

We explore the combined effects of nonlinearity and gain-guidance on the propagation and amplification of high power parabolic pulses within fibers. By choosing a suitable gain coefficient, group-velocity dispersion profile, and fiber size one can increase output power and reduce the time-bandwidth product of pulses.

Frequency-time identical and reversal in ultrafast optical parametric processes

We demonstrate identical and reversal relations between temporal pulse shapes and their spectrum envelopes through ultrashort optical parametric processes in the picosecond and femtosecond regimes.

Spectral mirror imaging in ultrafast optical parametric processes

We experimentally demonstrate and theoretically explore a spectral imaging system where two spectral sidebands produced through an optical parametric process always have reversed spectral profiles with respect to the center frequency of the pump.