Mid-infrared supercontinuum generation in suspended core tellurite microstructured optical fibers.

We report the fabrication of a tellurite optical fiber with a suspended core design, formed on a 220-nm-wide filament of glass. The fiber was pumped at two different wavelengths (1500 and 2400 nm) using femtosecond pulses generated from an optical parametric oscillator (OPO) in order to produce mid-infrared supercontinuum (SC). We observed that SC spectra extending to 3 µm were readily generated. To further optimize the design, detailed numerical study was performed, which revealed how the fiber structural characteristics dramatically influence the spectral broadening because of the changes in the dispersion profile and in turn, the interplay of nonlinear effects that give rise to SC generation. We found that an accurate control of the core shape can be employed to contain the generated SC spectra within well-defined spectral regions or to provide a broad extension of the continuum to beyond 4 µm.

Four-wave mixing and octave-spanning supercontinuum generation in a small core hydrogenated amorphous silicon fiber pumped in the mid-infrared.

An octave-spanning supercontinuum is generated in a hydrogenated amorphous silicon core fiber when pumped in the mid-infrared regime. The broadband wavelength conversion which extends from the edge of the telecommunications band into the mid-infrared (1.64-3.37 µm) is generated by four-wave mixing (FWM) and subsequent pulse break-up, facilitated by the high material nonlinear figure of merit and the anomalous dispersion of the relatively small 1.7 µm diameter core fiber. The FWM sidebands and corresponding supercontinuum can be tuned through the pump parameters, and show good agreement with the predicted phase-matching curves for the fiber.

Mid-infrared ZBLAN fiber supercontinuum source using picosecond diode-pumping at 2 µm.

We present the first demonstration of mid-IR supercontinuum generation directly pumped with picosecond pulses from a Thulium fiber-amplified gain-switched laser diode at 2 µm. We achieve more than two octaves of bandwidth from 750 - 4000 nm in step-index ZBLAN fiber with Watt-level average power and spectral flatness of less than 1.5 dB over a 1300 nm range in the mid-IR from 2450 - 3750 nm. The system offers high stability, power-scaling capability to the 10 W regime, and demonstrates an attractive route towards relatively inexpensive, versatile and practical sources of high power broadband mid-IR radiation.

High energy femtosecond fiber chirped pulse amplification system with adaptive phase control.

We demonstrate increased peak power from an Yb fiber CPA system operating with strong self-phase modulation by shaping the spectral-phase of the input pulses. An adaptive control loop used feedback from the output autocorrelation. We investigated pre-compensation of both SPM phase distortion at high energies, and residual dispersion from mismatched stretcher/compressor technologies at low energies. Phase shaping resulted in improved pulse quality. When using a bulk grating stretcher, shaping increased the autocorrelation peak by a factor of 2.9, and with a fiber stretcher, shaping increased the autocorrelation peak by a factor of 3.4. High-quality 800 fs, 65 microJ recompressed pulses were produced. This technique could benefit a wide variety of fiber amplifier systems and is self-optimising for operation at both low and high pulse energies.

Pulse compression at 1.06 microm in dispersion-decreasing holey fibers.

We report compression of low-power femtosecond pulses at 1.06 microm in a dispersion-decreasing holey fiber. Near-adiabatic compression of 130 fs pulses down to 60 fs has been observed. Measured spectra and pulse shapes agree well with numerical simulations. Compression factors of ten are possible in optimized fibers.

Practical low-noise stretched-pulse Yb(3+)-doped fiber laser.

We report on the development of what we consider to be a practical and highly stable stretched-pulse laser based on Yb(3+) -doped silica fiber. The Fabry-Perot cavity uses nonlinear polarization rotation as the mode-locking mechanism, and a semiconductor saturable-absorber mirror to ensure robust self-starting and incorporates a diffraction grating pair to compensate for the normal dispersion of the fiber. Use of a single-mode grating-stabilized telecommunications-qualified pump laser diode ensures reliable, low-noise operation (~0.05% amplitude fluctuations at 10-Hz measurement bandwidth). The laser generates high-quality, 60-pJ pulses of <110-fs duration at a repetition rate of ~54 MHz (3-mW average power).

Synchronously pumped optical parametric oscillator driven by a femtosecond mode-locked fiber laser.

A femtosecond all-fiber laser source incorporating a cw mode-locked Yb-doped silica fiber oscillator and amplifier has been used to synchronously pump an optical parametric oscillator based on periodically poled lithium niobate. The signal output, consisting of 330-fs pulses at a 54-MHz repetition rate and average powers up to 90 mW, was tuned from 1.55 to 1.95microm , with a corresponding idler range of 2.30-3.31microm .