Seeded optical parametric generation in CdSiP2 pumped by a Raman fiber amplifier at 1.24 µm.

We report a seeded optical parametric generator (OPG) producing tunable radiation from 4.2-4.6 µm. The seeded OPG employs a 13 mm long CdSiP2 (CSP) crystal cut for non-critical phase-matching, pumped by a nanosecond-pulsed, MHz repetition rate Raman fiber amplifier system at 1.24 µm. A filtered, continuous-wave fiber supercontinuum source at 1.72 µm is used as the seed. The source generates up to 0.25 W of mid-infrared (MIR) idler power with a total pump conversion of 42% (combined signal and idler).

Nanosecond pulsed 620 nm source by frequency-doubling a phosphosilicate Raman fiber amplifier.

We demonstrate a nanosecond pulsed source at 620 nm with watt-level average power by frequency-doubling a 1240 nm phosphosilicate Raman fiber amplifier. A gain-switched laser diode operating at 1064 nm is amplified in an ytterbium fiber master oscillator power amplifier system and then converted to 1240 nm using a phosphosilicate Raman fiber amplifier with a conversion efficiency of up to 66%. The Raman fiber amplifier is seeded with a continuous-wave 1240 nm laser diode to obtain narrow-linewidth radiation, which is subsequently frequency-doubled in a periodically poled lithium tantalate crystal. A maximum average power of 1.5 W is generated at 620 nm, corresponding to a pulse energy of 300 nJ at a repetition rate of 5 MHz. The source has excellent beam quality (M2≤1.16) and an optical efficiency (1064 nm to 620 nm) of 20%, demonstrating an effective architecture for generating red pulsed light for biomedical imaging applications.

Highly efficient nanosecond 560 nm source by SHG of a combined Yb-Raman fiber amplifier.

We demonstrate a nanosecond 560 nm pulse source based on frequency-doubling the output of a combined Yb-Raman fiber amplifier, achieving a pulse energy of 2.0 µJ with a conversion efficiency of 32% from the 976 nm pump light. By introducing a continuous-wave 1120 nm signal before the cladding pumped amplifier of a pulsed Yb:fiber master oscillator power amplifier system operating at 1064 nm, efficient conversion to 1120 nm occurs within the fiber amplifier due to stimulated Raman scattering. The output of the combined Yb-Raman amplifier is frequency-doubled to 560 nm using a periodically poled lithium tantalate crystal with a conversion efficiency of 47%, resulting in an average power of 3.0 W at a repetition rate of 1.5 MHz. The 560 nm pulse duration of 1.7 ns and the near diffraction-limited beam quality (M2≤1.18) make this source ideally suited to biomedical imaging applications such as optical-resolution photoacoustic microscopy and stimulated emission depletion microscopy.

High average power parametric wavelength conversion at 3.31-3.48 m in MgO:PPLN.

We present results of high average power mid-infrared (mid-IR) generation employing synchronized nanosecond pulsed ytterbium and erbium fiber amplifier systems using periodically poled lithium niobate. We generate greater than 6 W of mid-IR radiation tunable in wavelength between 3.31-3.48 µm, at power conversion efficiencies exceeding 75%, with near diffraction limited beam quality (M2 = 1.4). Numerical modeling is used to verify the experimental results in differing pump depletion regimes.

Highly efficient mid-infrared difference-frequency generation using synchronously pulsed fiber lasers.

We report the development of a high average power, picosecond-pulse, mid-infrared source based on difference-frequency generation (DFG) of two synchronous master oscillator power fiber amplifier systems. The generated idler can be tuned over the range 3.28-3.45 µm delivering greater than 3.4 W of average power, with a maximum pump to total DFG power conversion efficiency of 78%. The benefits of a synchronously pumped scheme, compared to CW seeding of DFG sources, are discussed.

Fiber-integrated frequency-doubling of a picosecond Raman laser to 560 nm.

We report the development of a fiber-integrated picosecond source at 560 nm by second harmonic generation of a Raman fiber laser. A picosecond ytterbium master oscillator power fiber amplifier is used to pulse-pump a Raman amplifier, which is seeded by a continuous wave distributed feedback laser diode operating at 1120 nm. The pulse train generated at 1120 nm is frequency-doubled in a fiber-coupled periodically-poled lithium niobate crystal module, producing 450 mW of average power at 560 nm with a pulse duration of 150 ps at a repetition rate of 47.5 MHz. The near diffraction-limited (M(2) = 1.02) collimated output beam is ideal for super-resolution microscopy applications.

Duration-tunable picosecond source at 560 nm with watt-level average power.

A pulse source at 560 nm that is tunable in duration between 50 ps and 2.7 ns with >1 W of average power and near diffraction-limited beam quality is demonstrated. The source is based on efficient (up to 50%) second-harmonic generation in a periodically poled lithium tantalate crystal of a linearly polarized fiber-integrated Raman amplifier operating at 1120 nm. A duration-tunable ytterbium master-oscillator power-fiber amplifier is used to pulse-pump the Raman amplifier, which is seeded by a continuous-wave distributed-feedback laser diode at 1120 nm. The performance of the system using two different master oscillator schemes is compared. A pulse energy of up to 765 nJ is achieved with a conversion efficiency of 25% from the ytterbium fiber pump, demonstrating a compact and turn-key architecture for obtaining high peak-power radiation at 560 nm.

Fiber-integrated 780 nm source for visible parametric generation.

We report the development of a fully fiber-integrated pulsed master oscillator power fibre amplifier (MOPFA) source at 780 nm, producing 3.5 W of average power with 410 ps pulses at a repetition rate of 50 MHz. The source consists of an intensity modulated 1560 nm laser diode amplified in an erbium fiber amplifier chain, followed by a fiber coupled periodically poled lithium niobate crystal module for frequency doubling. The source is then used for generating visible light through four-wave mixing in a length of highly nonlinear photonic crystal fiber: 105 mW at 668 nm and 95 mW at 662 nm are obtained, with pump to anti-Stokes conversion slope efficiencies exceeding 6% in both cases.

Simultaneous scalar and cross-phase modulation instabilities in highly birefringent photonic crystal fiber.

We report the experimental observation of scalar and cross-phase modulation instabilities by pumping a highly birefringent photonic crystal fiber in the normal dispersion regime at 45° to its principal polarization axes. Five sideband pairs (two scalar and three vector ones) are observed simultaneously in the spontaneous regime, four of which have a large frequency shift from the pump, in the range 79-93 THz. These results are in excellent agreement with phase-matching arguments and numerical simulations.

Synchronously pumped photonic crystal fiber-based optical parametric oscillator.

We report the development of a compact, tunable synchronously pumped photonic crystal fiber (PCF)-based optical parametric oscillator (FOPO). The oscillator is pumped using a gain-switched laser diode producing 220 ps pulses around 1062 nm, amplified in a ytterbium doped amplifier to peak powers of 3.5 kW. The FOPO produces anti-Stokes pulses at wavelengths between 757 and 773 nm, with durations of 150 ps at average output powers exceeding 290 mW. The output slope efficiency of the device varies with output wavelength from 1.9 to 6.0%.

Stability of chlorpyrifos for termiticidal control in six Australian soils.

Chlorpyrifos [O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate] is the most widely used soil-applied termiticide in Australia. It is relatively stable, has low water solubility, is absorbed by organic matter, and has a high affinity for soil with low partitioning potential from soil matter to soil water. The purpose of this degradation study is to determine the effect of soil alkalinity on the longevity of termite protection when chlorpyrifos is applied as a termiticide in a range of Australian soils, particularly high-pH substrates. The study also examines the effects of initial soil concentration on the degradation of chlorpyrifos in the range of soils. At an initial soil concentration of 1000 mg kg(-)(1) for termite control, the degradation rate of chlorpyrifos is very strongly retarded in soils tested when compared with lower soil concentrations of 100 and 10 mg kg(-)(1) in the same soils. The degradation data correlated with a logarithmic model of decay, and it was thus possible to produce half-lives and predict likely periods of termite control. Average half-lives for all soils for the three concentrations were 385, 155, and 41 days, respectively. Soil pH had no effect on the rate of degradation at all concentrations tested.