Stable, High-Average-Power, Degenerate Optical Parametric Oscillator at 2.1 μm

We describe a degenerate 1.064-μm-pumped pulsed optical parametric oscillator based on MgO:PPLN in compact Littrow-grating cavity configuration, providing 2.7W of average power at 2.1μm with high spectral and power stability in good spatial beam quality.Peer ReviewedPostprint (author's final draft

Optical parametric generator based on orientation-patterned gallium phosphide

We report the first pulsed optical parametric generator based on Orientation-patterned Gallium Phosphide. The output is tunable from 1721-1850 nm (signal) and 2504-2787 nm (idler), providing a total output power of 18 mW.Peer ReviewedPostprint (author's final draft

Singly-Resonant Optical Parametric Oscillator Based on Orientation-Patterned Gallium Phosphide

We report a pulsed singly-resonant optical parametric oscillator based on orientation-patterned gallium phosphide pumped by a Q-switched Nd:YAG laser. The mid-IR idler can be tuned across 2.8-3.1 μm with an average power of 20 mW.Peer ReviewedPostprint (author's final draft

Optical parametric generation in orientation-patterned gallium phosphide

We report an optical parametric generator (OPG) based on the new nonlinear material, orientation-patterned gallium phosphide (OP-GaP). Pumped by a Q-switched nanosecond Nd:YAG laser at 1064 nm with 25 kHz pulse repetition rate, the OPG can be tuned across 1721–1850 nm in the signal and 2504–2787 nm in the idler. Using a 40-mm-long crystal in single-pass configuration, we have generated a total average output power of up to ∼18  mW∼18  mW, with ∼5  mW∼5  mW of idler power at 2670 nm, for 2 W of input pump power. The OPG exhibits a passive stability in total output power better than 0.87% rms over 1 h, at a crystal temperature of 120°C, compared to 0.14% rms for the input pump. The output signal pulses, recorded at 1769 nm, have duration of 5.9 ns for input pump pulses of 9 ns. Temperature-dependent loss measurements for the pump polarization along the [100] axis in the OP-GaP crystal have also been performed, for the first time, indicating a drop in transmission from 28.8% at 50°C to 19.4% at 160°C.Peer ReviewedPostprint (author's final draft

Tunable high-average-power optical parametric oscillators near 2 μm

We report on the development of high-average-power nanosecond and picosecond laser sources tunable near 2 μm based on optical parametric oscillators (OPOs) pumped by solid-state Nd:YAG and Yb-fiber lasers at 1.064 μm. By exploiting 50-mm-long MgO-doped lithium niobate (MgO:PPLN) as the nonlinear crystal and operating the OPO in a near-degenerate doubly resonant configuration with intracavity wavelength selection elements, we have generated tunable high-average-power radiation across 1880–2451 nm in high spectral and spatial beam quality with excellent output stability. In nanosecond operation, pumping with a Q-switched Nd:YAG laser and using an intracavity prism for spectral control, we have generated more than 2 W of average power in pulses of 10 ns duration at 80 kHz repetition rate with narrow linewidth (<3 nm), with M2 < 2.8, and a passive power stability better than 2.2% rms over 1 h. In picosecond operation, pumping with a mode-locked Ybfiber laser and using a diffraction grating as the wavelength selection element, we have generated more than 5 W of average power in pulses of 20 ps at 80 MHz repetition rate with narrow bandwidth (∼2.5 nm), with M2 < 1.8 and a passive power stability better than 1.3% rms over 2 h. The demonstrated sources represent viable alternatives to Tm3 ∕Ho3 -doped solid-state and fiber lasers for the generation of high-power radiation in the ∼2 μm spectral range.Peer ReviewedPostprint (author's final draft

Nanosecond difference-frequency-generation in orientation-patterned gallium phosphide

We report a tunable, single-pass, pulsed nanosecond difference-frequency generation (DFG) source based on the new semiconductor nonlinear material, orientation-patterned gallium phosphide (OP-GaP). The DFG source is realized by mixing the output signal of a nanosecond OPO tunable over 1723–1827 nm with the input pump pulses of the same OPO at 1064 nm in an OP-GaP crystal, resulting in tunable generation over 233 nm in the mid-infrared from 2548 to 2781 nm. Using a 40-mm-long crystal, we have produced ∼14  mW∼14  mW of average DFG output power at 2719 nm for a pump power of 5 W and signal power of 1 W at 80 kHz repetition rate. To the best of our knowledge, this is the first single-pass nanosecond DFG source based on OP-GaP. The DFG output beam has a TEM00TEM00 spatial mode profile and exhibits passive power stability better than 1.7% rms over 1.4 h at 2774 nm, compared to 1.6% and 0.1% rms for the signal and pump, respectively. The OP-GaP crystal is recorded to have a temperature acceptance bandwidth of 17.7°C.Peer ReviewedPostprint (author's final draft

Immigrant assimilation and BMI and waist size: A longitudinal examination among hispanic and chinese participants in the multi‐ethnic study of atherosclerosis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/99611/1/oby20104.pd

The electrical conductivity of Al2O3 under shock-compression

Sapphire (Al2O3) crystals are used below 100 GPa as anvils and windows in dynamic-compression experiments because of their transparency and high density. Above 100 GPa shock pressures, sapphire becomes opaque and electrically conducting because of shock-induced defects. Such effects prevent temperature and dc conductivity measurements of materials compressed quasi-isentropically. Opacities and electrical conductivities at ~100 GPa are non-equilibrium, rather than thermodynamic parameters. We have performed electronic structure calculations as a guide in predicting and interpreting shock experiments and possibly to discover a window up to ~200 GPa. Our calculations indicate shocked sapphire does not metallize by band overlap at ~300 GPa, as suggested previously by measured non-equilibrium data. Shock-compressed Al2O3 melts to a metallic liquid at ~500 GPa and 10,000 K and its conductivity increases rapidly to ~2000 Ω−1cm−1 at ~900 GPa. At these high shock temperatures and pressures sapphire is in thermal equilibrium. Calculated conductivity of Al2O3 is similar to those measured for metallic fluid H, N, O, Rb, and Cs. Despite different materials, pressures and temperatures, and compression techniques, both experimental and theoretical, conductivities of all these poor metals reach a common end state typical of strong-scattering disordered materials

Performance characterization of mid-infrared difference-frequency-generation in orientation-patterned gallium phosphide

We present a detailed characterization of the optical properties of the recently developed nonlinear material, orientation-patterned gallium phosphide (OP-GaP), by performing difference-frequency-generation experiments in the 2548-2782 nm wavelength range in the mid-infrared (mid-IR). Temperature and spectral acceptance bandwidth measurements have been performed to study the phase-matching characteristics of OP-GaP, and the dependence of nonlinear gain on the polarization of input incident fields has been investigated. The transmission of the OP-GaP crystal at the pump and signal wavelengths has been studied and found to be dependent on polarization as well as temperature. Further, we have observed a polarization-dependent spatial shift in the transmitted pump beam through the OP-GaP sample. We have also measured the damage threshold of the OP-GaP crystal to be 0.84 J/cm2 at 1064 nm.Peer ReviewedPostprint (published version