RESUMO
We report a high-power picosecond optical parametric oscillator (OPO) based on cylindrical MgO:PPLN synchronously pumped by an Yb-fiber laser. The singly resonant OPO is tunable in the near-infrared signal across 1413-1900 nm and mid-infrared idler over 2418-4307 nm by angle tuning of the crystal at room temperature. With non-optimized output coupling of â¼10%, the OPO simultaneously delivers 2.4 W of signal at 1664 nm and 1.7 W of idler at 2950 nm at an overall extraction efficiency of â¼45% with high beam-pointing stability <30 µrad and <14 µrad for the signal and idler, respectively. The generated signal and idler exhibit passive power stability better than 1% rms and 0.8% rms over 15 h, respectively, in high beam quality with TEM(00) profile. The extracted signal pulses from the OPO have duration of 15.2 ps with a spectral bandwidth of 0.7 nm, corresponding to a time-bandwidth product of ΔυΔτâ¼1.2.
RESUMO
We conceived a unique fully parametric source based on two independent cylindrical OPOs simultaneously pumped by the same Nd:YAG laser. Each OPO delivers more than 2 mJ and is continuously tunable between 1.41 µm and 4.3 µm. This source is of particular interest for the study of the generation of infrared parametric light in nonlinear crystals. It was validated by performing difference frequency generation experiments in CdSe crystals with output in the range 8 - 10 µm.
RESUMO
A 5 mm thick and 38 mm long 5% MgO-doped periodically poled lithium niobate (MgO:PPLN) cylinder with a grating period of 28 µm has been engineered as a partial cylinder with an angular aperture of 45°. An optical parametric oscillator based on this crystal and pumped at 1.064 µm is reported. The output energy is comparable to that generated in the same kind of sample cut as a slab, but the wavelength tunability from 1.41 to 4.3 µm is much broader and continuous.
RESUMO
We directly measured the second harmonic generation and difference frequency generation phase-matching directions of the nonlinear crystal CdSiP(2) until 9.5 µm using the sphere method. The simultaneous fit of the experimental angular data allowed the Sellmeier equations of the ordinary and extraordinary principal refractive indices to be refined over the entire transparency range of the crystal.
RESUMO
We report on transient 2D Fourier transform infrared spectroscopy (2DIR) after vibrational ladder climbing induced in the CO-moiety longitudinal stretch of carboxyhemoglobin. The population distribution, spreading up to seven vibrational levels, results in a nonequilibrium 2DIR spectrum evidencing a large number of peaks that can be easily attributed to individual transitions thanks to the anharmonicity of the vibrational potential. We discuss the physical origin of the observed peaks as well as the qualitative behavior of the subsequent dynamics governed by population relaxation in the vibrational ladder.
RESUMO
This Letter presents a comparison between experimental and simulated 2D mid-infrared spectra of carboxy-hemoglobin in the spectral region of the carbon monoxide stretching mode. The simulations rely on a fluctuating potential energy surface that includes both the effect of heme and the protein surroundings computed from molecular dynamics simulations. A very good agreement between theory and experiment is obtained with no adjustable parameters. The simulations show that the effect of the distal histidine through the hydrogen bond is strong and is directly responsible for the slow decay of the frequency-frequency correlation function on a 10 ps time scale. This study confirms that fluctuations in carboxy-hemoglobin are more inhomogeneous than those in the more frequently studied carboxy-myoglobin. The comparison between simulations and experiments brings valuable information on the complex relation between protein structure and spectral diffusion.