6450 nm wavelength tissue ablation using a nanosecond laser based on difference frequency mixing and stimulated Raman scattering

A four-stage laser system was developed, emitting at a wavelength of 6450 nm with a 3-5 ns pulse duration, < or = 2 mJ pulse energy, and 1/2 Hz pulse repetition rate. The laser system successfully ablated rat brain tissue, where both the collateral damage and the ablation rate compare favorably with that previously observed with a Mark-III Free-Electron Laser.     

Electronic, Magnetic, and Magnetoresistance Properties of the n=2 Ruddlesden-Popper Phases Sr3Fe2−xCoxO7−δ (0.25≤x≤1.75)

A series of oxygen-deficient n=2 Ruddlesden-Popper phases, Sr₃Fe_2−xCo_xO_7−δ (0.25≤x≤1.75), were prepared by solid-state reactions. Temperature-dependent susceptibility and field-dependent magnetization data indicate that for x≥0.25 the dominant magnetic interactions are ferromagnetic. The onset of strong ferromagnetic interactions is evident at ∼200 K, and a transition to a cluster-glass state is observed for all compositions below ∼45 K. The temperature variation of resistivity for all the compounds shows variable-range hopping behavior with two different localization energy scales: one for T<40 K and another for T>80 K. Large negative magnetoresistance (the largest MR ∼−65% for x=0.25) is observed for all phases. The magnetic susceptibility, Mössbauer and X-ray absorption near-edge spectroscopy data indicate that the formal oxidation state of Fe is close to 4+. The key role of d delocalization in the Sr₃Fe_2−xCo_xO_7−δ system is compared to the Sr₃Fe_2−xMn_xO_7−δ series, where d localization dominates the properties.     

Parametric generation of low-frequency sound in the propagation of high-intensity modulated noise

With the use of the one-dimensional Burgers equation, the evolution of a high-intensity noise with periodically modulated intensity is analyzed. The nonlinearity is shown to lead to partial suppression of the amplitude modulation and to the generation of a regular low-frequency component. The probability distributions and the power spectra of the field are studied.     

Highly efficient narrow-line generation by difference-frequency mixing of a green pump and the stokes seed in RbTiOPO4 crystals: excitation of 943-nm emission

An efficient and compact scheme for diode-pumped Nd:YLF laser wavelength conversion to 943 nm was demonstrated by use of difference-frequency mixing and stimulated Raman scattering. We believe that this is the highest conversion efficiency from the laser fundamental wavelength reported to date. It is shown that RbTiOPO4 crystals are capable of providing highly efficient frequency mixing as a nonlinear medium.