Carl Liebig

Tuning spectral properties of ultrafast laser ablation plasmas from brass using adaptive temporal pulse shaping

Using automated laser pulse temporal shaping we report on enhancing spectral emission characteristics of ablation plasmas produced by laser irradiation of brass on ultrafast time scales. For different input irradiance levels, control of both atomic and ionic species becomes possible concerning the yield and the excitation state. The improved energy coupling determined by tailored pulses induces material ejection with lower mechanical load that translates into hot gas-phase regions with higher excitation degrees and reduced particulates.

Optical dephasing in saturable-absorbing organic dye IR140

Room-temperature degenerate four-wave mixing in the forward two-pulse geometry, has been performed on ajet of organic saturable-absorbing laser dye IR140 dissolved in dimethylsulfoxide and ethylene glycol. Numerical solutions to the optical Bloch equation were fitted to the experimental data in order to extract a value of T2 = 50 +/- 5 fs for the homogeneous dephasing time; this value is comparable to those measured for similar organic dyes using other techniques.

Simulation of interactions of high-intensity ultrashort pulses with dielectric filters

Modern table-top laser systems are capable of generating ultrashort optical pulses with sufficiently high intensity to induce nonlinear optical effects in many of the materials that are used in the construction of optical components. We discuss the interaction of such pulses with three types of dielectric filters: (a) dielectric stacks composed of a sequence of two dielectric layers with quarterwave optical thickness, (b) idealized rugate filters, i.e., filters with a refractive index profile that is sinusoidally modulated on the length scale of an optical wavelength, and (c) a rugate filter composed of two materials. We present finite difference time-domain (FDTD) computer simulations of optical pulse propagation through dielectric filters for pulses with widths in the range 5 to 100 fs and with peak intensities up to 10 TW/cm 2 . At low intensities the reflective properties of the dielectric filters determined using FDTD simulations are directly comparable to the results calculated using the characteristic matrix method, while at high intensities optical nonlinearity in the dielectric layers is responsible for a decrease in the reflectance of the filter and causes stretching and distortion of the reflected pulses.

Simulation of high-intensity ultrashort pulse interactions with dielectric filters

Modern table-top laser systems are capable of generating ultrashort optical pulses with sufficiently high intensity to induce nonlinear optical effects in many of the materials that are used in the construction of optical components. In this paper we discuss the interaction of such pulses with two types of dielectric filters: (a) dielectric stacks composed of a sequence of two dielectric layers with quarter-wave optical thickness and (b) rugate filters, i.e. filters with a refractive index profile that is sinusoidally modulated on the length scale of an optical wavelength. Our simulations were performed using the finite difference time domain (FDTD) technique to numerically integrate the Maxwell curl equations for both the electric and magnetic fields. This technique enables the reflection of an optical pulse from a multilayer dielectric stack to be accurately simulated and also allows the incorporation of dispersion and nonlinearity through an auxiliary differential equation. We present computer simulations of optical pulse propagation through dielectric filters for pulses with pulsewidths in the range 5-100 fs with peak intensities up to ~10 TW/cm2. At low intensities the reflective properties of the dielectric filters determined using FDTD simulations are directly comparable to the results calculated using the characteristic matrix method, while at high intensities, optical nonlinearity in the dielectric layers is responsible for a decrease in the reflectance of the filter and causes stretching and distortion of the reflected pulses.