Optical EngineeringSimulation of interactions of high-intensity ultrashort pulses with dielectric filters
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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/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.