The fabrication and optimization of plasmonic nanostructures have many interesting and important applications including advancements in surface-enhanced Raman spectroscopy (SERS). One popular and cost-effective method to fabricate plasmonic nanopatterns is by a colloid template. By combining close-packed colloid monolayer and dynamic shadowing growth, we demonstrate that a variety of nanopatterns, such as nano-triangles, nano-cup triangles, hexagonal holes, and dual triangles, can be fabricated by varying vapor deposition angle, the substrate azimuthal rotation, as well as the evaporation configuration. Especially when a two-source evaporator is used, dual triangles with different shapes and compositions are simultaneously formed. The formation of these nanopatterns can be predicted by numerical and Monte Carlo simulations. In addition, the visible localized surface plasmon resonance (LSPR) of these patterns can be tuned systematically by changing the deposition conditions and the colloidal monolayer. Their plasmonic properties can be understood through finite-difference time-domain simulations. The tunability of LSPR can be used to design optimized substrate for SERS.
Recent experiments on optical damage by ultrashort laser pulses have demonstrated that the temporal pulse shape can dramatically influence plasma generation in fused silica. We use a modified 3+1D nonlinear Schrödinger equation for the pulse propagation coupled to a rate equation for the plasma density in the dielectric material to simulate pulse propagation and plasma formation in fused silica. We use these simulations to analyze the influence of pulse shape and beam geometry on the formation of the electron plasma and hence modification in the bulk material. In particular, we simulate the effect of pulses reconstructed from experimental data. It is expected that a better understanding of the dynamics of laser-induced plasma generation will enable the accurate simulation of optical damage in a variety of dielectrics, ultimately leading to an enhanced control of optical damage to real materials and optical devices.
Recent experiments on optical damage by ultrashort laser pulses have demonstrated that the temporal pulseshape
can dramatically influence plasma generation in fused silica and sapphire. In this work a modified 3+1D
nonlinear Schroedinger equation for the pulse propagation coupled to a rate equation for the plasma density
in the dielectric material is used to simulate pulse propagation and plasma formation in a range of dielectric
materials. We use these simulations to analyze the influence of
pulse-width, pulse-shape and beam geometry on
the formation of the electron plasma and hence damage in the bulk material. In particular, when possible, we
simulate the effect of pulses reconstructed from experimental data. It is expected that a better understanding
of the dynamics of laser-induced plasma generation will enable the accurate simulation of optical damage in a
variety of dielectrics, ultimately leading to an enhanced control of optical damage to real materials and optical
devices.
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.
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.
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