Metal-insulator-metal metasurfaces (MIM-M) structures can achieve near-unity absorptance at sub-wavelength volumes. A conventional approach to tune the absorption wavelength and the bandwidth of MIM-Ms is to change the geometrical parameters of the structure. In this research, we investigate numerically a new approach to achieve enhanced absorption in MIM-Ms in the mid-infrared spectral region by using both lossy metals and a lossy dielectric. The absorption in the dielectric spacer layer is attributed to the Berreman and epsilon near-zero modes in combination with the dielectric intrinsic loss. The simulations have revealed the presence of additional absorption peaks compared with the case of lossless dielectrics. In particular, the effects of the dielectric thickness and the radiation incident angle on the absorption spectra of the proposed MIM-M structures have been investigated.
In this paper, effective magnetic of an arrangement of periodically close-packed conducting square rings have been studied theoretically. A non-resonant model has been introduced in order to determine the magnetic permeability of the structure from the microscopic quantities. The core of this work covers the analysis of the lattice ordering and magnetic interactions between the building blocks, i.e. a collective feature has been considered. Finally, corresponding suggestions for obtaining the lowest possible values of the magnetic permeability have been made.
In real thin disk laser systems, a fraction of absorbed pump power is dissipated as heat. Consequently, the thin disk lasers experience a temperature gradient in the axial direction of the disk which produces inhomogeneous stress and strain distributions. In this paper, we present the numerical calculation of Von Mises stress and the thermal lensing due to temperature gradient, stress gradient and deformation. Based on the results of our numerical study, it was proved that the most dominant parameters, which cause optical path difference and therefore thermal lensing, are temperature-dependent refractive index and deformation of the disk. Moreover, these are both directly related to absolute temperature values within the crystal.
A detailed study of axicon-based Bessel-Gauss resonator for the thin disk laser has been carried out. A paraxial ray
analysis is performed to find the self-consistency condition to have stable periodic ray trajectory after one or two round
trips.
By using the Fox-Li method, it is possible to find the lowest mode shape and associated optical loss for an arbitrary
optical resonator. Nevertheless, the mentioned routine is very time-consuming and therefore, we make use of a technique
in order to convert the Huygens-Fresnel integral self-consistency equation into a matrix one and then find the
eigenvalues and the eigenfields of the resonator. Here, special attention is paid to investigate the dependence of the
transverse profile and the loss on the cavity length.
Edge-pumping is very advantageous for pumping disk lasers because it provides a long absorption path for the pump
compared with end-pumped one. In the current work, we report an edge-pumped Yb:YAG disk laser pumped from four
sides with diode laser stacks. For delivering the pump light into the gain medium, asymmetric hollow ducts have been
employed. For any type of disk laser system, the key criterion is a uniform deposition of absorbed pump power and in
turn a uniform temperature distribution throughout the disk. We try to meet this restriction by designing an appropriate
asymmetric hollow duct. In order to obtain laser output power, a self-consistent numerical model has been developed for
simulating lasing properties of our configuration. A Monte Carlo ray tracing based code and two-dimensional finite
element analysis have been utilized to calculate the absorption power and temperature distribution inside the crystal,
respectively. The model is used to investigate the influence of the effective parameters on the operational efficiency of
the disk laser.
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