Hybrid metal mesh-dielectric mirrors for optically pumped far infrared lasers

Abstract

A hybrid metal metal-dielectrically coated mirror, highly reflecting in the near ir and partially transmitting in the far ir, for use in optically pumped molecular lasers, is described. Ge and CaF(2) were used for the dielectric films, along with Ni meshes deposited on Si substrates. The dielectric dispersion properties of the CaF(2) thin films were studied in the 2-15-microm range to provide design data. With a four layer dielectric coating and a metal mesh, the specular reflection of the mirror could be maintained greater than 90% over a 2-mum range in the near ir, and by choice of mesh, the transmittance in the 400-600-microm range varied from 0% to greater than 40%.

Power Stored and Quality Factors in Frequency Selective Surfaces at THz Frequencies

“…Commercial HFSS software based on finite element method (FEM) is employed in this study. Surface impedance boundaries were used, where was calculated from the classical model (see (13) in the next section), which agrees well with the values of obtained from real optical properties at the frequencies simulated. The fields inside the structure are not solved, but this is a reasonable approximation because the thickness of the conductor is much larger than the skin depth at the frequencies simulated.…”

“…For good conductors , the surface impedance can be approximated by the resistive model of (12). However, for increasing frequency this approximation does not hold and the more general classical model described by (13) must be employed [44] ( 13) where , and represent the complex magnetic permeability, the complex dielectric permittivity, and the complex conductivity of the metal, respectively. For non-magnetic materials the permeability becomes that in free-space .…”

“…FSS can be designed to enhance the purity of a laser [13] and to act as reflecting element in infrared lasers or Fabry-Perot cavities [14], [15]. Unique FSS emission/absorption characteristics can be employed in infrared sources [16]- [19].…”

Novel material with narrow-band transparency window in the bulk

“…The condition for excitation of the first-order surface mode in a small sphere is derived from the sphere polarizability in the form or (23) where are the dielectric functions of the sphere and host, respectively. In general, for coated spherical implants the condition for surface modes is the vanishing of the denominator of the polarizability given in (9). In our case, however, singularities appear also in the numerator and, thus, we have to examine the issue in terms of the equivalent permittivity.…”

“…Casting the dispersive behavior of the composite in the form common for conducting dielectrics at microwave frequencies, its bulk conductivity is defined as (12) The parametric analysis of the transparency windows requires the real and imaginary parts of the polarizability, which, from (9), are given as (13) (14) where we have defined…”