Optical Conductivity and Loss Function of Noble Metals in Nonequilibrium Thermalized Stage

Abstract

In continuation of a series of papers I1 to 31 having investigated theoretically the optical properties of laser irradiated noble metal layers in the nonequilibrium thermalized stage we discuss here the time and frequency dependence of the optical conductivity and the loss function for gold, silver, and copper in the vicinity of the threshold energy for d-s interband transitions (Au: 2.38 eV, Ag:3.98 eV, Cu: 2.15 eV) as an addendum to 131.Our theory in 11 to 3/ results in a special form of the macroscopic dielectric function (MDF) 141, which depends on time on a coarse grained axis in the picosecond region, c(w,Te(t)) = E1(w,t) + is2(w,t) . (1)The optical conductivity is defined as As discussed in more detail in 1 2 1 , the intraband imaginary part of the MDF can be dropped and the optical conductivity is very sensitive for excitations near the threshold frequency.The light field of the laser pulse acting in the layer with the metal electrons loses energy due to inelastic scattering. The loss probability for this process is proportional to the negative imaginary part of the reciprocal MDF 151, and the loss function 1( w , t ) reads l ) Head Post Office, POB 79, SU-101000 Moscow, USSR.

Refractory Plasmonics with Titanium Nitride: Broadband Metamaterial Absorber

“…As a result, it is relatively easy to achieve good absorption in the spectral range of 400–550 nm using Au metamaterials as implied in Figure S3 in the Supporting Information. For Ag in this range, although its metallicity is not very strong either, its loss is very low, as shown in Figure S1 in the Supporting Information, because the threshold energy for the d ‐ s interband transition of Ag is as high as 3.98 eV . We can clearly see from Figure S2 in the Supporting Information that Ag thin film only shows a negligible absorption.…”

“…However, it is also notable that in the range of λ < 550 nm the conductivity of Au is quite low, as can be inferred from Figure S1 in the Supporting Information. The threshold energy for the d ‐ s interband transition of Au is 2.38 eV such that the loss due to the interband transition becomes large between 400 and 550 nm. Figure S2 in the Supporting Information indicates that the absorption of only a thin flat film of Au can still reach 60% in this spectrum.…”