Interaction of surface plasmon–phonon polaritons with terahertz radiation in heavily doped GaAs epilayers

Abstract

We report on experimental studies of the surface plasmon-phonon polariton excitations in heavily doped GaAs epitaxial layers. Reflection and emission of radiation in the frequency range of 2–19 THz were investigated for samples with surface-relief grating, as well as for samples with planar surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances attributed to excitations of different surface plasmon-phonon polariton modes. The observed resonances lie beyond the limits of the Reststrahlen band. Terahertz radiation emission from the samples was studied in nonequilibrium conditions under the pulsed electric field excitation. Two contributions to the spectral density of the terahertz radiation have been revealed, the first being due to bulk plasmon–phonon polaritons (PPhPs), while the second originating from the surface PPhPs. A field dependence of the effective temperature of the bulk PPhPs has been established. Polarization dependence of the terahertz radiation related to surface PPhPs has been experimentally examined for the first time.

Tuning Electrical and Raman Scattering Properties of Cadmium Sulfide Nanoribbons via Surface Charge Transfer Doping

“…The plasmon frequency (ω p ) is determined by the concentration of free carriers, following the formula , where n , e , ε ∞ , and m * represent the electron concentration of CdS NR, elementary charge, high-frequency dielectric constant of CdS, and electron effective mass of CdS, respectively (see the detailed values in Table S2). , According to this formula, the plasmon frequency of intrinsic CdS NR with electron concentration of 7 × 10 16 cm –3 is deduced to be 83 cm –1 . After SCTD, the plasmon frequency of the CdS NR monotonically increases (or decreases) as the electron concentration in the CdS NR increases (or decreases) (Table S3).…”

Transition from surface phonon-polariton to surface phonon–plasmon-polariton by thermal injection of free carriers

“…Nevertheless, the increase in temperature of the material can lead to a high density of hot electrons excited in the conduction band and becoming quasi-free electrons. Then, the collective oscillation modes of these electrons couple with the optical phonon modes to give rise to hybrid surface electromagnetic modes known as surface plasmon-phonon-polariton (SPPP) modes, whose properties can be significantly different from those of SPP and SPhP modes [25][26][27][28]. Moreover, increasing the temperature increases the phonon and electron scattering rates, and increasing the free carrier density increases the phonon-electron scattering rate, which affects the characteristics of surface electromagnetic waves.…”