Femtosecond optical polarization switching using a cadmium oxide-based perfect absorber

Light‐Induced Tuning and Reconfiguration of Nanophotonic Structures

“…The much faster and stronger response of the ITO deviates from that of the metals (where e–ph relaxation dominates) because of two major reasons: (1) the free‐electron density in ITO is two orders of magnitude smaller than that of noble metals such as gold, resulting in much smaller electron heat capacity and larger change in the electron temperature if all other parameters are held constant; (2) owing to the non‐parabolicity of the conduction band, the time‐dependent of the photoexcited electrons is strongly dependent on the Fermi distribution function (i.e. electron temperature); and (3) owing to a relatively smaller free‐electron density, the Fermi level is quite low in the conduction band (∼1 eV for ITO). Due to the last property, infrared radiation at ENZ wavelengths can excite even the electrons of the lowest‐energy conduction band (in contrast, the Fermi level of gold is 6.42 eV and infrared light excites only those electrons that sit near the Fermi level) …”

Two-fluid hydrodynamic model for semiconductors

“…[25,29,30], and In:CdO was used in Refs. [33,42]. Apart from the advantages that TCOs share with other semiconductors (such as tunability), they are particularly suitable for the creation of thin films and often allow for heavy doping [67].…”

“…Furthermore, intrinsic semiconductors may contain plasmas created either thermally or by external excitations (e.g., from a laser), and here the electron density can be controlled dynamically with the temperature or the excitation energy, respectively. Plasmonics has already been shown in several papers for doped semiconductors [16][17][18][19][20][21][22][23][24][25][26][27][28], biased semiconductors [29][30][31][32], laser excited semiconductors [33], and thermally excited intrinsic semiconductors [34][35][36][37].…”

Broadband, High‐Speed, and Large‐Amplitude Dynamic Optical Switching with Yttrium‐Doped Cadmium Oxide

“…The exploration of alternative nanophotonic and plasmonic materials in the last decade has led to the demonstration of practical, low‐loss, and high‐speed optical devices. These emerging materials have been utilized in high‐speed, on‐chip electroabsorption modulators, ultrafast all‐optical switches, high‐temperature broadband absorbers, plasmon‐enhanced optical sensors, low‐loss hybrid photonic‐plasmonic waveguides, and tunable metasurfaces . In particular, transparent conducting oxides (TCOs) have received considerable attention in nanophotonics and plasmonics due to their low optical losses .…”

“…More importantly, TCO optical properties can be dynamically tuned post‐fabrication through thermal effects, electrical biasing or optical pumping, an essential property for ultrafast switches. Moreover, TCOs uniquely exhibit low losses near their epsilon‐near‐zero wavelength that have led to the demonstration of novel phenomena such as large reflection modulation and nonlinearity enhancement on planar, unpatterned films.…”