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Nonlinear hopping absorption of ultrasound and electromagnetic waves in amorphous and doped semiconductors is considered. It is shown that even at low amplitudes of the electric (or acoustic) field the nonlinear corrections to the…
Ta$_{3}$N$_{5}$ is among the most intensively studied photoanode materials for solar-driven water oxidation, yet its performance often remains limited by short carrier lifetimes and defect mediated recombination. Although transient…
We use linear response theory in order to compute the light absorption spectrum, in the terahertz band, of a polariton system composed by excitons in a quantum dot very strongly coupled to the lowest photon mode of a thin micropillar. In a…
We present a theory for interpreting the sodium lines detected in transmission spectra of exoplanetary atmospheres. Previous analyses employed the isothermal approximation and dealt only with the transit radius. By recognising the…
Experimental and numerical investigation of single-beam and pump-probe interaction with a resonantly absorbing dense extended medium under strong and weak field-matter coupling is presented. Significant probe beam amplification and conical…
We present femtosecond pump-probe measurements of the nondegenerate (1960$\,$nm excitation and 1176--1326$\,$nm probe) two-photon absorption spectra of 8 $\,$nm GaAs/12$\,$nm Al$_{0.32}$Ga$_{0.68}$As quantum well waveguides. Experiments…
We present an experimental and theoretical study of the absorption and emission spectra of Yb atoms in a solid Ne matrix at a resolution of 0.025 nm. Five absorption bands were identified as due to transitions from the $4f^{14}5d^06s^2\…
Spectroscopy has played the key role in revealing, and thereby understanding, the structure of atoms and molecules. A central drive in this field is the pursuit of higher precision and accuracy so that ever more subtle effects might be…
We present a non-perturbative numerical technique for calculating strong light shifts in atoms under the influence of multiple optical fields with arbitrary polarization. We confirm our technique experimentally by performing spectroscopy of…
In this work we study the properties of a two-subband quasi-two-dimensional electron system in a strong magnetic field when the electron filling factor is equal to four. When the cyclotron energy is close to the intersubband splitting the…
Magnetic field-induced giant modification of the probabilities of five transitions of $5S_{1/2}, F_g=2 \rightarrow 5P_{3/2}, F_e=4$ of $^{85}$Rb and three transitions of $5S_{1/2}, F_g=1 \rightarrow 5P_{3/2}, F_e=3$ of $^{87}$Rb forbidden…
Nolinear Absorption of CT TFF+ aggregates in PMMA matrix was studied with resonant excitation around 800 nm in the femtoseconds regime with the Z-Scan technique with 100 Hz pulse repetition rate. The saturated absorption profiles were…
We discuss nonlinear spectra of selective reflection from high-density rubidium atomic vapor, where the self-broadening of the resonant transition $5S_{1/2}-5P_{3/2}$ dominates over the Doppler width. In the experiments, the hole-burning…
We have obtained high signal:to:noise optical spectroscopy at 5\AA\ resolution of 27 quasars from the APM z$>$4 quasar survey. The spectra have been analyzed to create new samples of high redshift Lyman-limit and damped Lyman-$\alpha$…
Exploring and understanding ultrafast processes at the atomic level is a scientific challenge. Femtosecond X-ray Absorption Spectroscopy (XAS) is an essential experimental probing technic, as it can simultaneously reveal both electronic and…
The quantum dynamics of a system of Rb atoms, modeled by a V-type three-level system interacting with intense probe and pump pulses, are studied. The time-delay-dependent transient-absorption spectrum of an intense probe pulse is thus…
We present deep ground based imaging of the environments of five QSOs that contain sub-Damped Lyman-alpha systems at z<1 with the SOAR telescope and SOI camera. We detect a clear surplus of galaxies in these small fields, supporting the…
Transient field-resolved spectroscopy enables studies of ultrafast dynamics in molecules, nanostructures, or solids with sub-cycle resolution, but previous work has so far concentrated on extracting the dielectric response at frequencies…
When light is absorbed by a semiconductor, photoexcited charge carriers enhance the absorption of far-infrared radiation due to intraband transitions. We observe the opposite behavior in monolayer graphene, a zero-gap semiconductor with…
Spectroscopy is a powerful tool to probe physical, chemical, and biological systems. Recent advances in microfabrication have introduced novel, intriguing mesoscopic quantum systems including superconductor-semiconductor hybrid devices and…