Photoellipsometry, a new contactless spectroscopic method, was applied to n-AlGaAs/GaAs heterojunction structures. Two samples were measured and analyzed, each having an epitaxially grown AlGaAs layer of a thickness of about 100 nm, with a different Al composition and a different doping density, on top of an undoped GaAs substrate. The objective of this research was to determine surface built-in electric field strength, depletion width, broadening, and critical point energies of AlGaAs for each given sample. The measured spectra were analyzed using the Franz-Keldysh theory with the inclusion of field inhomogeneity and nonuniform broadening effects. Good agreement between the measured and calculated spectra indicates that theories and models used were appropriate for the samples investigated and that the calculated results were reliable.
The analytical form of the emission probability produced by the interaction of an ultracold three-level atom with an electromagnetic bimodal cavity field with multi-photon transitions of the atoms (multi-photon mazer) is analysed in the framework of the dressed-state formalism, but is distinguished from other treatments by the inclusion of the spatial variation along the cavity axis. In particular, the cavity field mode profile is considered by using the mesamode function and differences in the collapse-revival patterns are reported. We demonstrate that, when propagation effects are taken into consideration, the emission probability is influenced significantly. We provide the necessary arguments to justify the validity of our conclusions for emission probability and the micromaser, whose dynamics are governed by the wavefunction. Our main conclusion is that, in the present system, the inclusion of the spatial dependence is necessary and important. The numerical illustrations provide evidence that, in cases of physical interest, the emission probability can be significant and can be reliably estimated for a broad range of field parameters using the present formalism.(Some figures in this article are in colour only in the electronic version)
OverviewThe centre-of-mass (CM) motion of atoms coupled to the electromagnetic field in a micro-resonator has become a central problem in current research on cavity quantum electrodynamics [1]. Some recent developments have been devoted to the interaction of ultracold atoms with microwave cavities [2][3][4][5][6][7][8]. These studies treated the interaction between an incident atom in an excited state and a cavity field containing n photons, taking into account
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