The goal of this work is the investigation of optical spectra features of zinc selenide (ZnSe), silver iodide (AgI) and its two-phase composite AgI-ZnSe nanostructures produced by laser ablation method, which can be used to design optical sensors and diffractive structures in integrated optics. Shifted to blue wavelengths relatively to the bulk semiconductor material band edge transmission spectra minima have been discovered for the ZnSe and AgI-ZnSe films. The observed minima of the transmission spectra are peculiar to the quantum energy spectra of semiconductor nanostructures. Discovered transmission spectra minima for the ZnSe and AgI-ZnSe films shifted to the short-wavelength region from the energy of the bulk material band gap can be the evidence of nanocrystals formation during the film growth by laser ablation, and which are characterized by the energy spectrum quantization and lower electron and upper hole quantum confinement levels shifts from the bottom of the conduction and the top valence bands, respectively.
The fluorescence and non-linear absorption spectra of Cs133 vapour in an extremely thin cell were calculated by using the perturbation theory with respect to the pumping field intensity. The problem of the atoms’ non-linear polarization was solved for arbitrary values of the total momenta of the resonance levels pumped by a linearly-polarised laser field. It was demonstrated that the spontaneous emission from the upper level affects the amplitude and sign of the lower level longitudinal alignment and results in a change of the amplitude and sign of the non-linear absorption resonance at the closed transition. The comparison of the numerical calculations with the experimental data for the D2 line of 133Cs shows a very good agreement.
The interest in quantum dots fluorescence is connected with the problem of implementing new protective luminescence markers and labels. We studied the luminescence spectra of multi-sized quantum dots fluorescent labels and quantum dots fluorescent labels with different matrix pore size.
μInterest to the narrow band gap semiconductors for example Pb1-xCdxSe is connected with problem of creation of new
sources of IR radiation. Possibility of control of the properties of polycrystalline films of the lead chemical compounds
by luminescent and Raman methods is considered.
A model for description of the shapes of the coherent population trapping (CPT) resonances at different geometries of
excitation and observation is developed. The numerical calculations, based on the irreducible tensor operator formalism,
take into account the experimental geometry, the velocity distribution of the atoms, the Gaussian distribution of the laser
beam intensity and the high rank polarization moments (HRPM). The results for different laser beam diameters, aperture
of the detection, position of the photodetector etc. are compared with the experimental data. A method for description of
the experimental shapes is proposed.
Comparative studies of MO resonances and MG responses with and without resonant laser irradiation were
carried out to establish the interconnection of the effects and the influence of the self-alignment destruction on the MO
signal in positive column discharge. These studies aim to clarify the possible formation mechanisms of the neon 1 si
(2p53s) states coherences and to examine the possibility to use the galvanic resonances for estimation of the relaxation
constants of the neon 1 s5 state.
Numerical simulations are used to obtain the amplitudes and the widths of the nonlinear resonances related to the
different ranks of the tensor components &rgr;kq in dependence on the atomic system parameters, and the laser field power
(Rabi parameter - d.E/ℏ). The main attention is paid to the effect of the velocity distribution of the atoms on the
hexadecapole (k = 4) components and their influence on the fluorescence and/or absorption signals. A detailed
examination of our basic equations allows us to directly find out a relation between different rank components for a
chosen transition and to clarify their role in the observed resonances for a given geometry.
In the present work we consider theoretically the influence of an arbitrary oriented additional magnetic field on the main properties of the Coherent Population Trapping (CPT) resonances in fluorescence and/or in absorption. The exact numerical solutions are obtained for the tensor components Ρk0 (ρ = f, φ) which describe the population and the longitudinal alignment of the resonant (f) levels with quantum numbers Ff 0 and Ff =1, exited with a single frequency laser field from the ground (φ) state with Fφ=l and Fφ=2. Numerical simulations was used to obtain the width and the amplitude dependences of the resonances under different parameters and parasitic fields. The results are in qualitative agreement with resent experimental investigations.
In this work we discuss Hanle absorption resonances obtained in a room temperature NO2 cell, irradiated by a single mode Ar+ laser. The method used is based on measuring the changes of polarization of the transmitted laser beam crossing the NO2 cell, placed in a transverse magnetic field. The resonant changes in the measured absorption signal, that occur in the magnetic field, could be explained as destruction of the alignment of the absorbing rotational state(s), belonging to the ground state (0,0,0) X2A1. The observed signal is described as a sum, taken over all F'u and F"g values, for the chosen N",J"→N',J' transition. The numerical calculations show, that despite the contributions of terms with different signs, the total signal for all examined cases preserves its sign, the determining role being played by the most intensive hf components. Thus a confirmation of Chaika's hypothesis for creation of NO2 ground state levels (self)alignment is obtained as well an estimation of the effective life time for coherences τ(2).
By the method of saturation absorption of counterpropagating light waves, the gas-phase spectrum of SiF4 is obtained without Doppler broadening of spectral lines. In the frequency range of the generation of a low-pressure CO2 laser (the 9.4-μm band), multplets of the superfine structure (associated with tunneling transitions between the states of rotation about the equivalent symmetry axes of the SiF4 molecule) of the spectrum were observed. Weak satellites were observed in the vicinity of the multiplets.
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