Proceedings Volume 4243

Saratov Fall Meeting 2000: Laser Physics and Photonics; and Spectroscopy and Molecular Modeling

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Proceedings Volume 4243

Saratov Fall Meeting 2000: Laser Physics and Photonics; and Spectroscopy and Molecular Modeling

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Volume Details

Date Published: 9 May 2001
Contents: 4 Sessions, 30 Papers, 0 Presentations
Conference: Saratov Fall Meeting 2000 2001
Volume Number: 4243

Table of Contents

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Table of Contents

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  • Laser Physics and Nonlinear Dynamics
  • Nonlinear Optics
  • Atom and Quantum Optics
  • Spectroscopy and Molecular Modeling
Laser Physics and Nonlinear Dynamics
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Direct write exposure and ablation of photoresist in fine scale interconnect circuits
William A. Beck, Jeff Strole, John Yarno, et al.
Interconnect to high density electronic components is an increasingly important problem in electronics production. While most commercial circuit boards and flex circuits are limited to interconnect spacing in the range of 100 microns, standard photo imaging methods can be pushed down to the range of 50 microns, although typically with significantly reduced yields; further increases in interconnect densities requires the use of more exotic methods. Here we discuss two such methods, direct write exposure of photo-resist using a low power UV laser to produce a positive image of the interconnect pattern, and the closely related, somewhat higher power UV laser ablation of photo-resist to produce a negative image of the circuit. These methods currently offer reduced trace size, increased flexibility in trace placement, and up to a factor of two reduction in interconnect spacing with excellent yields; further improvements in trace density are anticipated with improved laser optics and non-Gaussian beam shaping techniques.
Pulse-train dynamics simulation in Kerr-lens mode-locked solid state laser using a full spatio-temporal numerical model
Andrey I. Konukhov, Leonid A. Melnikov
A full spatio-temporal model of the Kerr-lens mode-locking laser is first presented. Nonlinear dynamics of the Z-cavity Ti:Sph laser with Kerr-lens mode locking is numerically investigated.
Nonlinear coherence transformation for pulsed multimode laser radiation
Mikalai U. Karelin, Alexander M. Lazaruk
Nonlinear self-action of light fields in a layer of cubic nonlinear medium can serve as a convenient tool for controllable coherence manipulation. In the present work this scheme is considered for partially coherent input light. Due to experimental requirements, we consider the model of multimode laser. For the purely phase statistics of the input beam (when the average intensity can be represented in factorized form I(r,t) equals I(r)I(t)), it is possible to find out rather simply the dependence of the effective number of (coherent) modes in output radiation on the input number of modes and the nonlinearity parameter.
Processes in hollow cathode discharge excited by steady-state and pulse currents
Galina A. Kalinchenko, Igor G. Ivanov
A semi-analytical method to simulate the local and integral pumping rates of spectral lines in multi-component hollow cathode discharge plasma has been proposed. The contribution of different mechanisms into pumping rate of upper level of laser line 441.6 nm CdII in He-Cd mixture is discovered for CW regime. The excitation of discharge by current pulses has been analyzed. The results of theoretical calculations are in good agreement with experimental measurements.
Effect of noise on probability measure of saddle cycles
I. A. Khovanov, N. A. Khovanova, G. A. Okrokverckhov
Saddle cycles play an important role in solving the problem of controlling complex dynamics in optical systems. Therefore studying the influence of noise on the structure and properties of saddle cycles is actual task. In the paper, the pointwise dimension of saddles cycles for different types of chaotic attractors is considered in the presence and in the absence of noise. The obtained results are analyzed from a controlling chaotic dynamics viewpoint.
Forming of single-pulse regime of ruby laser oscillation with electro-optical negative feedback
Boris V. Anikeev, S. A. Kutzenko, V. A. Yasynok
We report the development of the pulse ruby laser with the controlled external electro-optical integral negative feedback (NFB) and the investigation of its parameters. Double Poc kels shutter based on the KDP* crystal is used for the Q-switching regime. It is proved that by means of the variation of the NFB loop the stable single pulse oscillation regime in ruby laser can be provided.
Possibility of straight gamma-lasing experiments based on nuclei-candidates activated by a rigid bremsstrahlung
Stanislav V. Karyagin
The gamma-laser (GL)-system 'SPTEN' (Soft Prompt Transplantation of Excited Nuclei) proposed recently is universal over the means for the creation of the excited laser-active nuclei (ELAN) at its input. The neutron flux's action at the SPTEN's input is well known from the previous works. Here the feasibility of the straight GL-experiments based on the use of the other type of nuclear radiation, viz., the rigid bremsstrahlung of high intensity, on the input of the SPTEN are researched. The main differences concern the processes at the input part of the SPTEN, so called Multi Beam Emitter. The rest processes of the SPTEN system: the ELAN separation, their delivery to the site of the active medium (AM) of GL, the cooling of the AM and the gamma-generation (GG) are the same as like as in the well known 'neutronic'2*) variant of the SPTEN. The search and choice of the ELAN-candidates for such 'photonic' GL is accomplished here on the bases of the criteria ensuing from the joint theory of the real GG and radiation-heat (RH) regime in the AM. The GL on the base of the photo-nuclear reactions initiated by the bremsstrahlung via use of the Mega-Ampere accelerators is proven.
Dynamics and dispersion of populations for multilevel systems in the intense-radiation and external magnetic fields
Tamara Ya. Karagodova, Alexander I. Karagodov, Andrey A. Eliseev
The theory of interaction of the elementary atomic systems with resonant laser fields is well known. At the same time multilevel systems are investigated in less details. We consider T1 atoms as multilevel system due to removal of degeneracy of levels with different magnetic quantum number in strong radiation and magnetic fields. It is known that recently investigated effect, connected with the quantum interference of states is coherent population trapping (CPT). We propose the method of numerical calculations of interaction of real atoms with strong radiation fields and magnetic field, valid in the case when the values of Rabi frequencies considerably exceed the line widths. This method can be applied to investigate the CPT effect and influence of the external magnetic field on it.
Modernization of the automated CARS spectrometer system based on an IBM-compatible PC
Boris V. Anikeev, D. I. Chadaev
We describe the updated automated system for coherent anti- Stokes Raman spectroscopy (CARS) that includes a laser spectrometer, automatic data processing and control units, based on an IBM-compatible personal computer.
Optical dynamic chaos in gas-discharge laser with delayed feedback
The scenario of the transition from a stationary state to the regime of generation of optical dynamic chaos is studied, which appears in He-He laser with delayed feedback. The coefficient of feedback is proportional to the output laser power and the changes of the discharge current. Depending on the coefficient of the signal of feedback subharmonic we observed the cascade of bifurcations of doubling period, the inverse cascade, the cycles with period f/3 and f/5, and the regime of dynamic chaos whose spectrum has no resonance frequencies. The range of existence of the observed regimes depended greatly on the degree of nonlinearly of the watt- ampere energy characteristics, defined by the processes of saturation of inversion of population and the controlled pressure of gas in the active element. Optical chaos in such non-linear systems appears, when the delay is greater than the life times of the metastable states of helium and neon that determine the internal dynamics of the laser. These results can be used for creation of optical generators of amplitude and frequency noise and information security systems.
Nonlinear Optics
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Numerical modeling in nonlinear optics: accumulation of the products of nonlinear optical interactions in multispan fiber transmission systems
Marian Marciniak, Adam Sedlin
There are reported the fundamentals and results of numerical investigation of the influence of the nonlinear optical phenomena on transmission quality and nonlinear products accumulation in multispan dense wavelength-division multiplexed (DWDM) optical fiber telecommunication systems. Four-Wave Mixing (FWM), Self-Phase Modulation (SPM), Cross- Phase Modulation (XPM), and Stimulated Raman Scattering (SRS) phenomena are taken into account. Various types of optical fibers as well as different channel number and channel spacing are taken into account in the analysis.
Diffraction and transmittance of two-dimensional photonic crystal fiber
We describe the fabrication, characterization and possible application of a new type of optical material -- a 2- dimensional air-glass photonic crystal.
Fine structure of the photonic bandgaps and photonic band windows and saddle points in the dispersion characteristics of one-dimensional photonic crystals
General description of 1D photonic crystal structures is presented. Waveguiding and band-gap properties are treated simultaneously using of the generalization of Kronig-Penny model for TE and TM modes. Saddle points for TM polarization are observed in the regions where the light propagation is possible.
Two-surface plasmon interaction to femtosecond surface spectroscopy
Frequency mixing is demonstrated in degenerate three-wave mixing with two noncollinear beams of femtosecond laser pulses on a metal grating. The observed enhancement of the nonlinear optical response is connected with the synchronized excitation of two surface plasmon-polaritons waves, their nonlinear interaction and photon generation with the sum frequency. The dependencies of this process versus the temporal delay between laser pulses and the mutual spatial overlapping of the beams on the grating surface are studied. Experiments of this type opens a possibility of development of femtosecond time- resolved surface SPP optics and spectroscopy.
Transmission spectra of cw beams affected by self-action under inversionless amplification conditions
Inna L. Plastun
The transmission spectra of inversionless amplification are investigated. Propagation of a weak probe optical beam through a three-level medium pumped with a microwave strong beam is numerically modeled. Three various schemes of transitions under the conditions providing the amplification of the probe field without inversion are taken to calculate the atomic polarization, which enters the paraxial wave equations. Diffraction and self-action of beams due to nonlinear absorption and refraction are properly taken into account. These effects together with linear absorption and refraction form a complex distribution of gain across the beams. As a result the amplified beam acquires ring transverse patterns and slight asymmetry in the frequency characteristics.
Optical traps formed by different laser modes
M. A. Rakhmatulin, Svetlana P. Kotova, V. V. Filkin
The most promising sphere of the application of the laser trapping of neutral particles is microbiology. To determine the optimum parameters of the laser trap for transparent neutral particles, a computer model of the interaction of tightly focused laser beams of various modes with a transparent dielectric sphere was created based on the laws of the ray and wave optics. In modeling the Laguerre-Gaussian laser modes L-G00, L-G01, L-G02, L-G03, L-G04, L-G10, L-G20 and L- G11 were used and latex spheres suspended in water were simulated to serve as transparent dielectric particles. The reason why transparent latex spheres had been selected is that many bio-objects are transparent for red and near IR of the light ranges. For all applied laser modes their forces of action on the sphere are calculated both in axial and transversal directions of the beam propagation. It was revealed that the Laguerre-Gaussian beams generate axial reverse forces exceeding those of the zero Gaussian mode. At the same time, the transversal forces of trapping are stronger at the zero Gaussian mode. Besides, the forces of interaction of the Gaussian mode (TEM00), focused with different micro- objectives for latex spheres of various diameters, are calculated. It was found that for the three simulated micro- objectives in the transversal direction of the largest force of trapping is provided by the micro-objective with the smallest numerical aperture (NA equals 0,4) while and in the longitudinal direction -- by the micro-objective with the maximum numerical aperture (NA equals 1,25).
Computer analysis of the CPT-dip properties
Anna V. Kuptsova
In our work we develop the computer analysis of the CPT-dip properties. We investigate the dependencies of CPT-dip width, depth and contrast on the radiation fields intensities and detunings, the magnetic fields strength, and the relaxation constants. CPT is observed in the population dynamics of two real three-level atomic systems. One of them is a (Lambda) - type system composed of the magnetic sublevels of 6P1/2, 6P3/2 and 7S1/2 states of Tl atom, the other one is a (Xi) -type system of the magnetic sublevels of 3S1/2, 3P3/2, 5S1/2 states of Na atom. The systems interact with two monochromatic laser fields and magnetic field, which is perpendicular to the laser propagation direction for the lambda-system and parallel for the (Xi) -system. On both cases polarization and mutual configurations of the fields are chosen specific, so that one can select the isolated three- level subsystems in multilevel atomic systems. We observe that the obtained dependencies are different from those in reference 1. It may be explained with non-equal Rabi frequencies and decay rates of neighboring transitions, which are the characteristic feature of real atoms.
Newton's method for evaluation of stationary modes in nonlinear waveguides and boson traps
Vladislav V. Serov, Vladimir L. Derbov, Sergey I. Vinitsky
Basing on the continuous analog of Newton's method, we propose an efficient numerical scheme for solving stationary Schrodinger equations with cubic nonlinearity that arise in the scalar paraxial theory of optical waveguides as well as in the theory of boson traps.
Excitation of antiprotonic helium by a single laser pulse of variable intensity
Vladimir L. Derbov, Leonid A. Melnikov, Natalia I. Teper, et al.
We report the results of numerical modeling of the coherent action of a single short laser pulse on a multilevel quantum system of metastable and short-lived states of antiprotonic helium. Increasing the pulse intensity we observed more new states getting involved into the coherent interaction, their populations being affected by the pulse. Examples of intensity-dependent dynamics of the metastable states populations are considered. Extraction of spectroscopic information about the states of antiprotonic helium from the experiments with fixed-frequency variable-intensity laser pulses is discussed.
Numerical analysis of nonlinear resonant polarization phenomena in strong fields
Tamara Ya. Karagodova, Anna V. Kuptsova
The numerical analyses of polarization phenomena is developed for the radiation fields resonant with the transitions nS1/2-nP1/2,3/2 and nP1/2,3/2 -- (n+2)S1/2 of alkaline atoms. The method of computer simulation of nonlinear resonant polarization phenomena is used, which is based on the solution of the problem of interaction of the real multilevel atom with two laser fields of arbitrary intensity and polarization and with a constant magnetic field. This method is known to be successful applied for the investigation of the polarization phenomena in the atomic gases of the alkaline atoms Na and K. In present paper the whole alkaline group is considered. The represented spectra of rotation of plane of polarization are appear to be qualitatively different for different atoms since atom fine- structure intervals differ very much from each other. The obtained spectra for Rb are in good agreement with the experimental spectra.
Atom and Quantum Optics
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Dynamic critical phenomena in trapped Bose gases
V. I. Yukalov, E. P. Yukalova, Vanderlei Salvador Bagnato
Nonlinear dynamics of a trapped Bose-Einstein condensate, subject to the action of a resonant external field, is studied. This field produces a spatio-temporal modulation of the trapping potential with the frequency close to the transition frequency between the ground state and a higher energy level. The evolution equations of fractional populations display a kind of critical phenomena at a critical line on the manifold of the system parameters. It is demonstrated that there exists a direct analogy between dynamical instability at this line and critical phenomena at a critical line of a related averaged system.
Quantum theory of superradiance in two-level and three-level systems
The chain of kinetic equations for two-level and three-level macroscopic systems, interacting with the electromagnetic field, is obtained on the basis of the method of elimination of the boson variables, taking a new type of decoupling for three-particle correlators into account. These equations yield a better description of experimentally observed shape of super-radiant pulse than the standard theories based on the decoupling of the Tyablyakov's type.
Problems of superradiant lasing in magnetized quantum wells: two-color regime, inhomogeneous broadening, and VCSEL scheme
A. A. Belyanin, V. V. Kocharovsky, Vl. V. Kocharovsky, et al.
We analyze super-radiant lasing, i.e. superfluorescence (SF) under continuous pumping, due to collective interband recombination of electron-hole (eh) pairs in quantum wells (QWs) placed in a strong magnetic field oriented perpendicular to the well plane. In such semiconductor systems, cooperative radiation processes lead to generation of coherent femtosecond pulses and can be observed even at room temperature due to complete quantization of particle motion, high spectral density of carrier states, high spatial density of effective 'cyclotron quantum dots,' and partial suppression of intraband scattering. Our simulations based on the Maxwell-Bloch equations show that, in the case of two neighboring transitions between electron and hole Landau levels connected by scattering, two-color super-radiant lasing of the corresponding pair of resonance modes is possible under cascade cw pumping. We investigate analytically and numerically threshold conditions for this two-color lasing as well as for super-radiant lasing modified by 'discrete' inhomogeneous broadening due to fluctuations of the number of atomic layers in actual QW heterostructures. Also, we present an example of real design and discuss necessary conditions for a vertical cavity surface-emitting laser (VCSEL) to operate in the super-radiant regime.
Fokker-Planck equations for quantum amplifiers and squeezing
The Fokker-Planck equations (FPE) which determine the time dependence of P -- symbol of the density matrix of quantum parametric amplifiers are derived and their group properties are investigated. Exploring the coherent states method, constructing the dynamical symmetry group of FPE and generalizing the well known Wei-Norman method to the case of FPE, we have found FPE solutions exactly. The initial squeezing influence of the thermal reservoir is discussed.
Spectroscopy and Molecular Modeling
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Real-time dynamics in atoms and molecules: fractional revivals of wave packets
Vadim V. Eryomin, Nikolai E. Kuz'menko, Igor M. Umanskii
Universal properties of electronic and nuclear wave packets created in atoms and molecules by ultrashort (pico- and femtosecond) laser pulses are considered. The phenomenon of fractional revivals of wave packets moving in anharmonic quantum systems is examined in detail. Experimental manifestations of fractional revivals and the mechanisms of their decay in atoms and molecules are discussed.
Vibrational effects in the (e,2e) ionization of diatomic targets by fast electron impact
Boghos B. Joulakian, Philippe Weck
Assuming similar electronic structure for hydrogen, deuterium and tritium diatomic molecules in the limits of the Born- Oppenheimer separation, we have undertaken a study of the differential cross section of the (e,2e) ionization of these three isotopes to show the influence of the vibrational motion in the ionization process. We have considered vertical transitions from the lowest vibrational state of the fundamental 1(Sigma) g state of the target to the vibrational levels of the fundamental 2(Sigma) g state of H2+, D2+ or T2+. The results obtained by two different approaches; one considering the inter-nuclear distance as a target variable just like electronic coordinates in the transition matrix element of the problem, and the second, considering the problem as a purely electronic transition modulated by the probability density of finding the diatomic system at a given inter-nuclear distance, show that vibrational effects could be important in high energy resolution (leV) experiments, and that, in the case of low resolution the two approaches present contradictory results, which could be elucidated by new experiments.
Vibrational spectra structure and features of fluorinated derivatives of carboxylic acids
Lev M. Babkov, E. S. Vedyaeva, S. K. Truchatchev, et al.
The results of investigation of polymorphism and mesomorphic states of fluorinated derivatives of alkylcyclohexanecarboxylic acids nFACHCA (where n is the number of carbon atoms in the fluoroalkyl radicals) and the new results for n equals 4, 7 are discussed. The methods of vibrational spectroscopy (experimental, theoretical modeling) have been used. The samples were investigated in the 290 - 500 K temperature range. The spectra were recorded in the range of 400 - 4000 cm-1. The frequencies of normal modes and IR band intensities are calculated for conformers of H- complexes with various orientations of fluoroalkyl radical and carboxylic group relative to the rest of the molecular complex. The polymorphism of the nFACHCA is conformational. The influence of H-bonds on the dynamics of H-complex, polymorphic crystalline modification and mesophase formation was determined. The transitions 'solid crystal -- liquid crystal -- isotropic liquid and solution' are accompanied by H-bonds system reconstruction, in which the dimers, associates, chain associates and monomers appear.
Effect of surface implantation of impurities on LiF crystal luminescence spectra
Yuliya G. Konyukhova, Vyacheslav I. Kochubey, Konsuella E. Gyunsburg, et al.
Photoluminescence and excitation spectra of radiation-induced defects in LiF single crystals with modified surface were studied. Both the change of host defect formation efficiency and arising of new spectral bands in consequence of impurity effect were demonstrated.
Pair interaction of excimer of pentyloxycyanobiphenyl
Valery N. Ryzhov, Konstantin I. Gurjev, Natalia N. Melnichenko
The energies of pair interaction of molecular systems, namely, the first excited state and the ground state of pentyloxycyanobiphenyl molecules were calculated and the equilibrium configuration of these molecular systems was determined. The pair-oriented destabilization energies evaluation is carried out for the absorption and emission processes.
Use of EXAFS- and optical spectroscopy for analysis of NaCl-Ni,Cu crystal structure modification resulting from X-irradiation
Vyacheslav I. Kochubey, Yuliya G. Konyukhova, Konsuella E. Gyunsburg, et al.
On the basis of the optical and FLEXAFS spectral data the conclusion about influence of copper and nickel impurities interaction on spectral characteristics of nickel clusters contained in a NaCl-Ni, Cu crystal is derived. The distinction in spectra of excitation can be caused both competitions in absorbency and distortion of the explored defect structure.