Photon Counting Applications, Quantum Optics, and Quantum Information Transfer and Processing III, 2011
ABSTRACT A strong control field coupling two empty states of a lambda system makes the medium tra... more ABSTRACT A strong control field coupling two empty states of a lambda system makes the medium transparent for a probe pulse. This phenomenon known as electromagnetically induced transparency is here modified by switching a weak microwave field coupling two lower states of the system. As a response to the control and microwave fields, the medium itself acts as a source of an electromagnetic wave which interferes with the incoming pulse. The properties of the net pulse leaving the sample, in particular its magnitude and multipeak shape, will be analyzed in detail, depending on the model parameters.
Near-threshold photodetachment in strong laser fields has been discussed in the case of the pres-... more Near-threshold photodetachment in strong laser fields has been discussed in the case of the pres- ence of an autoionizinglike state in the ionic continuum. The role of a real negative pole of the propagator is stressed. The corresponding terms in transition amplitudes give rise to a new struc- ture of the photoelectron spectrum and to the population trapping.
We describe a detailed account of an experiment demonstrating light-induced stabilization against... more We describe a detailed account of an experiment demonstrating light-induced stabilization against photoionization. The choice of initial state and atom is discussed in relation to the laser wavelength and laser pulse duration. In combination with a 100-fs, 620-nm probe pulse, the optimum choice is the circu- lar Sg state in neon. A picosecond pump laser was used to prepare this Rydberg state. Initially, the pop- ulation in this state was probed with a nanosecond laser pulse. Subsequently, the nanosecond probe pulse was replaced by an intense, (sub)picosecond pulse and the photoionization signa1 was studied. When the probe intensity is several times 10" W/cm' a decrease in yield with respect to a less intense pulse with the same fiuence is observed, which indicates stabilization. The results are in accordance with recent theoretical predictions.
Model photoionization by a pulse with a modulated frequency is discussed. An approximation genera... more Model photoionization by a pulse with a modulated frequency is discussed. An approximation generalizing that of Weisskopf-Wigner is proposed, with a pole moving in the rhythm of the modulation. A model taking into account the ionization threshold is adopted, and relatively simple formulas for the nondecay probability and the photoelectron spectrum are obtained. A nonexponential character of the decay curves is demonstrated together with a raising and narrowing of the peaks in the photoelectron spectra. ͓S1050-2947͑98͒01803-4͔
Different definitions of the photoionization spectra corresponding to various realizations of the... more Different definitions of the photoionization spectra corresponding to various realizations of the experiment are discussed using the language of quantum collision theory. Formal expressions for the transition amplitudes are compared, with stress put on the shift of the spectra. The general results are illustrated on a demonstrative nonperturbative model.
ABSTRACT Three moments of the collision induced absorption spectral density are computed with two... more ABSTRACT Three moments of the collision induced absorption spectral density are computed with two- and three-body effects taken into account. A model free of adjustable parameters is applied to reproduce the density-dependent spectrum.
An evaluation is attempted of the influence of quantum effects on collision-induced absorption sp... more An evaluation is attempted of the influence of quantum effects on collision-induced absorption spectrum of He + Xe. The quantum-corrected moments are used in lowest orders of the quantum-mechanical Mori formulae with a gaussian closure. The corrected spectral functions differ considerably from their classical counterparts and exhibit a flat maximum. The applicability of this approach is limited by its sensitiveness to quantum corrections to higher moments.
The method of continued fractions of Hor&k and Sasakawa is adapted to calculate transition probab... more The method of continued fractions of Hor&k and Sasakawa is adapted to calculate transition probabilities in multichannel scattering. Numerical tests are performed for an exactly soluble two-channel model and accurate results are obtained after a small number of iterations even for strong coupling potentials. A modified version of the method is also presented and tested
Abstract Accurate quantum-mechanical and classical results are obtained for the collision-induced... more Abstract Accurate quantum-mechanical and classical results are obtained for the collision-induced absorption coefficient in the binary-collision approximation. The contribution of quantum effects does not exceed a few percent. For a given HFD interaction potential the parameters of the induced dipole moment are chosen to obtain a good agreement with experiment.
Photodetachment in an ultrastrong laser field in two spatial dimensions is investigated ab initio... more Photodetachment in an ultrastrong laser field in two spatial dimensions is investigated ab initio. A qualitative behavior of the packet for a short-range binding potential is contrasted with that for a soft-core potential, in particular dynamical effects due to a rescattering of fragments separated from the main packet are demonstrated.
We report the measurement of the photoionization cross sections of the 5S 1/2 and 5P 3/2 states o... more We report the measurement of the photoionization cross sections of the 5S 1/2 and 5P 3/2 states of 87 Rb in a two-species Hg and Rb magneto-optical trap (MOT) by the cooling laser for Hg. The photoionization cross sections of Rb in the 5S 1/2 and 5P 3/2 states at 253.7 nm are determined to be 1 +4.3 −1 × 10 −20 cm 2 and 4.63(30) × 10 −18 cm 2 , respectively. To measure the 5S 1/2 and 5P 3/2 states fractions in the MOT we detected photoionization rate of the 5P 3/2 state by an additional 401.5 nm laser. The photoionization cross section of Rb in the 5P 3/2 state at 401.5 nm is determined to be 1.18(10) × 10 −17 cm 2 .
The propagation, storage, and release of two quantized light fields in an optically dressed atomi... more The propagation, storage, and release of two quantized light fields in an optically dressed atomic medium in the tripod configuration are studied. Using the formalism of spinor dark-state polaritons, the probabilities are obtained of finding outgoing photons of two possible localizations and two possible types, i.e., having different frequencies or polarizations. An additional interaction at the storage stage is applied which modifies the atomic coherences due to the stored photons; this results in a modification of the states of the outgoing photons. The conditions are examined for the photons' spatial and type coalescence typical of the Hong-Ou-Mandel effect, i.e., a zero probability of finding the outgoing photons having not only different localizations but also types. These results can possibly be observed in rubidium vapors.
Simultaneous propagation of two probe pulses in a medium of four-level atoms irradiated by three ... more Simultaneous propagation of two probe pulses in a medium of four-level atoms irradiated by three control fields is studied. The double Λ configuration has been closed by a fifth field, coupling the lower levels. It is shown that the propagation can be described in terms of four modes characterized by particular effective susceptibilities, which have absorption or gain peaks and transparency windows. For incoming one-peak pulses, multipeak spectra are built during the propagation including a few components of well-defined frequencies. They evolve along the sample with some of their spectral components being transmitted, absorbed, or amplified.
Pulse propagation is studied in an EIT medium with the control field having a periodically varyin... more Pulse propagation is studied in an EIT medium with the control field having a periodically varying phase (chirp). Based both on numerical calculations and on an approximate approach neglecting absorption and nonadiabatic effects, it is shown that transparency occurs for probe pulses having a sufficiently narrow envelope and an appropriately suited chirp. For other chirped pulses the evolution of their spectra along a sample is studied. Using a projection method one can divide a pulse into a part for which the medium is transparent and a rest for which it is opaque.
The dynamics of the bound state population and the photoelectron energy spectra due to photoioniz... more The dynamics of the bound state population and the photoelectron energy spectra due to photoionization by a double pulse are calculated for a model atomic system. The splitting of the ATI peaks due to the structure of the pulse is presented and discussed. @ 1997 Published by Elsevier Science B.V.
ABSTRACT Photoionization in the regime of the barrier suppression is investigated within a three-... more ABSTRACT Photoionization in the regime of the barrier suppression is investigated within a three-dimensional, fully quantum-mechanical, time-dependent model. It is shown how a structure is formed in the envelope of the above threshold ionization spectra, for energies smaller than the ponderomotive potential. A correspondence between this structure and the shape of the initial-state decay curve, as well as the radial distribution of the electron wave packet, is proven.
Photon Counting Applications, Quantum Optics, and Quantum Information Transfer and Processing III, 2011
ABSTRACT A strong control field coupling two empty states of a lambda system makes the medium tra... more ABSTRACT A strong control field coupling two empty states of a lambda system makes the medium transparent for a probe pulse. This phenomenon known as electromagnetically induced transparency is here modified by switching a weak microwave field coupling two lower states of the system. As a response to the control and microwave fields, the medium itself acts as a source of an electromagnetic wave which interferes with the incoming pulse. The properties of the net pulse leaving the sample, in particular its magnitude and multipeak shape, will be analyzed in detail, depending on the model parameters.
Near-threshold photodetachment in strong laser fields has been discussed in the case of the pres-... more Near-threshold photodetachment in strong laser fields has been discussed in the case of the pres- ence of an autoionizinglike state in the ionic continuum. The role of a real negative pole of the propagator is stressed. The corresponding terms in transition amplitudes give rise to a new struc- ture of the photoelectron spectrum and to the population trapping.
We describe a detailed account of an experiment demonstrating light-induced stabilization against... more We describe a detailed account of an experiment demonstrating light-induced stabilization against photoionization. The choice of initial state and atom is discussed in relation to the laser wavelength and laser pulse duration. In combination with a 100-fs, 620-nm probe pulse, the optimum choice is the circu- lar Sg state in neon. A picosecond pump laser was used to prepare this Rydberg state. Initially, the pop- ulation in this state was probed with a nanosecond laser pulse. Subsequently, the nanosecond probe pulse was replaced by an intense, (sub)picosecond pulse and the photoionization signa1 was studied. When the probe intensity is several times 10" W/cm' a decrease in yield with respect to a less intense pulse with the same fiuence is observed, which indicates stabilization. The results are in accordance with recent theoretical predictions.
Model photoionization by a pulse with a modulated frequency is discussed. An approximation genera... more Model photoionization by a pulse with a modulated frequency is discussed. An approximation generalizing that of Weisskopf-Wigner is proposed, with a pole moving in the rhythm of the modulation. A model taking into account the ionization threshold is adopted, and relatively simple formulas for the nondecay probability and the photoelectron spectrum are obtained. A nonexponential character of the decay curves is demonstrated together with a raising and narrowing of the peaks in the photoelectron spectra. ͓S1050-2947͑98͒01803-4͔
Different definitions of the photoionization spectra corresponding to various realizations of the... more Different definitions of the photoionization spectra corresponding to various realizations of the experiment are discussed using the language of quantum collision theory. Formal expressions for the transition amplitudes are compared, with stress put on the shift of the spectra. The general results are illustrated on a demonstrative nonperturbative model.
ABSTRACT Three moments of the collision induced absorption spectral density are computed with two... more ABSTRACT Three moments of the collision induced absorption spectral density are computed with two- and three-body effects taken into account. A model free of adjustable parameters is applied to reproduce the density-dependent spectrum.
An evaluation is attempted of the influence of quantum effects on collision-induced absorption sp... more An evaluation is attempted of the influence of quantum effects on collision-induced absorption spectrum of He + Xe. The quantum-corrected moments are used in lowest orders of the quantum-mechanical Mori formulae with a gaussian closure. The corrected spectral functions differ considerably from their classical counterparts and exhibit a flat maximum. The applicability of this approach is limited by its sensitiveness to quantum corrections to higher moments.
The method of continued fractions of Hor&k and Sasakawa is adapted to calculate transition probab... more The method of continued fractions of Hor&k and Sasakawa is adapted to calculate transition probabilities in multichannel scattering. Numerical tests are performed for an exactly soluble two-channel model and accurate results are obtained after a small number of iterations even for strong coupling potentials. A modified version of the method is also presented and tested
Abstract Accurate quantum-mechanical and classical results are obtained for the collision-induced... more Abstract Accurate quantum-mechanical and classical results are obtained for the collision-induced absorption coefficient in the binary-collision approximation. The contribution of quantum effects does not exceed a few percent. For a given HFD interaction potential the parameters of the induced dipole moment are chosen to obtain a good agreement with experiment.
Photodetachment in an ultrastrong laser field in two spatial dimensions is investigated ab initio... more Photodetachment in an ultrastrong laser field in two spatial dimensions is investigated ab initio. A qualitative behavior of the packet for a short-range binding potential is contrasted with that for a soft-core potential, in particular dynamical effects due to a rescattering of fragments separated from the main packet are demonstrated.
We report the measurement of the photoionization cross sections of the 5S 1/2 and 5P 3/2 states o... more We report the measurement of the photoionization cross sections of the 5S 1/2 and 5P 3/2 states of 87 Rb in a two-species Hg and Rb magneto-optical trap (MOT) by the cooling laser for Hg. The photoionization cross sections of Rb in the 5S 1/2 and 5P 3/2 states at 253.7 nm are determined to be 1 +4.3 −1 × 10 −20 cm 2 and 4.63(30) × 10 −18 cm 2 , respectively. To measure the 5S 1/2 and 5P 3/2 states fractions in the MOT we detected photoionization rate of the 5P 3/2 state by an additional 401.5 nm laser. The photoionization cross section of Rb in the 5P 3/2 state at 401.5 nm is determined to be 1.18(10) × 10 −17 cm 2 .
The propagation, storage, and release of two quantized light fields in an optically dressed atomi... more The propagation, storage, and release of two quantized light fields in an optically dressed atomic medium in the tripod configuration are studied. Using the formalism of spinor dark-state polaritons, the probabilities are obtained of finding outgoing photons of two possible localizations and two possible types, i.e., having different frequencies or polarizations. An additional interaction at the storage stage is applied which modifies the atomic coherences due to the stored photons; this results in a modification of the states of the outgoing photons. The conditions are examined for the photons' spatial and type coalescence typical of the Hong-Ou-Mandel effect, i.e., a zero probability of finding the outgoing photons having not only different localizations but also types. These results can possibly be observed in rubidium vapors.
Simultaneous propagation of two probe pulses in a medium of four-level atoms irradiated by three ... more Simultaneous propagation of two probe pulses in a medium of four-level atoms irradiated by three control fields is studied. The double Λ configuration has been closed by a fifth field, coupling the lower levels. It is shown that the propagation can be described in terms of four modes characterized by particular effective susceptibilities, which have absorption or gain peaks and transparency windows. For incoming one-peak pulses, multipeak spectra are built during the propagation including a few components of well-defined frequencies. They evolve along the sample with some of their spectral components being transmitted, absorbed, or amplified.
Pulse propagation is studied in an EIT medium with the control field having a periodically varyin... more Pulse propagation is studied in an EIT medium with the control field having a periodically varying phase (chirp). Based both on numerical calculations and on an approximate approach neglecting absorption and nonadiabatic effects, it is shown that transparency occurs for probe pulses having a sufficiently narrow envelope and an appropriately suited chirp. For other chirped pulses the evolution of their spectra along a sample is studied. Using a projection method one can divide a pulse into a part for which the medium is transparent and a rest for which it is opaque.
The dynamics of the bound state population and the photoelectron energy spectra due to photoioniz... more The dynamics of the bound state population and the photoelectron energy spectra due to photoionization by a double pulse are calculated for a model atomic system. The splitting of the ATI peaks due to the structure of the pulse is presented and discussed. @ 1997 Published by Elsevier Science B.V.
ABSTRACT Photoionization in the regime of the barrier suppression is investigated within a three-... more ABSTRACT Photoionization in the regime of the barrier suppression is investigated within a three-dimensional, fully quantum-mechanical, time-dependent model. It is shown how a structure is formed in the envelope of the above threshold ionization spectra, for energies smaller than the ponderomotive potential. A correspondence between this structure and the shape of the initial-state decay curve, as well as the radial distribution of the electron wave packet, is proven.
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Papers by A. Raczyński