Optical Double-resonance Spectra with Time-dependent Pulses

Abstract

The optical double-resonance spectrum for a three-level atom interacting with two monochromatic laser pulses with arbitrary temporal profiles is calculated by use of Light's perturbation theory. Unlike some earlier work, the theory is not restricted to exact resonance of the pump laser, or to pulse areas which are exact multiples of 2π. A variety of pulse profiles are investigated, and the spectra are found to depend strongly on the detuning of the pump laser.     

Mid/far-infrared few-cycle-pulse emission via resonant mixing in semiconductor heterostructures

Abstract

Mid/far-infrared emission from a semiconductor multiple quantum well structure under femtosecond optical pulse excitation is studied. It is shown that resonant nonlinear-wave mixing in the quantum wells can be used for the generation of ultra-short mid/far-infrared pulses with a duration of a few cycles or even a single cycle. Explicit analytical formulas for the mid/far-infrared radiation field and polarization in a simple three-level model of a quantum well are presented and compared with numerical simulations. The power of the mid/far-infrared emission and the down conversion efficiency of the resonant nonlinear-wave mixing are discussed.     

The dynamics of the electron in a homonuclear driven molecular ion

Abstract

The radiation diffused by a one-dimensional homonuclear molecular ion driven by a laser field is studied as a function of the time. When the photon energy is resonant with the energy gap between the ground and the first excited state, the electronic probability density is seen to undergo slow and deep oscillations between the two nuclei. Synchronous to such oscillations, deep modulations of the emitted power are observed. The period of oscillation is of the order of 10 optical cycles. Detection of the variation in the intensity of the emitted electromagnetic spectrum therefore brings information on the position of the electron in the molecule.     

Meetings Calendar

Abstract

In this Letter, we report on the generation of pulses as short as 18 fs by means of an optimized two-stage optical fibre-grating pair and high-order soliton-effect pulse compressor. These are the shortest pulses yet reported in the near-infrared spectral region and correspond to four optical cycles at 1·32 μm.     

Crystallographic orientation dependence of bulk optical rectification

Abstract

We present a study on the use of bulk optical rectification (difference frequency mixing (DFM) for the generation of terahertz (THz) pulses. The emitted radiation field is calculated and measured at normal and off-normal incidence for a wide range of GaAs samples with different surface orientations. The dependence of the visible-to-THz conversion efficiency on the crystallographic orientation is determined.     

Emission Spectra of a Two-level Atom in a Kerr-like Medium

Abstract

We have investigated the spectrum of light emitted by a single atom interacting with a single mode of the radiation field in an ideal cavity filled with a Kerr-like medium. It is shown that owing to the Kerr-like nonlinearity in the system the spectrum of the emitted light exhibits a single-peaked structure for sufficiently high intensities of the initial coherent field instead of the triplet structure in the case of the standard Jaynes-Cummings model.     

Two-photon excitation of atoms by ultrashort electromagnetic pulses in a discrete spectrum

Abstract

The paper is devoted to the theoretical investigation of two-photon excitation of atom in a discrete energy spectrum by ultrashort electromagnetic pulses of femto- and subfemtosecond ranges of durations. An analytical expression for the total probability of the process is derived. Numerical simulations are made for hydrogen and sodium atoms. It is shown that the total probability of the process is nonlinear function of pulse duration and character of this function depends strongly on the frequency detuning of pulse carrier frequency from two-photon resonance.     

Quantum theory of light in nonlinear media with dispersion and absorption

Abstract

We present a canonical quantum theory of radiation in nonlinear media taking into account the effects of linear dispersion and absorption in a consistent way. We start from a microscopic model and apply recently developed concepts of the quantization of radiation in dispersive and absorbing linear media and extend the theory in order to include nonlinear optical processes. We derive propagation equations in space and time for the quantized radiation field, with special emphasis on the propagation of quantum-light pulses in Kerr media. In particular, the method enables us to derive systematically the noise sources that arise naturally in the nonlinear terms.     

Are Free-free Transitions a Good Basis for Nonlinear Optics?

Abstract

It is known that a low-frequency light induces very efficient transitions between the continuous spectrum states of an atom. We show, however that these transitions are not effective sources of nonlinear optical processes, such as generation of higher harmonics of the low frequency light.     

Generation of Optical Harmonics by Intense Pulses of Laser Radiation

Abstract

We discuss effects of optical depth, beam focusing and non-perturbative atomic response on the spectrum of optical harmonics generated by an intense beam of laser radiation (up to 10¹⁴W cm^?2) in a small volume of atomic vapour. We find remarkable enhancement of high harmonics at intensities beyond the perturbative limit.     

The Interaction of Displaced Number State and Squeezed Number State Fields with Two-level Atoms

Abstract

The time-evolution of a single two-level atom in a single-mode high-Q cavity is sensitive to the quantum fluctuations of the cavity radiation field and to its photon statistics: this sensitivity is realizable experimentally in the Rydberg atom micromaser. We study the effects of the interaction of a two-level atom with two new non-classical radiation fields: the squeezed number state and the displaced number state realizable by nonlinear and linear transformations of field number states which have an initially precise occupation number. The time-varying field fluctuations caused by the atomic interaction are described using the Q-function quasi-probability.     

Introduction of color centers in fluorinated sol gel quartz glasses by radiation thermal treatment

Data are presented to show how fluorination influences the optical quality and radiation resistance of quartz glasses fabricated by the sol gel method. It is found that under the action of gamma radiation, mainly E′ centers form in the glasses. The incorporation of fluorine in the xerogel lattice promotes the removal of hydroxyl groups and enhances the radiation optical resistance of the synthesized samples in the red. It is observed that the radiation resistance of the glass is enhanced in the ultraviolet by using irradiation-annealing cycles and this is attributed to a decrease in the concentration of radiation-induced E′ centers. Pis’ma Zh. Tekh. Fiz. 23, 74–79 (December 26, 1997)     

Formation of quasisteady supersonic flow with a pulse-periodic plasma heat source

An analysis is made of experimental data on the influence of a pulse-periodic optical discharge in a supersonic argon stream on the aerodynamic drag of streamlined objects. The interrelation established between the parameters of the laser radiation and the stream is used to determine the threshold frequency of the laser pulses which determines the transition to quasi-steady-state flow. Pis’ma Zh. Tekh. Fiz. 24, 8–13 (August 26, 1998)     

Transitions in Presence of Short Laser Pulses

Abstract

Accurate numerical calculations are carried out to investigate the validity of the two-state approximation in the case of resonant interactions between electromagnetic radiation and atoms. Short pulses are considered and the presence of the atomic spectrum is modelled by introducing a third, non-resonant, state. We show that the harmonics of the pulse profile may play a significant role in the dynamics of the process and may cause energy non-conserving transitions between the atomic states.     

Computation of the Optical Constants of a Thin Dielectric Layer from the Envelopes of the Transmission Spectrum,at Inclined Incidence of the Radiation

Abstract

A mathematical expression for the transmission of a thin dielectric layer on a transmitting substrate is found. The finite dimensions of the substrate and its absorption are taken into account. The cases of inclined incidence of non-polarised, s- and p-polarised radiation to the layer are investigated. A way of determining the optical constants n(λ) and k(λ) of the layer from the envelopes of the transmission spectrum is offered. Computation of n(λ) and k(λ) of a model optical system at different angles of radiation incidence is performed as well as analysis of the results obtained.     

Quantum Optics with One Atom in an Optical Cavity

Abstract

The quantum mechanical master equation for a single two-level atom in a single-mode optical cavity is numerically solved in both the quantum and the semiclassical limits. The quantum limit of few cavity photons shows semiclassically forbidden behaviour such as steady state two-level population inversion. Qualitatively new fluorescent spectra, having sidebands broadened by the cavity interaction, also occur. The quantum theory of the single-atom laser with injected signal is presented. At the interface between its quantum and semiclassical dynamics we elucidate the signature of semiclassical limit cycles.     

High-power broad-band single-mode InGaAsP/InP superluminescent diode

An InGaAsP/InP separate-confinement double heterostructure having a broad gain profile was used to fabricate superluminescent diodes having high optical power (40 mW), a broad radiation spectrum (65 nm at half-width), and low percent modulation (<1%). Using a cw pump current of 150 mA, 1mW of superluminescence radiation was obtained at the exit from a single-mode optical fiber. Pis’ma Zh. Tekh. Fiz. 25, 16–22 (August 12, 1999)     

Emission spectrum of a Λ-type three-level atom driven by the squeezed coherent field and grey-body radiation field

Abstract

By means of quantum electrodynamics, an analytical expression of emission spectrum for a Λ-type three-level atom with the two non-degenerate lower levels in the cavity is given. The character of the emission spectrum for the input in pure number state, a squeezed coherent state and grey-body state are exhibited. The effects of the atomic initial state, the field property, the cavity absorptivity and the system temperature on the time-dependent physical spectrum are analysed.     

Shapes of laser radiation pulses modified by nonlinear scattering in aqueous suspension of carbon nanotubes

An improved scheme of z-scanning was used to study the parameters of nanosecond 1064-nm laser radiation pulses scattered at right angle under the conditions of optical limiting in an aqueous suspension of purified carbon nanotubes (CNTs). CNTs were synthesized by the electric-arc evaporation of graphite. It is established that the amplitude, shape, duration, and temporal position of the peak of scattered light pulses significantly depend on the laser radiation power density. The results agree with the mechanism of thermoinduced nonlinear scattering that is operative during the optical limiting of laser pulses in CNT suspensions.     

A scheme for the simultaneous measurement of atomic position and momentum

Abstract

We propose an optical scheme for the simultaneous measurement of the position and momentum of a single atom. The scheme involves the coupling of the atom of two light fields with different spatial and polarization characteristics. The proposed technique is closely related to the Arthurs-Kelly measurement scheme; the principal difference is that in the present case the values of the position and momentum are inferred from phase shifts in electromagnetic fields rather than from shifts in the position of a pointer.