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.     

Optical switching and normal mode splitting in hybrid semiconductor microcavity containing quantum well and Kerr medium driven by amplitude-modulated field

ABSTRACT

We theoretically investigate optical bistability/multistability for all optical switching signature in a hybrid semiconductor microcavity system comprising a quantum well and a Kerr nonlinear substrate. The system is essentially two optically coupled microcavities with one of the microcavity being driven by an external amplitude-modulated pump laser. We show that the switching between bistable and multistable behaviour is influenced by the modulated pump laser, Kerr nonlinearity and the optical coupling between the two microcavities. We further investigate the intracavity spectrum of quantum fluctuations which exhibit the well-known normal mode splitting (NMS). The NMS behaviour is also found to be influenced by the system parameters. These results demonstrate that the present hybrid nonlinear system can be used in designing sensitive optical devices.     

Influence of elasticity and dynamic surface tension on the wave motion spectrum of a charged liquid surface

It is shown that the combined influence of the relaxation of viscosity and surface tension on the position of the boundary of the capillary wave spectrum established in a system is not a simple summation of each effect separately because of the nonlinearity of the dispersion equation in the corresponding physical parameters. Pis’ma Zh. Tekh. Fiz. 23, 32–37 (August 26, 1997)     

Nonlinear quantum optical computing via measurement

Abstract

We show how the measurement induced model of quantum computation proposed by Raussendorf and Briegel (2001, Phys. Rev. Letts., 86, 5188) can be adapted to a nonlinear optical interaction. This optical implementation requires a Kerr nonlinearity, a single photon source, a single photon detector and fast feed forward. Although nondeterministic optical quantum information proposals such as that suggested by KLM (2001, Nature, 409, 46) do not require a Kerr nonlinearity they do require complex reconfigurable optical networks. The proposal in this paper has the benefit of a single static optical layout with fixed device parameters, where the algorithm is defined by the final measurement procedure.     

Fock states generation in a kicked cavity with a nonlinear medium

Abstract

We discuss a model of a cavity filled with a passive nonlinear ?Kerr‘ medium and periodically kicked by a series of ultra-short laser pulses. The nonlinear medium is described by the (2q ? 1)th nonlinearity X ^(2q?1). We find analytical formulas describing the field states inside the cavity. We show that such a system can produce, depending on the order of the nonlinearity, superpositions of several Fock states with the small photon numbers (0,1; 0,1,2; etc). In particular, the one-photon state can be approached during the evolution of the system with X ⁽³⁾ nonlinearity provided the cavity losses are negligible. The purity of states generated in this process, however, can be seriously degraded by the cavity damping. We perform numerical calculations to validate our analytical results.     

Population trapping in the Jaynes-Cummings model with a Kerr nonlinearity in the cavity

Abstract

An electromagnetic field state is found which maintains the population inversion of the atom stationary during the interaction with the field through a Jaynes-Cummings model (JCM) with a Kerr type nonlinearity in the cavity. The condition of stationarity of the population inversion includes the phase coupling of atomic dipole with the field. We have shown that the Kerr nonlinearity in the cavity field significantly modifies the photon statistics of the trapped field state through an intensity dependent detuning in the field compared to the normal JCM trapping state. We have also demonstrated the novel features of sub-Poissonian character and the squeezing of the trapped field state. The dynamics of the initial trapped field is studied in terms of squeezing and the Q-function.     

Periodic and solitary wave solutions for ultrashort pulses in negative-index materials

Abstract

We present a detailed analysis for the existence of dark and bright solitary waves as also fractional-transform solutions in a nonlinear Schrödinger equation model for competing cubic–quintic and higher-order nonlinearities with dispersive permittivity and permeability. Parameter domains are delineated in which these ultrashort optical pulses exist in negative-index materials (NIMs). For example, dark solitons exist for the case of normal second-order dispersion, anomalous third-order dispersion, self-focusing Kerr nonlinearity, and non-Kerr nonlinearities, while the bright solitons exist for the case of anomalous second-order dispersion, normal third-order dispersion, self-focusing Kerr nonlinearity, and non-Kerr nonlinearities. This is contrary to the situation in ordinary materials.     

Spatiotemporal Dynamics of Optical Parametric Oscillators

Abstract

The coupling of diffraction and the x ⁽²⁾ nonlinearity is shown to lead to pattern formation in parametric oscillators in optical cavities. In particular the threshold for the generation of signal and idler waves is lowered by an off-axis emission for negative detunings. The output intensity is spatially modulated just above threshold while more complicated patterns appear for larger values of the pump amplitude. Competition between domains of rolls with different orientations leads to long transients until boundary effects prevail. In the case of finite-size input beams, the roll orientation is locally perpendicular to the boundary and the pattern tends to rotate. Finally, the effect of spatial structures on the spectrum of quantum fluctuations of the vacuum is considered and discussed.     

Instabilities of Lateral Modes in Semiconductor Fabry-perot Interferometers

Abstract

The stability of the transverse fluctuations in the semiconductor Fabry-Perot interferometer with concentration mechanism of optical nonlinearity is investigated. We take into consideration spatio-temporal medium dynamics. The conditions of static stratification and exciting of transverse waves of the envelope field and concentration were found. Some nonlinear structures which arose as the result of instability development were simulated.     

Characterisation of heterogeneous microstructure in large forged products using nonlinear ultrasonic method

ABSTRACT

A comparative study between the ultrasonic attenuation and the nonlinearity is presented for the characterisation of microstructure in large dimension forgings. Results are provided for two austenitic stainless steel forgings of AISI type 304L with a diameter 200?mm, where microscopic observations reveal abnormal grain growth near the surface of one of the forgings. Frequency dependence of the nonlinearity parameter is used to discern variations in grain size in these forgings more precisely than attenuation measurements. The distribution of grain size is shown to have a significant influence on the nonlinearity parameter. Relative changes in the nonlinearity parameter with applied frequency were correlative with the microstructural variations in both the forgings.     

Nonlinear Optical Properties of a Soluble Form of Polyisothionaphthene

Abstract

The third-order nonlinearity of a low-bandgap conjugated organic polymer has been assessed. Degenerate four-wave mixing experiments (at 1·064 μm using picosecond pulses from a passively mode-locked neodymium-doped yttrium aluminium garnet laser) on solutions of the polymer have permitted the determination of the microscopic third-order nonlinearity γ. The polymer exhibits unusual behaviour which is solution concentration dependent. This behaviour is thought to be due to aggregation effects and strongly suggests that the bulk response of the material is large, the third-order nonlinearity being of the order of ten times greater than that of polythiophene.     

Noiseless amplification in cavity-based optical systems with an internal two-photon process. I. General approach

Abstract

We study the features of noiseless amplification in a general class of optical systems, characterized by an intracavity nonlinearity which induces a two-photon process, in the limit where the damping constant of the mode which undergoes the two-photon process greatly exceeds all other relaxation rates of the system. By applying a previously formulated analytical approach, we write the universal-form expressions for the linear amplification factor and the noise figure. Noiseless amplification is attainable under resonance conditions.     

Nonlinearity-induced Modes and the Frequency Response of Coupled Nonlinear Fabry-Pérot Cavities

Abstract

We study the frequency response of a system of two coupled Kerr nonlinear cavities with the same or opposite signs of nonlinearity. In the framework of a slowly varying envelope approximation, we show the possibility of having various hysteresis loops in the transmission characteristics of the structure. We also investigate the power-dependent modes of the structure. For large powers we demonstrate the existence of new modes which do not have any linear analogue. These nonlinearity-induced modes show up in the multistable output when the input power is varied.     

Second-harmonic Generation in Glass Fibres

Abstract

Experiments on frequency doubling of 1064 nm and 1053 nm radiation with non-phase-matched and (close to) phase-matched germania-doped silica fibres are reported. The greatest conversion efficiencies are obtained with non-phase-matched fibres that are single-mode at the second-harmonic wavelength, in which phase-matching is thought to arise from a self-written grating. Competition between grating self-writing and self-erasure in these fibres in the absence of an external seed is also reported. Phase-matched fibres allow the formation of the nonlinearity to be studied independently of the phase matching. The nonlinearity is optically induced by exposing the fibre to short-wavelength visible radiation. An enhancement of 10⁴ to 10⁵ in conversion efficiency between the fundamental and the phase-matched LP₃₁ second-harmonic mode over the intrinsic background second harmonic has been observed. We also report on the occurrence of phase-matched second-harmonic generation (SHG) and non-phase-matched SHG in the same fibre.     

Dynamics of self-similar sub-10-fs-pulses in an inhomogeneous highly nonlinear fibre amplifier

ABSTRACT

We study the propagation of ultrashort pulses of width around sub-10 femtosecond in an inhomogeneous highly nonlinear single-mode fibre within the framework of a generalized higher-order nonlinear Schrödinger equation with derivative non-Kerr nonlinear terms and spatially inhomogeneous coefficients. Additional effects to the cubic model include the distributed third-order dispersion, self-steepening, self-frequency shift due to stimulated Raman scattering, quintic nonKerr nonlinearity, derivative non-Kerr nonlinear terms, and gain or loss. The exact self-similar brightand dark-solitary-wave solutions of the governing equation are derived via a transformation connected with the constant-coefficient higher-order nonlinear Schrödinger equation with non-Kerr nonlinearity. The constraint relations among the optical fibre parameters for the existence of these self-similar structures are also discussed. Based on these exact solutions, we investigate the dynamical behaviours of self-similar localized pulses in a periodic distributed fibre system for different parameters.     

Comparisons of spectra determined using detector atoms and spatial correlation functions

Abstract

We show how two level atoms can be used to determine the local time dependent spectrum. The method is used in a one-dimensional cavity. The spectrum obtained is compared with the mode spectrum determined using spatially filtered second-order correlation functions. The spectra obtained using two level atoms give identical results with the mode spectrum. One benefit of the method is that only one time averages are needed. It is closely related to a realistic spectrum measurement.     

Self-deflection of Three-dimensional Optical Beams by a Thin Nonlinear Layer with Saturable Dispersive and Absorptive Nonlinearity

Abstract

This paper describes self-deflection effects arising from the propagation of symmetric and asymmetric three-dimensional scalar optical beams through thin nonlinear layers. The model of nonlinearity used includes both saturation and absorption. In several cases, significant differences are observed between the present three-dimensional results and previous two-dimensional results based on the Kerr model of nonlinearity. Also, the existence of a large axial component of the self-deflected beam for a three-dimensional geometry against the absence of this component for a two-dimensional geometry is discussed.     

Optical solitons for cascaded system: Jacobi elliptic functions

Abstract

In this work, the coupled NLSE is studied that appears in a cascased system. Exact solutions of this coupled system acquire by using Jacobi elliptic functions. The presented system will be studied with two forms of nonlinearity. The forms are kerr law and power law. Dark, bright, singular solitons and Jacobi elliptic solutions will be acquired. We present constraint conditions for the existence of obtained solitons. Our obtained solitons will be controlled by changing the diffraction coefficients.     

Surface light waves on the boundary of a photorefractive crystal with a diffusion-drift nonlinearity mechanism

All the possible types of surface light wave that can exist on the boundary of a photorefractive uniaxial crystal with a diffusion-drift nonlinearity mechanism are identified. It is shown that by varying the magnitude and direction of an external electric field E₀ one can control both the parameters and the type of the surface wave. In the particular case of zero field E₀ (the diffusion nonlinearity mechanism) the general solution agrees with the solution obtained in Ref. 5. Pis’ma Zh. Tekh. Fiz. 23, 31–36 (June 26, 1997)     

Study on the spectrum of phase fractal structure

Abstract

In this paper, the term of phase fractal structure is presented. The Cantor relief structure was designed and fabricated by photolithography. We derived its recurrence formulas for the Fourier spectrum function and pointed out that its power spectrum is composed of two parts, the spectrum for the main structure and the spectrum for the accompanying structure. The power spectrum of six concurrent generations and the experimental power spectrum are also illustrated and its characteristics are analysed.