In this paper, the spatially dispersive finite-difference time-domain (FDTD) method in cylindrical coordinates is applied to model the hyperlenses formed by a tapered array of metallic wires. The hyperlens device is modeled using the effective medium theory as a frequency and spatially dispersive dielectric. The gradual increase in spacing between wires along the radial direction of the physical structure is represented by the reduction of plasma frequency of the effective medium. Simulation results show that the image transfer and magnification capability of the hyperlens is insensitive to its transverse dimension. A seven-fold magnification of a subwavelength source distribution transferred to a distance of three wavelengths is demonstrated using a hyperlens with high plasma frequency at its front interface.

A white-light continuum is generated in bulk sapphire using 280 fs, 1053 nm centre wavelength pulses at peak powers well above the critical power. The resulting spectrum extends from 400 nm up to at least 1100 nm with good conversion efficiency. A high-pass filter is used to remove the residual peak at the pump wavelength, producing a broad, flat spectrum in the near infrared region. We characterize the intensity and phase of the continuum by using cross-correlation frequency-resolved optical gating. We show that using pump pulses above 1 µm is a very interesting approach for generating broad continua with favourable characteristics.

Temporal analysis of both the photorefractive mechanism and soliton propagation in a slab semiconductor waveguide is presented. As an example, a structure based on GaAs/AlGaAs MQWs was investigated. Both a numerical and simple analytical approach based on the bipolar band-transport model is used to derive a temporal photorefractive response on localized illumination. The corresponding propagation problem describing the evolution of screening soliton profiles in media with quadratic electro-optic effect was also discussed.

In this paper, we have presented a simple, stable, highly sensitive and timesaving method based on a double-grating interferometer in conjunction with a pump–probe technique for measuring the nonlinear refractive index. A pump laser beam is aligned collinearly with an expanded plane parallel probe beam by a dichroic mirror. These beams pass through the sample, while right behind the sample using a suitable bandpass filter the pump beam is intercepted. The distorted probe beam then passes through a double-grating interferometer. One of the lateral shearing interference patterns is recorded by use of a CCD camera and, after digitization, has been stored in a computer. The interference pattern is analyzed by means of a Fourier transform algorithm. The refractive index changes have been obtained from phase distribution of the recorded fringe patterns. The implementation of the technique is straightforward and the arrangement is very simple and stable yet its sensitivity is comparable...

An experimental system has been set up to determine the coherence lengths of nonlinear optical crystals in the vacuum-ultraviolet (VUV) spectral region by measuring the Maker fringes in the VUV region. Using this system, the Maker fringes generated by frequency conversion from 354.7 to 177.3 nm in the BPO ₄ crystal were obtained and the coherence length corresponding to the nonlinear optical (NLO) coefficient d ₃₆ of the BPO ₄ crystal was determined to be l _c( d ₃₆) = (0.785 ± 0.002) μm. To the best of our knowledge, this is the first time that the coherence length of NLO crystals in VUV was determined by experiment, and the result could be an essential parameter for designing a quasi-phase-matched BPO ₄ device.

We report a theoretical formulation for the nonlinear Kerr-induced focal shift of converging lenses in a high intensity regime. A numerical relation expressing the on-axis intensity of a focused Gaussian beam is derived in the case of a nonlinearly absorbing and diffracting lens induced in a medium. The concept of an effective Fresnel number is used to provide a simple linear relationship between the focal displacement and the nonlinear phase distortions. The influence of nonlinear absorption on the sensitivity of the focal shift measurements is also discussed.

It is very important for daytime Raman lidar measurement of water vapor to determine the parameters of a band-pass filter, which are pertinent to the lidar signal to noise ratio (SNR). The simulated annealing (SA) algorithm method has an advantage in finding the extremum of a certain cost function. In this paper, the Raman spectrum of water vapor is simulated and then a first realization of a simulated annealing algorithm in the optimization of a band-pass filter of a Raman lidar system designed to detect daytime water vapor is presented. The simulated results indicate that the narrow band-pass filter has higher SNR than the wide filter does but there would be an increase in the temperature sensitivity of a narrowband Raman water vapor lidar in the upper troposphere. The numerical simulation indicates that the magnitude of the temperature dependent effect can reach 3.5% or more for narrow band-pass Raman water vapor measurements so it is necessary to consider a new water vapor R...

In this paper, the electric susceptibility of a two-dimensional electron gas (2DEG) system in the presence of the Rashba spin–orbit interaction (RSOI) is calculated by using the quantum Liouville’s density matrix method. A controllable blue-shift with increasing RSOI strength at the resonance frequency of the real and imaginary parts of the susceptibility is obtained. We relate this blue-shift to the broadening of the electron energy levels due to the increasing of the RSOI. Increase of the amplitudes and broadening of the real and imaginary parts of the curves with temperature and loss are also demonstrated respectively.

The authors have previously reported on the micro-machining of intrinsic fibre Fabry–Perot cavities in fused silica optical fibres using a 157 nm excimer laser. The current paper reports on a technique for estimating the depth of the cavity by measuring the transmitted light intensity during the micro-machining of optical fibres using a 157 nm laser. Single and multiple cavities were created in silica and sapphire optical fibres and the feasibility of using micro-machined cavities for monitoring chemicals is demonstrated.

A general procedure is presented for the evaluation of the modes of a thin annular scalar source, whose angular mutual intensity is of the Schell-model type. Starting from the knowledge of the modes, the coherence properties of the field propagated from the source in paraxial conditions can be evaluated. When the propagated field is collimated by a suitable converging lens, presented results apply to the synthesis of propagation-invariant partially coherent beams.