Influence Of Phase Mismatch Research Articles

Exchange of optical vortices using an electromagnetically-induced-transparency–based four-wave-mixing setup

We propose a scheme to exchange optical vortices of slow light using the phenomenon of electromagnetically induced transparency in a four-level double-$\mathrm{\ensuremath{\Lambda}}$ atom-light coupling scheme illuminated by a pair of probe fields as well as two control fields of larger intensity. We study the light-matter interaction under the situation where one control field carries an optical vortex, and another control field has no vortex. We show that the orbital angular momentum (OAM) of the vortex control beam can be transferred to a generated probe field through a four-wave-mixing process and without switching on and off of the control fields. Such a mechanism of OAM transfer is much simpler than in a double-tripod scheme in which the exchange of vortices is possible only when two control fields carry optical vortices of opposite helicity. The losses appearing during such OAM exchange are then calculated. It is found that the one-photon detuning plays an important role in minimizing the losses. An approximate analytical expression is obtained for the optimal one-photon detuning for which the losses are minimum while the intensity of generated probe field is maximum. The influence of phase mismatch on the exchange of optical vortices is also investigated. We show that in presence of phase mismatch the exchange of optical vortices can still be efficient.

Influence of pump-field scattering on nonclassical-light generation in a photonic-band-gap nonlinear planar waveguide

Optical parametric process occurring in a nonlinear planar waveguide can serve as a source of light with nonclassical properties. The properties of the generated fields are substantially modified by scattering of the nonlinearly interacting fields in a photonic-band-gap structure inside the waveguide. A general quantum model of linear operator amplitude corrections to the amplitude mean values and its numerical analysis provide conditions for efficient squeezed-light generation as well as generation of light with sub-Poissonian photon-number statistics. The destructive influence of phase mismatch of the nonlinear interaction can fully be compensated using a suitable photonic-band-gap structure inside the waveguide. Also an increase of the signal-to-noise ratio of the incident optical field can be reached in the waveguide.

Spatial trapping of short pulses in Ti-indiffused LiNbO_3 waveguides

We show numerically and experimentally that spatial trapping can be induced in quadratic media even if the pump pulse's duration is shorter than the group-delay mismatch between fundamental wave and second-harmonic components. The influence of phase mismatch and pulse power on the trapping effect is discussed. Spatial, temporal, and spectral behaviors that accompany self-trapped propagation are highlighted.

Third-harmonic generation in the field of ultrashort laser pulses in leaky modes of a gas-filled hollow fibre

The influence of phase mismatch, group delay, andoptical losses of waveguide modes on third-harmonic generation in a hollow fibre is investigated. An analytical solutionto the equation governing the slowly varying envelope of thethird-harmonic pulse in a leaky mode of a gas-filled hollowfibre is derived. Optimal conditions for third-harmonic generation in such a fibre are determined for different pump pulsedurations and various rare gases.

Strong-interaction approximation in the theory of second harmonic generation of intense short laser pulses

The method of strong interaction of nonlinear waves has been developed to analyse the second harmonic generation of intense laser radiation in the transient regime. Analytic solution for frequency conversion efficiency – taking into account the pump radiation depletion, influence of phase mismatch, dispersion of group velocities and higher nonlinearities – has been first obtained. A comparison of theoretically derived results and known experimental data has been conducted, and a general agreement of these results has been obtained. The optimal conditions of the second harmonic generation of neodymium laser radiation into femtosecond pulse duration range have been determined.

Influence of phase mismatch on a spectral inverter based on four-wave mixing in dispersion-shifted fiber at 10 Gb/s

We investigate the influence of phase mismatch on the performance of a spectral inverter based on four-wave mixing in a commercial dispersion-shifted fiber. The inverter operates at 10 Gb/s. When the pump wave is tuned /spl plusmn/0.3 mn around the zero-dispersion wavelength of the fiber, the power penalty at 10/sup -9/ bit-error rate remains within the range of 1-2 dB, although the conjugate power is reduced considerably by almost 6 dB. A numerical calculation of the inverter's efficiency is also presented, which takes into account longitudinal variation of the zero-dispersion wavelength along the fiber.

Power exchange between generated frequencies in single-mode optical fibers

The stimulated four-photon mixing process may generate multiple new frequencies from a single input in single-mode optical fibers operating in the minimum-dispersion region. The coupled power equations that describe this process show an aperiodic exchange of power between the generated frequencies. We investigate this behavior numerically and find that the process is chaotic. We also examine the influence of phase mismatch on power exchange.

Influence of phase mismatching in a nonlinear crystal and in air on intracavity frequency conversion of ultrashort pulses

A theoretical analysis is made of intracavity second harmonic generation of ultrashort laser pulses under conditions of active modulation for the cavity (resonator) losses. An allowance is made of the changes in the phases of the light waves at the fundamental and second-harmonic frequencies in a nonlinear crystal and in air. It is shown that both linear and nonlinear changes in the phases of the light waves during the interaction process have a strong influence on the time characteristics and on the efficiency of second harmonic generation: the shape of the pulses of the fundamental-frequency wave becomes strongly distorted and a complex time structure is formed in the case of the second harmonic pulses. The solution of the problem makes it possible to find the conditions under which minimal distortions occur in the shape of the pulses of the converted radiation but the conversion efficiency remains maximal.

The influence of phase mismatch on pulse shapes in second-harmonic generation

The influence of phase mismatch on pulse shapes in second-harmonic generation