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1.
We analyze light self-confinement induced by multiple nonlinear resonances in a two-dimensional chi(2) photonic crystal. With reference to second-harmonic generation in a hexagonal lattice, we show that the system can not only support two-color (1+1)D solitary waves with enhanced confinement and steering capabilities but also enable novel features such as wavelength-dependent soliton routing. 相似文献
2.
In an amplifier, nonlinear feedback from mismatched backward second-harmonic generation leads to strong enhancement of parametric conversion. With reference to LiNbO(3) quasi-phase-matched waveguides, we propose a parametric bistable device that operates simultaneously in two colors and in the cw or the self-pulsed regime. 相似文献
3.
Alfredo De Rossi Gaetano Assanto Stefano Trillo William E. Torruellas 《Optics Communications》1998,150(1-6):390-398
We have identified a family of (2+1)D spatial solitary waves which can stably propagate in bulk media in the presence of coexisting diffraction, self-focusing Kerr and quadratic nonlinearities. In a conspicuous range of excitation conditions close to the stationary solutions, the emerging wavepackets are immune to the detrimental occurrence of filamentation and collapse, typical of pure Kerr media. The presence of a second-order contribution to the cubic nonlinear response is, therefore, able to prevent optical damage in applications relying on self-guidance. We show that the cross-phase modulation plays an important effect on stability. Our estimate shows that the effects of the cubic susceptibility cannot be neglected below a certain beam size in realistic crystals (e.g. KTP or similar). 相似文献
4.
Using three-dimensional time-domain numerical simulations of the nonlinear dispersive Maxwell equations for a defect microcavity in a photonic crystal wire, we show that the transmission through the bandgap can be all-optically modulated via the generation of transient states associated with the nonlinear splitting of the defect mode. Analytical results based on time-domain coupled-mode theory are derived as well. 相似文献
5.
A. C. Busacca R. L. Oliveri A. C. Cino S. Riva-Sanseverino A. Parisi G. Assanto 《Laser Physics》2007,17(6):884-888
The compatibility of low concentration (α-phase) proton exchange channel waveguides with electric field surface periodic poling of congruent lithium niobate (SPPLN) crystals has been experimentally demonstrated. With such waveguides, we obtained ultraviolet second harmonic generation (SHG) by first order quasi-phase-matching (QPM), a result made possible by the fabrication, on Z-cut LN crystals, of periodic structures with a pitch down to 750 nm. Nonlinear copropagating QPM-SHG measurements have been carried out on such structures. The pump source was a Ti:sapphire laser with a tunability range of 700–980 nm and a 40 GHz linewidth. We have measured UV continuous wave light at 390 nm by means of a lock-in amplifier and a photodiode with an enhanced response in the UV. The measured conversion efficiency was about 1% W?1 cm?2. 相似文献
6.
U. K. Sapaev I. A. Kulagin T. Usmanov G. Assanto 《Journal of Russian Laser Research》2011,32(1):41-46
We investigate numerically the second-harmonic generation from near infrared 100 fs pulses in periodically and aperiodically poled lithium niobate crystals, taking into account the group-velocity mismatch, the group-velocity dispersion, and self-action effects. For the first time, we show that a tenfold pulse compression can be obtained at both fundamental and second-harmonic frequencies. The mechanism of compression and the pertinent quality factors are discussed. 相似文献
7.
A. Piccardi M. Trotta M. Kwasny A. Alberucci R. Asquini M. Karpierz A. D’Alessandro G. Assanto 《Applied physics. B, Lasers and optics》2011,104(4):805-811
We investigate the propagation of nematicons in various nematic liquid crystals. Following some general considerations on
the role of material parameters in light self-trapping via a reorientational nonlinear response, we discuss numerical results
on light self-action and transverse localization. Finally, we validate our findings with experimental measurements in three
liquid crystalline mixtures featuring different amounts of birefringence. 相似文献
8.
Gaetano Assanto Catherine García-Reimbert Antonmaria A. Minzoni Noel F. Smyth Annette L. Worthy 《Physica D: Nonlinear Phenomena》2011,240(14-15):1213-1219
We investigate the interaction of three optical solitary waves propagating with angular momentum in bulk nematic liquid crystals. The resulting cluster of solitary waves, or nematicons, is shown to orbit about its common centre of “mass”. An elongated isosceles triangle configuration is derived, this solution being the equivalent of the Lagrange solution of Newtonian gravitation. This triangle solution is found to be stable owing to diffractive radiation. A modulation theory explains the existence of the triangle solution as due to the non-monotonicity of an effective potential for the interaction of the solitary waves. This modulation theory also gives good agreement with numerical solutions for the trajectories of the nematicons in the three colours. Finally, it is shown that a cut-off in the shed diffractive radiation prevents the break-up of the triangle due to radiative losses. 相似文献
9.
Barthelemy A. Bourliaguet B. Kermene V. Costantini B. Angelis C. De Modotto D. Assanto G. 《Optical and Quantum Electronics》1998,30(7-10):923-935
We present analytical, numerical and experimental results of the interactions between Type II vectorial spatial solitary waves (QSSW) in second-order non-linear media. We show that the outcome of the interaction can be changed from beam coalescence to steering, crossing or repulsion through a non-coherent control (i.e. the control does not rely on the relative phase between the interacting QSSW). We also provide experimental evidence that both quasi-elastic and inelastic collision between QSSW are feasible in second order non-linear media, depending on the relative velocity of the interacting QSSW. We determine (analytically, numerically and experimentally) the critical transverse velocity for elastic collision to be observed, when the fundamental frequency component of the two interacting beams are orthogonally polarized at the input face of the non-linear crystal. 相似文献
10.
We investigate total internal reflection of nonlocal spatial optical solitons at the interface between two differently oriented regions of a highly birefringent nematic liquid crystal. The solitons survive the interaction with an induced index mismatch and undergo nonspecular reflection, with an emerging angle differing appreciably from the incidence angle. 相似文献