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تسجيل مستخدم جديدStimulated globular scattering and photonic flame effect: new nonlinear optics phenomena
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Novel nonlinear optical phenomena - photonic flame effect (PFE) and stimulated globular scattering (SGS) are discussed.PFE consisted in the appearance of the few seconds duration emission in blue-green spectral range under 20 ns ruby laser pulse excitation and simultaneous excitation of several spatially separated synthetic opal crystalls situated on the Cu plate. SGS was observed both in forward and backward directions. Spectral and energetical SGS characteristics were measured.
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The results of the spectral, energetical and temporal characteristics of radiation in the presence of the photonic flame effect are presented. Artificial opal posed on Cu plate at the temperature of liquid nitrogen boiling point (77 K) being irradiat
ed by nanosecond ruby laser pulse produces long- term luminiscence with a duration till ten seconds with a finely structured spectrum in the the antistocks part of the spectrum. Analogous visible luminescence manifesting time delay appeared in other samples of the artificial opals posed on the same plate. In the case of the opal infiltrated with different nonlinear liquids the threshold of the luminiscence is reduced and the spatial disribution of the bright emmiting area on the opal surface is being changed. In the case of the putting the frozen nonlinear liquids on the Cu plate long-term blue bright luminiscence took place in the frozen species of the liquids. Temporal characteristics of this luminiscence are nearly the same as in opal matrixes.
We observed new effect which we called photonic flame effect (PFE). Several 3-dimensional photonic crystals (artificial opals) were posed on Cu plate at the temperature of liquid nitrogen (77K). Typical distance between them was 1-5 centimeters. Long
-continued optical luminescence was excited in one of them by the ruby laser pulse. Analogous visible luminescence manifesting time delay appeared in other samples of the crystals. Experiments were realized for opal crystals and for nanocomposites (opals filled with nonlinear liquids).
Stimulated globular scattering (SGS) characteristics (frequency shifts, threshold, conversion efficiency) have been studied in photonic crystals (synthetic opal matrices and opal nanocomposites) at different temperatures. Results have been compared w
ith stimulated Raman scattering investigations in calcite single crystals. In both cases temperature lowering from +20 C to -196 C resulted in the stimulated scattering energy increase and its redistribution to the higher order components.
Highly selective and reconfigurable microwave filters are of great importance in radio-frequency signal processing. Microwave photonic (MWP) filters are of particular interest, as they offer flexible reconfiguration and an order of magnitude higher f
requency tuning range than electronic filters. However, all MWP filters to date have been limited by trade-offs between key parameters such as tuning range, resolution, and suppression. This problem is exacerbated in the case of integrated MWP filters, blocking the path to compact, high performance filters. Here we show the first chip-based MWP band-stop filter with ultra-high suppression, high resolution in the MHz range, and 0-30 GHz frequency tuning. This record performance was achieved using an ultra-low Brillouin gain from a compact photonic chip and a novel approach of optical resonance-assisted RF signal cancellation. The results point to new ways of creating energy-efficient and reconfigurable integrated MWP signal processors for wireless communications and defence applications.
We compute the SBS gain for a metamaterial comprising a cubic lattice of dielectric spheres suspended in a background dielectric material. Theoretical methods are presented to calculate the optical, acoustic, and opto-acoustic parameters that describ
e the SBS properties of the material at long wavelengths. Using the electromagnetic and strain energy densities we accurately characterise the optical and acoustic properties of the metamaterial. From a combination of energy density methods and perturbation theory, we recover the appropriate terms of the photoelastic tensor for the metamaterial. We demonstrate that electrostriction is not necessarily the dominant mechanism in the enhancement and suppression of the SBS gain coefficient in a metamaterial, and that other parameters, such as the Brillouin linewidth, can dominate instead. Examples are presented that exhibit an order of magnitude enhancement in the SBS gain as well as perfect suppression.
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