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Register a new userStimulated Globular Scattering of Laser Radiation in Photonic Crystals: Temperature Dependences
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Added by
Nikolay Tcherniega V.
Publication date
2007
fields
Physics
and research's language is
English
Authors
V. S. Gorelik
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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 with 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.
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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.
We describe a smooth transition from (fully ordered) photonic crystal to (fully disordered) photonic glass that enables us to make an accurate measurement of the scattering mean free path in nanostructured media and, in turn, establishes the dominant role of the density of states. We have found one order of magnitude chromatic variation in the scattering mean free path in photonic crystals for just $sim 3%$ shift around the band-gap ($sim 27$ nm in wavelength).
We demonstrate that photonic crystals can be used to generate powerful and highly coherent laser radiation when injecting a beam of free electrons. Using theoretical investigations we present the startup dynamics and coherence properties of such laser, in which gain is provided by matching the optical phase velocity in the photonic crystal to the velocity of the electron beam.
We clarify theoretically that the topological ring-cavity (TRC) modes propagating along the interface between two honeycomb-type photonic crystals distinct in topology can be exploited for achieving stable single-mode lasing, with the maximal intensity larger than a whispering-gallery-mode counterpart by order of magnitude. Especially, we show that the TRC modes located at the bulk bandgap center benefit maximally from the gain profile since they are most concentrated and uniform along the ring cavity, and that, inheriting from the Dirac-like dispersion of topological interface states, they are separated in frequency from each other and from other photonic modes, both favoring intrinsically single-mode lasing. A TRC mode running in a specific direction with desired orbital angular momentum can be stimulated selectively by injecting circularly polarized light. The TRC laser proposed in the present work can be fabricated by means of advanced semiconductor nanotechnologies, which generates chiral laser beams ideal for novel photonic functions.
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 describe 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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