Light generation at the anomalous dispersion high energy range of a nonlinear opal film

Abstract

Abstract:We study experimentally and theoretically light propagation and generation at the high energy range of a close-packed fcc photonic crystal of polystyrene spheres coated with a nonlinear material. We observe an enhancement of the second harmonic generation of light that may be explained on the basis of amplification effects arising from propagation at anomalous group velocities. Theoretical calculations are performed to support this assumption. The vector KKR method we use allows us to determine, from the linear response of the crystal, the behavior of the group velocity in our finite photonic structures when losses introduced by absorption or scattering by defects are taken into account assuming a nonzero imaginary part for the dielectric constant. In such structures, we predict large variations of the group velocity for wavelengths on the order or smaller than the lattice constant of the structure, where an anomalous group velocity behavior is associated with the flat bands of the photonic band structure. We find that a direct relation may be established between the group velocity reduction and the enhancement of a light generation processes such as the second harmonic generation we consider. However, frequencies for which the enhancement is found, in the finite photonic crystals we use, do not necessarily coincide with the frequencies of flat high energy bands. ©2009 Optical Society of America

Self‐Assembled Photonic Structures

“…For example enhanced second harmonic generation was measured for silicon‐SiO2498 and YIG‐SiO2 composite opals 499. This enhanced SHG has been recently measured in polystyrene artificial opals, where the spheres were coated with a non linear molecule 500…”

Linear and Nonlinear Optical Properties of Colloidal Photonic Crystals

“…Although the first studies attributed the enhancement of nonlinearities in the PhCs exclusively to birefringence or to phase matching, , which should be strongly influent in the case of the more exotic nonlinear PhCs, ,, in recent publications the effect of the group velocity ( v g ) has acquired more importance. This effect has been specifically studied in slow-light waveguides. , …”

“…In another experiment performed in 2009 also by the group of Martorell, the effect of the PhBG at the wavelength corresponding to the fundamental beam was studied. Polystyrene spheres (380 nm diameter) coated with Crystal Violet, modified to allow chemical bonding, were deposited, forming a photonic crystal with a band gap centered at 810 nm.…”

Optical Properties of Porous Alumina Assisted Niobia Nanostructured Films–Designing 2-D Photonic Crystals Based on Hexagonally Arranged Nanocolumns

“…[ 137 ]. An explanation for it was given later, and at present, this phenomenon serves both as a means of studying the properties of materials and is used in photonics [ 138 , 139 ].…”