Resonant optical scattering in nanoparticle-doped polymer photonic crystals

Abstract

A broadband hyperspectral technique is used to measure the coherent optical backscatter across a wide spectral bandwidth, showing the resonant suppression of the photon transport mean free path around the photonic bandgap of a shear-assembled polymer photonic crystal. By doping with carbon nanoscale scatterers that reside at specific points within the photonic crystal lattice, the ratio between photon mean free path and optical penetration is tuned from 10 to 1, enhancing forward scatter at the expense of back-scatter. The back-scattering strength of different polarisations is not explained by any current theory.

Broadband coherent backscattering spectroscopy of the interplay between order and disorder in three-dimensional opal photonic crystals

“…50,52,53 Polarization effects have also been found in Ref. 22, where in particular cross-polarized CBS cones were reported. Our measurements of the cross-polarized channel only showed an angle-independent response; no cross-polarized CBS cones were detected.…”

“…A reduction of the enhancement factor below the stop band was also reported in Ref. 22. The ideal enhancement factor of two is expected in any multiple scattering sample, whether absorbing and of finite size or not, as long as the sample obeys reciprocity.…”

“…10, consistent with the behavior reported in other work. 8,22 We see a minimum in the stop gap with two wings of high scattering at the band edges. Inside the stop gap, the Bragg reflection removes intensity from the diffuse scattering.…”

“…6,7,21 Recently the first broadband investigations of opal photonic crystals around the stop band have been reported. 22 Modifications of CBS cones around the photonic stop bands have been observed which were attributed to two contributions related to the modification of the diffuse source by Bragg reflection, and to variations of the internal reflection conditions at the escape angle of the diffuse light, as shown schematically in Fig. 1(b).…”

Disordered packings of core-shell particles with angle-independent structural colors

“…An alternative approach that does not involve making a disordered system is to dope ordered structures (colloidal crystals) with nanoparticles [12], which act as scattering sites. The structural color in all of these materials -bird feathers, binary packings, photonic glasses, and nanoparticle-doped crystals -is not due to Bragg reflection, which requires a weakly scattering system with long-range order, but is instead a result of scattering with a strong wavelength dependence [7,11,13] that arises from correlations in the colloidal structure. Thus the production of synthetic materials with angle-independent color requires control over both scattering and correlations.…”