Selective-frequency-gap-induced negative anisotropic scattering in designer photonic structures with short-range order

Polymer-based self-assembled photonic crystals to tune light transport and emission

“…4c. The measured reflectivity spectrum confirms the presence of a (111) stop gap in the light transport at B610 nm, which agrees well with a first-order stop gap at 0.6 a/l in the GL direction. Similarly, reflectivity spectra acquired in the high-energy region indicate the existence of high-order stop gaps in the GL direction.…”

“…Optical reflectivity and transmission experiments are performed using commercial spectrophotometers. The (111) stop gap at near-normal incidence for a self-assembled photonic crystal composed of PS microspheres with a diameter of 280 nm features as a peak (trough) in the reflectivity (transmission) spectrum, as shown in Fig. 4c.…”

“…In self-assembled photonic crystals with fcc symmetry, photonic stop gaps originate from Bragg diffraction related to the fcc crystal planes; hence, the stops gaps are both angle-and orientation-dependent. Self-assembled photonic crystals are inevitably grown with (111) planes stacked on top of each other. The scanning electron microscopy (SEM) image shown in Fig.…”

“…The scanning electron microscopy (SEM) image shown in Fig. 4a displays the hexagonal packing of polystyrene (PS) microspheres forming the (111) plane of the fcc lattice on the top surface and in the bulk of the photonic crystal sample. This image also highlights the hexagonal facet of the Brillouin zone of the crystal with fcc symmetry with the relevant high-symmetry points.…”

“…The generation of a stop gap relating to light transport is evident in the measured reflectivity and transmission spectra. Upon the normal incidence of light, a photonic stop gap is obtained for the [111] direction. The light incidence angle is varied away from the normal to access stop gaps based on crystal planes with other orientations.…”