Highly directive light sources using two-dimensional photonic crystal slabs

Abstract

We have designed a microcavity with periodic microstructure that extracts nearly all the power emitted by a luminescent source and confines 80% of the energy radiated in the superstrate in a cone of half width 0.2° about the normal of the device.

Photonic-crystal GaN light-emitting diodes with tailored guided modes distribution

“…[3][4][5] Two schemes can be considered for PhC-assisted LEDs: formation of band gaps to prevent emission into guided modes, 6 or PhCs acting as diffraction gratings to extract guided light. [7][8][9][10][11] While good results have been reported regarding the former scheme for low-temperature photoluminescence experiments, 12 extension to room temperature may be limited by increased loss due to nonradiative recombination. Hence, we focus on the second scheme, using PhCs as diffraction gratings for guided modes.…”

“…One is the azimuthal anisotropy of the PhC ͑e.g., which crystal directions can extract light͒ and another is parasitic diffraction to the substrate, as additional diffraction orders can couple guided light to substrate light. 8,11 We believe that future efforts addressing these points are the path to ultraefficient PhC LEDs.…”

Efficient optimization method for the light extraction from periodically modulated LEDs using reciprocity

“…Good results have been obtained by random surface roughening [1], but there is also much interest in periodic structures i.e. two-dimensional gratings (photonic crystals) [2][3][4]6,7]. In unpatterned LEDs, the light is mostly trapped by total internal reflection and it radiates primarily from the sides of the device.…”

Combinations of low/high permittivity and/or permeability substrates for highly directive planar metamaterial antennas

“…The structures considered here consist of a grounded metamaterial layer that may have either high or low values of permittivity and/or permeability, excited by either an electric or a magnetic dipole source. Such structures are different from those where a cavity is created under a partially reflective surface that is formed by highpermittivity dielectrics [5][6][7], metallic FSS layers [8,9] or other periodic dielectric structures [10,11]. Although different in structure, the metamaterial antennas considered in this work are similar in terms of the mechanism of radiation: in fact, all the antennas in [1 -11] radiate a narrow beam because the feed excites slowly attenuating leaky waves, as demonstrated in the work of Lovat et al [4] and Jackson and Oliner [6].…”