Light transport regimes in slow light photonic crystal waveguides

Abstract

The dispersive properties of waves are strongly affected by inevitable residual disorder in man-made propagating media, in particular in the slow wave regime. By a direct measurement of the dispersion curve in k space, we show that the nature of the guided modes in real photonic crystal waveguides undergoes an abrupt transition in the vicinity of a band edge. Such a transition that is not highlighted by standard optical transmission measurement, defines the limit where k can be considered as a good quantum number. In the framework of a mean-field theory we propose a qualitative description of this effect and attribute it to the transition from the "dispersive" regime to the diffusive regime. In particular we prove that a scaling law exists between the strength of the disorder and the group velocity. As a result, for group velocities v g smaller than c / 25 the diffusive contribution to the light transport is predominant. In this regime the group velocity v g loses its relevance and the energy transport velocity v E is the proper light speed to consider.

Slow-light-enhanced gain in active photonic crystal waveguides

“…It is well known that as the band edge is approached, scattering losses are enhanced due to slow-light propagation [28][29][30][31] . This loss enhancement was included phenomenologically using a thirdorder polynomial dependency on n g .…”

“…With present technology, passive PhC waveguides exhibit a propagation loss of B2 dB mm À 1 in the conventional 'fast-light' region, while propagation losses strongly depend on n g in the slow-light regime 28 . Even though the propagation loss therefore is much higher than for well-designed ridge waveguides, a positive net gain coefficient up to B700 cm À 1 is measured (Fig.…”

Statistics of Anderson-localized modes in disordered photonic crystal slab waveguides

“…With regards to waveguide geometries, PC slab waveguides (PCWs) have attracted much attention as a platform for single photon generation 12,13 , optical buffering 14 , and for enhancing non-linear optical processes in the slow-light regime [15][16][17] However, PCWs are known to be extremely sensitive to fabrication disorder [18][19][20] , which becomes relevant for practical applications [21][22][23] . Interestingly, structural disorder in PCs can also induce coherent scattering of light 24 , giving rise to the formation of random cavities where the field can be strongly localized, leading to the quasi-1D Anderson localization regime 2,25 .…”

Enhanced spontaneous emission from quantum dots in short photonic crystal waveguides

“…[10][11][12][13][14] In this work we examine a mixed approach where a combination of the slow-light effect with cavity enhancement is achieved by embedding semiconductor quantum dots in short (10-25 m) PhC WGs. In these short PhC WGs the localization due to disorder is not expected to occur since the PhC WG length becomes smaller than the photon localization length.…”