Retroreflection of light from nanoporous InP: correlation with high absorption

Abstract

Pronounced retroreflection behavior is reported for a fishnet nanoporous strongly absorbing semiconductor material. Retroreflection appears along with diffusive specular reflection for all angles of incidence for light wavelength corresponding to interband optical transitions, where absorption coefficient is of the order of 10 5 cm -1 (green and red light). Retroreflection is apparent by the naked eye with daylight illumination and exhibits no selectivity with respect to wavelength and polarization of incident light featuring minor depolarization of retroreflected light. Retroreflection vanishes for wavelength corresponding to optical transparency range where photon energy is lower than the InP bandgap (1.064 lm). The phenomenon can be classified neither as coherent backscattering nor as Anderson localization of light. The primary model includes light scattering from strongly absorptive and refractive super-wavelength clusters existing within the porous fishnet structure. We found that retroreflection vanishes for wavelength where absorption becomes negligible.

Anomalous retroreflection from nanoporous materials as backscattering by ‘dark’ and ‘bright’ modes

“…Due to these regularities it was possible to observe the phenomenon of anomalous retroreflection in a strongly absorbing nanostructured medium in a wide frequency range [9,10] upon illumination of samples by sun radiation. The performed analysis allows one to put forward the hypothesis that at ε 1 ?ε 2 in 'tracery' nanostructures fulfilling the condition of f o =1, but made from nanostructured dissipating materials (for instance, from metals or carbon nanotubes) with a high degree of ordering, there should be no any reflected transverse waves.…”

“…It was suggested that the observed phenomenon can be classified neither as coherent backscattering nor as Anderson localization of light, since strong absorption inhibits multiple reflection, the necessary prerequisite for coherent backscattering and Anderson localization. Pronounced correlation of the phenomenon with strong absorption has been further established experimentally [10].…”

“…In this paper, we propose an explanation of the mechanism of anomalous retroreflection observed in [9,10] on the basis of formation of both 'dark' and 'bright' modes in a nanoporous strongly absorbing semiconductor material. The proposed model explains also the observed peculiarities of the anomalous retroreflection, namely correlation with strong absoprtion and differences for s-and p-polarizations of incident radiation.…”

Possible coherent backscattering of lightwaves from a strongly absorbing nanoporous medium

“…In recent work, we have reported on the unusual effect of pronounced retroreflection from a nanoporous semiconductor material (InP) in the spectral range of the interband transitions with a simultaneously high refractive index (n= 3.8) and absorption coefficient (α=10 5 cm −1 ) [18]. The effect was experimentally proved to vanish for weakly absorbed light (when photon energy is less than the band gap energy, E g ) [19]. Retroreflection was observed with coherent and incoherent, monochromatic and wide-band radiation and was apparent to the naked eye with sunlight.…”

Preparation and novel photoluminescence properties of the self-supporting nanoporous InP thin films

“…In recent years, III-V semiconductors have been widely used in microelectronics and optoelectronic devices [1][2][3][4][5][6][7][8] . In particularly, indium phosphide (InP), which is a well-known direct bandgap semiconductor, has attracted great attention in optoelectronic devices 1,2,7 .…”