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Effective light polarization insensitive and omnidirectional properties of Si nanowire arrays developed on different crystallographic planes
摘要： In this paper, fabrication of vertical Si nanowire arrays (SiNWAs) by a facile metal assisted electroless etching approach on different crystallographic planes of Si has been reported. A very low specular reflectance (Rspec) of 0.04% and 0.03% has been achieved in the whole visible range for SiNWAs grown on Si(100) and Si(111) oriented substrates, respectively. High broadband enhancement has been detected for vertical SiNWAs due to multiple scattering paths inside the nanowire arrays. On the other hand, inclined nanowires showed a fascinating behavior at the longer wavelength regime, where light gets the longer path to reflect back-forth and ease to reflect back outward at normal incidence. Moreover, for [100] SiNWAs, transverse electric (TE) field component demonstrates the strong polarization insensitive properties at the expense of transverse magnetic (TM) field component with a minimum reflectance of < 2% up to 1200 nm. The [100] SiNWAs demonstrates extra-ordinary omnidirectional properties at θB ≥ 58o. Theoretical validation of COMSOL with an effective medium approach reveal the effective dipole coupling and the presence of strong absorption modes for vertical SiNWs at a typical wavelength regime. The highly bound states of the particle tunneling through classical forbidden region shows a strong enhancement in light absorption effect.
关键词： nanocavities,Si nanowires,light coupling effect,omnidirectional,polarization
更新于2025-09-23 15:22:29
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Single-photon superradiance in waveguide-quantum-electrodynamical systems with whispering-gallery-mode resonators
摘要： As a manifestation of cooperative interactions between a single photon and a cluster of atoms, single-photon superradiance has attracted considerable attention recently but has been studied insofar as that only quantum emitters are involved in the superradiance process. Here we expand the scope of investigation to study single-photon superradiance in a waveguide-quantum-electrodynamical system containing whispering-gallery-mode (WGM) resonators which are essential for many nanophotonic devices. It is shown analytically and numerically that single-photon superradiance can also occur when WGM resonators are present. The criteria for the emergence of the superradiant emission peak and the enhanced atom-light coupling strength are derived. Finally, the general case of a cascade of WGM resonators is investigated by a renormalization approach. Single-photon frequency comb generation is demonstrated via a frequency-modulated superradiant effective atom in chiral waveguide-quantum-electrodynamical systems with WGM resonators.
关键词： single-photon superradiance,whispering-gallery-mode resonators,atom-light coupling,waveguide-quantum-electrodynamical systems,frequency comb generation
更新于2025-09-23 15:19:57
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Coupling and Trapping of Light in Thin-Film Solar Cells Using Modulated Interface Textures
摘要： Increasing the e?ciency of solar cells relies on light management. This becomes increasingly important for thin-?lm technologies, but it is also relevant for poorly absorbing semiconductors like silicon. Exemplarily, the performance of a-Si:H/μc-Si:H tandem solar cells strongly depends on the texture of the front and rear contact surfaces. The rear contact interface texture usually results from the front surface texture and the subsequent absorber growth. A well-textured front contact facilitates light-coupling to the solar cell and light-trapping within the device. A variety of di?erently textured ZnO:Al front contacts were sputter deposited and subsequently texture etched. The optical performance of a-Si:H/μc-Si:H tandem solar cells were evaluated regarding the two e?ects: light-coupling and light-trapping. A connection between the front contact texture and the two optical e?ects is demonstrated, speci?cally, it is shown that both are induced by di?erent texture properties. These ?ndings can be transferred to any solar cell technologies, like copper indium gallium selenide (CIGS) or perovskites, where light management and modi?cations of surface textures by subsequent ?lm growth have to be considered. A modulated surface texture of the ZnO:Al front contact was realized using two etching steps. Improved light-coupling and light-trapping in silicon thin-?lm solar cells lead to 12.5% e?ciency.
关键词： thin-?lm solar cell,light-trapping,ZnO:Al,front contact,light-scattering,surface texture,light-coupling
更新于2025-09-16 10:30:52