For selected device concepts that are members of an evolving class of photonic devices enabled by guided-mode resonance (GMR) effects, we review physics of operation, design, fabrication, and characterization. We summarize the application potential of this field and provide new and emerging aspects. Our chosen examples include resonance elements with extremely wide reflection bands. Thus, in a multilevel structure with conformal germanium (Ge) films, reflectance exceeds 99% for spectral widths approaching 1100 nm. A simpler design, incorporating a partially etched single Ge layer on a glass substrate, exhibits a high-reflectance bandwidth close to 900 nm. We present a couple of interesting new device concepts enabled by GMRs coexisting with the Rayleigh anomaly. Our example Rayleigh reflector exhibits a wideband high-efficiency flattop spectrum and extremely rapid angular transitions. Moreover, we show that it is possible to fashion transmission filters by excitation of leaky resonant modes at the Rayleigh anomaly in a subwavelength nanograting. A unique transmission spectrum results, which is tightly delimited in angle and wavelength as experimentally demonstrated. We update our application list with new developments including GMR-based coherent perfect absorbers, multiparametric biosensors, and omnidirectional wideband absorbers.
We theoretically explain and experimentally demonstrate light trapping in thin-film solar cells through guided-mode resonance (GMR) effects. Resonant field enhancement and propagation path elongation lead to enhanced solar absorption. We fabricate nanopatterned solar cells containing embedded 300-nm period, one-dimensional gratings. The grating pattern is fabricated on a glass substrate using laser interference lithography followed by a transparent conducting oxide coating as a top contact. A ∼320-nm thick p-i-n hydrogenated amorphous silicon solar cell is deposited over the patterned substrate followed by bottom contact deposition. We measure optical and electrical properties of the resonant solar cells. Compared to a planar reference solar cell, around 35% integrated absorption enhancement is observed over the 450 to 750-nm wavelength range. This light-management method results in enhanced short-circuit current density of 14.8 mA/cm 2 , which is a ∼40% improvement over planar solar cells. Our experimental demonstration proves the potential of simple and well-designed GMR features in thin-film solar cells.
We present measured optical and electrical characteristics of guided-mode resonant hydrogenated amorphous silicon (a-Si:H) thin-film solar cells. Nano-patterns with a 300-nm period and a 50-nm grating depth are fabricated on glass
substrates, followed by the deposition of a transparent conducting oxide layer as a top contact. About 320-nm thick p-i-n thin-film a-Si:H solar cell is deposited on indium-tin-oxide coated glass substrate, followed by the deposition of a
bottom contact layer. Compared to a planar reference solar cell, ~40% integrated absorption enhancement is observed for the 450–750-nm wavelength range. Short circuit current density of the nano-patterned solar cell is obtained as 14.1mA/cm2, which is ~50% improvement over the reference planar cell.