Large-area lithography-free perfect absorbers, color filters, and photodetectors at visible frequencies using ultra-thin silver or amorphous silicon films (Presentation Recording)

Plasmonic materials and metamaterials have been widely utilized to achieve spectral transmission, reflection and absorption filters based on localized or delocalized resonances arising from the interaction of photons with nanoscale patterns. However, the realization of visible-frequency, high-performance, large-area, optical filters based on nanoplasmonic materials is rather challenging due to nanofabrication related problems (cost, fabrication imperfection, surface roughness) and optical losses of metals. Here, we propose and demonstrate large-area perfect absorbers and transmission color filters and photodectors that could overcome the difficulties associated with nanofabrication using a lithography-free approach. Our resonant flat optical design is based on a modified, asymmetric metal-insulator/semiconductor-metal (MI/SM) based Fabry-Perot cavity incorporated with plasmonic, lossy ultra-thin (~ 30 nm) Ag or (~ 5-15 nm) amorphous Si films. We demonstrated a narrow bandwidth (~17 nm) super absorber with 97% maximum absorption with a performance comparable to nanostructure/nanoparticle-based super absorbers. We also investigated transmission filters in which different colors can be obtained by controlling the spacer thickness of silicon dioxide or amorphous silicon. With measured performance of transmission peak intensity reaching 60% and a narrow-band of ~ 40 nm, our color filters exceed the performance of widely studied plasmonic nanohole array based color filters and make a good candidate for large-area narrow-band photodetection devices. Such plasmonic loss incorporated Fabry-Perot cavities using ultra-thin metallic or semiconductor films could suggest active and practical applications in spectrally selective optical (color and absorber) filters, optoelectronic devices with controlled bandwidth such as narrow-band photodetectors, and light-emitting devices.