Plasmonic nanostructures can efficiently absorb and scatter light, and thus exhibit vibrant colors. Colors originate from the excitation of plasmon resonances – collective oscillations of free electrons in metallic nanoparticles. Semicontinuous metal films (SMF) are a special type of disordered plasmonic structures that can be mass-produced in a rather inexpensive physical vapor deposition process. SMFs are comprised of random in their nature nano-island structures of various sizes and shapes resonating at different wavelengths. When irradiated with high-intensity laser radiation, the nanostructures can be locally modified. Spatially local restructuring originates from highly localized SMF absorption of light in hotspots, regions of a high local electric field. Thus, the optical response of the film can be altered in a spectrally selective manner. Hence, locally different colors are obtained. In this work, we demonstrate the generation of structural plasmonic colors through femtosecond laser-induced modification of thin semicontinuous aluminum films deposited on an aluminum mirror coated with an isolator layer. The structures show vivid colors in reflection. The effects of laser parameters on final color are explored. In addition, we report laser-induced control of diffuse reflectance of aluminum SMF structures. Self-passivation effect of aluminum results in the long-term stability of generated colors.
In this work we, propose a tunable 2D-hydrid epsilon-near-zero (ENZ) platform in telecom windows. Taking advantage to the intrinsically ENZ of the Indium-thin-oxide (ITO) and exploiting the graphene capability to dynamically tune the plasmon polaritons we were able to adjust the cross-over frequency, where the epsilon vanishes, in four telecom bandwidth windows. Additionally, tunabilty can be achieved via electrical gating of the ITO leading to an interplay modulation of the surface plasmon polaritons at the graphene-ITO interface. Furthermore, a giant Purcell factor (PF) was observed at ENZ regimes. These results show how 2D-hybrid ENZ materials potentially find applications in multifunctional nonlinear nanophotonic systems such as ultrafast modulators, data processing and photonic quantum computers (QPCs).
In this paper a two liquid crystal (LC) modulators for mid-wave infrared radiation (MWIR) are presented. A two electrooptical effects (EOE) in liquid crystalline structures have been utilized for MWIR modulation: electric field induced cholesteric - nematic (Ch-N*) phase transition (ChN mode) and switching of the twisted-nematic (TN) structure (TN mode). At the Ch-N* mode an intensity modulation depth was of order of 15% but there wasn’t a dark state. In case of the modulation induced at TN mode was near full. These modulators are quite slow, switching times are order of a few hundreds of milliseconds for Ch-N* mode electrooptical effect and dozens of minutes in case of TN mode.
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