Paper published as part of the special topic on Emerging Directions in Plasmonics Note: This paper is part of the JCP Special Topic on Emerging Directions in Plasmonics.

We report a large chiro-optical response from a nanostructured film of aperiodic dielectric helices decorated with ellipsoidal metal nanoparticles. The influence of the inherent fabrication variation on the chiro-optical response of the wafer-scalable nanostructured film is investigated using a computational model which closely mimics the material system. From the computational approach, we found that the chiro-optical signal is strongly dependent on the ellipticities of the metal nanoparticles and the developed computational model can account for all the variations caused by the fabrication process. We report the experimentally realized dissymmetry factor ∼1.6, which is the largest reported for wafer scalable chiro-plasmonic samples till now. The calculations incorporate strong multipolar contributions of the plasmonic interactions to the chiro-optical response from the tightly confined ellipsoidal nanoparticles, improving upon the previous studies carried in the coupled dipole approximation regime. Our analyzes confirm the large chiro-optical response in these films developed by a scalable and simple fabrication technique, indicating their applicability pertaining to manipulation of optical polarization, enantiomer selective identification and enhanced sensing and detection of chiral molecules.

Materials and devices for artificial synapse are being increasingly investigated owing to their promise for brain-inspired computing. Here, we demonstrate an optoelectronic synapse with light-modulated memory capability in back-gated ferroelectric channel field-effect transistors made of multi-layered 2D α-In2Se3 on Ta2O5. The optical tunability is achieved by exploiting the frequency of the optical signal in vertically stacked layers of In2Se3, which generate a unique persistent photoresponse due to trapping at the In2Se3/Ta2O5 interface. For the 527nm source wavelength at intensities of 15 mW/cm2, the In2Se3-FET exhibits a high photoresponsivity at 850 AW1. These devices can replicate synaptic functions such as photo-induced short-term memory and long-term memory, paired-pulse facilitation – all via optical modulation. We have also demonstrated common memory effects that occur in the brain such as memory loss, memory transitions that depend upon the stimulation rate (i.e., the interval between stimulation pulses). These demonstrations provide a simple and effective strategy for fabricating light-stimulated synaptic transistors with memory and learning ability which are attractive for building vision-inspired neuromorphic systems.

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Recent interests in layered transition-metal dichalcogenides (TMDCs), such as WSe2, MoS2, etc., arise due to their attractive electrical, optical, and mechanical properties with potential applications in energy storage, generation, and many more. Embedding these 2D materials in plasmonic cavities can further enhance light-matter interactions and alter their properties, resulting in diverse and efficient optoelectronic applications. The strain due to the geometry and charge transfer due to the plasmonic materials can further modify the TMDCs’ optical response for sensing applications and as single photon emitters in on-chip optoelectronic applications. This work discusses one such 2D-plasmonic hybrid configuration of a silver sphere on a gold disc with WSe2 sandwiched in between. We perform non-invasive Raman and PL studies of this system to estimate the field enhancement and discuss strain and doping induced in the TMDC.

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