Programmable Multiplex Optical Bandpass Filter via Laser Reshaping of Gold Nanostructure

Optical bandpass filters allow or reject a range of wavelengths. Metallic nanorods (NRs) and their assemblies are a promising platform for such components due to their intense light-matter interactions and ability to tune optical cross-section based on the NR's aspect ratio and volume. Fabrication of arbitrary NR filter design however is challenging due to synthetic limitations on aspect ratio and inherent polydispersity. Herein we demonstrate design and fabrication of arbitrary optical notch filters with a flat top profile using new synthetic strategies combined with wavelength selective particle resphaping. Bandwidth and spectral profile is defined by a collection of NRs with narrow longitudinal plasmon resonances (LSPR) that define absorption and sharp roll-off at the filter edges. Laser irradiation transcribes transmission notches by reshaping a population of NRs in resonance with the LSPR. Furthermore, single or multiple transmission windows across the visible to mid-IR can be fabricated using polydisperse NRs or nanowires. Experimental validation of fabrication models confirm rational design of position, depth, and width of the transmission window, enabling manufacturing of complex optical elements (solutions or solid) not found in natural media.