Broadly wavelength-tunable bandpass filters based on long-range surface plasmon-polaritons

Broad spectral tunability is a desired feature of many photonic and plasmonic components, such as optical filters, semiconductor lasers, and plasmonic materials. Here I show that unique properties of long-range surface plasmon polaritons (LR SPP) allow one to produce optical components with very wide tuning range using small variations in the refractive index of the dielectric cladding material. As a proof-of-concept demonstration, I present operation of LR-SPP-based bandpass optical filters in which a 0.004 variation in the refractive index of the cladding dielectric translates into 210 nm of bandpass tuning at telecom wavelengths. The tuning mechanism proposed here may be used to create monolithic bandpass filters with tuning range spanning over more than an optical octave, compact and widely-tunable diode and quantum cascade laser systems, multi-spectral imagers, and other plasmonic components with broadly-tunable optical response.