Leaky-mode resonance photonics: technology for biosensors, optical components, MEMS, and plasmonics

Resonant leaky modes can be induced on dielectric, semiconductor, and metallic periodic layers patterned in one or two dimensions. Potential applications include bandpass and bandstop filters, laser mirrors, ultrasensitive biosensors, absorption enhancement in solar cells, security devices, tunable filters, nanoelectromechanical display pixels, dispersion/slow-light elements, and others. As there is now a growing realization worldwide of the utility of these devices, it is of interest to summarize their physical basis and present their applicability in photonic devices and systems. In particular, we have invented and implemented highly accurate, label-free, guided-mode resonance (GMR) biosensors that are being commercialized. The sensor is based on the high parametric sensitivity inherent in the fundamental resonance effect. As an attaching biomolecular layer changes the parameters of the resonance element, the resonance frequency (wavelength) changes. A target analyte interacting with a bio-selective layer on the sensor can thus be identified without additional processing or use of foreign tags. Another promising pursuit in this field is development of optical components including wideband mirrors, filters, and polarizers. We have experimentally realized such devices that exhibit a minimal layer count relative to their classical multilayer thin-film counterparts. Theoretical modeling has shown that wideband tuning of these filters is achievable by perturbing the structural symmetry using nano/microelectromechanical (MEMS) methods. MEMS-tuned resonance elements may be useful as pixels in spatial light modulators, tunable lasers, and multispectral imaging applications. Finally, mixed metallic/dielectric resonance elements exhibit simultaneous plasmonic and leaky-mode resonance effects. Their design and chief characteristics is described.