Development of optical dark-state resonance sensor chips

The objective of this Phase II project is to develop advanced, innovative optical sensor technology based on resonant photonic lattices. In brief, subwavelength photonic lattices can be designed to generate out-of-plane resonance radiation producing versatile nonconventional spectra. By tailoring one-dimensional or two-dimensional periodic films, high-efficiency output radiation is enabled by bright or dark resonant channels. The bright channel populates under guided-mode resonance (GMR) whereas the dark channel exists via a bound state in the continuum (BIC). The dark state can be reached by breaking local lattice symmetry relative to the incident wave. We engage two dissimilar unexplored concepts to effectively induce dark state resonance and apply them to realize compact sensor platforms. As a first method, we engage the angular spectrum inherent in transversely finite (Gaussian) beams of light. Related initial theoretical and experimental results show promise and support the proposal effort by reducing risk. By illuminating an array of microlenses with a beam of normally-incident white light, hundreds of Gaussian beams are immediately generated. Each of these interacts with a matched photonic lattice and generates a dark-state resonance whose details depend on the Gaussian beam characteristics and lattice design. As a second method, we propose to include structural defects in resonance lattices to bring out the dark-state resonance. This idea is grounded in substantive theoretical modeling that shows the existence of such states at defects. The radiation channel thus fashioned is then useful in generating the optical waves that convert changes in any analytes to be detected to changes in light-based signals. Under the project, dark-state sensors will be designed using rigorous numerical methods for both the finite-beam and defect-state concepts. Compact sensor arrays having a single period will be fabricated with laser interference lithography. High-density sensor chips with each sub-sensor having a different period will be fabricated with electron-beam lithography enabling expeditious readout of all the sub-sensors simultaneously with a spectrum analyzer. The dark-state sensors explained and proposed excel on account of being lossless, compact, economic, power-tolerant, and lightweight. We will determine the technical feasibility of the proposed concepts. We will design, fabricate, and test sensor arrays containing hundreds of individual sensors on a chip with the size of a US penny. The team has complete analytical and experimental tooling to accomplish the proposed research.