This talk will summarize two distinct research directions, new optical bound states in the continuum based on photonic crystals, and a novel type of transparent display based on resonant nanoparticle scattering.
A bound state in the continuum (BIC) is an unusual localized state lying inside the continuous spectrum normally reserved for spatially extended ones. Even though the concept of BIC was proposed as early as 1929, its realization remains elusive except for trivial cases. Here, we describe optical BIC in general classes of photonic crystal structures [1,2], with one that we characterized and observed experimentally [2]. We also propose a topological interpretation of BIC, where the symmetry and conservation of topological charges can be used to predict the behaviors of these states.
The resonant scattering from nanostrucures is rich in both applications and basic science. Based on the frequency-selective and angle-independent properties of resonant scattering, we come up with a new type of transparent display that features wide viewing angle and scalability to large sizes [3]. Even richer phenomena occur when the nanostructure has multiple resonances. We show that interference between resonances can lead to non-scattering states where light scattering is completely suppressed or dramatically reduced [4].
[1] C.W. Hsu et al, Light: Science & Applications 2, e84 (2013).
[2] C.W. Hsu et al, Nature 499, 188 (2013).
[3] C.W. Hsu et al, Nature Communications 5, 3152 (2014).
[4] C.W. Hsu et al, under review.