Eleana Makri

Reflective Optical Limiter Based on Resonant Transmission

Optical limiters transmit low-level radiation while blocking electromagnetic pulses with excessively high energy (energy limiters) or with excessively high peak intensity (power limiters). A typical optical limiter absorbs most of the high-level radiation which can cause its destruction via overheating. Here we introduce the novel concept of a reflective energy limiter which blocks electromagnetic pulses with excessively high total energy by reflecting them back to space, rather than absorbing them. The idea is to use a defect layer with temperature dependent loss tangent embedded in a low-loss photonic structure. The low energy pulses with central frequency close to that of the localized defect mode will pass through. But if the cumulative energy carried by the pulse exceeds certain level, the entire photonic structure reflects the incident light (and does not absorb it!) for a broad frequency window. The underlying physical mechanism is based on self-regulated impedance mismatch which increases dramatically with the cumulative energy carried by the pulse.

Experimental Realization of a Reflective Optical Limiter

We report the first realization of a reflective optical limiter, which transmits low-level radiation while offering broadband reflection for high-intensity beams. The design consists of a nonlinear lossy defect embedded in a multilayer photonic structure.

Hypersensitive Transport in Photonic Crystals with Accidental Spatial Degeneracies

A localized mode in a photonic layered structure can develop nodal points (nodal planes), where the oscillating electric field is negligible. Placing a thin metallic layer at such a nodal point results in the phenomenon of induced transmission. Here we demonstrate that if the nodal point is not a point of symmetry, then even a tiny alteration of the permittivity in the vicinity of the metallic layer drastically suppresses the localized mode along with the resonant transmission. This renders the layered structure highly reflective within a broad frequency range. Applications of this hypersensitive transport for optical and microwave limiting and switching are discussed.

Waveguide Photonic limiters based on topologically protected resonant modes

We propose a concept of chiral photonic limiters utilizing topologically protected localized midgap defect states in a photonic waveguide. The chiral symmetry alleviates the effects of structural imperfections and guarantees a high level of resonant transmission for low intensity radiation. At high intensity, the light-induced absorption can suppress the localized modes, along with the resonant transmission. In this case the entire photonic structure becomes highly reflective within a broad frequency range, thus increasing dramatically the damage threshold of the limiter. Here we demonstrate experimentally the loss-induced reflection principle of operation which is at the heart of reflective photonic limiters using a waveguide consisting of coupled dielectric microwave resonators.

Topologically induced optical limiter

The emerging field of topological photonics aims to realize photonic structures which are resilient to fabrication imperfections by utilizing ideas developed in topology[1]. In photonics, the topological phases are defined on the reciprocal space and usually are associated with the formation of topologically protected (TP) defect states within photonic band-gaps. In this endeavor the manipulation of various symmetries have been proven extremely useful. An example case are resonator arrays with chiral symmetry where a topological defect state appears to be insensitive to positional imperfections of the resonators[2]. By connecting the chiral symmetric array to leads, the TP defect mode turns to a quasi-localized resonant mode enabling the realization of a new class of reñective waveguide photonic limiters[3].

Reflective optical limiter based on gallium arsenide

We show that a photonic structure composed of silicon dioxide, silicon nitride, and gallium arsenide layers can act as a reflective optical limiter at near-infrared wavelengths. The limiter transmits low intensity light while totally reflecting high intensity laser radiation, thereby protecting the limiter and the sensor from overheating and destruction.