Ultrathin broadband reflective optical limiter

TL;DR

This paper presents an ultrathin broadband reflective optical limiter that uses VO2's insulator-to-metal transition to achieve high on-off transmittance ratios, offering a simple, fast, and wideband solution for protecting sensitive optical components.

Contribution

The authors demonstrate a novel, ultra-thin reflective optical limiter utilizing VO2's phase transition, overcoming fabrication complexity and bandwidth limitations of previous multilayer structures.

Findings

Achieved high on-off transmittance ratios with low-Q resonators.

Operates broadband over > 2 μm wavelength range.

Maintains performance at incident angles up to 50 degrees.

Abstract

Optical limiters are nonlinear devices that feature decreasing transmittance with increasing incident optical intensity, and thus can protect sensitive components from high-intensity illumination. The ideal optical limiter reflects rather than absorbs light in its active ("limiting") state, minimizing risk of damage to the limiter itself. Previous efforts to realize reflective limiters were based on embedding nonlinear layers into relatively thick multilayer photonic structures, resulting in substantial fabrication complexity, reduced speed and, in some instances, limited working bandwidth. We overcome these tradeoffs by using the insulator-to-metal transition in vanadium dioxide (VO2) to achieve intensity-dependent modulation of resonant transmission through aperture antennas. Due to the dramatic change of optical properties across the insulator-to-metal transition, low-quality-factor resonators were sufficient to achieve high on-off ratios in device transmittance. As a result, our ultra-thin reflective limiter (thickness ~1/100 of the free-space wavelength) is broadband in terms of operating wavelength (> 2 um at 10 um) and angle of incidence (up to ~50$\deg$ away from the normal).