Omni-resonant optical micro-cavity

TL;DR

This paper introduces a novel achromatic optical micro-cavity that achieves broadband transparency by angular multiplexing, enabling resonant enhancement over wide spectral ranges in ultrathin photonic devices.

Contribution

It demonstrates a bio-inspired grating design that creates a continuous, broadband resonance in a planar Fabry-Perot cavity, breaking the traditional narrow linewidth limitation.

Findings

Achromatic transmission over a 60-nm spectral range achieved.

Resonance bandwidth decoupled from photon lifetime.

Potential for broad-bandwidth optical enhancement in ultrathin devices.

Abstract

Optical cavities are a cornerstone of photonics. They are indispensable in lasers, optical filters, optical combs and clocks, in quantum physics, and have enabled the detection of gravitational waves. Cavities transmit light only at discrete resonant frequencies, which are well-separated in micro-structures. Despite attempts at the construction of `white-light cavities', the benefits accrued upon optically interacting with a cavity -- such as resonant field buildup -- have remained confined to narrow linewidths. Here, we demonstrate achromatic optical transmission through a planar Fabry-Perot micro-cavity via angularly multiplexed phase-matching that exploits a bio-inspired grating configuration. By correlating each wavelength with an appropriate angle of incidence, a continuous spectrum resonates and the micro-cavity is rendered transparent. The locus of a single-order 0.7-nm-wide resonance is de-slanted in spectral-angular space to become a 60-nm-wide achromatic resonance spanning multiple cavity free-spectral-ranges. This approach severs the link between the resonance bandwidth and the cavity-photon lifetime, thereby promising resonant enhancement of linear and nonlinear optical effects over broad bandwidths in ultrathin devices.