Polarization-Controlled Cavity Input-Output Relations

TL;DR

This paper demonstrates that in strong-scattering cavity systems, the input-output relations differ significantly from traditional models, allowing for polarization-controlled tailoring of the cavity's transmission properties, with experimental validation.

Contribution

It introduces a new understanding of cavity input-output relations in the strong-scattering regime and shows how they can be manipulated via polarization control.

Findings

Over 90% coupling efficiency achieved in strong-scattering regime.

CIOR can be tailored by controlling scattering strength.

Experimental spectra show polarization-dependent bandpass and bandstop behavior.

Abstract

Cavity input-output relations (CIORs) describe a universal formalism relating each of the far-field amplitudes outside the cavity to the internal cavity fields. Conventionally, they are derived based on a weak-scattering approximation. In this context, the amplitude of the off-resonant field remains nearly unaffected by the cavity, with the high coupling efficiency into cavity modes being attributed to destructive interference between the transmitted (or reflected) field and the output field from the cavity. In this Letter, we show that, in a whispering gallery resonator-waveguide coupled system, in the strong-scattering regime, the off-resonant field approaches to zero, but more than 90% coupling efficiency can still be achieved due to the Purcell-enhanced channeling. As a result, the CIORs turn out to be essentially different than in the weak-scattering regime. With this fact, we propose that the CIOR can be tailored by controlling the scattering strength. This is experimentally demonstrated by the transmission spectra exhibiting either bandstop or bandpass-type behavior according to the polarization of the input light field.