Optical Modulation Due to Energy Exchange Between Photonic and Exciton Modes in the Intermediate Coupling Regime

TL;DR

This paper demonstrates a tunable optical modulation mechanism in the near-infrared region based on energy exchange between photonic and exciton modes in an intermediate coupling regime, enabling broadband signal control.

Contribution

The study introduces a novel scheme utilizing intermediate exciton-photon coupling in NIR-absorbing materials for dynamic optical modulation.

Findings

Energy exchange process depends on detuning between excitonic and photonic modes.

Near resonance, a crossover regime exhibits distinct energy exchange behavior.

The approach enables broadband optical modulation into the NIR spectral region.

Abstract

Actively tunable photonic devices are vital for next-generation optoelectronics requiring rapid switching and high bandwidth. Although organic optoelectronic devices have found wide application, their use as optical modulators has been limited by low absorption in the critical near-infrared (NIR) region, slow response time, and weak nonlinearities. To address these limitations, we developed a scheme based on intermediate exciton-photon coupling in a NIR absorbing squaraine-dye based photonic structure. Using energy-momentum resolved pump-probe spectroscopy, we show that the sign and magnitude of the optical response of our system depends strongly on the energy detuning between the excitonic and photonic modes. These data are analyzed using temporal coupled-mode theory to show that near resonance, a distinct energy exchange process emerges in the cross-over regime between strong and weak light-matter coupling. This effect enables dynamical control over the photoinduced response, providing a pathway for broadband optical signal modulation extending into the NIR spectral region.