Saturation and bistability of defect-mode intersubband polaritons

TL;DR

This paper investigates the linear and nonlinear optical behaviors of intersubband cavity polaritons in a defect-mode photonic crystal, demonstrating saturation and bistability phenomena at high cooperativity levels.

Contribution

It introduces a defect-mode photonic crystal slab with tunable Q-factor, enabling control over polariton nonlinearities and revealing bistability at the crossover between coupling regimes.

Findings

High cavity Q-factor (up to 85) achieved.

Observation of sharp saturation and bistability of polaritons.

Nonlinear effects occur at the weak-strong coupling crossover.

Abstract

In this article we report about linear and nonlinear optical properties of intersubband cavity polariton samples, where the resonant photonic mode is a defect state in a metallo-dielectric photonic crystal slab. By tuning a single geometric parameter of the resonator, the cavity Q-factor can reach values as large as 85, with a consequent large cooperativity for the light-matter interaction. We show that a device featuring large cooperativity leads to sharp saturation, or even bistability, of the polariton states. This nonlinear dynamics occurs at the crossover between the weak and the strong coupling regimes, where the weak critical coupling concept plays a fundamental role.