Intensity fluctuations in bimodal micropillar lasers enhanced by quantum-dot gain competition

TL;DR

This paper studies intensity fluctuations and mode competition in a bimodal micropillar laser with quantum-dot gain, revealing anti-correlated mode behavior and switching dynamics through experiments and theoretical modeling.

Contribution

It provides a combined experimental and theoretical analysis of mode competition and intensity fluctuations in bimodal quantum-dot micropillar lasers, extending existing models to two interacting modes.

Findings

Photon bunching and anti-correlation between modes.

Mode switching behavior near threshold.

Qualitative agreement with microscopic semiconductor theory.

Abstract

We investigate correlations between orthogonally polarized cavity modes of a bimodal micropillar laser with a single layer of self-assembled quantum dots in the active region. While one emission mode of the microlaser demonstrates a characteristic s-shaped input-output curve, the output intensity of the second mode saturates and even decreases with increasing injection current above threshold. Measuring the photon auto-correlation function g^{(2)}(\tau) of the light emission confirms the onset of lasing in the first mode with g^{(2)}(0) approaching unity above threshold. In contrast, strong photon bunching associated with super-thermal values of g^{(2)}(0) is detected for the other mode for currents above threshold. This behavior is attributed to gain competition of the two modes induced by the common gain material, which is confirmed by photon crosscorrelation measurements revealing a clear anti-correlation between emission events of the two modes. The experimental studies are in excellent qualitative agreement with theoretical studies based on a microscopic semiconductor theory, which we extend to the case of two modes interacting with the common gain medium. Moreover, we treat the problem by an extended birth-death model for two interacting modes, which reveals, that the photon probability distribution of each mode has a double peak structure, indicating switching behavior of the modes for the pump rates around threshold.