The origin and influence of non-cavity modes in a micropillar Bragg microcavity

TL;DR

This paper investigates non-cavity modes in cylindrical micropillar Bragg microcavities, revealing their origin from geometry and their impact on photon collection and Purcell enhancement, which are crucial for quantum light source design.

Contribution

It identifies and characterizes non-cavity modes in micropillar microcavities, showing their independence from Bragg reflectors and dependence on geometry, aiding better modeling of emission properties.

Findings

Non-cavity modes arise from pillar geometry, not Bragg reflectors.

These modes influence photon collection efficiency.

Simulation reproduces non-cavity modes in uniform pillars.

Abstract

Controlling the photonic environment of emitters is essential to the design of classical and quantum light sources. We study the case of a dipole-like emitter in a cylindrical pillar etched into a planar Bragg microcavity, which is a common design of quantum-dot single photon source. In addition to the well-known cavity modes created by the high-reflectivity of the Bragg mirrors at small in-plane wavevectors, we show the presence of broad spectral features that play a key role in controlling photon collection efficiency and Purcell enhancement. These non-cavity modes are insensitive to the periodic index modulation of the Bragg reflectors, but arise from the cylindrical pillar geometry, as we show by comparison with simulations of uniform pillars, which reproduce the non-cavity modes. This approach provides a tool for understanding and modelling these often-disregarded decay channels as a function of source height, cavity dimensions and surface layers.