Abstract
Microscale and nanoscale lasers inherently exhibit rich photon statistics due to complex light-matter interaction in a strong spontaneous emission noise background. It is well known that they may display superthermal fluctuations—photon superbunching—in specific situations due to either gain competition, leading to mode-switching instabilities, or carrier-carrier coupling in superradiant microcavities. Here we show a generic route to superbunching in bimodal nanolasers by preparing the system far from equilibrium through a parameter quench. We demonstrate, both theoretically and experimentally, that transient dynamics after a short-pump-pulse-induced quench leads to heavy-tailed superthermal statistics when projected onto the weak mode. We implement a simple experimental technique to access the probability density functions that further enables quantifying the distance from thermal equilibrium via the thermodynamic entropy. The universality of this mechanism relies on the far-from-equilibrium dynamical scenario, which can be mapped to a fast cooling process of a suspension of Brownian particles in a liquid. Our results open up new avenues to mold photon statistics in multimode optical systems and may constitute a test bed to investigate out-of-equilibrium thermodynamics using micro or nanocavity arrays.
- Received 11 August 2017
DOI:https://doi.org/10.1103/PhysRevX.8.011013
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Light sources such as lasers are mostly characterized by their intensity fluctuations. Above a certain intensity threshold, standard laser sources exhibit small (Gaussian) fluctuations. Below that threshold, however, the fluctuations become large since the emission is dominated by spontaneous emission noise. The statistics of the intensity becomes thermal; that is, from a quantum perspective, photons are emitted in chaotic bunches. Superthermal light denotes fluctuations that are stronger than thermal, also known as superbunching. Generating superthermal light with a compact laser source could lead to potential applications for advanced imaging techniques (such as ghost imaging in the time domain) as well as nonlinear energy conversion and quantum information. In this paper, we reveal a new and generic physical mechanism of superthermal emission in semiconductor nanolasers called the “far-from-equilibrium route.”
Our strongly coupled or “photonic molecule” nanolaser has two modes: a fundamental, out-of-phase mode with low optical losses (known as the antibonding, or AB, mode) and an excited, in-phase mode with higher losses (known as the bonding, or B, mode). In continuous wave (CW) pumping, the AB mode is likely to operate in a laser regime, while the B mode remains below the lasing threshold. We show that when short pump pulses are used instead of CW excitation, the system is prepared in a quenched state, and the energy flows towards the AB mode in a manner that is far from equilibrium, leaving its statistical fingerprints in the form of long-tailed, superthermal photon distributions in the B mode.
Our experimental and theoretical results open up new prospects in the molding of photon statistics in multimode cavity arrays that are driven far from equilibrium.