Critical Behavior of Light

TL;DR

This paper demonstrates that light in passive mode-locked lasers exhibits critical phenomena, including phase transitions and critical points, with observed fluctuations and calculated exponents aligning with mean field theory.

Contribution

It provides the first example of critical behavior in a one-dimensional many-body light system, revealing novel phase diagrams and fluctuation phenomena.

Findings

Identification of phase regimes with continuous wave and pulses

Observation of enhanced fluctuations at critical points

Critical exponents match mean field predictions

Abstract

Light is shown to exhibit critical and tricritical behavior in passive mode-locked lasers with externally injected pulses. It is a first and unique example of critical phenomena in a one-dimensional many body light-mode system. The phase diagrams consist of regimes with continuous wave, driven para-pulses, spontaneous pulses via mode condensation, and heterogeneous pulses, separated by phase transition lines which terminate with critical or tricritical points. Enhanced nongaussian fluctuations and collective dynamics are observed at the critical and tricritical points, showing a mode system analog of the critical opalescence phenomenon. The critical exponents are calculated and shown to comply with the mean field theory, which is rigorous in the light system.