Photon statistics of amplified spontaneous emission

TL;DR

This paper investigates the photon statistics of amplified spontaneous emission (ASE), demonstrating through simulations that ASE exhibits thermal-like coherence properties with g^(2)(0)=2, distinguishing it from laser radiation.

Contribution

The study provides the first reliable theoretical estimates and experimental insights into the photon statistics of ASE, clarifying its thermal nature and potential for applications like ghost imaging.

Findings

ASE exhibits g^(2)(0)=2, similar to thermal light.

Photon statistics of ASE are independent of pump power.

ASE differs fundamentally from laser radiation.

Abstract

Developments in quantum technologies lead to new applications that require radiation sources with specific photon statistics. A widely used Poissonian statistics are easily produced by lasers; however, some applications require super- or sub-Poissonian statistics. Statistical properties of a light source are characterized by the second-order coherence function g^(2)(0). This function distinguishes stimulated radiation of lasers with g^(2)(0)=1 from light of other sources. For example, g^(2)(0)=2 for black-body radiation, and g^(2)(0)=0 for single-photon emission. One of the applications requiring super-Poissonian statistics (g^(2)(0)>1) is ghost imaging with thermal light. Ghost imaging also requires light with a narrow linewidth and high intensity. Currently, rather expensive and inefficient light sources are used for this purpose. In the last year, a superluminescent diode based on amplified spontaneous emission (ASE) has been considered as a new light source for ghost imaging. Even though ASE has been widely studied, its photon statistics has not been settled - there are neither reliable theoretical estimates of the second-order coherence function nor unambiguous experimental data. Our computer simulation clearly establishes that coherence properties of light produced by ASE are similar to that of a thermal source with g^(2)(0)=2 independent of pump power. This result manifests the fundamental difference between ASE and laser radiation.