Incoherent "Slow and Fast Light"

TL;DR

This paper demonstrates that phenomena attributed to slow and fast light due to spectral hole-burning and coherent population oscillations can also be observed with incoherent light and simple objects, questioning the interpretation of these effects.

Contribution

The study shows that incoherent light can produce effects similar to slow and fast light, challenging the assumption that these are caused solely by spectral hole-burning and CPO.

Findings

Incoherent light reproduces slow and fast light effects.

Objects with pure-intensity nonlinearity exhibit these effects.

No conclusive evidence for CPO-based slow or fast light.

Abstract

We show experimentally that the effects of "slow and fast light" that are considered to be caused by spectral hole-burning under conditions of coherent population oscillations (CPO) can be universally observed with incoherent light fields on objects with the pure-intensity nonlinearity, when such an interpretation is inapplicable. As a light source, we used an incandescent lamp and as objects for study, a photochromic glass and a thermochromic coating. The response of the objects to intensity modulation of the incident light reproduced in all details the commonly accepted experimental evidences of the "light with a negative group velocity" and "ultraslow light". We come to conclusion that so far there are no experimental works providing evidence for real observation of the "CPO-based slow or fast light".