Thermalization of one-dimensional photon gas and thermal lasers in erbium-doped fibers

TL;DR

This paper demonstrates thermalization and Bose-Einstein distribution of photons in erbium-doped fibers at room and cryogenic temperatures, revealing coexistence of thermal equilibrium and lasing without inversion in 1D fiber cavities.

Contribution

It provides the first experimental evidence of photon thermalization and Bose-Einstein distribution in standard erbium-doped fibers, including open fiber configurations.

Findings

Photon thermalization observed in erbium-doped fibers.

Bose-Einstein distribution of photons confirmed.

Coexistence of thermal equilibrium and lasing without inversion.

Abstract

We demonstrate thermalization and Bose-Einstein (BE) distribution of photons in standard erbium-doped fibers (edf) in a broad spectral range up to ~200nm at the 1550nm wavelength regime. Our measurements were done at a room temperature ~300K and 77K. It is a special demonstration of thermalization of photons in fiber cavities and even in open fibers. They are one-dimensional (1D), meters-long, with low finesse, high loss and small capture fraction of the spontaneous emission. Moreover, we find in the edf cavities coexistence of thermal equilibrium (TE) and lasing without an overall inversion. The experimental results are supported by a theoretical analysis based on the rate equations.