Laser cooling in a silica optical fiber at atmospheric pressure

Abstract

For the first time, to the best of our knowledge, laser cooling is reported in a silica optical fiber. The fiber has a 21-µm diameter core doped with 2.06 wt.% Y b 3 + and co-doped with A l 2 O 3 and F − to increase the critical quenching concentration by a factor of 16 over the largest reported values for the Yb-doped silica. Using a custom slow-light fiber Bragg grating sensor, temperature changes up to − 50 m K were measured with 0.33 W/m of absorbed pump power per unit length at 1040 nm. The measured dependencies of the temperature change on the pump power and the pump wavelength are in excellent agreement with predictions from an existing model, and they reflect the fiber’s groundbreaking quality for the radiation-balanced fiber lasers.

Laser cooling of ytterbium-doped silica glass

“…While this paper was under review in another Nature Research journal, we became aware of the successful report of laser cooling of silica fiber by Knall et al 42 , where they report temperature changes up to −50 mK in a fiber with a 21 μm diameter core doped with 2.06 wt% Yb 3+ , and co-doped with Al 2 O 3 and F − to increase the critical quenching concentration by a factor of 16 over the largest reported values for the Yb-doped silica.…”

Radiation-Balanced Lasers: History, Status, Potential

“…In 2019, laser cooling with anti-Stokes fluorescence was demonstrated in two separate silica samples: a silica fibre [52] and a bulk silica preform [53]. These results were breakthroughs for development of silica-based athermal lasers.…”

Glass: The carrier of light—Part II—A brief look into the future of optical fiber

“…109,110 However, per "If you can do it with silica, do it with silica," most important was the recent validation in a low-loss, CVD-derived silica fiber. 111,112 The greatest obstacle to that cooling demonstration was the excess heat generated through nonradiative relaxation processes, such as energy transfer to impurities. This leads to another important consideration in the power budget of high-power fiber lasers-the quantum conversion efficiency (QCE).…”

“…Anti‐Stokes fluorescence cooling was first experimentally observed in a bulk fluoride glass, 105 then in a variety of glasses and crystals, 106‐108 and, in fluoride glass fibers 109,110 . However, per “ If you can do it with silica, do it with silica ,” most important was the recent validation in a low‐loss, CVD‐derived silica fiber 111,112 . The greatest obstacle to that cooling demonstration was the excess heat generated through nonradiative relaxation processes, such as energy transfer to impurities.…”