Bubble laser
An ordinary bubble can serve as an optofluidic laser. Such lasers have been made of dye-doped soap solutions and smectic liquid crystal. In a bubble laser, the bubble itself serves as the optical resonator.[1] Bubble lasers exhibit hundreds of regularly spaced optical resonances called whispering gallery modes.[2]
History
Research on bubble lasers began in the early 2020s at the Jožef Stefan Institute in Slovenia. A paper on the subject, Smectic and Soap Bubble Optofluidic Lasers, was published on 5 January 2024 in Physical Review X.[1]
Principle of action
One suitable material for a bubble laser is soap solution to which a few drops of laser dye have been added. When a pump laser is shone onto the bubble, the dye molecules are excited. When the excited dye molecules emits a photon into one of the bubble's optical resonances (the whispering gallery modes), it stimulates other molecules to emit more matching photons, amplifying the light.[1]
A soap bubble's thickness is constantly changing due to freely flowing water inside the bubble. This results in an unstable lasing spectrum. More stable results were achieved when the bubbles were made of smectic liquid crystal. This has the added benefit of longer-lasting bubbles.[1]
Applications
The whispering gallery modes spacing is directly related to the bubble's circumference.[1] This means that bubble lasers may be used as pressure sensors. Bubble lasers have measured pressure changes as high as 100 bar (10,000 kPA) and as low as 1.5 Pa, an "exceptionally large" dynamic range, far outperforming other pressure sensors of comparable size [2].
In the future, bubble lasers may be used to study thin films and phenomena such as Cavity optomechanics.[2]
References
- ^ a b c d e Miller, Johanna. "Bubble lasers can be sturdy and sensitive". Physics Today. American Institute of Physics. Retrieved 2 April 2024.
- ^ a b c Korenjak, Zala (5 January 2024). "Smectic and Soap Bubble Optofluidic Lasers". Physical Review X. 14 (1). doi:10.1103/PhysRevX.14.011002. Retrieved 2 April 2024.