Soap bubbles can be turned into lasers that are exceptionally good at sensing electric fields and pressure.
鈥淭o get lasing, almost any bubble is fine. We鈥檝e used regular hand soaps or a mixture that you can buy for children. You just need to put a small amount of fluorescent dye inside, and it works perfectly,鈥� says at the Jo啪ef Stefan Institute in Slovenia, who produced the bubble lasers with Zala Korenjak, also at the Jo啪ef Stefan Institute .
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Lasers require three key components. The first is a cavity in which light can bounce back and forth. This is often constructed with mirrors, but the researchers used the interior volume of bubbles instead 鈥� some of which were smaller than half a millimetre in diameter and some measuring a few centimetres across.
Lasers must also contain a material that amplifies light, so the team added fluorescent dye to the bubble mixture. The dye shines brightly and emits light when illuminated.
The final component is light itself, which in the case of the bubble lasers came from an optical fibre that the researchers shone on to the bubble through a focusing lens. Doing so made the bubble produce its own laser light.
Humar and Korenjak also experimented with using liquid crystals instead of soap to make the bubble lasers. This made the lasers more stable and longer lived, allowing the researchers to turn them into sensors for pressure and electric fields. Exposure to either changes the bubble鈥檚 physical shape, and in so doing also changes the properties of its laser beam in a way that the team could measure.
The bubble lasers are so sensitive they can be used to detect pressure changes as small as 0.001 per cent of atmospheric pressure, the聽 researchers say. They can also sense electric fields in ambient air on a perfectly sunny day with no electricity-generating thunderstorms in sight, says Humar.
at the University of Central Florida says the team creatively combined the concept of 鈥渕icro-ring lasers鈥� 鈥� within which light bounces in a circular way 鈥� with the idea of pushing light through liquid films, where it has been seen to behave dramatically before. 鈥淭hey take these ideas to a totally new platform, thereby opening the door to a plethora of novel applications,鈥� he says.
Humar says that he and Korenjak are already working on handheld sensing devices based on bubble lasers.
Journal reference:
Physical Review X,
