(credit: https://doi.org/10.1103/PhysRevX.12.021007 )
Science is often viewed as utilitarian. We explore the natural world so that we can plunder its secrets for our own benefit. Indeed, this is often precisely the sort of science that funding agencies seek. But, for most scientists, the utilitarian comes second to other motivating factors: The observation of beauty and the challenge of a unique puzzle are the two that spring to mind. Today, in the particular spirit of observing beauty, I’d like you to sit back and enjoy the view of light flowing like water .
Light exiting an optical fiber and flowing through a thin film of soapy water. (credit: Anatoly Patsyk )
The picture above looks like a river delta, with many tributaries and rivulets coming together in one Amazonian outflow. All that is missing is the fish. But that will be light flowing out of an optical fiber and into the layer of soap. The soap layer traps the light, so it only spreads out in the plane of the cleaning soap. Yet the layer is also uneven, so the light cannot spread out evenly, and you get this branching pattern. This is one of the pictures from a new group of scientists exploring how light flows in thin films.
The making of an optical river
To create an optical river, you need to do the following: start with a nice flat surface plus place a layer of detergent (soapy water) with a tiny bit of dye in it. After some time (and given typically the right mixture of soap), the detergent film will settle down therefore that it is not moving around. Then, shine some gentle on the edge of this soap layer. If you get the focusing conditions just right, often the light will be trapped within your soap layer. The light will then start to spread out across and through the soap, exiting from other edges.
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