Utrecht researchers find path for light through opaque materials

Playing ping pong with light to find open channels

Publicatie Jeroen Bosch in Optics Express
By sending light through a material several times, it is possible to find a path through which much more light can pass through the material. The researchers then measure the amount of light that makes it through this path at different wavelengths.

Shining a light through opaque materials: it seems impossible. And yet researchers at the Debye Institute for Nanomaterials Science and the 木瓜福利影视 of Twente have managed to increase the transmission of light through an opaque material by shining it along special paths. This could lead to a better understanding of the transport of light through materials such as skin. The researchers have published their results in the prestigious journal Optics Express on 7 November, 2016.

Light diffusion is a phenomenon that occurs when light waves come into contact with an uneven surface or in an object with an inhomogeneous structure. This diffusion makes it impossible to see through skin, paper or clouds, for example. These materials are largely opaque, and only a small percentage of the light can penetrate through them. And yet these materials do have open channels, special paths through the material that the light waves can follow, no matter how thick the material is. Utrecht PhD student Jeroen Bosch has managed to find these open channels to send much more light through an opaque material.

Ping pong with light

In order to discover precisely how the light should be projected on the material, the researchers 鈥榩layed ping pong鈥 with the light. 鈥淲e send the light through the material in a random manner, and then we use data about the scattering of the light to send it along the same path in a slightly different manner鈥, Bosch explains. 鈥淭hat way, more light passes through the material.鈥 By repeating the process several times - sending the light back and forth through the material - the researchers discovered which shape the light wave must have to make its way through the material.

All colours are different

The shape of the wave front - the front edge of the light wave - determines the degree to which the light can penetrate through the material. And the optimal shape of the wave front is different for every colour of light. 鈥淭he principle works for all wavelengths, but for each wavelength there is only a single shape of wave front that works鈥, according to Bosch. 鈥淚f you fix the shape of the wave front and then change the wavelength, you see that less and less light penetrates through the material.鈥 This knowledge of wavelength dependency of open channels provides the researchers with a measurement for the 鈥榩ath length鈥 of these open channels. How long does the light travel along such a special path? The answer to this question provides insight into the transport of light through diffusive materials, which is extremely useful for looking into and through such materials.

Publication

Frequency width of open channels in multiple scattering media
Jeroen Bosch*, Sebastianus A. Goorden, Allard P. Mosk*
*Affiliated with Utrecht 木瓜福利影视
Optics Express 24, 2016,

More information

Nieske Vergunst, press officer Faculty of Science of Utrecht 木瓜福利影视, +31 6 2490 2801, N.L.Vergunst@uu.nl.