Photonics, “intelligent” materials help to manage light propagation

A study by UNIFI and LENS on Advanced Optical Materials opens up new perspectives in the control of light signals, as a vehicle for information.

Light permeates our daily life. It enables the vision of objects, but it is also a formidable vehicle of information: as a powerful example, the use of optical fibers for signal communication, which have contributed to the development of the Internet.

Its fortune lies, in particular, in the possibility of superimposing light signals that propagate along a single path. At will, the signals should be also divided one from the other in order to be manipulated or received. So far this problem, in telecommunications as well as biomedical imaging or display technology, has been solved through the use of mirrors that, moved electromechanically, direct the light along different directions. The electronic mechanism that moves the mirror, however, is difficult to integrate into microcircuits and complex to manage.

Now a study on Advanced Optical Materials led by the Department of Physics of the University of Florence and the European Non-linear Spectroscopy Laboratory (LENS), opens a new perspective with the use of photonics — that part of optical science that studies the control of light propagation on scales one million times smaller than one meter (“micrometer”). The project has seen the participation of the National Institute of Optics of the National Research Council (INO-CNR) [“Structured Optical Materials Controlled by Light” doi: 10.1002 / adom.201800167].

The central idea was to replace the mirror with “intelligent” materials, defined also as artificial muscles, known for their ability to deform under an optical stimulus in a sub-millisecond timescale, which then reversibly return to their original shape. By sending multiple light beams with different wavelengths (one control beam and one probe beam) to these micro-structured polymers, the light signals are thus separated in different directions according to the different shapes that the material acquires under light activation. “These are responsive polymers that combines the properties of liquid crystal with the elasticity of the rubbers and that can be patterned by a laser manufacturing technique, “ explains Sara Nocentini, research fellow at the University of Florence, active at LENS and first signatory of the article, and Simone Zanotto, National Research Council researcher affiliated to LENS.

“The application of ‘intelligent’ polymers in optics and photonics leads, therefore, to a remote and non-invasive control on light,” comments Diederik S. Wiersma, professor of physics of matter at the University of Florence and member of LENS. “This type of material can be miniaturized on a micrometric scale and it works both in air and in water: the range of applications is potentially very wide. Even in everyday life.”