Publication and cover on Nature Photonics for an article by P. Berto, G. Tessier (researchers of the Institut de la Vision) and his colleagues from Barcelona and Paris.

Credits for the cover picture to Clément Molinier.


Manipulating light with an electronic device or a computer is not as easy as it seems, particularly at small scales or in confined spaces. Building an adjustable zoom lens in a mm-thick cell phone, in a miniaturized microscope, or at the distal end of a medical endoscope requires complex lenses that can handle the full optical spectrum and be reshaped electrically within milliseconds.

In “tunable and free-form planar optics”, P. Berto and his colleagues from Barcelona and Paris demonstrate an adjustable technique to manipulate light without any mechanical movement, which they called Smartlenses. As a current is passed through a well-optimized micrometer-scale resistor, the heating locally changes the optical properties of the transparent polymer plate holding the resistor. In much the same way as a mirage bends light passing through hot air to show distant lakes, this microscale hot region is able to deviate light. Within milliseconds, a simple slab of polymer can be turned into a lens and back: small, micrometer-scale smartlenses heat up and cool down quickly and with minimal power consumption. They can even be fabricated in arrays, and the authors show that several objects located at very different distances can be brought into focus within the same image by activating the Smartlenses located in front of each of them, even if the scene is in colours.

By modelling the diffusion of heat and the propagation of light, the authors show that complex optical devices can be optimized using algorithms inspired by the laws of natural selection to go way beyond simple lenses: a properly engineered resistor can deviate light in a chosen direction, while another will bend it into a ring, or other specific shapes. If the right resistor is imprinted on it, a piece of polymer could be activated or deactivated at will to generate a given “freeform” and correct specific defects in our eyesight, or the aberrations of an optical instrument. Most importantly, once the thermal and optical calculations are done, imprinting masses of transparent resistors on polymers can be done at very small costs, for high-end technological systems as well as simple consumer-oriented imaging devices.

You can read the full article here