Dynamically Tunable 'Smartlens' Can Shape Light for Various Functions

The integration of an adjustable-dynamic zoom lens in a thin cellphone, in a miniaturized microscope, or at the remote end of a medical endoscope requires complex lenses that can handle the full optical spectrum and be reshaped electrically within milliseconds.

To meet this challenge, scientists from the Institut de la Vision teamed up with a group from the Institute of Photonic Sciences (ICFO) to develop a dynamically tunable lens that, according to the scientists, is capable of achieving almost any complex optical function. The lens, called Smartlens, is able to manipulate light without any mechanical movement. The Smarlens design is based on a method of deterministic phase-front shaping using a planar thermo-optical module and designed microheaters to locally shape the refractive index distribution.

This is a schematic illustration of the location where the Smartlens is placed within the optical instrument (in this case a microscope). Courtesy of ICFO/Marc Montagut.

An electrical current is passed through an optimized, micrometer-scale resistor. The heating locally changes the optical properties of the transparent polymer plate holding the resistor. This microscale “hot region” is able to refract light in a way similar to how light passing through hot air is refracted to form a mirage. Within milliseconds, a simple slab of polymer can be turned into a lens and back.

The team led by professor Romain Quidant showed that several objects located at distinctly different distances from a camera could be brought into focus within the same image, even if the scene was in color, by activating the Smartlenses located in front of each object.

When combined with a genetic algorithm optimization, the Smartlens can produce free-form optical wavefront modifications. For example, if imprinted with an appropriate resistor, a piece of polymer could be activated or deactivated at will to generate a given freeform to correct specific defects in eyesight or the aberrations of an optical instrument.

This is a schematic illustration of the Smartlens. Courtesy of ICFO/Marc Montagut.

The micrometer-scale Smartlenses heat up and cool down quickly and with minimal power consumption. They can be fabricated in arrays. The compact Smartlens complements scientists’ existing “optical-shaping toolbox” by offering low-chromatic-aberration, polarization-insensitive, and transmission-mode components that can be integrated into existing optical systems.

“The Smartlens technology is cost effective and scalable, and has proven to have the potential to be applied to high-end technological systems as well as simple end-user-oriented imaging devices,” Quidant said. The research could open a new window for the development of low-cost, dynamically tunable devices for optical systems.

The research was published in Nature Photonics (https://doi.org/10.1038/s41566-019-0486-3).

A team of researchers reports on a dynamically tunable lens capable of achieving almost any complex optical function. Courtesy of ICFO/Marc Montagut.