ICFO researchers, along with teams from CIC Nanogune, IIT and Columbia University, have developed a graphene-based phase modulator capable of tuning the light phase between 0 and 2π in situ.

To this end, the researchers exploited the unique wavelength tunability of graphene plasmons, light coupled to electrons in graphene. In their work, they used ultra-high quality graphene to build a fully functional phase modulator with a device footprint of only 350 nm, which is 30 times than the wavelength of the infrared light used for this experiment.

A near-field microscope was used to excite and image the plasmons, allowing insight into the plasmon properties such as their wavelength and phase. This new type of phase modulator enables graphene plasmons to be used for ultra-compact light modulators and phase arrays with the possibility to control, steer and focus light in situ. This may have potential applications for on-chip biosensing and two dimensional transformation optics.