Modulating the amplitude and phase of light is considered to be a vital ingredient for a number of applications that include transformation optics, wavefront shaping, phased arrays, sensors and modulators. Executing this task with small footprint and high efficiency is a significant challenge for the development of optoelectronic devices.
Phase modulation due to a local wavelength change. © Achim Woessner/ICFO
A phase modulator based on graphene capable of tuning the light phase between 0 and 2 π in situ has been developed by
ICFO Researchers Dr. Achim Woessner and Dr. Mark Lundeberg, headed by ICREA Prof. at ICFO Frank Koppens, in association with Prof. Rainer Hillenbrand from CIC Nanogune, Iacopo Torre and Prof. Marco Polini from IIT and Dr. Yuanda Gao and Prof. James Hone from Columbia University. A paper on this development has been recently published in Nature Photonics.
The Researchers were able to achieve this by exploiting the unique wavelength tunability of graphene plasmons, which refer to light coupled to electrons in graphene. They used ultra-high quality graphene in their experiment and built a completely functional phase modulator with a device footprint of just 350 nm, which is considered to be 30 times smaller than the wavelength of the infrared light used for this experiment. The team used a near-field microscope to excite and image the plasmons, permitting an exceptional insight into the plasmon properties such as their phase and wavelength.
With this new kind of phase modulator, it is possible to use graphene plasmons for ultra-compact light modulators and phase arrays and also control, steer and focus light in situ. This indeed has promising applications for on-chip biosensing and two-dimensional transformation optics.
The European Research Council, the European Graphene Flagship, the Government of Catalonia, Fundació Cellex and the Severo Ochoa Excellence program of the Government of Spain partially supported this research.