To achieve this light phase modulation, the research team exploited the wavelength tunability of graphene plasmons. In their experiment, they used high quality graphene and build a fully functional phase modulator with a device footprint of 350nm, which was 30 times smaller than the wavelength of the infrared light used for the experiment.
A near-field microscope was used to excite and image the plasmons, which the researchers claim gave them an unprecedented insight into the plasmon properties, such as their wavelength and phase.
Modulating the amplitude and phase of light is a key ingredient for many applications such as wavefront shaping, transformation optics, phased arrays, modulators and sensors. According to the researchers, performing this task with high efficiency and small footprint is a major challenge for the development of optoelectronic devices.
This new type of phase modulator could enable 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 has potential applications for on-chip biosensing and 2D transformation optics.