| A local wavelength change produces phase modulation of light of up to 2π in a graphene layer. (Image: Achim Woessner/ICFO) |
Modulating the amplitude and phase of light is a key ingredient for many applications such as communications, sensors, phased arrays, wavefront shaping, and transformation optics. Performing this task with high efficiency and small footprint is a major challenge for the development of optoelectronic devices.
Researchers from the Institut de Ciencies Fotoniques (ICFO; Barcelona, Spain), Columbia University (New York, NY), NEST (Pisa, Italy), the National Institute for Materials Science (Namiki, Japan), CIC nanoGUNE and UPV/EHU (Donostia-San Sebastian, Spain), IKERBASQUE (Bilbao, Spain), and the Institució Catalana de Recerça i Estudis Avancats (ICREA; Barcelona, Spain) have developed a phase modulator based on graphene capable of tuning the light phase between 0 and 2π in situ.1
To do this, they exploited the unique wavelength tunability of plasmons (light coupled to electrons) in graphene. In their experiment, they used ultrahigh-quality graphene and built a fully functional phase modulator with a device footprint of only 350 nm, which is 30 times smaller than the size of the 10.6 μm (free-space) wavelength used for this experiment. A near-field microscope was used to excite and image the plasmons, allowing an unprecedented insight into the plasmon properties such as their wavelength and phase.
This new type of phase modulator enables graphene plasmons to be used for ultracompact light modulators and phased arrays with the possibility to control, steer, and focus light in situ. This has potential applications for on-chip biosensing and two-dimensional transformation optics.
Source: https://www.icfo.eu/newsroom/news/article/3636
REFERENCE:
1. Achim Woessner et al., Nature Photonics (2017); doi:10.1038/nphoton.2017.98