An international group of scientists, including ones from the UK's University of Bath, Friedrich Schiller University Jena in Germany and the University of Pisa in Italy, recently set out to investigate the ultrafast opto-electronic and thermal tuning of nonlinear optics in graphene.
Opto-electronic modulation of third harmonic generation in a graphene field-effect transistor. The illustration includes a sketch and a microscopic optical image of the device. Image credit: University of Bath
Nonlinear optics explores how powerful light (e.g. lasers) interacts with materials, resulting in the output light changing color (i.e. frequency) or behaving differently based on the intensity of the incoming light. This field is important for developing advanced technologies such as high-speed communication systems and laser-based applications. Nonlinear optical phenomena enable the manipulation of light in novel ways, leading to breakthroughs in fields like telecommunications, medical imaging, and quantum computing. Graphene's exceptional electronic properties, related to relativistic-like Dirac electrons and strong light-matter interactions, make it promising for nonlinear optical applications, including ultrafast photonics, optical modulators, saturable absorbers in ultrafast lasers, and quantum optics.
This study shows a new way to control high-harmonic generation in a graphene-based field-effect transistor. The team investigated the impact of lattice temperature, electron doping, and all-optical ultrafast tuning of third-harmonic generation in a hexagonal boron nitride-encapsulated graphene opto-electronic device.
They demonstrated up to 85% modulation depth along with gate-tunable ultrafast dynamics, a significant improvement over previous static tuning.
Furthermore, by changing the lattice temperature of graphene, the team could enhance the modulation of its optical response, achieving a modulation factor of up to 300%.
The experimental fabrication and measurement took place at Friedrich Schiller University Jena. University of Bath's Dr. Habib Rostami played a significant role in the study by crafting theoretical models. These models were developed in collaboration with another theory team at the University of Pisa to elucidate new effects observed in graphene.
This research opens the door to developing ultrafast switching of optoelectronic devices, potentially revolutionizing technologies such as high-speed internet and advanced computing.