Breakthroughs

EXPERIMENTAL DEMONSTRATION OF GRAPHENE'S NEGATIVE KERR NONLINEARITY

Through joint theoretical and experimental research efforts, we have demonstrated by means of the in-house developed Chirped-Pulse-Pumped Self-Phase Modulation method that graphene's Kerr nonlinearity is negative, in contrast to common belief. This new insight has a major impact on how graphene should be implemented in nonlinear optical devices, and has been published in Physical Review Applied. These research findings have also been taken up in the news item sent out at the end of the GRAPHENICS project. 


DEVELOPMENT OF OPTICAL-QUALITY CHEMICAL GRAPHENE DOPING

We have developed a new method for chemically doping graphene that fulfills for the first time the optical-quality requirements for practical use in photonic applications. Our method relies on the deposition of F4-TCNQ dissolved in methyl ethyl ketone, providing both a high optical transparency and a low surface roughness while also yielding efficient and controllable graphene doping. Our results have been published in RSC Advances.


DEVELOPMENT OF NANOPARTICLE-BASED GRAPHENE DOPING

To enable extremely strong graphene doping, we have also explored the use of tetrachloroauric acid on graphene, yielding the formation of Au nanoparticles while inducing very strong p-doping in the graphene. While this resulted in a stronger doping than our F4-TCNQ-based approach, the latter performs better in terms of optical-quality requirements. Our results on tetrachloroauric-acid-based graphene doping have been published in Carbon.


CHEMICALS-FREE PATTERNING OF GRAPHENE ON SILICON WAVEGUIDES

We have introduced a new approach to remove monolayer graphene transferred on top of a silicon-on-insulator (SOI) photonic integrated chip. Femtosecond laser ablation is used for the first time to remove graphene from SOI waveguides, whereas oxygen plasma etching through a metal mask is employed to peel off graphene from the grating couplers attached to the waveguides. As opposed to commonly used lithographic patterning techniques, our approach does not require the use of chemicals and as such does not alter the graphene's optical properties. This work has been published in Optics Express.



GRAPHENE NONLINEARITY CALCULATIONS

Starting from the tight-binding model, we have carried out detailed calculations for graphene's optical nonlinearities as a function of, amongst others, doping level, scattering parameters, and saturation level. These calculations provide new insights in the complex behavior of graphene's nonlinear optical properties and have been published in New Journal of Physics, Optics Express, Physical Review B and Scientific Reports.


DEVELOPMENT OF A COMPACT MID-INFRARED MODE-LOCKED FIBER LASER

We have developed and downscaled a mid-infrared mode-locked Holmium fibre laser operating well beyond 2.1 micron. Our research results have been presented at the EPS-QEOD Europhoton Conference 2016.

 

ARTICLES IN PRESS

The kickoff of the GRAPHENICS project has been covered in several press articles:

http://www.graphene-info.com/young-researchers-eu-develop-ultra-compact-graphene-based-mid-infrared-broadband-light-source

http://www.photonics.com/Article.aspx?AID=55911

http://www.paneuropeannetworks.com/science-technology/graphene-based-light-source-to-be-developed/


Our graphene nonlinearity calculations have been taken up in the research highlights of the August 2014 edition of Nature Photonics (see paragraph on Nonlinear Optics – Chemical potential effect)

http://www.nature.com/nphoton/journal/v8/n8/full/nphoton.2014.186.html?WT.ec_id=NPHOTON-201408


Our theoretical work has also been selected for “the top 30 of most exciting optics research in 2014,” published in the December 2014 issue of Optics&Photonics News:

http://www.osa-opn.org/home/articles/volume_25/december_2014/extras/turning_on_graphene_s_optical_nonlinearities/#.VLkJcCvF9DA