Project Summary: Graphene is an attractive material for all-optical modulation because of its ultrafast optical response and broad spectral coverage. However, all-optical graphene modulators reported so far require high pump fluence due to the ultrashort photo-carrier lifetime and limited absorption in graphene. We present modulator designs based on graphene-metal hybrid plasmonic metasurfaces with highly enhanced light-graphene interaction in the nanoscale hot spots at pump and probe (signal) wavelengths. Based on this design concept, we have demonstrated high-speed all-optical modulators at near and mid-infrared wavelengths (1.56 μm and above 6μm) with significantly reduced pump fluence (1–2 orders of magnitude) and enhanced optical modulation. Ultrafast near-infrared pump-probe measurement results suggest that the modulators’ response times are ultimately determined by graphene’s ultrafast photocarrier relaxation times on the picosecond scale. The proposed designs hold the promise to address the challenges in the realization of ultrafast all-optical modulators for mid-and far-infrared wavelengths. The detailed findings are published in Light: Science & Applications, 2022, 11:102.
2DCC Role: Large area samples of monolayer graphene on Cu foil used in this work were grown by CVD in the 2DCC Thin Films facility.
What Has Been Achieved: Design and demonstration of an ultrafast optical modulator operating at near-IR and mid-IR based on a graphene metallic metasurface absorber (GMMA) structure.
Importance of the Achievement: Ultra-fast optical modulation in the mid- and far-IR wavelengths is highly desirable for molecular spectroscopy, space communication, remote sensing and biomedical diagnostics. Graphene holds great promise for ultra-fast optical modulation from visible to teraherz frequencies due to its linear and gapless dispersion and ultrafast carrier relaxation. The limited absorption in ultra-thin graphene has been a major challenges to development. In this study, graphene was integrated with plasmonic metasurface absorbers to enhance light-graphene interaction. The mid-IR all-optical optical modulator, to our best knowledge, is the first experimental demonstration of
high-speed all-optical modulators for wavelengths beyond 6 μm with a pump fluence of <70 μJ cm−2.
Unique Feature(s) of the MIP that Enabled this Achievement: Synthesis of high-quality monolayer graphene on copper foil by CVD technique.
(If Applicable) Publication:
Ali Basiri, Md Zubair Ebne Rafique, Jing Bai, Shinhyuk Choi, Yu Yao, Light: Science & Applications (2022) 11:102. DOI:10.1038/s41377-022-00787-8
This research was supported in part by the AFOSR YIP under Grant no. FA9550–16–1–0183, the National Science Foundation under grant ECCS-1809997 and 2DCC-MIP national user facility under Grant no. DMR-1539916, and Arizona State University startup funds provided to Y.Y. The devices were fabricated in the NanoFab and Eyring Materials Center (EMC) at Arizona State University. Access to the NanoFab and/or EMC was supported, in part, by the NSF contract ECCS-1542160.