报告人：Prof. Xuetao Gan
School of Science, Northwestern Polytechnical University, Xi'an 710072, China
题目：Chip-integrated graphene optoelectronic devices
Graphene has attracted great interesting in the development of optoelectronic devices due to its broadband optical response, ultrahigh carrier mobility, and potentially CMOS-compatible. Although light-graphene interaction is strong given its single atomic thickness, devices relying on single-pass operation are ineffective for either light absorption or strong nonlinear response in photonics applications. Here, we describe techniques for enhancing the interaction of photons with graphene using chip-integrated nanophotonic devices, enabling high performance graphene optoelectronic devices.
Transferring single-layer graphene onto planar photonic crystal nanocavities enables a spectrally selective, order-of-magnitude enhancement of optical coupling with graphene. We observed dramatically cavity-enhanced absorption, hot photoluminescence emission, and Raman scattering of the monolayer graphene . By electrically gating the graphene monolayer coupled with a planar photonic crystal nanocavity, electrooptic modulation of the cavity reflection was possible with a contrast in excess of 10 dB and a switching energy of 300fJ . Moreover, a novel modulator device based on the cavity-coupled graphene-boron nitride-graphene capacitor was fabricated, showing a modulation speed up to 1.2 GHz .
A waveguide-integrated graphene photodetector that simultaneously exhibits high responsivity, high speed and broad spectral bandwidth has also been reported. Using a metal-doped graphene junction coupled evanescently to the waveguide, the detector achieves a photoresponsivity exceeding 0.1 A/W together with a nearly uniform response between 1,450 and 1,590 nm. Under zero-bias operation, a response rate exceeding 20 GHz and an instrumentation-limited 12 Gbit/s optical data link.
The integration of graphene with nanophotonic architectures promises a new generation of compact, energy-efficient, and ultrafast electrooptic graphene devices for on-chip optical communications.
. X. Gan, K. F. Mak, Y. Gao, et al. Nano Lett. 12, 5626 (2012).
. X. Gan, R. Shiue, Y. Gao, et al. Nano Lett. 13, 691 (2013).
. X. Gan, R. Shiue, Y. Gao, et al. IEEE, J. Sele. Top. Quant. Electron. 20, 6000311 (2014).
X. Gan, R. Shiue, Y. Gao, et al. Nature Photon. 7, 883 (2013).
Xuetao Gan received the B.S. and Ph.D. degrees from Northwestern Polytechnical University, Xi’an, China, in 2007 and 2013, respectively. From 2010 to 2012, he was a visiting scholar at Columbia University, New York, USA. He is currently an Associate Professor of applied physics at Northwestern Polytechnical University. His research interests mainly include nanophotonics, optoelectronics in graphene and other layered materials, and applications of photonic crystals.