title: Ultracompact (3 μm) silicon slow-light optical modulator.
abstract: Wavelength-scale optical modulators are essential building blocks for future on-chip optical interconnects. Any modulator design is a trade-off between bandwidth, size and fabrication complexity, size being particularly important as it determines capacitance and actuation energy. Here, we demonstrate an interesting alternative that is only 3 μm long, only uses silicon on insulator (SOI) material and accommodates several nanometres of optical bandwidth at 1550 nm. The device is based on a photonic crystal waveguide: by combining the refractive index shift with slow-light enhanced absorption induced by free-carrier injection, we achieve an operation bandwidth that significantly exceeds the shift of the bandedge. We compare a 3 μm and an 80 μm long modulator and surprisingly, the shorter device outperforms the longer one. Despite its small size, the device achieves an optical bandwidth as broad as 7 nm for an extinction ratio of 10 dB, and modulation times ranging between 500 ps and 100 ps.
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: Aron
authors.initials: A
authors.lastname: Opheij
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: Nir
authors.initials: N
authors.lastname: Rotenberg
authors.affiliation: 1] Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands [2] Centre for Quantum Photonics, University of Bristol, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL [3] Centre for Quantum Photonics, University of Bristol, HH Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL.
authors.forename: Daryl M
authors.initials: DM
authors.lastname: Beggs
authors.affiliation: School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK.
authors.forename: Isabella H
authors.initials: IH
authors.lastname: Rey
authors.affiliation: 1] School of Physics and Astronomy, University of St Andrews, St Andrews, Fife, KY16 9SS, UK [2] Department of Physics, University of York, York, YO10 5DD, UK.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Krauss
authors.affiliation: Center for Nanophotonics, FOM Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands.
authors.forename: L
authors.initials: L
authors.lastname: Kuipers