Electro-optic metal–insulator–semiconductor–insulator–metal Mach-Zehnder plasmonic modulator

• Published in: Photonics and nanostructures Vol. 10; no. 1; pp. 183 - 189
• Main Authors: Thomas, Roney, Ikonic, Zoran, Kelsall, Robert W.
• Format: Journal Article
• Language: English
• Published: Tokyo Elsevier B.V 01.01.2012; Elsevier
• Subjects: Accumulation; Exact sciences and technology; Finite element simulations; Fundamental areas of phenomenology (including applications); Inversion; Mach-Zehnder; Optical elements, devices, and systems; Optical processors, correlators, and modulators; Optics; Physics; Quantum mechanical; Schrodinger–Poisson; Size-quantisation; Wave optics; Wave propagation, transmission and absorption; Finite element simulations; Size-quantisation; Inversion; Mach-Zehnder; Schrodinger–Poisson; Quantum mechanical; Accumulation; MIS structures; Refractive index; Theoretical study; Electrooptical modulator; Oxides; Schrodinger―Poisson; Layer thickness; Finite element method; Optical losses; Electromagnetic wave propagation; Silicon; Plasmonics
• ISSN: 1569-4410; 1569-4429
• DOI: 10.1016/j.photonics.2011.12.004

► The performance of an electro-optic metal-insulator-semiconductor-insulator-metal Mach-Zehnder plasmonic modulator on a buried oxide layer was investigated using electromagnetic and carrier transport simulations. ► The subject of research is both timely and important because sub-wavelength confinement of light in plasmonic structures provides the opportunity to integrate photonic devices with silicon electronics on the same platform, with considerably reduced device lengths and power consumption. ► A strongly confined plasmon mode exists in the thin oxide layer between the metal and the semiconductor layer. Electron densities near the oxide/silicon interface were calculated taking account of size-quantisation effects, their presence leads to a large change in the effective plasmon mode index within the MISIM structure for an applied bias. ► Our design exhibits a large change in effective plasmon mode index leading to considerably reduced device length with an acceptable insertion loss. The performance of a CMOS-compatible electro-optic Mach-Zehnder plasmonic modulator is investigated using electromagnetic and carrier transport simulations. Each arm of the Mach-Zehnder device comprises a metal–insulator–semiconductor–insulator–metal (MISIM) structure on a buried oxide substrate. Quantum mechanical effects at the oxide/semiconductor interfaces were considered in the calculation of electron density profiles across the structure, in order to determine the refractive index distribution and its dependence on applied bias. This information was used in finite element simulations of the electromagnetic modes within the MISIM structure in order to determine the Mach-Zehnder arm lengths required to achieve destructive interference and the corresponding propagation loss incurred by the device. Both inversion and accumulation mode devices were investigated, and the layer thicknesses and height were adjusted to optimise the device performance. A device loss of <8dB is predicted for a MISIM structure with a 25nm thick silicon layer, for which the device length is <3μm, and <5dB loss is predicted for the limiting case of a 5nm thick silicon layer in a 1.2μm long device: in both cases, the maximum operating voltage is 7.5V.