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Slow light in silicon photonic crystal waveguides

T.F. Krauss, L. O’Faolain, D.M. Beggs, T.P. White and A. di Falco School of Physics and Astronomy, University of St. Andrews, St. Andrews, KY16 9SS, UK

Corresponding author email: [email protected]

The keen interest in slow light in nanostructured dielectrics is motivated by the fact that slow light adds functionality to a material by structuring alone. Such nanostructuring is wavelength-independent, i.e. it can be adjusted to any wavelength of interest within the transparency window of the material. Furthermore, it enhances the weak light-matter interaction in a material that may be of interest otherwise, such as silicon, and it adds another degree of freedom to already highly electro-optic or nonlinear materials such as, e.g. chalcogenide glasses [1]. Operating in the slow light regime enhances linear effects such as gain, thermo-optic and electro-optic interactions, which scale as the slowdown factor, whereas nonlinear effects may scale with its square [2]. In comparison to single cavities, which are widely studied in the photonic crystal and nanophotonics community and which also offer sizeable enhancement of these effects, slow light structures offer more bandwidth, i.e. a broader wavelength range of operation. A corresponding figure of merit is the mode order m, i.e. a cavity of mode order m offers m-times less bandwidth for the same enhancement as a slow light waveguide. Therefore, devices based on slow light waveguides are a platform that can address two key issues in communications: Bandwidth and switching power. The enhanced nonlinearity enables the design of low power all-optical switching and data processing devices, while simulataneously accomodating the large bandwidth of future ultrahigh-speed systems. As an example for the slow light enhancement available in these structures, we discuss an optical switch in directional coupler geometry that is ≈40 times shorter Figure 1 Slow light enhanced optical switch. The photonic crystal section is than a comparable 8µm long, while the switching section switch requiring the is only 5µm long. same refractive index change (fig. 1). Furthermore, we will discuss the systematic tuning of the slow light properties [4] and the fact that slow light can even be achieved in slotted waveguides, thus enabling the possibility of achieving Figure 2. Photonic crystal slotted substantial enhancements of the light-matter interaction waveguide for dispersion control. in other materials such as colloidal quantum dots and polymers (fig. 2).

[1] S. J. Madden, D-Y Choi, M. R.E. Lamont, V. G. Ta’eed, N. J. Baker, M. D. Pelusi, B. Luther- Davies and B. J. Eggleton, Opt. Photon. News, 19, 18 (2008) [2] T F Krauss, Journal of Physics D: Applied Physics, 40, 2666 (2007) [3] D. M. Beggs, T. P. White, L. O'Faolain, and T. F. Krauss, Opt. Lett. 33, 147 (2008) [4] J. Li, T.P. White, L. O’Faolain, A. Gomez-Iglesias andd T.F. Krauss, Opt. Exp. (accepted). [5] A. di Falco, L. O’Faolain and T.F. Krauss, Appl. Phys. Lett. 92, 083501 (2008). ------PRIMARY TOPIC: Q SECONDARY TOPIC: P THIRD TOPIC: M PREFERRED FORMAT OF PRESENTATION (ORAL/POSTER): Invited ------Corresponding author name: Thomas F Krauss

Corresponding author email: [email protected]

Please name this file: LastName_Topic1_Topic2 TOPICS

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A Optical properties of materials A1 General A2 Crystals A3 Polycrystalline bulk and film A4 Amorphous and organics A5 Nanostructures, including photonic crystals B Preparation and Characterization of Quantum Dots, Quantum Wires and Other Quantum Structures C Excitonic Processes D Luminescence, Phosphors, Scintillators and Applications E Photoinduced Effects and Applications F Photoconductivity and Photogeneration G Nonlinear Optical Effects and Applications H Electro-Optic Effects and Applications I Glasses for Optics, Optoelectronics and Photonics (including ZBLAN, fluozirconate, oxyfluoride and other glasses) J Polymers for Optics, Optoelectronics and Photonics K Semiconductors for Optoelectronics J1 Semiconductors for Optoelectronics: Wide Bandgap J2 Semiconductors for Optoelectronics: Narrow Bandgap J3 Semiconductors for Optoelectronics: Heterostructures L Light Emitting Devices (including organics) M Photonic and Optoelectronic Materials and Devices (including devices for telecommunications, laser and detectors) N Optical Storage O Photovoltaics (materials and devices, and their properties) P Waveguides and Integrated Photonics Q Silicon Photonics R Optical Fibers and Fiber Sensors S Experimental Techniques T Femtosecond Spectroscopy U Teraherz (THz) techniques, including materials, emitters and detectors V Defect Spectroscopy W Plasmons and Surface Plasmons X Selected Topics (e.g. Photocatalysts in Materials, Materials for Energy Conversion etc)

Invited Abstract submission

Before: 1 February, 2008