22 Nov, 2018 (Thu)Time:
SpeakerDr. Gordon Wong
Max Planck Institute for the Science of Light,
Over the last few years we have successfully demonstrated a series of experimental, analytical and numerical studies of solid and hollow cores, as well as coreless helical PCFs. These novel fibers were produced by thermal post-processing technique or by spinning the glass preform during fiber drawing. The chiral periodic array of hollow microchannels causes light to spiral around the fiber axis, with fascinating effects [1-5], such as transmission of orbital angular momentum (OAM) modes, the appearance of dips in the transmitted spectrum (an effect that can be used to measure mechanical twist), circular dichroism (this enables transmission of only one circular polarization state with high efficiency), suppression of unwanted higher-order modes and low loss guidance in coreless PCF. In order to yield more insight into the behavior of these special fibers, an interferometric technique based on spatial light modulated holograms has been developed to measure the phase and amplitude distributions of the electric field of a fiber mode. This allows the modal OAM components and spatial polarization distribution of helical fibers to be fully characterized. Helical PCFs have many applications, for example in generating pure circularly polarized light in the deep and vacuum UV, photochemistry of chiral isomeric molecules, elimination of polarization mode dispersion and polarization instability, filtering, structural sensing and high power circularly polarized fiber lasers and amplifiers.
 G. K. L. Wong, M. S. Kang, H. W. Lee, F. Biancalana, C. Conti, T. Weiss, and P. St.J. Russell, “Excitation of orbital angular momentum resonances in helically twisted photonic crystal fiber,” Science 337, 446 (2012).
 X. M. Xi, G. K. L. Wong, M. H. Frosz, F. Babic, G. Ahmed, X. Jiang, T. G. Euser, and P. St.J. Russell, “Orbital-angular-momentum-preserving helical Bloch modes in twisted photonic crystal fiber,” Optica 1, 165 (2014).
 R. Beravat, G. K. L. Wong, M. H. Frosz, X. M. Xi, P. St.J. Russell, “Twist-induced guidance in coreless photonic crystal fiber: A helical channel for light,” Sci. Adv. 2, e1601421 (2016).
 P. St.J. Russell, R. Beravat, and G. K. L. Wong, “Helically twisted photonic crystal fibres,” Philos. Trans. R. Soc. London A 375, 20150440 (2017).
 P. Roth, Y. Chen, M. C. Günendi, R. Beravat, N. N. Edavalath, M. H. Frosz, G. Ahmed, G. K. L. Wong, and P. St.J. Russell, “Strong circular dichroism for the HE11 mode in twisted single-ring hollow-core photonic crystal fiber,” Optica 5, 1315 (2018).
Biography of the speaker:
Gordon Wong obtained his PhD in 2008 at the University of Auckland, New Zealand, where he was working on fiber optical parametric oscillators under the supervision of Prof. John Harvey and Prof. Stuart Murdoch. In 2010 he joined Prof. Philip Russell’s group at the Max Planck Institute for Science of Light in Erlangen, Germany and began to work on helical photonic crystal fibers.
OrganizerProf. K.Y. Wong
IEEE photonics society
Most seminars are open to the general public, free of charge, unless otherwise stated. Registration is not required. Arrangement for car parking facilities on campus please contact us for details.
For enquiries, please contact:
Department of Electrical and Electronic Engineering,
Room 601, Chow Yei Ching Building,
Pokfulam Road, Hong Kong
Tel: (852) 2859 7093