H C Ong
The Chinese University of Hong Kong, Hong Kong
Title: Study of the angular momentum of light from plasmonic crystals
Biography
Biography: H C Ong
Abstract
In analogy to electron waves, electromagnetic waves also carry spin and orbital angular momentum (AM) and this property has been fascinating the world of optical science and engineering for many years. With the rise of nanotechnology, photonic systems can now be fabricated at the length scale of nanometers, manifesting many intriguing phenomena including the spin-orbit interaction in an observable extent. The polarization, the spatial field distribution, and the propagation direction are no longer treated separately and controlling one with another has become feasible. Plasmonic arrays are one of the most popular nanophotonic systems owing to their simplicity and well-defined structures for yielding controllable optical properties. They have been used in extraordinary transmission, fluorescence, photovoltaics, nonlinear optics, sensing, etc. In addition, since surface plasmon polaritons (SPPs) carry transverse spin AM, they should modify the AM of the outgoing radiation under the conservation of angular momentum. Unfortunately, this transverse spin is not properly taken into consideration even though plasmonic research has been carried out for years. Here, I will talk about the AM of light from plasmonic crystals. We have observed substantial polarization conversion and spin-orbital coupling from square lattice circular nanohole arrays, which do not possess intrinsic chirality. We find the transverse spin AM possessed by SPPs play a deterministic role in governing the far-field radiation. The experimental results are supported by finite-difference time-domain simulations and temporal coupled mode theory. Based on the AM study, we propose the AM can be used as a new parameter in surface plasmon resonance (SPR) sensing. As the transverse spin AM of SPPs is strongly dependent on the complex propagation wave vector, which is sensitive to the change of the local refractive index, the change in the AM of light thus reflects the sensing environment. The performance of the spin-SPR will be discussed.
Recent Publications
- Cao ZL, Yiu LY, Zhang ZQ, Chan CT, Ong HC (2017) Understanding the role of surface plasmon polaritons in two-dimensional achiral nanohole arrays for polarization conversion. Phys. Rev. B (in press).
- Lin M, Cao ZL, Ong HC (2017) Determination of the excitation rate of quantum dots mediated by momentum resolved Bloch-like surface plasmon polaritons. Opt. Exp. 25: 6092-6103.
- Cao ZL, Ong HC (2016) Momentum-dependent group velocity of surface plasmon polaritons in two-dimensional metallic nanohole array. Opt. Exp. 24: 12489-12500.
- Liu C, Chan CF, Ong HC (2016) Direct deconvolution of electric and magnetic responses of single nanoparticles by Fourier space surface plasmon resonance microscopy. Opt. Comm. 378: 28-34.
- Liu SD, Leong ESP, Li GC, Hou YD, Deng J, Teng JH, Ong HC, Lei DY (2016) Polarization-independent multiple fano resonances in plasmonic nonamers for multimode-matching enhanced multiband second-harmonic generation. ACS Nano 10: 1442-1452.