Departmental Seminar

Light propagation in micro/nano-structures and its applications

Dr Lei Xu
Nankai University, China

The flow of light can be delicately molded with micro/nano-structures, especially with photonic lattices, due to the richness of the associated band structure and diffraction relation when compared to the homogenous bulk media. Lattices of coupled waveguides also provide an excellent platform of the observation and manipulation of quantum properties of photons, which may exhibit very different behaviors from those with a classical light wave due to the quantum interference effect. When introducing structure disorder into such systems, the transverse Anderson localization of light occurs. For light propagating in disordered random medium, the weak localization effect – coherent backscattering of light can be observed in the backscattering direction due to multiple scattering.

Here, theoretically, I studied the anomalous refractive behaviors of light propagating in disordered photonic lattices, classical and non-classical light in complex photonic structures, such as the passive parity-time-symmetric lattices. Furthermore, I extended my study into the nanostructures, and present a facile method to effectively manipulate the trajectory of surface plasmons along a rationally designed metasurfaces. Anomalous properties of surface plasmons along the metasurfaces, such as self-focusing, plasmons bending, have been demonstrated and realized numerically.

Experimentally, I proposed a method to generate slow and fast light at arbitrary signal wavelength in nonlinear media based on the nonlinear effect, which eliminates the requirement on the optical nonlinearity or the resonant effect at the signal wavelength. Furthermore, I also studied one of the applications of coherent backscattering of light – the lensless imaging based on coherent backscattering in random medium both theoretically and experimentally. The imaging system was optimized to improve the image contrast and resolution.

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