light propagation with phase discontinuities: generalized ...€¦ · kats, francesco...
TRANSCRIPT
Nanfang Yu, Patrice Genevet, Mikhail A. Kats, Francesco Aieta,Jean-Philippe Tetienne, Federico Capasso, Zeno Gaburro
Light Propagation with Phase
Discontinuities: Generalized Laws of
Reflection and Refraction
Xing Zhenping
Department of Optical Engineering
Zhejiang University
Page 2
Shape the wavefront
• conventional optical component
Lens and wavefront- Wikipedia
Gradual phase shift
accumulated during
propagation
Lack of freedom
• abnormal refraction & reflection
Metarefraction - Wikipedia
How to manipulate the
refraction angle when
the incident angle is
fixed ?
Page 3
Light propagation with phase discontinuities
Fermat's principle - the principle of the stationary phase
QED:光和物质的奇妙理论
Reflection:
Page 4
How to inprint phase discontinuities
•V - antenna
•2 modes - polarization
•B and C have a π phace difference
•scattered light from a
straight rod antenna
first-order antenna resonance
S: h ≈λeff/2 A: 2h ≈ λeff/2
brighter color - large currents
colored gradiant - directions of the currents
When the angle between the incident polarizationand the antenna symmetry axis is 45°
Page 5
Changing the angles
Analytically calculated amplitude and phase shift cross-polarized scattered light for V-antennas
gold rods with a circular cross section
λ=8 um
Page 6
V- antenna array
Γ
|dΦ/dx|= 2π/Γ
(G) FDTD simulations of the scattered electric field for the individual antennas
composing the array in (F)
Page 7
From materials to the 2-dimentional structures
A two-dimensional array of optical resonators
Spatially varying phase response
Subwavelength separation
Page 8
Experimental results
red curves: measured with a polarizer (magnified by a factor
of two for clarity)
black curves : measured with a polarizer
grey arrows: calculated results from EQU 6
Page 9
negative refraction & reflection
blue arrow: critical angle
Page 10
Discussion
• Gratings? Diffraction?
subwavelength spacing between the antennas
provide efficient scattering
prevent the occurrence of grating diffraction.
not too near - avoid the near-field coupling phenomena
Page 11
Discussion(2)
Fresnel lens ?
When can we apply the generalized laws of refraction & reflection?
deeply subwavelength thickness of the array
abrupt phase changes with no contribution from propagation
Fresnel lens - Wikipedia
Reference
Yu, Nanfang, et al. "Light propagation with phase discontinuities: generalized
laws of reflection and refraction." Science 334.6054 (2011): 333-337.
Further reading: Biagioni, Paolo, Jer-Shing Huang, and Bert Hecht. "Nanoantennas for visible
and infrared radiation." Reports on Progress in Physics 75.2 (2012): 024402.
Special thanks to lens(optics) - Wikipedia
meta material - Wikipedia
fresnel lens - Wikipedia