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CATEGORIES:Metamaterials and Nanophotonics Group Seminars
SUMMARY:Nonlinear Optical Metasurfaces: From Enhanced Ligh
t-Matter-Interaction to Full Phase Tailoring - Pro
f Thomas Zentgraf (Paderborn University)
DTSTART:20191014T123000Z
DTEND:20191014T133000Z
UID:TALK3866AT
URL:/talk/index/3866
DESCRIPTION:For efficient nonlinear processes\, the engineerin
g of the nonlinear optical properties of media bec
omes an important task. The most well-known techni
que for spatially engineering nonlinear optical pr
operties is the quasi-phase-matching scheme for se
cond-order processes like second harmonic generati
on. However\, the widely used technique of periodi
c polling of natural crystals only provides a bina
ry state for the nonlinear material polarization\,
which is equivalent to a discrete phase change of
π of the nonlinear polarization. The continuous t
ailoring of the phase of the nonlinear susceptibil
ity would greatly enhance flexibility in the desig
n and reduce parasitic effects.\nIn this talk\, we
will discuss nonlinear metamaterials with a conti
nuously controllable phase of the local effective
nonlinear polarizability. We will focus on plasmon
ic metasurfaces with various designs for the meta-
atom geometry together with different polarization
states of the light. In particular\, for circular
polarization states\, the controllable nonlineari
ty phase results from the phase accumulation due t
o the polarization change along the polarization p
ath on the Poincare Sphere (the so-called Panchara
tnam-Berry phase) and depends therefore only on th
e spatial geometry of the metasurface. By using a
fixed orientation of the meta-atom\, the nonlinear
phase can be spatially arbitrarily tailored over
the entire range from 0 to 2π. In contrast to the
quasi-phase-matching scheme\, the continuous phase
engineering of the effective nonlinear polarizabi
lity enables complete control of the propagation o
f harmonic generation signals\, and therefore\, it
seamlessly combines the generation and manipulati
on of the harmonic waves for highly compact nonlin
ear nanophotonic devices. \n\nWe will discuss the
concepts of enhancing nonlinear processes with sim
ultaneous phase engineering for the manipulation o
f second- and third-harmonic generation from metas
urfaces and the restrictions with respect to symme
try and geometry of meta-atoms. As an example for
novel applications based on nonlinear metasurfaces
\, we will discuss in detail the properties of a n
onlinear metalens and generalize the lens equation
s to include nonlinear processes.
LOCATION:Aston Webb WG12
CONTACT:Dr Miguel Navarro-Cia
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