Workshop on High-Field THz Science
High Power THz Generation and THz Field
Enhancement in Nanostructures
Fabian Brunner1, Salvatore Bagiante2, Florian
Enderli1, Justyna Fabianska1, and Thomas
Feurer1
1Institute
of Applied Physics, University of Bern, Switzerland
2Laboratory for Micro- and Nanotechnology, Paul Scherrer
Institut, Switzerland
Outline
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Introduction:
Applications of strong electric and magnetic fields at
THz frequencies
Generation of intense THz pulses in nonlinear optical
crystals
THz field enhancement in metallic nanostructures
THz SHG in lithium niobate crystals
Conclusions
Outline
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Applications of strong electric and
magnetic fields at THz frequencies
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Nonlinear optics at THz frequencies (bulk
semiconductors, quantum dots, …)
Direct excitation of transverse optical phonons or antiferromagnetic spin waves
Acceleration of charged particles and measurements of
electron bunch profiles (THz streak camera)
Single shot imaging
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Introduction
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Efficient THz generation in NLO crystals:
Requirements for the crystals
A large tensor element of the nonlinear optical
susceptibility
> Low linear and nonlinear optical absorption
> Low THz absorption
> Phase-matching:
— collinear:
(organic nonlinear optical crystals: DAST, OH1,…)
— Cherenkov-type:
(LiNbO3)
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THz generation in nonlinear optical crystals
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High power THz time-domain
spectroscopy
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Comparison of laser-based methods for
THz pulse generation
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Peak electric field vs. pulse energy
Assumptions:
> Single cycle pulse
> Focusing with F# = 1
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Non-resonant enhancement:
array of slits
Typical field enhancement of a slit
Gold slit array on silicon
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Ideal periodicity of slit array
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most effective harvesting
of incident field
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Nonlinear signal: trade-off
between volume of high
field strength and high
field enhancement
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Resonant enhancement:
Split ring resonators
31 nm
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Second harmonic generation in LiNbO3
Fabrication of the sample
Simulated spectra of
transmitted pulses
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Conclusions
Combination of high power THz source with local field
enhancement enables new experiments
> Fabrication of gold nano-structures on silicon
> New fabrication process for gold nano-slits filled with
lithium niobate
> Simulation of SHG spectra and optimization of geometry
parameters for the highest conversion efficiency
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