Terahertz (THz) - Falcon Analytics · 2009-02-25 · Avnet-37 Project Detection of Concealed...
Transcript of Terahertz (THz) - Falcon Analytics · 2009-02-25 · Avnet-37 Project Detection of Concealed...
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Yehoshua Socol
Terahertz (THz)
Technology and Applications
16.07.2008
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Contents
" Introduction
" Commercial systems and components
" Spectral signatures
" Case study: Avnet-37 project
" Summary and Outlook
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AcknowledgementsAcknowledgements
�� Prof. B. Prof. B. KapilevichKapilevich Ariel UCAriel UC
�� Prof. N. Prof. N. VinokurovVinokurov BudkerBudker INPINP
�� Dr. N. WeissDr. N. Weiss ELTA Systems Ltd.ELTA Systems Ltd.
�� Dr. M. Dr. M. ManelaManela RAFAEL Ltd.RAFAEL Ltd.
�� Dr. S. Dr. S. ZvyaginZvyagin FZD FZD -- DresdenDresden
�� Mr. M. Mr. M. LebelLebel Ministry of Industry Ministry of Industry
& Trade, Israel& Trade, Israel
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THz radiation
Attenuation (typical): 0.1 dB/ m
50-100 m – still measurable
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THz radiation
" Solid-State physics: Spectroscopy" Astrophysics & Planet Science: Molecular Spectroscopy" Earth science: Upper atmosphere sensing from satellites
Present Applications
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THz radiation
" Biochemistry: Composition of Biomaterials, Spectroscopy" Biology: Changes of Conformational State" Chemistry: Molecular Binding States/Fast Reactions" Electronics: High speed circuits, Visualizing Charge" Genetics: Gene Sequencing" Mathematics: Scattering (RADAR Cross-Section & Modeling)" Medical Diagnostics: Disease States" Pharmaceuticals: Isomer identification/Tablet integrity" Physiology: Tissue Identification/Distinguishing Disease" Reconnaissance: Imaging through smoke" Safety: Chem & Biohazard Identification/Plume Detection" Security: Hidden Weapons/Contraband detection
Potential Applications (after P. Siegel, Caltech)
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Contents
� Introduction
" Commercial systems and components
" Spectral signatures
" Case study: Avnet-37 project
" Summary and Outlook
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THz Sources Detectors
•Thermal Radiation
•BWO
•RF up-converter
•Beat frequency
•Pulse laser
•Free Electron Laser
•Thermal
(pyro-, bolometers)
•RF down-converter
•Quantum
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THz systems evolution
ThruVisionThruVision (UK(UK--US)US)PicometrixPicometrix (US)(US)
2005
2008
Considerable progress 2005-2008
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THz systems performance
ThruVision
Distance: 3-25 m
Resolution: ~ cm
Numerical example:
λ = 0.3 mm (1 THz)
F# = 1
d = 5 m f = 5 cm
Resolution =λ F# d / f = 3 cm
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THz Components: Sources
Vendors (sample)
Thermal Radiation (passive)
BWO Microtech Instr.
RF up-converter Virginia Diodes
Beat frequency Topica
Pulse laser Picometrix
Free Electron Laser NL,DE,US,RU
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THz Source - example
Tripler up to 1.7 THz
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Contents
" Introduction
" Commercial systems and components
" Spectral signatures
" Case study: Avnet-37 project
" Summary and Outlook
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THz Spectral SignaturesTHz Spectral Signatures
TeraView - APS March meeting 2005 W. R. Tribe et al. SPIE 5354, 168 (2004)
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Theory: dielectric properties fully described by
complex dielectric constant ε = ε' + i ε'' (D = ε E)
Practice: other characteristics are more convenient
Complex refraction index n' + i n'' = n + i κ = √ (ε'+iε'')
Intensity I(x) decay with depth x I(x)=I(0) exp(- a x)
Absorption coefficient a = 4 π κ / λ
n'' = κ = a λ / 4π
λ radiation wavelength (in vacuum)
SignaturesSignatures’’ RepresentationsRepresentations
Dielectric CharacteristicsDielectric Characteristics
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““VectorVector”” THz spectraTHz spectracomplex refraction indexcomplex refraction index
n’
n’’
n’
n’’
D.J.Cook, B.K.Decker and M.G.Allen PSI-SR-1196 (2005)
Difficult to measure
Very rare in literature
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Understanding spectral shapesUnderstanding spectral shapes
Optical ResonancesOptical Resonances
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ε = 1+(Nf e2 / ε0 m [ω2 – ω02 – i γ ω])
n = √ ε
n = n' + i n'' Complex refraction index
n' refraction
n'' absorption
ε = ε' + i ε'' Complex dielectric constant
m,e – electron mass, charge
Nf – resonance strength
γ = ω0 / Q (analog of Q-factor in RF)
Understanding spectral shapesUnderstanding spectral shapes
Optical ResonancesOptical Resonances
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Theory – complex ε
0 0.5 1 1.5 2 2.5 30
2
4
6
8
10
12
ε'
fres
=1THz Qres
=10
0 0.5 1 1.5 2 2.5 30
2
4
6
8
10
ε''
Frequency, THz
ε’’
ε’
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Theory – complex n
0 0.5 1 1.5 2 2.5 31
1.5
2
2.5
3
3.5
n'
fres
=1THz Qres
=10
0 0.5 1 1.5 2 2.5 30
0.5
1
1.5
2
n''
Frequency, THz
n’’
n’
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Comparison with ExperimentComparison with Experiment
n’
n’’
n’
n’’
Experiment
Simulation
0 0.5 1 1.5 2 2.5 30
0.5
1
1.5
n'
n''
arb
. units
Frequency, THz
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7
<= n’’ ~ f
Why linear trend in absorption?
Understanding spectral shapesUnderstanding spectral shapes
Optical ResonancesOptical Resonances
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7
ε = 1+(Nf e2 / ε0 m [ω2 – ω0
2 – i γ ω])
ω<< ω0 => ε = 1+ …/ (– ω02 – i γ ω)
ε = 1– … /(ω02 + i γ ω)
<= n’’ ~ ω !
“Tails” of strong IR and visible resonances
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Contents
" Introduction
" Commercial systems and components
" Spectral signatures
" Case study: Avnet-37 project
" Summary and Outlook
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Avnet-37 Project
Detection of Concealed Objects
Israeli Ministry of Industry & Trade
THz Detection sector:
Ariel UC / ELTA Systems Ltd.
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Ariel UC THz facility
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Thomas Keating Ltd, UKTHz Absolute
Power Meter System
4
Newport Corporation
High-Performance Mid-Range
Travel Linear Stage ILS-100PP
With Universal Motion
controller ESP-300
3
Microtech Instruments, IncPyro-electric Detector
(based on LiTaO3
Crystal)
2
GYCOM
Nizhny Novgorod, Russia
THz source GBWO-103
0.8 – 1.1 THz
1
Manufacturer
Ariel UC THz facility
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Experimental set-up
Top view Optical scheme
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THz lenses
Material Polyethylene
Cost in-house prod. $ 75
Cost Microtech Inc. $ 700
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Experimental set-up
Transmission mode
+ : Absorption measurable
– : Impossible to measure high-loss samples
Sample
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Experimental set-up
Reflection mode
– : Impossible to measure absorption
+ : Possible to measure high-loss samples (refraction index)
Sample
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Reflection - quantitativeFresnel formulas
R(TE) = | r(TE) |2
R(TM) = | r(TM) |2
where
r (TE) = { cos (θ ) – √ [ε – sin 2(θ)] } / { cos (θ) +√ [ε – sin2(θ)] }
r (TM) = { ε cos (θ) – √ [ε – sin 2(θ)] } / { ε cos (θ) +√ [ε – sin2(θ)] }
θ – angle of incidenceε – complex dielectric constant
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Reflection - quantitative
Theory: reflection depends on absorption
Practice: the dependence is negligible, unless absorption
unreasonably high
0 20 40 60 800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
TM wave
Angle of Incidence
Reflection
Bre
wste
r angle
ε =10.0+ 0.0 i
ε =10.0+ 0.1 i
ε =10.0+ 1.0 i
ε =10.0+10.0 i
0 20 40 60 800
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Angle of Incidence
TE wave
ε =10.0+ 0.0 i
ε =10.0+ 0.1 i
ε =10.0+ 1.0 i
ε =10.0+10.0 i
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Measurements : Powders
0.85 0.9 0.95 1 1.05 1.1 1.150
5
10
15
20
25
30
Frequency, THz
Absorp
tion c
oeff
, cm
-1Aspirin
Paracetamol
TeraView, Freiburg Univ.
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Summary and Outlook
1. Through-clothes imaging is feasible
2. Identification of chemical hazards is feasible
“Terahertz has the opportunity to be a breakthrough
technology that can be used in several large markets
within non-destructive testing, homeland security and
defense. It is entering the high reliability application and
market development phase, which will take some time
to blossom.”
R. Kurtz, The Wall Street Transcript, Mar 2007