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THz Waveguides: The Evolution Rajind Mendis University of Wollongong, Australia
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Transcript of THz Waveguides: The Evolution - University of Wollongongweb/@eng/documents/...THz Endoscope Copper...
THz Waveguides: The Evolution
Rajind MendisUniversity of Wollongong, Australia
“Chronological” series of experimental investigations into
the guided-wave propagation andthe associated coupling of
THz pulses
Approach……
f
λ
Microwaves OpticsTHz
Ideas
IdeasTechniques
Techniques
Outline
• THz-TDS System
• Incorporating the Waveguide
• Important Considerations
• Waveguides…………….….
• Guided-Wave THz-TDS
Parabolic Mirror
Mirror
Lens
LIA
THz Beam
Chopper
Manual Delay
Aperture
Pump Laser
Ti:Sapphire Laser
Scanning Delay
Attenuator
Spectrometer
Periscope
Polarizer
InAs (Tx)
ZnTe (Rx)
λ/4 Plate
Si Plate
Wollaston Prism
Balanced Photo Detector
Beam Splitter
Pump
Probe
University of Wollongong
Schematic Diagram
THz-TDS System
THz-TDS System
Purge Chamber
Sample Position
Ti:SapphireLaserInAs
(Tx)
Pump Laser
ZnTe(Rx)
BalancedPhoto Detector
SpectrometerManual Delay
λ/4Plate
WollastonPrism
Quasi-Optic Coupling
Sample ≡ Lens-Waveguide-Lens
Waveguide
High Resistivity Si Lens(Hyper-Hemispherical or Plano-Cylindrical)
THzBeam
Sample
THz Beam
Incorporating the Waveguide
• Attenuation• Dispersion – Group-Velocity (vg)
• Input/Output Coupling – Mode-Matching
• Single-Mode Propagation
LLjrefout ee ozTCEE αββωω −−−= )()()( 2
AttenuationConstant
PropagationLength
PhaseConstant
2π /λ0CouplingCoefficient
TransmissionCoefficient
OutputField
ReferenceField
Important Considerations
Waveguides……
Hollow Metallic Circular WaveguideStainless Steel240 µm diameter
24 mm long
Negative Chirp 1ps 70 ps !
R. W. McGowan, G. Gallot, D. GrischkowskyOpt. Lett. 24, 1431 (1999)
Multi-Mode
0 10 20 30 40 50 60 70−30
−20
−10
0
10
20
30
Time (ps)
Ave
rage
Cur
rent
(pA
)
0 5 10−500
0
500
Ave
rage
Cur
rent
(pA
)
Time (ps)0 0.5 1 1.5 2 2.5 3 3.5 4
0
200
400
600
800
1000
1200
1400
Frequency (THz)
Rel
ativ
e A
mpl
itude
(0.76)TE11
TM11
TE12
Rel
ativ
e Am
plitu
de
Frequency (THz)
Fiel
d A
bsor
ptio
n (c
m-1
)
Frequency (THz)
AttenuationTE11
TM11
TE12
G. Gallot, S. P. Jamison, R. W. McGowan, D. GrischkowskyJ. Opt. Soc. Am. B 17, 851 (2000)
Hollow Metallic Circular WaveguideStainless Steel240 µm diameter
24 mm long
Vel
ocity
/c
Frequency (THz)
Dispersion
TE11
TM11
TE12 vp
vg
Hollow Metallic Rectangular Waveguide
0 5 10 15 20 25 30-30
-20
-10
0
10
20
30
Ave
rage
Cur
rent
(pA
)
Time (ps)
0 5-400
0
400
Brass250 µm × 125 µm
25 mm long
G. Gallot, S. P. Jamison, R. W. McGowan, D. GrischkowskyJ. Opt. Soc. Am. B 17, 851 (2000)
Negative Chirp 1ps 25 ps
“Effectively”Single-Mode (TE10)
0 1 2 3 4 50
100
200
300
400
Rel
ativ
e A
mpl
itude
Frequency (THz)
(0.6)TE10
G. Gallot, S. P. Jamison, R. W. McGowan, D. GrischkowskyJ. Opt. Soc. Am. B 17, 851 (2000)
Fiel
d A
bsor
ptio
n (c
m-1
)
Frequency (THz)
AttenuationTE10
TE30
TM12
Hollow Metallic Rectangular WaveguideBrass
250 µm × 125 µm25 mm long
Vel
ocity
/c
Frequency (THz)
TE10
TM12TE30
Dispersion
vp
vg
Single Crystal Sapphire325 µm diameter
7.3 mm long
S. P. Jamison, R. W. McGowan, D. GrischkowskyAppl. Phys. Lett. 76, 1987 (2000)
Negative Chirp 1ps 15 ps
Single-Mode (HE11)
Dielectric Fiber
0 1 2 3 40
100
200
300
400
500
Frequency (THz)A
mpl
itude
50 55 60 65
−20
−15
−10
−5
0
5
10
15
20
25
Time (ps)
pA
(a) 325µm diameter
−1 0 1 2−100
0
100
Reference
Dashed Lines – 150 µm dia.
Frequency (THz)
Pow
er A
bsor
ptio
n (c
m-1
)
Cou
plin
g C
oeffi
cien
t
Attenuation
Coupling
HE11
Frequency (THz)
Velo
city
/c
vp
vg
Dispersion
HE11
Dielectric FiberSingle Crystal Sapphire
325 µm diameter7.3 mm long
S. P. Jamison, R. W. McGowan, D. GrischkowskyAppl. Phys. Lett. 76, 1987 (2000)
Dielectric Slab (Plastic Ribbon)
-500
0
500
0 10 20 30 40 50-150
-100
-50
0
50
100
150
Aver
age
Cur
rent
(pA)
Time (ps)
High Density Polythene120 µm thick20 mm long20 mm wide
R. Mendis, D. GrischkowskyJ. Appl. Phys. 88, 4449 (2000)
Positive Chirp 1ps 45 ps
THz Beam
Dielectric Slab
Si Lens
Single-Mode (TM0)
0 1 2 30.0
0.2
0.4
0.6
0.8
1.0
Frequency (THz)R
elat
ive
Ampl
itude
Dielectric Slab (Plastic Ribbon)
R. Mendis, D. GrischkowskyJ. Appl. Phys. 88, 4449 (2000)
Dashed Line – High Resistivity Si (αBulk = 0.05 cm-1)
0 1 2 30.0
0.1
0.2
0.3
0.4
0.5
0.6
Fiel
d Ab
sorp
tion
(cm
-1)
Frequency (THz)
αBulk = 1 cm-1
TM0
Slab
Attenuation
0 1 2 30.6
0.7
0.8
0.9
1.0
vg
vp
Vel
ocity
/c
Frequency (THz)
TM0
Dispersion
THz Beam
Dielectric Slab
Si Lens
High Density Polythene120 µm thick20 mm long20 mm wide
Parallel-Plate Waveguide
0 5 10 15 20
-200
0
200
-200
0
200
400-200
0
200
400
A
vera
ge C
urre
nt (p
A)
Time (ps)
THz BeamE
E
E Parallel Plate Waveguide
Reference
12.6 mm long
24.4 mm long
Copper108 µm separation
20 mm wide
Single-Mode (TEM)
Undistorted propagation!!
R. Mendis, D. GrischkowskyOpt. Lett. 26, 846 (2001)
0.0
0.2
0.4
0.6
α
TM2
TM1
TEM
TM2
TM1
TEM
(cm
-1)
0
1
2
vg
vp
Velo
city
/ c
0 1 2 3 40.998
1.000
Frequency (THz)
0 1 2 3 40.0
0.2
0.4
0.6
0.8
1.0
5 6 7 8
-200
0
200
400
Rel
ativ
e Am
plitu
de
Frequency (THz)
Time (ps)
Aver
age
Cur
rent
(pA
)
Reference
12.6 mm
24.4 mm
Atte
nuat
ion
Dis
pers
ion
Parallel-Plate Waveguide
< 0.1 % change in velocity
R. Mendis, D. GrischkowskyOpt. Lett. 26, 846 (2001)
Copper Shims90 µm separation
15 mm wide
R. Mendis, D. GrischkowskyIEEE Microwave Wireless Comp. Lett. 11, 444 (2001)
x
r’
r
Waveguide
Si Lens
r = 11.5 mmr’ = 27.5 mm
250 mm longFlexible
Adhesive Tape
Parallel-Plate Waveguide
741 746 751 756 761
-15
0
15
30
Ave
rage
Cur
rent
(pA
)
Time (ps)
Photonic Crystal Fiber
H. Han, H.Park, M. Cho, J. KimApp. Phys. Lett. 80, 2634 (2002)
High Density Polythene500 µm diameter Tubes
20 mm long
Tubes
Filament
High-IndexCore
Time (ps)
Cur
rent
(pA
)
Frequency (THz)
Rel
ativ
e Am
plitu
de
Positive Chirp 1ps 35 ps Single-Mode
Field Attenuation < 0.25 cm-1
Coaxial Waveguide
T.-I. Jeon, D. GrischkowskyApp. Phys. Lett. 85, 6092 (2004)
260 µm (inner) diameter Cu Tube80 µm diameter Al-W Core
Teflon105 mm long
0 0.2 0.4 0.6 0.8 1.0 1.20
0.05
0.1
0.15
Rel
ativ
e A
mpl
itude
Frequency (THz)
(c)
Rel
ativ
e Am
plitu
de
Frequency (THz)
“Effectively”Single-Mode (TEM)
Direct Generation & Detection
Undistorted Propagation
Conduction Loss+
Dielectric Loss
0 20 40 60 80 100−40
−20
0
20
40
60
80
100
Time (ps)
Ave
rage
Cur
rent
(pA
) (c)
1.56ps
Time (ps)
Ave
rage
Cur
rent
(pA
)
1.56 ps
Al - W
TE11
Metal Wire Waveguide
THz Pulse
Cu Wire Teflon Support
Laser Excitation Beam
Laser Detection Beam
SOS Chip SOS Chip
T.-I. Jeon, J. Zhang, D. GrischkowskyApp. Phys. Lett. 86, 161904 (2005)
K. Wang, D. MittlemanNature 432, 376 (2004)
THz Endoscope
Copper0.52 mm diameter
Time (ps)
Ave
rage
Cur
rent
(pA
)
20 cm long
64 cm long104 cm long
Undistorted Propagation Single-Mode (Sommerfeld)
Metal Wire Waveguide
T.-I. Jeon, J. Zhang, D. GrischkowskyApp. Phys. Lett. 86, 161904 (2005)
Frequency (THz)
Fiel
d A
bsor
ptio
n (c
m-1
)R
elat
ive
Am
plitu
de 20 cm64 cm104 cm
Time (ps)
Ave
rage
Cur
rent
(pA
)
∆h =
17 cm
∆h
Atte
nuat
ion
Bending Loss
Copper0.52 mm diameter
Dashed Line – Air-Filled Coaxial (TEM)
Metal Sheet Waveguide
T.-I. Jeon, D. GrischkowskyApp. Phys. Lett. 88, 061113 (2006)
Al Sheet
Al Plate
PPWGTx Rx
LEB LDB THz Pulse L1
L2
L3
Aluminium51 µm thick10 cm wide14 cm long
Frequency (THz)
Am
plitu
de (a
.u.)
Time (ps)
Cur
rent
(pA
) Plate Out
Plate In
Undistorted Propagation Single-Mode (Zenneck)
Parallel-Plate Variations
A. Bingham, Y. Zhao, D. GrischkowskyApp. Phys. Lett. 87, 051101 (2005)
Parallel-Plate Photonic Waveguide
30 4020100Time (ps)
Frequency (THz)
Tran
smis
sion
(dB
)A
mpl
itude
(a.u
.)C
urre
nt (n
A)
Dielectric-FilledParallel-Plate Waveguide
R. MendisOpt. Lett. 31, 2643 (2006)
-50
0
50
100
-50
0
50
0 2 4 6 8
-50
0
50
100
Time (ps)
Elec
tric
Fiel
d (a
.u.)
THz
THz70 µm
Positive Chirp
Guided-Wave THz-TDS
4 6 8 10
-50
0
50
-150
0
150
300
Time (ps)
Aver
age
Cur
rent
(pA
)
0.0
0.2
0.4
0.6
0.8
1.0
Rel
ativ
e A
mpl
itude
R. MendisElectron. Lett. 42, 26 (2006)
0 1 2 3 3.520
40
60
80
100
Frequency (THz)
Con
duct
ivity
(S/c
m)
Parallel-Plate Waveguide
N = 1.6×1018 cm-3
µ = 398 cm2V-1s-1
5.75 mm long130 µm separation
• Highly-Doped Semiconductors• Conducting Polymers• Superconductors• Metals
Metal
Highly-Doped Si
Air
Reference
Sample
Reference
Sample
CollaboratorsOklahoma State University, USA
Dan Grischkowsky
Roger McGowan
Alan Cheville
Tae-In Jeon
Guilhem Gallot
Weili Zhang
John O’Hara
Jianquang Zhang
Steve Jamison
Abul Azad
University of Wollongong, AustraliaChao Zhang
Roger Lewis
Rodney Vickers
Michael Smith
