B THz TechnologyB THz TechnologyProf. Dr.-Ing. Franko KüppersGroup Photonics and Optical Communications Department of Electrical Engineering and Information TechnologyTechnische Universität Darmstadt
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 1
Workpackage B – THz Technologyp g gyOverview: projects and project leads
A THzSensors and Sensor Concepts
C THz System Technologyand Sensor Systems
B THz-Technology
The technology basis for workpackages A and C
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 2
The technology basis for workpackages A and C.
Workpackage B – THz Technologyp g gyOverview: projects and project leads
Technology for all components along
B2 B1 B5 B4 B3
Technology for all components alongthe THz signal path from sender to receiver
Interconnection of workpackages with well-defined transit points
B2 B1 B5 B4 B3 Optical
transmitter(laser/VCSEL)
Photo-conductive
mixer
Micro-mechanicalswitch
(waveguide)
Tunable,passive
components
Schottky-detectors
B THz-Technology
The technology basis for workpackages A and C
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 3
The technology basis for workpackages A and C.
B1- Prof. JakobyO ti i ti f h t d ti i fOptimization of photo-conductive mixers for CW THz systems
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 4
Optimization of photo-conductive mixers for p pCW THz systems
MotivationMotivation Freespace-CW-setup as a working platform for Test, Characterization and Characterization, and Optimization of components and concepts
Cross-linkingA B2 B5 C2
Beat signal Fiber
A, B2, B5, C2 Fraunhofer Heinrich-Hertz-Institute: World market leader for InGaAs semiconductor
production for photo-conductive THz applicationsproduction for photo conductive THz applications Semiconductor material will be provided to other
project partnners Many options for THz charakterization offer
possibilites for verification
Si lens
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 5
possibilites for verification
Setup and principal of a p p pphoto-conductive CW THz system
Photo conductive mixer coverts
Two CW laser signals at
slightl
Photo-conductive mixer coverts optical beat signal into electrical
THz signal
Quasi-optical guidance of
opticalheterodyne
downward mixing
slightly different
frequencies
gbeam in free space using
mirrors, lenses,
apertures
control
Detection of THz-signals through
coherent superposition with optical beat signal
h itidelaydetector
Correctly chosen wavelengths of lasers delivers beat signal at
THz frequenciesDelay to determine the complex amplitude of the THz signal thro gh ariation of the phase relation bet een
→ phase sensitive measurement
delay
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 6
signal through variation of the phase relation between the two signal paths
Options for implementation of a p pCW THz system
Free-space Integrated 1 55 mFree space Maximum flexibility
for experimental material characterization
Integrated Integrated structures enable
a higher measurement dynamic range through
1.55 m Optical components from
telecommunications are cost-efficient and mature
Providing the foundation for other workpackages
Optimizing efficiency of THz-output power through finger
y g gshortened signal paths
Robust and cost-efficient
Reduced sample size
Commercialization becomes significantly easier
output power through „finger mixer“ and antenna innovation
p
Hugh micromechanic challenge
Comprehensive adaptation
Mixers have to be adapted to new substrate
p pof mixers necessary
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B2 – Prof. KüppersW l th t bili d t bl VCSEL fWavelength-stabilized tunable VCSEL for THz generation
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 8
Wavelength-stabilized tunable VCSEL for gTHz generation
Realization of a tunable compact THz source basedLaser 1 f1Opticalcoupler
Realization of a tunable, compact THz source based on VCSEL(“Vertical-cavity surface-emitting laser”) Mixer generates THz signal from optical beat signal
Laser 2 f2
g g p g Wavelength tuning of one laser
enables tuning of THz signal Emission of THz signal through planar antenna
THz signalOptical beat
signalg
Frequency stabilization and control
Photomixer structure Semiconductor substrate
with antenna
Lens
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 9
Antenna (~1.5 mm)(~10 µm)
Tunable laser source (VCSEL)Tunable laser source (VCSEL)
Relatively easy itegration since emission normal with respect to wafer surfaceM d ti ibl / i t t d VCSEL Mass production possible / integrated VCSEL arrays Cost-efficient optics at telecom wavelength (1550 nm) because of mass market Low power consumption and low heat build-up integrability
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 10
Wavelength tuningWavelength tuning
Properties of our VCSEL:Properties of our VCSEL: Highest wavelength tuning range:
> 100 nm→ relates to tuning rangeof approx. 10 THz(current systems: < 2 THz)
Wavelength tuning speed up to 200 kHz(current systems: < 1 Hz)
High spectral purity: Side-mode suppression > 45 dB
Output power > 3 mWSelected reference:Selected reference: C. Gierl et al.,
“Surface micromachined tunable 1.55 μm-VCSEL with 102 nm continuous single-mode tuning ”mode tuning,Opt. Express 19, 17336-17343 (2011).
Cross-linking: A, B1, C2
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B3 – Prof. JakobyyLow-noise sensitive Schottky detectors
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 12
El t f th d t tElements of the detector
Increased responsivity considering2
Nonlinear properties andSelection with respect to Internal noise
Temperature behaviour of diodes Temperature dependence
OutputInput Impedancematching
Detectordiode
Antennaelement
Low-noisepre amp
Selection criteria Polarization Bandwidth
Cross-linking:C1 Detector arra s
matching diodeelement pre-amp
Optimization1 of Responsivity
N i dCross-linking:C4 TH A t Bandwidth
Impedance Emission charateristic
C1 – Detector-arrays(Jun.-Prof. „Systems“)
Noise- and RF-properties
C4 – THz Antennas(Jun.-Prof. „Systems“)
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Key component
Zero bias Schottky diodes
y pZero-Bias Schottky diode
Ad dZero-bias Schottky diodes for low-noise, sensitive Schottky detectors for room temperature applications
Advanced CompoundSemiconductor Technologies GmbH
Quasi-vertical setupDiscrete Diode mounted on CPW
Optimized thermal properties Minimized internal noise
Membran substrate (t = 4 µm, |r| = 2,8)Membran substrate (t 4 µm, |r| 2,8)
Minimized parasitic capacitance
Higher cutoff-frequency up to > 1 THz
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 14
Key component for mm- and Sub-mm applications
B4 – Prof. JakobyyTunable THz liquid crystal components
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T bl TH li id t l tTunable THz liquid crystal components
G lGoals Development and realization of novel tunable „high-performance“ THz components
based on specific synthesized nematic liquid crystals (LC)p y q y ( ) Adapted measuring methods and setups for material and device characterization Optimization of THz LC: High anisotropy and low dielectric losses Improved tuning speedImproved tuning speed Novel device concepts and designs for high tunability, high figure-of-merit (FoM) and high
linearity
Investigation of various conceptsInvestigation of various concepts Variable waveguide elements in planar and hollow waveguide based topology Discrete tunable capacitances for tuning elements and capacitive-load waveguides Quasi-optical setups like transmission phase shifter
Envisaged tunable LC components in the THz rangeEl t i ll t bl h hift l i filt t d l
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 16
Electronically tunable phase shifter, polarizers, filter, antenna-arrays and lenses
Liquid Crystal Microwave Technologyq y gy“Made in Darmstadt”
USP in LC based tunable wave components through10 years of USP in LC-based tunable -wave components through10 years of close interdisziplinary collaboration: TU MWT & Merck research
Novel synthesized LC compounds and novel device concepts in various technologies and waveguide topologies for various applications World-leading material/device properties in the -wave range
Materialgüte @ 30GHz ,|| ,r r
Steuerbarkeit: >25%First measurements up to 1 THz
>25%tan<0.006
,||r
maxtan
Materialgüte: >40
B t il üt (Ph hi b )tan 0.006 > 40 Bauteilgüte (Phasenschieber):
d F M t i it F
> 260°/dB
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 17
und FoM steigen mit Frequenz anStandard Liquid Crystals
Liquid-crystal tuning principle:q y g p pMicrostripline phase shifter
RF
~
RF
U
Est
VV
r
||r
U
SubstratePlated GoldPreorientation layer Polyimide layer
Spacers
|||| tan , r
Vth
tan
U
LC orientation withPolyimide layer
tan,r
2( ) ) ( )0(U U
VVth Vmax
||tan U Polyimid film static E-field: Est
static B-field: B t
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 18
0
( ) ) ( )0(r rU U
static B field: Bst (for characterization)
Vertical integration:gMaterial – component – system
System integration and functional testing atSystem integration
System integration and functional testing at SynView GmbH and DLR Use in phase-tuned antenna groups with
integrated THz detectors for electronic beamrolo
gy
Metrology, setup and RF characterization
integrated THz detectors for electronic beam steering for imaging systems (C1 und C4, Jun.-Prof “Systems”) Demonstration of functional principles and
Met
Technologies and design of new
LC componentsatio
n
Demonstration of functional principles and concepts (polarizer, phase shifter) Investigation of various topologies
Tunability and LC orientation
LC components
Sim
ula Innovative assembly technologies (B5)
Theory and modeling for in-house multiphysics simulation tools (C3)
Material optimization and characterizationat
eria
l Novel approaches and metrology for RF characterization in the THz range Specialized THz material synthesis (Merck)
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 19
and characterization
Ma Specialized THz material synthesis (Merck)
B5 – Prof. SchlaakMikromechanical switchable waveguides
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 20
Mik h i l it h bl idMikromechanical switchable waveguides
THz Schaltmatrix THz-Sensormatrix
THz-Welle
THz-Schaltmatrix THz Sensormatrix
THz-Welle
Block diagram of THz measuring system with switching matrix for parallel processing
Output 1(on)
Output 2(off)
Eingang
Schlaak/Jakoby/Küppers Schlaak/Jakoby/KüppersSchlaakPIs:
Design Manufacturing Characterization
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 21
C2, C3, A C2Cross-linking:
Micromechanical switchable waveguidesg„RF-MEMS“
Goal: Realization of mechanis for reversible change of signal paths in
the THz range („switch“)St t f th tState of the art: Micro-elektro-mecanical switch for microwave signals Micro-elektro-mecanical switch for optical signalsApproach:Approach: Adaptation to THz range and integration Various waveguides to be investigated
(in cooperation with C2, A) Switch geometry to be adapted to THz wavelengths Integration with THz transmitters and receivers for
characterization necessary (C2)Si l ti f it bl t t ( C3) Simulation of suitable structures (→ C3)
Implementation with available technologies(UV lithography, micro-electroplating, thermal /electro-static actuators)
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 22
Workpackage B – THz Technologiesp g gCross-linking with workpackages A+C
Technological coverage of all components alongthe THz signal path from transmitter to receiver
Cross-linking of workpackages with well-defined transfer points
A A AC2 C2 C1 C4C1 C3-4C2-4
B2 B1 B5 B4 B3B2 B1 B5 B4 B3 Optical
Sender(Laser/VCSEL)
Photo-conductive
Mixer
Mikro-mechanicalSwitch
(Waveguide)
Tunable,passive
Components
Schottky-Detectors
B THz Technologies
The technology basis for workpackages A and C
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 23
The technology basis for workpackages A and C.
Workpackage B – THz Technologiesp g gInput for demonstrator
Demonstrator:Lab-on-chip for
biomedicalanalytics
B2 B1 B5 B4 B3B2 B1 B5 B4 B3 Optical
Sender(Laser/VCSEL)
Photo-conductive
Mixer
Mikro-mechanicalSwitch
(Waveguide)
Tunable,passive
Components
Schottky-Detectors
B THz Technologies
The technology basis for workpackages A and C
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 24
The technology basis for workpackages A and C.
Workpackage B – THz Technologiesp g gInput for industry demonstrator
Industry demonstrator: 3D imaging or gas sensingIndustry demonstrator: 3D imaging or gas sensing
B2 B1 B5 B4 B3B2 B1 B5 B4 B3 Optical
Sender(Laser/VCSEL)
Photo-conductive
Mixer
Mikro-mechanicalSwitch
(Waveguide)
Tunable,passive
Components
Schottky-Detectors
B THz Technologies
The technology basis for workpackages A and C
April 11, 2013 | LOEWE Project “Sensors towards Terahertz” | Franko Küppers | 25
The technology basis for workpackages A and C.