Prof. Dr.-Ing. Franko Küppers · “Surface micromachined tunable 1.55 μm-VCSEL with 102 nm...

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


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




B1- Prof. JakobyO ti i ti f h t d ti i fOptimization of photo-conductive mixers for CW THz systems


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


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


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


B2 – Prof. KüppersW l th t bili d t bl VCSEL fWavelength-stabilized tunable VCSEL for THz generation


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


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


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


B3 – Prof. JakobyyLow-noise sensitive Schottky detectors


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“)


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


Key component for mm- and Sub-mm applications

B4 – Prof. JakobyyTunable THz liquid crystal components


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


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


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


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)


and characterization

Ma Specialized THz material synthesis (Merck)

B5 – Prof. SchlaakMikromechanical switchable waveguides


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


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)


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




Workpackage B – THz Technologiesp g gInput for demonstrator

Demonstrator:Lab-on-chip for

biomedicalanalytics


Sender(Laser/VCSEL)

Photo-conductive

Mixer


(Waveguide)

Tunable,passive

Components

Schottky-Detectors

B THz Technologies




Workpackage B – THz Technologiesp g gInput for industry demonstrator

Industry demonstrator: 3D imaging or gas sensingIndustry demonstrator: 3D imaging or gas sensing


Sender(Laser/VCSEL)

Photo-conductive

Mixer


(Waveguide)

Tunable,passive

Components

Schottky-Detectors

B THz Technologies




Prof. Dr.-Ing. Franko Küppers · “Surface micromachined tunable 1.55 μm-VCSEL with 102 nm...

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