Rapid Prototyping of Photonic Crystal Rapid Prototyping of Photonic Crystal based THz Components towards based THz Components towards

Integrated THz Micro-SystemIntegrated THz Micro-System

Ziran WuZiran Wu Department ofDepartment of PhysicsPhysics

Department of Electrical and Computer EngineeringDepartment of Electrical and Computer Engineering

wzr@email.arizona.eduwzr@email.arizona.edu

OutlineOutline 1

Background / Motivations

Photonic Crystal based Components

Polymer-Jetting Rapid Prototyping

Realizations of Various THz Components

Components Systematic Integration

Conclusions

THz BackgroundTHz Background

* D. Arnone et. al., Physics World, 0953-8585, April 2000* Optics.org, analysis article, Oct. 28, 2002

2

Unallocated communication region

Gigabit data capacity

High bandwidth

Scattering loss < optical regime

Coverage in IR and optical blind conditions

Concealed object screening

THz bio-medical image: Identify tissue, tumor, DNA, etc.

THz chemical signatures: Explosives

* B. Ferguson, XC. Zhang, Nature Mater., 1, 26 (2002)* Peter H. Siegel, IEEE Trans. Microwave Theory Tech., 50, 910 (2002)

MotivationsMotivations 3

We need THz componentsSource, detector, filter, waveguides, antenna, quasi-optics, materials…

We need integration of componentsPre-alignments, packaging, systematic fabrication…

We need universality and customizabilityPlug-and-play, easy customization…

We need THz rapid prototyping

THz Micro-system

DUI

ResultsSource Detector

Photonic Crystal based ComponentsPhotonic Crystal based Components 4

Photonic Crystal (PhC)

Periodic arrangement of dielectric/ metallic structures

Bragg Diffraction among lattices

Forbidden wave propagation in certain frequency band

Scalable dimensions with frequency

Band Gap

THz thermal radiation source

* H. Xin et al, IEEE Trans. Antennas Propag., 56, 2970 (2008)

Normal Planckspectrum from amorphous object

IR

Inte

ns

ity Enhanced THz

emission

3-D Photonic CrystalRadiation Core

PBG structure optimized to generate strong emission peak in the THzband.

Inte

ns

ity

Normal Planckspectrum from amorphous object

IR

Inte

ns

ity Enhanced THz

emission

3-D Photonic CrystalRadiation Core

PBG structure optimized to generate strong emission peak in the THzband.

PBG structure optimized to generate strong emission peak in the THzband.

Inte

ns

ity

PBG fiber electron accelerator

* C. Sears et al, Proceedings PAC07, THPMS052, Albuquerque, NW, 2007

PBG Components ContinuedPBG Components Continued 5

Antenna with PhC substrate

* Peter de Maagt, et. al., IEEE Trans. Antennas Propag., 51, 2667 (2003)

* K. F. Brakora et. al., IEEE. Trans. Antenn. Propag., 55, 790 (2007)

Woodpile defect horn antenna

* A. Weily et. al., IEEE Trans. Antenn. Propag. 87, 151114 (2005)

Sub-wavelength effective-medium lens

Line-defect waveguide and bend

* K. Busch, Phys. Report 444, 101 (2007)* Nielsen et.al.,OTST-2009, MB5, March 2009

THz 3-D Rapid PrototypingTHz 3-D Rapid Prototyping 6

Objet (TM) polymer jetting prototyping

Layer-by-layer printing of structures

Printing resolution 42um (x) by 42um (y) by 16um (z)

UV curable model material Support material removable by water flushing (Matt mode)

Non-support-material printing available (Glossy mode)

Possibility of mixing various printing materials to achieve arbitrary spatial material properties

Rapid prototyping of arbitrary shapes

Alignment and assembly not necessary

Mass production achievable with very low cost

Build Materials CharacterizationBuild Materials Characterization 7

THz Time Domain Spectrometer

THz DetectorTHz Transmitter

Collimating Optics

Dispersion Compensation Ultra-fastLaser

Control Unit

* Ziran Wu, J. App. Phys., 50, 094324 (2008)

Photoconductive antennas as transmitter/receiver

Ultra-fast gating enables time-domain measurement

Covering 50GHz to 1.2THz with 10GHz resolution

Transmission / Reflection setup available

Build Materials THz PropertiesBuild Materials THz Properties 8

Multiple-reflection excluded by using thick slabs

Comparable EM properties in one family of polymers

Large enough refractive index contrast to open PBG Acceptable material loss

100 150 200 250 300 350 400 450 500 5502.6

2.65

2.7

2.75

2.8

2.85

Frequency (GHz)

Rea

l Per

mit

tivi

ty

VeroBlackVeroGreyVeroWhite

100 150 200 250 300 350 400 450 500 5500

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Frequency (GHz)

Lo

ss T

ang

ent

VeroBlackVeroGreyVeroWhite

Vero Family

Printed woodpile prototype

Dielectric / metallic rods with woodpile stacking formations Square rod width w= 352um and periodicity d= 1292um Printing took about 30 minutes; Consumable cost of approximately $10

Excellent agreements with simulations on both gap positions and depths

Filter: Woodpile StructureFilter: Woodpile Structure 9

* S.Y. Lin et.al,, Nature 394, 251 (1998)

Printed Johnson Structure prototype

Filter: Johnson StructureFilter: Johnson Structure 10

* S. G. Johnson and J. D. Joannopoulos, Appl. Phys. Lett. 77, pp. 3490-3492, 2000

Hole layer – air holes in dielectric Rod layer – dielectric rods in air Triangle lattice formation in each layer

Practically difficult to fabricate

Triangular lattice constant x= 1346um Air hole radius r= 500um Air hole height h= 1713um Rod / hole layer height t= 1071um

Fabrication well verified by characterization* Ziran Wu, Opt. Express, 21, 16442-16451 (2008)

Triangular-lattice array of air cylinders in a dielectric background Center core defect to form the wave tunnel Defect modes within the band gap of the complete PhC* 90% energy concentration in the core low radiation and material losses

Waveguide: Hollow-core PCF DesignWaveguide: Hollow-core PCF Design 11

Energy Distribution

* MIT Ab-Initio MPB package

Cross-Section View

HE11 mode

Band Gap 1

Band Gap 2

Only modes above the light line can propagate

Wave vector kza/2Pi

F

req

uen

cy f

a/c

0

PEC circular waveguide, TE11 mode feeds 84mm long polymer PBG waveguide Lattice pitch 3mm, air hole radius 1.3mm, center core radius 4.2mm Transmission loss as low as 0.04 dB/mm in 1st pass-band; Low return loss

Waveguide: Wave-port SimulationWaveguide: Wave-port Simulation 12

80 100 120 140 160 180 200 220-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency (GHz)

S-p

aram

eter

(d

B)

S21

S11

Band Gap 1

Band Gap 2 2

21

2

11

| |ln( ) /( )

1 | |

Sl

S

Power Loss Factor

Identical coupling to free space at input and output interfaces Transmitted power exponentially decays as waveguide length increases (Neglect multiple-reflections) Calculated loss matches well with wave-port simulation

Waveguide: Gaussian Beam ExcitationWaveguide: Gaussian Beam Excitation 13

100 105 110 115 120 125 1301.26

1.28

1.3

1.32

1.34

1.36

1.38

1.4

1.42

Waveguide Length (mm)

Lo

g (

Tra

nsm

itte

d P

ow

er)

60 80 100 120 140 160 180 200 220 2400

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Frequency (GHz)

Po

wer

r lo

ss f

acto

r (d

B/m

m)

Waveport

Beam IncidenceGaussian BeamIncidence

Transmitted PowerEvaluation Plane

Beam waist 3mm ( 90% coupling to HE11 mode)

Semi-log plotSlope = Power Loss Factor

* GEMS conformal FDTD package

112GHz

Modal field overlapping with Gaussian beam get coupling efficiency Optimum beam waist ~ 2.7mm, over 90% coupling to HE11 mode Plano-convex lens fabricated by rapid prototyping to reach optimal beam size

Waveguide: Modal Simulation / CouplingWaveguide: Modal Simulation / Coupling 14

Mode simulation based on effective index method

Modal E-field Profile

74% power coupled to HE11 modewith a beam waist of 4.2mm

* Lumerical MODE Solution

Waveguide: Fabrication and Bench SetupWaveguide: Fabrication and Bench Setup 15

Fabricated THz waveguide samples (Glossy modes)

Quasi-optics to focus the beam waist to 2.7mm

Waveguides of 50, 75, 100, 125, and 150 mm long characterized Time-gating ensures no multiple reflection in the calculation Guided mode resonance seen in all waveforms Four pass bands clearly show up around 105, 123, 153, and 174 GHz

Waveguide: Characterization ResultsWaveguide: Characterization Results 16

100 200 300 400 500 600 700 800 900 1000-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

Time delay (ps)

Fie

ld m

agn

itu

de

(V)

Reference50mm75mm100mm125mm150mm

80 100 120 140 160 180 200 220 240-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Frequency (GHz)

Po

wer

Tra

nsm

itta

nce

(d

B)

50mm75mm100mm125mm150mm

Linear fitting of power (dB) vs. waveguide length to get loss factor Extracted loss agrees pretty well with the beam incidence simulation Downshift of about 7 GHz probably due to fabrication error (need support material)

Waveguide: Power Loss FactorWaveguide: Power Loss Factor 17

80 100 120 140 160 180 200 220 2400

0.05

0.1

0.15

0.2

0.25

Frequency (GHz)

Po

we

r lo

ss

(d

B/m

m)

MeasureBeam Inc

50 75 100 125 15045

46

47

48

49

50

51

52

Waveguide length (mm)

Tra

nsm

itte

d p

ow

er

(dB

)

Linear fitting at 107GHz

Antenna: Photonic Crystal HornAntenna: Photonic Crystal Horn 18

90 100 110 120 130 140 150 160 170-35

-34

-33

-32

-31

-30

-29

Frequency (GHz)

S11

(d

B)

100 110 120 130 140 150 160 1700.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Frequency (GHz)

Rad

iati

on

Eff

icie

ncy

Copper Horn

PCF Horn

Circular waveguide TE11 feedingPolymer loss: constant conductivity 0.23

4.2mm flared to 8mm aperture radii (12.4 degree)35mm optimized horn length along axis

Not bad considering1.5dB material loss

Directional beam obtained at two working frequencies Comparable main beam angle with copper horn; Side-lobe level not as low Works much better than copper horn (over-moded) at high frequency

Antenna: Radiation PatternsAntenna: Radiation Patterns 19

0 50 100 150 200 250 300 350-50

-40

-30

-20

-10

0

10

20

30

Theta Angle (Degree)

Dir

ecti

vity

(d

B)

Copper Horn

PCF Horn

114GHz

0 50 100 150 200 250 300 350-50

-40

-30

-20

-10

0

10

20

30

Theta Angle (Degree)

Dir

ecti

vity

(d

B)

Copper Horn

PCF Horn

164GHz

Far-Field Radiation Pattern of Phi= 0º Cut (x-z plane)

Transition: Waveguide-to-Planar CircuitTransition: Waveguide-to-Planar Circuit 20

Tapered cone helps impedance matching Power directed into the dielectric rod waveguide (TIR guiding)

Circular-to-square cross section transition Smooth surface generated by HFSS

Tapered wedge transit to microstrip substrate PEC flares on top and bottom shrink the field spread Mstrip single-mode operation up to 120GHz (400um trace width 127um substrate thick)

Transition: Waveguide-to-Planar CircuitTransition: Waveguide-to-Planar Circuit 21

70 80 90 100 110 120 130 140 150 160 170 180-50

-45

-40

-35

-30

-25

-20

-15

-10

Frequency (GHz)

S11

(d

B)

-6.75dB insertion loss best at 108GHz; low return loss Excluding 2.1dB waveguide loss 2.3dB loss at each transition section About 4dB more loss if polymer material loss included

70 80 90 100 110 120 130 140 150 160 170 180

-60

-50

-40

-30

-20

-10

0

Frequency (GHz)

S21

(d

B)

Mstrip connected

Mstrip disconnected

Sub-wavelength Effective MediumSub-wavelength Effective Medium 22

2 2

2 2 2 3

(1 ( 1) )(1 ( 1)( ))

1 ( 1)( 2 )

y z y y zzr r

xxeff

y x y y z x y zx zzr

a a a a aa

L L L La a a a a a a aa aa

L L L L L L

Capacitive Estimation of the Permittivity Tensor

Effective medium with artificially designed anisotropy

* K. F. Brakora et. al., IEEE. Trans. Antenn. Propag., 55, 790 (2007)

Source: Photonic Cavity ArraySource: Photonic Cavity Array 23

Array of cubes with ~ 200um sides Printed by polymer-jetting and metalized via sputtering Electroplating or electro-less deposition for 3-D metallization Complete band gaps between THz resonance frequencies Strong and sharp thermal emission at THz 500um

Source: PBG e-Accelerator at THz?Source: PBG e-Accelerator at THz? 24

Very cheap prototyping Arbitrary fiber / coupler design

Need a THz power source to drive it

* R. England et al., Bob Siemann Symposium and ICFA Workshop, July 8th, 2009

Integrated THz Micro-SystemIntegrated THz Micro-System 25

THz Micro-System

Source

FilterWaveguide

Metamaterial

THz ChipTHz

Sample

Transition to planar-circuits

Antenna

ConclusionsConclusions 26

THz rapid prototyping technique demonstrated

THz filter, waveguide, and antenna fabricated by prototyping

Characterizations of these components show good agreements with the designs

Prototype-able transition-to-planar circuit, effective medium, and source proposed and under study

Systematic integration of the aforementioned building blocks leads to THz micro-system

Acknowledgement Acknowledgement

Graduate StudentIan Zimmerman 1

For metal sputtering on cavity array

Wei Ren Ng 2

For sample fabrication and post-process

FacultyProf. Hao Xin 1

Prof. Richard Ziolkowski 3

Prof. Michael Gehm 2

For help on both EM modeling and sample fabrications

1 Millimeter Wave Circuits and Antennas Lab2 Non-Traditional Sensors Lab3 Computational Electromagnetics Lab

Thanks for your attention!

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