current trends in optical mems - eecs at uc berkeleywu/presentations/ofc2005.pdf · ming wu @ ofc...

1Ming Wu @ OFC 2005

Current Trends in Optical MEMSCurrent Trends in Optical MEMS

Ming C. Wu

University of California, BerkeleyEECS Department &

Berkeley Sensor and Actuator Center (BSAC)[email protected]

OFC 2005Tutorial

2Ming Wu @ OFC 2005

AcknowledgmentAcknowledgment

Providing viewgraphs Thomas Ducellier (Metconnex) Li Fan (Formfactor) Andres Fernandez (Glimmerglass) Roger Helkey, Olivier Jerphagnon (Calient) Dan Marom (Lucent) Katsu Okamoto (Okamoto Lab) Olav Solgaard (Stanford University) Rod Tucker (Univ. Melborne)

Graduate students and Postdocs at Berkeley and UCLA WSS: J.C. Ted Tsai, Dooyoung Hah, Sophia Huang PhC switch: M.C. Mark Lee MEMS Microdisk: M.C. Mark Lee, Jin Yao MEMS PLC switch: Josh C.H. Chi, Jin Yao

3Ming Wu @ OFC 2005

OUTLINEOUTLINE

Introduction

Optical design considerations

Space division switches 2D MEMS optical switches 3D MEMS optical switches

Spectral domain processors Wavelength-selective switches

Planar lightwave circuits (PLC)-MEMS Integration

Diffractive optical MEMS

New directions

Summary

4Ming Wu @ OFC 2005

25 Years of Optical MEMS25 Years of Optical MEMS

1980 1990 2000

Scanning Mirror (Petersen, IBM)

Digital Micromirror Device (DMD, TI)

TIsTIs DMDDMD

Free-Space Optical Bench(UCLA/Berkeley)

3D MEMSSwitches

Micromotoers(Berkeley)

?

Grating Light Valve(GLV, Stanford)

2D MEMS Switches(Tokyo U)

TITI Silicon Light MachineSilicon Light Machine

5Ming Wu @ OFC 2005

Bulk MicromachiningBulk Micromachining

Anisotropic wet chemical etching (restricted to fixed crystalline orientations)

VerticalSidewall

Deep reactive ion etching (DRIE or ICP-RIE)

Combine with silicon-on-insulator (SOI) or III-V epi wafer

Suspended structure in one-step etching + releasing

Multi-layer structure by additional wafer bonding

High aspect ratio (> 20:1) Independent of crystal orientation More efficient use of real estate of

substrate (e.g., can produce closely spaced structures)

6Ming Wu @ OFC 2005

SurfaceSurface--MicromachiningMicromachining::2 2 StandardStandard Foundry ProcessFoundry Process

MUMPsMUMPs SUMMiTSUMMiT

Poly 1Poly 2

2 um

Poly 0

6.25 um

Poly 2Poly 1

Poly 4

Poly 3

0.5 um1 um

CMP1

CMP2

12.75 um

Poly 0

MEMSCAP Sandia National Lab

Fairchild (SUMMiT-4)

Si Substrate Si Substrate

7Ming Wu @ OFC 2005

MEMS Technologies and Optical Element Size MEMS Technologies and Optical Element Size

ElectromagneticActuation Electrostatic Actuation

1 cm 1 mm 1 m100 m 10 m

Scanning displayImaging

3D-MEMSOXC

DiffractiveMEMS

2DMEMSSwitch

2x2 SwitchesVOA

Projectiondisplay

OpticalElement

Size

Applications

MainActuation

Mechanisms

Micro-resonators

PhotonicCrystals

Bulk-Micromachining(Single Crystalline Si, DRIE, Wafer Bonding)

Surface-Micromachining(Poly-Si, Al)

MainFabrication

Technologies

Mirror-basedVOA

OADMWSS

Gain equalizerDispersion

compensator

8Ming Wu @ OFC 2005

Optical DesignsOptical Designs

9Ming Wu @ OFC 2005

Direct Coupling Without LensesDirect Coupling Without Lenses

0 200 400 600 800 1000-5

-4

-3

-2

-1

0

Inse

rtion

Los

s (d

B)

Distance (um)

Single Mode Fiber (SMF)

Thermally Expanded Core(TEC) Fiber

SMF

TECAirAir

Index-Matching

Fluid

Short propagation distance May be used for small switches or VOAs

d

10Ming Wu @ OFC 2005

Example: 2x2 SwitchExample: 2x2 Switch

Marxer, et al., J-MEMS, vol.6, 1997. p.277-85.

CrossState

BarState


FreeFree--Space Optics: Space Optics: GaussianGaussian BeamBeam

Larger beam waist Long collimation length System size ~ 2b Mirror diameter ~ 2aw0, a ~ 1.5 to 2

20wb =

02w 022 w

+=

22

02 1)(

bzwzw (Confocal Parameter)

b


Space Division Switches:Space Division Switches:

(1) 2D MEMS Optical Switches

(2) 3D MEMS Optical Switches


Scaling of 2D MEMS Optical SwitchesScaling of 2D MEMS Optical Switches

Input Channels

OutputChannels

ADD Channels

DROPChannels

CollimatorArrays

2D MEMSSwitchChip

22

2

0

0

20

2

2

22

NaLwa

N

awRPR

wbNPL

PN

=

=

=

==

2 ~ a (vertical) Radius Mirror :

rMicromirro of Factor Fill :

Length Chip :

Pitch Fiber : Count Port :

PL = 2b

02w 022 w

b2


Port Count of 2D MEMS SwitchesPort Count of 2D MEMS Switches

0

20

40

60

80

0 50 100 150 200

1/e Beam Waist (m)

Max

imum

Por

t Cou

nt

Fill Factor =

30%

50%

70%

0

1

2

3

4

5

0 50 100 150 200

1/e Beam Waist (m)

Loss

due

to M

irror

Tilt

(dB

) Mirror Tilt =

0.05

0.1

0.2

Port Count vs Beam Size Loss Due to Mirror Tilt

Accuracy and uniformity of mirror angles impose a loss penalty, which limit the maximum port count2

2

2

0

2 NaL

wa

N

=

:Size Chip

:Count Port

1/e2 Beam Waist (m) 1/e2 Beam Waist (m)

Max

imum

Por

t Cou

nt

Loss

due

to M

irror

Tilt

(dB

)


SurfaceSurface--MicromachinedMicromachined2D MEMS Optical Switches (16x16)2D MEMS Optical Switches (16x16)

L. Fan, et al., OFC 200216x16 Switch

L. Fan, et al., OFC 2002

010203040506070

89.8

0

89.8

4

89.8

8

89.9

2

89.9

6

90.0

0

90.0

4

90.0

8

90.1

2

90.1

6

90.2

0

Mirror Angle (degree)

Num

ber

Absolute angular uniformity ~ 0.05


Scaling of 3D MEMS OXCScaling of 3D MEMS OXC

02 w

022 w

( )

( )

WaistBeam : 2) ~ ( Radius Mirror :

AngleScan Mechanical :

:Length Path Optical

size System

:Count Port

0

0

20

2

2

2

2

22

33

~

9

waawR

wbL

NaLa

LN

=

==

=

=

3~ L

InputCollimators

InputCollimators

2D Array of 2-Axis Micromirrors

OutputCollimators

2D Array of 2-Axis Micromirrors

OutputCollimators2D Array of 2-Axis

Micromirrors

17Ming Wu @ OFC 2005Calient Network proprietary and confidential. Do not copy or distribute without permission

Evolutionary Networking

Revolutionary Technology

ASIC Voltage drivers

MEMS mirror array

Collimator array0

2400

4800

7200

9600

12000

0 0.5 1 1.5 2 2.5 3 3.5 4

Insertion Loss (dB)

Num

ber o

f Con

nect

ions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%100%

Cum

ulat

ive

Perc

enta

ge

320x320 connections below 3.5 dB

Transparent from 1260 to 1625nmTypical Wavelength Dependent Loss

Note: the higher loss peak around 1400 nm is due to OH water absortion and can vary.

00.5

11.5

22.5

33.5

44.5

5

1250 1300 1350 1400 1450 1500 1550 1600 1650

Wavelength (nm)

Inse

rtio

n Lo

ss (d

B)

PX

O E S C L

Transparent from 1260-1625 nm

3D-MEMS Switching Technology

Glimmerglass 2005

Glimmerglass 3D-MEMS Switches

32x32 to 80x80 OEM Module 16x16 to 24x24 2U Chassis 32x32 to 160x160 8U Chassis

3D-MEMS Architecture

2 x 6 x 7

MEMSMirror Array

CollimatorArray

Glimmerglass 2005

Glimmerglass MEMS Module

Electrostatic Actuation Electrode

Gimbaled Mirror

Mirror Wafer

Multi-Layer Ceramic

Snap Guard Wafer

V

Snap Guard Prevents Electrostatic Snap-Down Failure Mirror Material Is Highly Reliable Single-Crystal Silicon on Insulator (SOI) Ceramic Substrate Contains Electrodes, Routing, And Hermetic Seal Ring

SPIE Vol. 5604, pp. 208-217

(Scan Angle ~ 3.5 @ ~ 200V)


WavelengthWavelength--Selective Switches (WSS)Selective Switches (WSS)


Fourier Transform Pulse ShaperFourier Transform Pulse Shaper

Shaping femtosecond pulses by modulating the phases and amplitudes of their spectral components

A. M. Weiner, J. P. Heritage, and E. M. Kirschner, J. Opt. Soc. Am. 1988


Dynamic WDM FunctionsDynamic WDM Functions

f

f

Grati

ngColli

mators

Femtosecond pulse shaperPiston Mirrors

Tunable dispersion compensator

Deformable mirrors

Wavelength-Selective Switch

(WSS)

1xN analog micromirrors

Optical add-drop multiplexer (OADM)

1x2 Digital micromirrors

Spectral (or gain) equalizer

Variable reflectivity

mirror

Wavelength blocker

ON-OFF reflectors

DynamicWDM

Functions

MEMS Spatial Light Modulator

Array

MEMS

Spati

al

Light

Modu

lator

Array


1x4 Wavelength1x4 Wavelength--Selective Switch (WSS)Selective Switch (WSS)

f

f

Grati

ng

Y

X Collimato

rs

Analog Micromirror

Array


1x4 WSS1x4 WSS

D. Marom et al. (Lucent), OFC 2002 1x4 WSS Channel spacing: 50 or 100 GHz MEMS performance: 12 ( > 55 V )

T. Ducellier et al. (JDS-U), ECOC 2002

1x4 WSS Channel spacing: 100 GHz MEMS performance: 2


WSS provides: Port switching Wide passbands 10 dB DSE Blocking Low insert loss Low PDL, DGD

64 Channel, Wavelength-Selective 41 Switch (D. Marom)Free-Space Implementation


Analog Micromirror Array (UCLA)Analog Micromirror Array (UCLA)

Fixed fingers

Movable fingers

Hidden springs

Mirror

Anchor

zy

x

+/- 6 (mechanical)Scan Angles

0.0035dBSystem (3hr)0.00085Stability (3hr)

3.4 kHzRes. Freq.98%Fill Factor6 VVoltage

0 5 10 15 20 250

2

4

6

8

Rot

atio

n A

ngle

(deg

)

Applied Voltage (V)

0.5m 1m2m

3m

DMD-Like

Comb Finger Spacing

Hah, et al (UCLA) J. MEMS, 2004, p. 279 Tsai, et al (UCLA) IEEE PTL 2004, p. 1041


Scaling of WSSScaling of WSS

Grating

spatial

=

#22 f

fNColl

MEMS wfw

=

System size ~ 2 f

Total capacity (Nspatial x N )is constant

Proportional to f

Collimators

f f

AnalogMicromirror

Array

CollwMEMSw

Gratingspatial

=

#22 ffBWNN


Approach for Increasing Port Count (1)Approach for Increasing Port Count (1)

Use anamorphic prism pair to compress lateral beam size on MEMS micromirrors

Elliptical beams on MEMS mirrors Rectangular micromirror

D. Marom(Lucent)


Approach for Increasing Port Count (2)Approach for Increasing Port Count (2)

1xN2 WSS: 2D collimator array 1D array of 2-axis

micromirror array

Port count is increased from N to N2

N is the diffraction-limited linear port count

High port count WSS 1x32 WSS has been

demonstrated

f

f

Grating

Resolution lens

Y

X

J.-C. Tsai, et al., (UCLA) ECOC 2004, Paper Tu1.5.2


HighHigh--Fill Factor 2Fill Factor 2--Axis Micromirror ArrayAxis Micromirror Array

2-DOF mirror joint

Mirror

Lever

Vertical combdrive actuators

Gimbal-less High Fill factor (> 98%)

Large scan angle 3x leverage Powerful vertical combdrive

actuatorsxy

Original mirror position

Tsai, Fan, Hah, Wu, Optical MEMS 2004


SEM of SEM of GimbalGimbal--less 2less 2--Axis Analog Micromirror Axis Analog Micromirror ArrayArray

SUMMiT-V 5-layer surface micromachining process Mirror pitch: 200 um Large scan angles: 6.7 (mechanically) @ 75 V Fill factor: 98% Resonant frequency = 5.9 kHz


Planar Lightwave Circuit (PLC) MEMS Planar Lightwave Circuit (PLC) MEMS


(a) Configuration of 16ch-100GHz OADM (b) Photograph of OADM

K. Okamoto et al., Electron. Lett., vol. 31, pp.723-724, 1995

Drop Main outputport port

Main Addinput portport

ReconfigurableReconfigurable Optical Add/Drop Optical Add/Drop MultiplexerMultiplexer(ROADM)(ROADM)

(VG courtesy of K. Okamoto)


PLC 1x9 WSSPLC 1x9 WSS

1x9 WSS

Thermal optic switch 450 mW / switch Total power ~ 14W

Loss ~ 5.4 dB

Isolation > 46 dBInput

Output 1

Output 2

Output 3

Output 4

Output 5

1x2

C.R. Doerr, et al. (Lucent), OFC 2002 Postdeadline Paper, FA3


2x2 MEMS 2x2 MEMS WaveguideWaveguide WSXCWSXC

D.T. Fuchs, et al (Lucent) IEEE PTL, Jan. 2004

100 GHz channel spacing 10.6 dB insertion loss 20 dB extinction ratio

3 diffraction orders by AWG Optical phases of (+1, 0, -1) orders

modulated by MEMS piston mirrors Chip ~ 5 x 9 mm2


40 Channel, Wavelength-Selective 12 Switch (D. Marom)

Port 1

Input

Port 2Cylindricalcollimators

PLC 1 and PLC 2

Fourierlens

MEMSmicro-mirrorarray

Hybrid PLC and Free-Space Implementation

0

< 0

> 0

Switch to Port 1 Switch to Port 2

Hybrid WSS provides: Same benefits as free space WSS Compact implementation Integration of additional functionality


Compact Spectral Pulse Shaper (D. Marom)

Hybrid PLC and Free-Space Implementation

Pulse Shaper provides: Spectral domain processing Polarization independent Gateway to optical arbitrary

waveform synthesis

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 20 40 60 80

Voltage

Phas

e [

]

MEMS piston motion micromirror array >2 phase modulation Polarization insensitive

Input Pulse Thru shaper Dispersion Compensated Shaped signal


2D arrangement of ports for scalable 1x9 2D arrangement of ports for scalable 1x9 WSSWSS

Array of Waveguide Dispersive Elements

Collimating/Focusing lenses MEMS mirror

linear array


Interleaved spectrum switched to all Interleaved spectrum switched to all output portsoutput ports


1x8 PLC MEMS Optical Switches1x8 PLC MEMS Optical Switches

Slab

CoreCladding

Cladding

Theoretical loss ~ 0.5 dB, primarily due to vertical diffraction loss

Compact, no bulk optical elements

C.H. Chi, et al. (UCLA and Okamoto Lab), OFC 2004

4.5 mm

3 mm

FiberRibbon

Low-LossButt Coupling

Deep-EtchedCylindricalMicrolens

Micromirror

Fan-ShapedWaveguide Array

Free PropagationSlab Region

50 um


Tunable Tunable FabryFabry--Perot FiltersPerot Filters


Tunable Tunable FabryFabry--Perot (FP) FiltersPerot (FP) Filters

FixedMirror MovableMirror

FreeSpectralRange(FSR)

Frequency,

Tran

smis

sion

f

f

d

Tuning Efficient nm

GHz 40

TunableBroadly nm 260 3 ~ d For

=

=

df

FSR

ddcd

dff

mdcfmkd

ddcFSR

==

=

=

==

22222

22

2

:Condition Resonance

h) wavelengt(in freq.) (in

FinesseFSRf dB =3


Tunable FP FiltersTunable FP Filters

Has been demonstrated in many material systems III-V Dielectric (e.g., Si/SiO2) Semiconductor Air gap DBR

Various actuation mechanisms Electrostatic (parallel plate actuators) Thermal actuators Piezoelectric actuators


Nonlinear Optical ResponseNonlinear Optical Response

Optical Power

VG courtesy of Prof. Rod Tucker (Univ. Melbourne)

Data supplied by CoreTek


k xFE

PoutcR

PF outR )1(2

=

Keff xFE

Pout

dfdG

RcFSRPkk ineff

=)1(

4

Filter Response Slope

Pout

Effective Spring Constant due to Effective Spring Constant due to Radiation PressureRadiation Pressure

VG courtesy of Prof. Rod Tucker (Univ. Melbourne)


Diffractive Optical MEMSDiffractive Optical MEMS


Grating Light ValveGrating Light Valve

Applications Projection display Variable optical attenuators (VOA) Gain equalizers Wavelength blockers

Companies Silicon light machine (Cypress),

Lightconnect, Polychromix, Kodak

Nitride withAl coating

Incident Light Reflected Incident Light Diffracted

O. Solgaard, F. S. A. Sandejas, D. M. Bloom, "A deformable grating optical modulator", Optics Letters, vol. 17, no. 9, pp. 688-690, 1 May 1992.

PolychromixSilicon Light Machine


Telecommunications ApplicationsTelecommunications Applications

Dynamic Spectral Equalizer (DSE)

Reconfigurable Channel Blocking Filter Dynamic Gain Equalizer


MEMS MEMS SwitchableSwitchable WDM WDM DeinterleaverDeinterleaver Based on Based on GiresGires--TournoisTournois InterferometerInterferometer

FocusingLens

OutputFiber Array

PowerDetectorPower

Detector

TunableLaser

TunableLaser

MEMSMirrorArray

BeamSplitter

Input fiber

Olav Solgaard, Stanford University

http://wdm.stanford.edu/snrc/kyoungsik12_10_01.ppt


Nanophotonic MEMSNanophotonic MEMS


ON

Defect

1D and 2D 1D and 2D PhotonicPhotonic Crystal SwitchesCrystal Switches

1D Photonic Crystal:ON-OFF Switch

2D Photonic Crystal:1x2 Switch

( NxN Switch)OFF

Waveguide

Waveguide

Left Path Right Path


1D MEMS 1D MEMS PhotonicPhotonic SwitchSwitch

FDTD Transfer Matrix

Wavelength ( m)

Tran

smitt

ance FDTD

Transfer Matrix

Wavelength ( m)

Tran

smitt

ance


Wavelength ( m)

Tran

smitt

ance


Wavelength ( m)

Tran

smitt

ance

TransmissionState

ReflectionState


Experimental ResultsExperimental Results

100-nm-wide beam with < 5 nm tolerance

ON-OFF switching with 11 dB extinction ratio

0.5 ms switching time

Wavelength ( m)

Tran

smitt

ance

(dB

)

Transmission

Reflection

11dB

Wavelength ( m)

Tran

smitt

ance

(dB

)

Transmission

Reflection

Wavelength ( m)

Tran

smitt

ance

(dB

)

Wavelength ( m)

Tran

smitt

ance

(dB

)

Transmission

Reflection

11dB

M.C. Lee, et al (UCLA) OFC 2002

Anchor

PC Slider

ActuatorV

Waveguide(WG)

Waveguide(WG)Lightwave

Anchor

PC Slider

ActuatorV

Waveguide(WG)


Anchor

PC Slider

ActuatorVV

Waveguide(WG)



Microring ResonatorMicroring Resonator--Based PICBased PIC

S. T. Chu, B. E. Little, V. Van, J. V. Hryniewicz, P. P. Absil, F. G. Johnson, D. Gill, O. King, F. Seiferth, M. Trakalo and J. Shanton (Little Optics) OFC 2004

Thermally Tuned with Vernier Architecture

42 m


MEMS Tunable MicroresonatorsMEMS Tunable Microresonators

Change resonant wavelength Thermal tuning Free-carrier injection

Change effective Q Increase cavity loss (e.g.,

electroabsorption) Change waveguide-disk coupling

Change resonant wavelength Move mirror

Change effective Q Increase media loss Tune mirror reflectivity (Hard)

Fabry-Perot Resonators

0

0

0

Microdisk Resonators

Input

Drop

Drop

Input


Microdisk Resonator with MEMS Tunable Microdisk Resonator with MEMS Tunable CouplersCouplers

Microdisk

Waveguides

Microdisk

Waveguides

VV

VV

VV

VV

M.C.M. Lee and M.C. Wu, Optical MEMS 2003


Dynamic Optical AddDynamic Optical Add--Drop MultiplexersDrop Multiplexers

0 0.2 0.4 0.6 0.80

0.2

0.4

0.6

0.8

1

Gap Spacing (um)

Tran

smitt

ance

ThroughPort

DropPort

Input Through

AddDrop


Spoiling Q by MEMS Metal MembraneSpoiling Q by MEMS Metal Membrane

Use a metal membrane to spoil the Q of microring resonator Low loss resonant wavelength sent to Drop port High loss all wavelengths transmitted to Through port

Enable resonance Disabled resonance

Gregory N. Nielson, et al., (MIT) MEMS based wavelength selective optical switching for integrated photonic circuits, CLEO 2004


SUMMARYSUMMARY

Tremendous progresses have been made in MEMS devices and manufacturing Micro-optics Packaging Control

New trends in Optical MEMS -- Integration Higher level of integration, less free-space alignment MEMS-PLC integration MEMS-nanophotonics integration Electronics integration Single-chip optical MEMS system

current trends in optical mems - eecs at uc berkeleywu/presentations/ofc2005.pdf · ming wu @ ofc...

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