Transcript
Introduction to
MOEMS
Potentialities & limitations for space applications Michel de Labachelerie, FEMTO-ST, CNRS, Besançon, France (
[email protected])
The application fields of MOEMS Micro Opto Electro Mechanical Systems are useful in all fields of information management • Acquisition Î Sensors • Transmission Î Communications • Storage • Display
MOEMS operate through optical beam • Total amplitude / Amplitude control distribution
• On axis phase / Phase distribution CCT - Toulouse 2007 • Wavelength
Why using MOEMS for standard optical functions ? NEW TECHNOLOGY Batch fabrication (decrease cost) Miniaturization Passive alignment (complex systems) Reliability NEW CONCEPTS Massively parallel systems (DMD displays, adaptive optics systems)
Î Low cost sophisticated optical systems are feasible CCT - Toulouse 2007
Optical beam amplitude control: attenuator & chopper
Microchopper based on an electrostatic micromotor (Sandia Lab.)
Infrared variable optical attenuator using an interdigited electrostatic actuator (Sandia Lab.)
CCT - Toulouse 2007
Amplitude distribution control: Beam angle control
2D torsion beam resonant scanner (doc. UCLA : Fan 1997 )
The « Digital Mirror Device » (doc. Texas Instr. 1997)
Single axis, large deflection resonant micro mirror (Henri Camon LAAS, Toulouse)
CCT - Toulouse 2007
Mirror: 3mm x 0.8 mm
Amplitude distribution control: Beam position control
Switching by optical fiber movement (doc. Darmstadt Univ.)
Switching by optical waveguide movement (doc. LETI / CEA)
Î Many applications in Optical switching for WDM CCT - Toulouse 2007
Phase / wavelength control: Interferometric control
VCSL with wavelength tuning by an external mirror (Tunability : 19 nm @15 V, Harris, Stanford Univ. 96)
Narrowband Fabry-Perot filter for WDM (BW 0.27 nm tunable on 70 nm @ 13 Volt, Time response : 200 kHz, Tayebati , CoreTek 98)
CCT - Toulouse 2007
Phase distribution control: Adaptive optics & synthetic spectrum
Adaptive optics mirror (actuation 0.9 μm @ 60 V, BW : 60 kHz , doc. Univ. Boston )
IR Optical spectrum synthetiser for correlation spectroscopy (MIT, Honeywell, Sandia)
Î New concepts taking advantage of large number of mirrors CCT - Toulouse 2007
Optical switching with MOEMS 2D switching matrix
3D switching matrix fiber number n
rotation of mirror number m
NxN switching matrix (Doc. AT&T : Lin 1999). 8X8 MUMPS prototype . Drive: 100 Volt. Response : 500 ms rotation of mirror number n
fiber number m
- A 1000 mirrors matrix is feasible - The beam angle should be closed-loop stabilized (Lucent 2000) CCT - Toulouse 2007
MOEMS applications • Sensors
Length measurement (absolute: fringe counting) Accelerometers, Pressure, Strain sensors Robot vision (laser scanning), Barcode reader (scanner) Biosensors & Chemical sensors
• Communications
Light amplitude/phase modulators Laser source control (frequency) Wavelength filtering & multiplexing Fiber-optics matrix switches, connectors Remote sensing through optical fiber
• Storage
SNOM read/write heads
• Display
TI display screen MICROVISION eye display Adaptive optics CCT - Toulouse 2007
Why using MOEMS for space applications ?
Mass reduction (lower launching cost for same
service, vibration resistance, high resonance frequency, faster thermal dissipation)
Reduced energy consumption Reliability improvement (self-aligned optical parts with less adjustments)
More micro-instruments on board (due to miniaturization)
More satellites (arrays of nano/pico satellites) More sophisticated instruments on board CCT - Toulouse 2007 Possible redundancy due to low cost
MOEMS application for space technology ?
Satellite monitoring • • •
On board instruments •
•
•
Attitude control sensors Structural health control (imaging, strain sensors,…) Distance control in formation flying Real time optical alignment for instruments (FT IR spectrometer, …) Aberrations compensation / focus adjustment with adaptive optics Spaceborne LIDAR technology for atmospheric monitoring
Communication • •
Beam tracking for inter-satellites communications Optical switching for telecommunication systems CCT - Toulouse 2007
Satellite monitoring : attitude control sensors
Adaptive Optics systems based on MOEMS are used for aberration control (smart vision) and improves pointing accuracy.
Small telescope imager for star pattern recognition & tracking used for attitude control (2W, 200 gr., 0.2 arc-sec). Source : USAF CCT - Toulouse 2007
Imaging devices Satellite integrity monitoring Smart dust camera concept
Scanning
Satellite inspector concept (CCD camera)
Reflected light LAAS prototype laser camera
(Image : H. Shea - EPFL)
MOEMS can be used for implementation of many ultra small laser cameras ( « smart dust » laser camera systems) the imaging of the satellite (even in small volumes). CCT - Toulouse 2007
Intersatellites optical links
MOEMS can be used for beam pointing in open space laser communication systems
Intersatellite optical communications Tracking
- Satellite to airplane (military) - Satellite to satellite (telecom)
Fine pointing mirror (Source : VTT)
Silicon mirror with variable focus (Doc. NipponDenso) CCT - Toulouse 2007
Micro-spectrometers & Hyperspectral imaging
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(Source : VTT)
(Source : US Air Force)
Spectral filtering is a very important application of MOEMS technology. A filtered image or spectral lines can be recorded. CCT - Toulouse 2007
III-V MOEMS filters Michel Garrigue, INL, Ecole Centrale de Lyon High index contrast air/SC Î High finesse resonator Electrostatic tuning of spectral response Integration of active optical functions (sources, detectors)
Air/InP Bragg Mirrors
Air gap cavity
Tuning voltag e
InP InGaAs Contacts
CCT - Toulouse 2007
10 x GaAlAs / Air
Ultra narrow bandwidth FP filters M. de Labachelerie, FEMTO-ST, Besançon
Concave stressed Bragg membrane
Specific MOEMS systems should be designed for narrow bandwidth FP systems Laser
Plane Bragg mirror
Longer cavities Spherical mirrors High reflectivity mirrors
Tuning
≈ 10 mm
Such MOEMS components can be used for many laser systems (Doppler LIDAR systems, stabilised lasers, …)
CCT - Toulouse 2007
Spherical mirror
Alignment Electrostati c actuator
ES actuator
Tunable laser sources Top filter contact n+ n
MOEMS mirrors for phase control are the basis of many laser systems: Tunable laser sources
InP/InGaAs
i P
MOEMS filter
I
Bottom filter & top VCSEL contact
N
N+-InP
N
air gap cavity
N-InP
N-cladding layer
Frequency stabilised laser sources
Laser spectroscopy OPO tuning for LIDAR technology Length measurements source Reference frequency for optical communications
Low linewidth (sub-MHz) SC lasers
Tunnel junction P-cladding layer Active layer
O+
O+
Regrown interface
N-cladding layer
N-Bragg mirror
N-InP substr. Bottom VCSEL contact
Monolithic tunable VCSEL
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Doppler velocimeters Laser system for atom cooling & trapping Sub-MHz linewidth externalcavity tunable laser CCT - Toulouse 2007
MOEMS switches for Telecom satellites MOEMS optical switching matrix can be used to switch telecommunication signals inside satellites Advantages: Unlimited signal bandwidth Low switching power consumption
Î A new concept of telecommunication satellite structure thanks to MOEMS CCT - Toulouse 2007 technology
MOEMS for telescopes NGST project Frederic Zamkotsian, LAM Marseille / Pierre KERN, LAOG Grenoble Field of view
Measured spectrum
Telescope
Light trap CCD Camera 20 µm pitch MM-Array
Spectrograph
Î Very efficient smart and massively parallel information processing systems CCT - Toulouse 2007 are feasible
Issues for MOEMS applications in space
Large technological investments - The low volume space market cannot justify large investments Î Usage of Commercial Off-TheShelf (COTS) devices is recommended - Space qualification of commercial devices (according to MIL-STD-883-E) is necessary
Immunity to space conditions - Radiations, Vacuum, Temperature - Understanding design rules for space applications CCT - Toulouse 2007
Performance of MOEMS for space applications
Optical quality of refracting / reflecting surfaces (originating from planar technology)
Rather high voltages for electrostatic actuations Bimorph type temperature T T + ΔT dependance More stringents requirements than ICs on packaging issues (since interface with outside environment is required) CCT - Toulouse 2007
Reliability issues for MOEMS in space
Immunity to vibrations / accelerations (mainly for the launching phase)
Immunity to ionizing radiations - Electrostatic sticking due to charge accumulation on this moving plates - Aging of some mechanical materials (stiffness variations) under radiations
Effects of temperature variations (strains) Effects of mechanical fatigue
CCT - Toulouse 2007
CONCLUSION / PROSPECTS MOEMS technology opens new prospects for space applications • Low cost capability allows for a large usage of MOEMS optical functions • New massively parallel concepts are possible • However some performance limitatins due to technology should be overcomed • And further work should be done on reliability issues for space environement CCT - Toulouse 2007
Thank you for your attention …
CCT - Toulouse 2007
CCT - Toulouse 2007
