Transcript Microsystems for Diverse Applications using recently

Examen cours Cristaux Photoniques
Mechanical tuning of Photonic Crystals
July 23, 2009
Fabio Jutzi
PhD student EDMI
Ecole Polytechnique Fédérale de Lausanne
Sensors, Actuators and Microsystems Laboratory
EPFL STI IMT SAMLAB
Rue Jaquet Droz 1
CH-2002 Neuchâtel, Switzerland
Phone: +41 32 720 55 20
[email protected]
Outline
• Tuning of Photonic Crystals
• Mechanical Tuning concepts
Examples:
– Changing periodicity of crystal
– Applications in Displays
– Waveguide switch with switching slab
– Wavelength-selective variable-reflection filter
– Actuator inserting defects
– Waveguide switch using evanescent interaction
• Conclusion
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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Tuning of photonic crystals (PhC)
• Electro-optic effect
• Thermo-optic effect
• Non-linear optic effect
• Index-modulation
– Surface acoustic waves
– Liquid crystals
• Mechanical tuning
Examen Photonic Crystals Course
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Mechanical tuning concepts
• Changing the periodicity of the Photonic Cristal (PhC)
• Introducing defects
• Approaching material (evanescent coupling)
 Changes the PhC’s optical transmission characteristic
 Using electrostatic actuated mechanics (e.g. MEMS)
Applications:
• Optical switches
• Display systems
• Tunable filter
• Sensor (when measuring the change in transmission)
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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Changing periodicity of crystal
• Si pillars (white cylinders) embedded in
flexible polymer (PDMS)
• Stretched using comb-drive actuators
10% stretched
5% stretched
No elongation
Numerical modeling using FDTD method
W. Park, J-B. Lee, Mechanically tunable photonic crystal structure, Appl. Phys. Lett., vol. 85, nr. 21, 2004, pp. 4845-4847
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Applications for Displays (1)
• Self-assembled silica spheres on
ITO electrode
• Polymer-solution infiltrated
between spheres
• Increase of lattice constant with
solven swelling
 red-shift of reflected light
• Solvent and ions are pushed
electrolyticly into the lattice (fully
reversible with reverse potential)
A. Arsenault, D. Puzzo, I. Manners, G. Ozin, Photonic-crystal full-colour display, Nature photonics, vol. 1, 2007 pp. 468-472
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Applications for Displays (2)
A. Arsenault, D. Puzzo, I. Manners, G. Ozin, Photonic-crystal full-colour display, Nature photonics, vol. 1, 2007 pp. 468-472
Examen Photonic Crystals Course
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Waveguide switch with switching slab (1)
• SOI-wafer:
– 203nm device layer = waveguide + beam thickness
– 3µm oxide layer = gap between substrate and electrode
• When potential is applied between electrodes, slab is pushed down
and waveguide is interrupted
SEM picture
K-I. Umemori, Y. Kanamori, K. Hane, Photonic crystal waveguide switch with a microelectromechanical actuator, Appl. Phys.
Lett. 89, 021102 (2006)
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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Waveguide switch with switching slab (2)
• Introducing holes in the slab
lowers the transmission at off
state
• Lowest transmission at
~400nm displacement
lower transmission
higher transmission
Examen Photonic Crystals Course
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Wavelength-selective variable-reflection filter (1)
• For free-standing PhC-slab light is coupled by guided resonance
(at resonance wavelength) giving 100% reflectance
• Evanescent coupling to substrate when moving the slab
Theoretical investigations:
W. Suh, M. Yanik, O. Solgaard, S. Fan, Displacement-sensitive photonic crystal structures based on guided resonance in
photonic crystal slabs, Appl. Phys. Lett., vol. 82, nr. 13, 2003, pp. 1999-2001
Y. Kanamori, T. Kitani, K. Hane, Control of guided resonance in a photonic crystal slab using microelectromechanical actuators,
Appl. Phys. Lett. 90, 031911 (2007)
Examen Photonic Crystals Course
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Wavelength-selective variable-reflection filter (2)
• Reflective filter with a theoretical spectral bandwidth of 0.38nm can
be obtained
• SOI-wafer with sputtered NiCr as bimorph actuator
• Decrease of reflectivity for gaps smaller than 500nm
At gap > 5µm, resonant wavelength = 1545nm
Y. Kanamori, T. Kitani, K. Hane, Control of guided resonance in a photonic crystal slab using microelectromechanical actuators,
Appl. Phys. Lett. 90, 031911 (2007)
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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Actuator inserting defects (1)
• PhC line-defect waveguide with air holes blocking incident light
• Actuator pulls rod (of same material as PhC) into holes
 incident light is transmitted
• Transmission efficiency depends on number of air holes
Y. Kanamori, K. Inoue, K. Horie, K. Hane, Photonic crystal switch by inserting nano-crystal defects using MEMS actuator,
Proceedings of the 2003 IEEE/LEOS International Conference on Optical MEMS Waikoloa, HI, USA, August 18–21 (2003),
pp. 107–108
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Actuator inserting defects (2)
•
•
•
•
PhC on SOI-wafer
LPCVD poly-Si cantilever with SiO2 as sacrificial spacer-layer
Actuation by voltage between Cr-layer on cantilever and substrate
No experimental measurements shown
Y. Kanamori, K. Inoue, K. Horie, K. Hane, Photonic crystal switch by inserting nano-crystal defects using MEMS actuator,
Proceedings of the 2003 IEEE/LEOS International Conference on Optical MEMS Waikoloa, HI, USA, August 18–21 (2003),
pp. 107–108
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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Waveguide switch using evanescent interaction (1)
• Line-defect waveguide
• Dielectric plate above the waveguide interacts with evanescent
field depending on distance
Microscope picture
SEM micrograph
S. Iwamoto, S. Ishida, Y. Arakawa, M. Tokushima, A. Gomyo, H. Yamada, A. Higo, H. Toshiyoshi, H. Fujita, Observation of
micromechanically controlled tuning of photonic crystal line-defect waveguide, Appl. Phys. Lett. 88, 011104 (2006)
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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Waveguide switch using evanescent interaction (2)
•
•
•
•
SOI-wafer (200nm device layer, 600nm oxide) e-beam patterned
1µm poly-Si on 300nm sacrificial oxide patterned as moving plate
In 5µm interaction length 10dB extinction is realized
Compared to conventional waveguide: group velocity in PhC
smaller (shorter interaction length needed)
Wavelength of 1568nm with highest transmission chosen
Response time ~1.5ms
S. Iwamoto, S. Ishida, Y. Arakawa, M. Tokushima, A. Gomyo, H. Yamada, A. Higo, H. Toshiyoshi, H. Fujita, Observation of
micromechanically controlled tuning of photonic crystal line-defect waveguide, Appl. Phys. Lett. 88, 011104 (2006)
Examen Photonic Crystals Course
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Conclusion
• Different concept studies for mechanical tuning of PhC were
shown
• Not all are fabricated and completely measured
• There is still lot to be done and optimized
• Combining MEMS technology with PhC is very promising
• Different possible applications:
– Optical switch
– Optical switchable filter
– Display systems
Examen Photonic Crystals Course
Fabio Jutzi – July 23, 2009
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