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Introduction to Nanomechanics (Spring 2012). Martino Poggio. Nanomechanical Measurements. Displacement measurement is crucial for force transduction Different types of nanomechanical displacement measurements (advantages & disadvantages) Focus on optical interferometry - PowerPoint PPT Presentation
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Introduction to Nanomechanics(Spring 2012)
Martino Poggio
Introduction to Nanomechanics 2
Nanomechanical Measurements
• Displacement measurement is crucial for force transduction
• Different types of nanomechanical displacement measurements (advantages & disadvantages)
• Focus on optical interferometry• Signal-to-noise ratio
04.04.2012
Introduction to Nanomechanics 3
Transduction vs. Sensing
• A transducer receives energy from one system and transmits it to another, often in a different form.
• A sensor responds to physical stimuli (e.g. heat, light, pressure, or motion) and generates an electronic signal for detection.
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Introduction to Nanomechanics 4
Mechanical Force Transducers
x
F
kxF
• Now we require a sensor for mechanical motion.
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Introduction to Nanomechanics 5
Sensors for Mechanical Motion
• Tunneling• Optical Deflection• Optical Interferometry• Microwave Interferometry• Magnetomotive• Piezoelectric• Capacitive
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Introduction to Nanomechanics 6
Displacement Measurements
STM Detection
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Introduction to Nanomechanics 7
Displacement Measurements
Laser deflection
Introduction to Nanomechanics 8
Displacement Measurements
Fixed mirror
“Movable” mirror
“spring”
x
Pin
Laser interferometry
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Introduction to Nanomechanics 9
Displacement MeasurementsLaser interferometry
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Introduction to Nanomechanics 10
Displacement Measurements
LIGO – Gravitational Wave Detection
Laser interferometry
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Introduction to Nanomechanics 11
Displacement Measurements
Hzm /10 13
Laser interferometry
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Introduction to Nanomechanics 12
Displacement Measurements
K. L. Lehnert, JILA
Microwave interferometry – capacitive detection
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Introduction to Nanomechanics 13
Displacement Measurements
K. L. Lehnert, JILAHzm /10 15
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Introduction to Nanomechanics 14
Displacement MeasurementsMagnetomotive detection (via Faraday’s Law)
A. Cleland & M. Roukes, 1999.
Figure from K.L. Ekinci, Boston U.
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Introduction to Nanomechanics 15
Displacement Measurements
Hzm /10 15
Capacitive detection
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Introduction to Nanomechanics 16
Displacement Measurements
Hzm /10 15
Capacitive detection
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Introduction to Nanomechanics 17
Displacement Measurements
Hzm /103 12
Piezoelectric detection
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Introduction to Nanomechanics 18
Displacement Measurements
Hzm /101 12
Capacitive detection
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13.10.2009 Introduction to Nanomechanics 19
QPC
L
R
2DEG
2DEG
e-
QPC as a mechanical displacement detector
Introduction to Nanomechanics 20
Spec
tral
Den
sity
(A2 /
Hz)
Spec
tral
Den
sity
(Å2 /
Hz)
4500 4750 5000 52501E-5
1E-4
1E-3
0.01
0.1
1
1E-25
1E-24
1E-23
1E-22
1E-21
Sp
ect
ral D
en
sity
(A
ng2 / H
z)
Frequency (Hz)
Sp
ect
ral D
en
sity
(A
mp2 / H
z)
4.5010-25
10-24
10-23
10-22
4.75 5.00 5.25
10-21
10-5
10-4
10-3
10-2
10-1
100
Frequency (kHz)
10-12 m / (Hz)1/2
Displacement MeasurementsMeasurement of Cantilever Thermal Noise at 4.2 K
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