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56 2 Extremely Short-External-Cavity Laser Diode
0.6
Dh 2 Dh 1
0.5 Lens
I 0
LD1
0.4
Amplitude (mm) 0.3 Dh 1 x
MB

0.2

0.1 Dh 2

0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Normalized laser spot position (x / l )
0
Fig. 2.28. Variation in MC vibration amplitude as a function of the illuminated
spot position on the MC

10 8
30
Amplitude (mV)
25
20
7
10
Resonal frequency (Hz) 10 6 5 4 80 5 0 990 Frequency (kHz) 1020
15
10
1010
1000
10
Amplitude (mV)
60
10
40
20
3
10
0
190 195 200 205 210
Frequency (kHz)
10 2
0 100 200
Cantilever microbeam length (mm)
Fig. 2.29. Resonance frequency and frequency spectra as a function of MC length
for GaAs
results calculated from (2.27) [2.23,2.24]

E
t 12ρ
f 0 = λ 2 , (2.27)
0 2
2πl
where λ 0 is the eigen value of 1.875 determined by the vibration mode, E is
Young’s modulus, ρ the density, l the cantilever length, and t its thickness.
The Q in air were approximately 250. In order to increase Q, dampingmech-
anisms such as imbalance and radiation at the supportingrim require further
studies. To increase the sensor sensitivity, the resonant frequency should be