We propose a new method for using a MEMS device for measuring the power and spot size of a laser beam. The device
consists of a doubly-clamped single crystal silicon micro-beam. A laser beam incident on the microstructure exerts an
optical pressure on it and consequently the micro-beam gets strained. Analysis and simulations show that the laser
power and spot size can be determined by measuring the strains at two different positions on the microstructure.
A reduced order thermal model of a one-dimensional (1D) electrothermally actuated micromirror device is reported.
Thermal bimorphs with integrated Pt resistors are used for generating the angular rotation. Neglecting the temperature
variation perpendicular to the length of the bimorphs, a 2D finite element thermal model with 4647 nodes is built. The
accuracy of the model is verified by comparing the simulation results with thermal imaging data. Using a Krylov
subspace based algorithm, a reduced order model is extracted from the finite element model. Results obtained from a
reduced model with order ≥ 5 agree well with finite element results. Hence, a reduced order thermal model that saves
computation time and resources without compromising the computation accuracy has been demonstrated.
A translationally-scanning mirror is always desired for the axial scanning in optical coherence tomography (OCT),
but conventional scanners are bulky and have relatively slow scanning speed. This paper reports a micromirror that
has the potential to achieve both the scanning speed and range required by OCT. The large piston motion of the
micromirror is obtained using a large-vertical-displacement (LVD) microactuator. The device is fabricated using a
deep-reactive-ion-etch (DRIE) CMOS-MEMS process. A pair of electrothermal bimorph actuators is employed to
achieve tilt-free mirror plate and large piston motion. A linear voltage divider with a voltage ratio of 1:2.3 between
the two electrothermal actuators has been used to obtain static displacements up to 200 &mgr;m. The frequency response
of this device was obtained using a laser Doppler vibrometer, and resonant peaks were observed at 1.18 and 2.62
kHz. AC signals at 50 Hz with a voltage ratio of 1:1.2 were supplied to the actuators, and the maximum dynamic
piston motion was measured to be 26 &mgr;m. The decreasing amplitude over increasing frequency was caused by the
heat-sink effect of the mirror plate. A phase delay between the two actuators was also observed.
Singly-clamped micron-sized cantilevers actuated by optical radiation pressure exerted by a laser are analyzed. An expression for optimum point of actuation giving the maximum amount of deflection is obtained.