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1.4 Integrated Systems with LDs and Micromechanics 21
(a) (b)

Fig. 1.26. Two kinds of optical rotors: a rotationally but not bilaterally symmetric
rotor which uses optical torque exerted on its side surfaces (a), and a cylindrical
optical rotor which has slopes for rotation on its upper surfaces (b)

accumulated. Today, such technology is used in various scientific and engi-
neeringfields to manipulate [1.59], align [1.60], and switch [1.61] many kinds
of micro-objects. Optical tweezers is described in detail in Chap. 3.
Usinga laser beam the rotation of artificial micro-objects fabricated by
micromachiningwas demonstrated. Figure 1.26 shows two kinds of optical
rotors: a rotationally but not bilaterally symmetric structured rotor to which
optical torque is exerted on its side surfaces (a) [1.62], and a cylindrical op-
tical rotor which has slopes for trappingand rotatingon its upper surfaces
(b) [1.63]. The rotation mechanism has been shown both experimentally and
theoretically.
The use of optical rotors is expected to solve the problems of an MEMS
motor, i.e., short lifetime due to friction and the requirement of electrical wires
for the power supply. Applications of directional high-speed optical rotation
may include an optical motor and a microgear for micromachines [1.64,1.65]
and a micromixer [1.66] for µ-TAS. These optical-rotor-related technolo-
gies could have a significant effect on developments in optical MEMS and
micromechanical photonic systems. Optical rotation is described in detail in
Chap. 4.

1.4 Integrated Systems with LDs and Micromechanics

In micromechanical photonics applications usingLDs of group III–V com-
pounds are predominant for monolithic integration of microstructures. They
include a GaAs-based integrated tunable laser [1.16, 1.67], a resonant sen-
sor [1.17], an optical encoder [1.68], an optical head [1.69], and an InP-based
free-standingmicrostructure [1.15], and a portable blood flow sensor [1.70],
which can be used to provide supersmall, cost-effective microdevices.

1.4.1 Tunable LD

Tunable LDs are desirable for use in WDM communications, multi-
wavelength optical data storage, sensing systems, and a variety of scientific