## Abstract

Long cylindrical objects have been observed to align their central
axis with the propagation axis of the illuminating laser beam through
the action of radiation-pressure-generated force and torque. A
cylindrically shaped microactuator based on this principle and suitable
for micromachine applications is examined theoretically. When four
in-plane laser beams converging at a common point centered on the
cylinder are used, the cylinder can be made to rotate about a pivot
point. In one mode, smooth, continuous, and reversible rotation is
possible, whereas the other cylinder can be step rotated and locked,
similar to the operation of conventional stepping motors. The
properties of the device are analyzed based on obtaining either a
constant rotation rate with variable beam power levels or a
quasi-constant rotation rate with constant beam power levels or on
using a fixed beam sequence rate that matches the system parameters and
produces smooth or stepped operation.

© 1999 Optical Society of America

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### Equations (10)

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(1)
$$\mathrm{\tau}=I\mathrm{\alpha}+b\mathrm{\omega}+k\mathrm{\theta}$$
(2)
$$\mathrm{\theta}=\frac{\mathrm{\tau}}{k}\left(1-exp\left(-\frac{\mathit{bt}}{2I}\right)\left\{cos\left(\frac{{\left(4\mathit{kI}-{b}^{2}\right)}^{1/2}}{2I}t\right)+\frac{b}{{\left(4\mathit{kI}-{b}^{2}\right)}^{1/2}}sin\left[\frac{{\left(4\mathit{kI}-{b}^{2}\right)}^{1/2}}{2I}t\right]\right\}\right),$$
(3)
$$\mathrm{\omega}=\frac{2\mathrm{\tau}exp\left(-\frac{\mathit{bt}}{2I}\right)sin\left[\frac{{\left(4\mathit{kI}-{b}^{2}\right)}^{1/2}}{2I}t\right]}{{\left(4\mathit{kI}-{b}^{2}\right)}^{1/2}}.$$
(4)
$$\mathrm{\tau}=\frac{b{\mathrm{\omega}}_{c}}{1-exp\left(-\frac{\mathit{bt}}{I}\right)}.$$
(5)
$${P}_{\mathrm{required}}=\frac{\mathrm{\tau}}{{\mathrm{\tau}}_{\mathrm{computed}}}100\mathrm{mW}.$$
(6)
$$\text{available power}=\left\{\begin{array}{l}{P}_{\mathrm{required}},\mathrm{when}{P}_{\mathrm{required}}\le 100\mathrm{mW}\\ 100\mathrm{mW}\left(\frac{100\mathrm{mW}}{{P}_{\mathrm{required}}}\right),\mathrm{when}{P}_{\mathrm{required}}100\mathrm{mW}\end{array}\right..$$
(7)
$$\mathrm{\alpha}=\frac{\mathrm{\tau}}{I}-\frac{b}{I}\mathrm{\omega}.$$
(8)
$$\mathrm{\omega}\left(t\to \infty \right)=\mathrm{\tau}/b.$$
(9)
$$\mathrm{\omega}\left(t+\mathrm{d}t\right)=\mathrm{\omega}\left(t\right)+\mathrm{\alpha}\left(t\right)t.$$
(10)
$$\mathrm{\theta}\left(t+\mathrm{d}t\right)=\mathrm{\theta}\left(t\right)+\left(t\right)+\frac{1}{2}\mathrm{\alpha}\left(t\right){t}^{2}.$$