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Direct Conversion of Pulsed UV Laser Energy to Mechanical Energy

IP.com Disclosure Number: IPCOM000101527D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 69K

Publishing Venue

IBM

Related People

Braren, B: AUTHOR [+2]

Abstract

The impact of pulsed UV laser radiation on an organic polymer film causes etching of the surface by a process called ablative photodecomposition. The absorption of photons by the polymer bonds breaks up the structure to yield small molecules (atoms, diatomics, volatile vapors, and low-molecular weight fragments of the polymer chain) which are expelled at velocities which are 4 to 20 times the velocity of sound in air. The momentum imparted to the polymer film as a reaction to the material leaving it at high velocity has been measured and found to amount to one quarter of the photon energy that is imparted to the film by the laser pulse. As a result of this momentum, the film can undergo a displacement if it is suitably mounted.

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Direct Conversion of Pulsed UV Laser Energy to Mechanical Energy

       The impact of pulsed UV laser radiation on an organic
polymer film causes etching of the surface by a process called
ablative photodecomposition.  The absorption of photons by the
polymer bonds breaks up the structure to yield small molecules
(atoms, diatomics, volatile vapors, and low-molecular weight
fragments of the polymer chain) which are expelled at velocities
which are 4 to 20 times the velocity of sound in air.  The momentum
imparted to the polymer film as a reaction to the material leaving it
at high velocity has been measured and found to amount to one quarter
of the photon energy that is imparted to the film by the laser pulse.
As a result of this momentum, the film can undergo a displacement if
it is suitably mounted.

      A simple illustration of how this effect can produce a
mechanical force is demonstrated by the pin-wheel 10 in Fig. 1.  The
blades 12 of this wheel are made of polyethylene terephthalate, a
common plastic sold under the name of MYLAR*.  When a stream of laser
pulses with a fluence above a threshold value is focused on a blade
of the pin-wheel, ablative photodecomposition of the surface occurs.
The recoil momentum imparts a force to the wheel which is kept in
motion in the direction of the arrow by successive photons falling on
the blades of the wheel.  It is evident that the wheel can be coupled
to any other mechanical device by a suitable drive train.  Instead of
a wheel, if a simple leve...