Accession Number:

ADA167691

Title:

Diffraction and the Radiometric Levitation of Carbon Aerosol Using a Nd: YAG Laser

Descriptive Note:

Technical rept.

Corporate Author:

AEROSPACE CORP EL SEGUNDO CA CHEMISTRYAND PHYSICS LAB

Personal Author(s):

Report Date:

1985-12-02

Pagination or Media Count:

25.0

Abstract:

Experimental observations of highly absorbing carbon particles trapped in the beam of a NdYAG laser are presented. The physical mechanism responsible is discussed along with possible application and implications of this phenomenon. In this work we report the levitation of highly absorbing particles with an infrared IR laser beam. Photophoresis is the force on a particle due to the rebounding of ambient gas molecules with greater velocities from parts of the surface that are at a higher temperature. Absorbing nonspherical particles driven by such a force are known to migrate along complex paths. The motion can be along helical paths, complex orbits, or just irregular, random movement. For all of these paths, with the exception of the random motion, there is always a preferred direction, e.g., the axis of the orbit, due to some external factor such as the direction of the light, gravity, and applied electric and magnetic fields. Using a linearly polarized IR laser, we are suspending highly absorbing spherical carbon particles. This is probably the first report of an absorbing particle being stably trapped in a beam of light for which external conditions have not been tailored to counteract the preferred direction of migration. In this communication we present the experimental observations and point out the physical mechanism that perhaps explains the phenomenon. Some of the possible implications of these results are then discussed with regard to providing a means for testing the electromagnetic diffraction theory of optical systems and to possible consequences of using laser beams for a variety of applications.

Subject Categories:

  • Radiation and Nuclear Chemistry
  • Thermodynamics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE