Measurement of Temperature and Stress within Glass Materials using the Method of Laser-Induced Fluorescence
EMSL Project ID
2083
Abstract
There is a need for a versatile laser to support research and development efforts funded under a DOE-OIT (Office of Industrial Technology) project. This work will continue for another two years at least. In this project noncontact sensors for 3D measurement of stress and temperature in glass products are being developed. Both sensors concepts require laser light for either a probe beam (stress sensor) or as an excitation source (temperature sensor). The Alexandrite laser represents an extremely flexible and versatile device for satisfying the experimental needs of this project. The temperature sensor utilizes an absorption peak at 380 nm to cause fluorescence in glass. The absorption is due to iron ions present in varying quantities in glass. The fluorescence lifetime and the total signal are temperature sensitive, and measurement of the fluorescence properties provides a temperature diagnostic. Development of the sensor requires a high power pulsed light source at 380 nm. The stress sensor requires two laser beams of different wavelengths and fairly high power. In the present embodiment of the concept, counterprapagating pulsed beams are used to create a standing wave within the glass. Absorption results in localized heating at the antinodes of the standing wave. Since the refractive index is temperature dependent, a thermal diffraction grating with spacing equal to half the laser wavelength is created. A probe beam, the second harmonic of the grating beam, is then conveniently coupled into the glass at various depths by Bragg scattering from the grating. This beam undergoes polarization changes due to stress -induced birefringence within the glass. There is no other known viable method for determining stress internal to a glass article. There are benefits to using a fundamental wavelength near 800 nm and the frequency doubled light at 400 nm. The Alexandrite laser, with accessories, can meet the needs of both sensor development tasks.
Project Details
Project type
Exploratory Research
Start Date
2000-11-28
End Date
2002-12-02
Status
Closed
Released Data Link
Team
Principal Investigator