Electrical and Computer Engineering ETDs

Publication Date



An investigation is made of microwave transmission through two types of dielectrics while being irradiated by a 15 Kw, CO2 continuous wave laser. The two materials, a high silica ceramic and a fiber­glass laminate, present two different problems for solution of their microwave transmission characteristics while being subjected to high intensity continuous wave irradiation.

The high silica ceramic was found to exhibit a slightly reduced transmission coefficient with an accompanying change in phase delay due to ablation of the material during laser irradiation. As much as -4db loss with a phase delay of +30° is observed at an intensity of 3.5 Kw/cm² for three seconds.

The fiberglass laminate exhibited surface charring at intensities as low as 0.5 Kw/ cm2 This char was measured to be 0.7mm + .09mm thick and its thickness was independent of laser intensity over a range of from 0.5 Kw/cm2 to 2.0 Kw/cm2. It produced microwave losses as great as - 29db and phase delays as great as -60°.

Theory for both problems is developed and compared with experimental data. After careful study of theory and experiment, it was concluded that the prediction of microwave transmission through materials which do not exhibit appreciable changes in material properties with the application of laser heating is fairly easily accomplished with moderate accuracy. However, microwave transmission through a material which has significant changes in material properties at the laser heated surface can at best be only empirically described from measurements on that material, or similar materials in the lab.

Document Type




Degree Name

Electrical Engineering

Level of Degree


Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

William Jackson Byatt

Second Committee Member

Donald Arthur Neaman

Third Committee Member

Shyam H. Gurbaxani