Accession Number : AD0891883

Title :   Three-Micron Laser Window Absorption Measurements.

Descriptive Note : Technical rept. Nov 70-Feb 71,

Corporate Author : AIR FORCE WEAPONS LAB KIRTLAND AFB NM

Personal Author(s) : Gilbert, Keith G.

Report Date : JAN 1972

Pagination or Media Count : 34

Abstract : Absorption of laser energy in exit windows can cause significant reduction in far-field brightness due to thermal window lensing. Absorption coefficients at a wave-length of 3 microns are measured calorimetrically for eight candidate materials. Measured values include Al2O3(0.0034/cm), CaF2(0.0025), BaF2(0.0030), Si(0.0085), and fused silica (0.088). A heat transport program calculates central window temperatures from the distant radial thermocouple data. The temperature difference established between the center and edge drives the thermal lensing mechanism. The effect of the resultant optical path difference on far-field brightness is discussed. An attempt to study this optical distortion by observation of the transmitted beam on a thermofluorescent screen was successful only in the case of fused silica. (Author)

Descriptors :   *INFRARED WINDOWS, *INFRARED OPTICAL MATERIALS, *GAS LASERS, INFRARED LASERS, CALORIMETRY, ALUMINUM COMPOUNDS, OXIDES, CALCIUM COMPOUNDS, FLUORIDES, BARIUM COMPOUNDS, SILICON, SILICON DIOXIDE, INFRARED RADIATION, ABSORPTION, THERMAL STRESSES, DISTORTION, LIGHT TRANSMISSION, TEMPERATURE.

Subject Categories : Lasers and Masers
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE