An Absolute Method of Measuring Energy Outputs from CO2 Lasers

Abstract

In the energy meter described here the CO₂ laser radiation is almost completely absorbed by an Al₂O₃ surface on an aluminum plate. The high absorption of the surface (≥95%) eliminates the need for calibration and the laser energy is computed by measuring the temperature rise of a plate with known thermal capacity. Experimentally we find that the calorimeter noise level corresponds to an energy density of about 2 mJ/cm². Calculations indicate that the instrument is capable of measuring the energy of a single pulse that is 1 nsec wide, provided the pulse contains an average energy density of 10 mJ/cm². We have estimated the radiation and convection losses and found them to be negligible. The calorimeter is good for radiation between 8.5 and 11 μ; however, with modifications the bandwidth could easily be increased.