Measurements of radiation characteristics of fused quartz containing bubbles.

We report experimental measurement of radiation characteristics of fused quartz containing bubbles over the spectral region from 1.67 to 3.5 microm. The radiation characteristics were retrieved by an inverse method that minimizes the quadratic difference between the measured and the calculated spectral bidirectional transmittance and reflectance for different sample thicknesses. The theoretical spectral transmittances and reflectances were computed by solving the one-dimensional radiative transfer equation by the discrete-ordinates method for a nonemitting, homogeneous, and scattering medium. The results of the inversion were shown to be independent of the sample thickness for samples thicker than 3 mm and clearly demonstrate that bubbles have an effect on the radiation characteristics of fused quartz.