Third-order optical susceptibility of glasses determined by third harmonic generation.

The third-order nonlinear optical susceptibilities of BK-7 glass and fused silica were measured by nonphasematched optical third harmonic generation (THG). Two methods were employed to determine these magnitudes relative to alpha-quartz: comparison of simple THG fringes arising in sequential measurements of individual wedges and analysis of the more complex fringes arising when both sample and standard wedges were placed simultaneously in the laser beam. It is shown that linear optical properties scale among the three materials with density and a generalized Miller delta parameter which includes density variation was seen to be superior to that without.