Feasibility of measuring the nonlinear index of refraction by third-order frequency mixing

An original frequency-mixing technique is described which conveniently measures the third-order optical susceptibility of any transparent material. Results are presented for χ
₁₁₁₁
⁽³⁾
(
^-
ω
₃
, ω
₁
, ω
₁
,
^-
ω
₂
) in a number of materials. These measurements permit estimates of the nonlinear index
n
₂
.