Measurement of nonlinear refractive-index coefficients using time-resolved interferometry: Application to optical materials for high-power neodymium lasers

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Abstract
An improved time‐resolved interferometric method for measuring intensity‐dependent changes in the refractive index of optical materials is described. An intense 125‐ps pulse from a 1064‐nm Nd : YAG laser‐glass amplifier system is propagated throguh the sample which is placed in one arm of a modified Michelson interferometer. The nonlinear refractive‐index coefficient is measured from the time‐dependent fringe formed at the output of the interferometer. Values are reported for several low‐index optical glasses (BK‐7, FC‐5, FK‐51), fused silica, a silicate laser glass (ED‐2), a Faraday rotator glass (FR‐5), and a nonlinear crystal (KH2PO4). Possible sources of error in using this approach are discussed.