Small third-order optical-nonlinearity detection free of laser parameters

We demonstrate a novel, versatile method for sensitive measurement of nonresonant third-order optical nonlinearities in waveguides. The measurement is referenced to a bulk sample with well-known nonlinear optical properties, thus ruling out the influence of laser pulse parameters like duration, contrast, and spectral phase or amplitude. Since the generated mixing product is heterodyne detected, extremely small third-order optical nonlinearities, e.g., from air-filled short waveguides, can be measured.