Measurement of the nonlinear refractive index of semiconductors included in monolithic étalons

We describe a measurement technique for the determination of the nonlinear refractive index of semiconductors embedded in a Fabry-Perot cavity. This method relates the intensity-dependent spectral shift of the resonance peak to the nonlinear index variations. The use of square pulses allows the decoupling of electronic and thermal nonlinearities. Our experimental results show that this method is particularly suitable for measuring the nonlinear-optical properties of monolithic semiconductor étalons with integrated Bragg reflectors.