Measurement of long wavelength, low power pulse-widths using two photon absorption in InGaAsP waveguides

The measurement of the pulsewidth of low power ultrashort pulses is often problematic when using second harmonic generation (SHG) for the nonlinear response in a autocorrelator because of the low power of the second harmonic signal. Photon counting techniques can alleviate the problem somewhat, but the sensitivity, defined as the product of the peak power and average power, of conventional SHG autocorrelators is typically only 1(mW)². In this paper we describe, for the first time, the use of InGaAsP rib optical waveguides as the nonlinear detector in an autocorrelator