Two Photon Absorption (TPA) in semiconductors has recently been shown to be a serious candidate for optical autocorrelation of short pulses, and all-optical switching and sampling of high speed optical data signals in optical time division multiplexed (OTDM) systems. In this paper we present the design and fabrication of a TPA detector that has been specially designed for TPA with an input wavelength around 880 nm. The device that we have constructed is based on a microcavity structure, which greatly enhances the interaction length. We also demonstrate the use of this non-linear detector for carrying out autocorrelation measurements on picosecond optical pulses.