HIGH SPEED INTEGRATED - OPTIC SAMPLER FOR TRANSIENT RADIOFREQUENCY AND MICROWAVE SIGNALS (ELECTROOPTIC, LASER, PHOTODETECTOR, DIRECTIONAL COUPLER)

The work reported here is devoted to the development of a novel high speed integrated optic device which has the capability of sampling transient RF and microwave signals. The device consists of a series of electrooptic couplers fabricated along an integrated-optic waveguide beneath a coplanar RF stripline. A traveling wave electrical signal propagates on the RF stripline and generates an electric field across each coupler, which in turn changes their coupling characteristics. A short optical pulse, which propagates in a direction opposite to the traveling wave electrical signal, passes sequentially through the electrooptic couplers, causing a small amount of light to couple into a series of output waveguides and propagate to optical detectors. The amount of coupled light is dependent on the local electric field induced by the electric signal. Each detector integrates the energy of the coupled optical pulses in the respective output waveguides in order to determine the associated instantaneous values of the electrical signal. The sampling rate of the device is determined by the spatial distance between the electrooptic couplers and the velocities of the optical pulse and the electrical signal. The device has the potential for sampling transient electrical signals with sampling rates in excess of 30 giga-samples per second.;The work includes a theoretical analysis of the sampler, a description of the integrated-optic device fabrication, and the results of a proof-of-principle demonstration.;It is also shown that the device can be configured to sample intensity-modulated optical signals using a short electrical pulse. In this configuration, the main integrated-optic waveguide propagates the intensity modulated optical signal through the electrooptic couplers. A short electrical pulse propagates down the RF stripline in a direction opposite to the optical signal and, again, induces an electric field which changes the coupling characteristics of the couplers. This optical sampler could be integrated into an optical fiber communication system and provide a new means of detecting and analyzing optical signals.