Integrated optoelectronic circuits and their modular designs for residue number computation

Integrated optoelectronic circuits (IOEC) have been fabricated in hybrid LiNbO3/Si substrates. Optical signals were carried in and out of the IOEC chip through optical fiber arrays. Interactions among guided light signals in the optical channels were achieved by blazed grating couplers and mode cutoff electrooptic modulators in LiNbO3, as well as etched mesa lateral phototransistors in Si. The rating couplers tapped the light signals from the optical channel waveguide, and the photodetectors converted the intercepted light signals into electrical currents. With a specially designed electrical routing or after the electronic signal processing in Si, the resulting current then changed the voltage applied to the electrooptic modulator via resistive contacts between the two substrates, thereby controlling the light output of the IOEC. Etched mesa Si lateral phototransistors (EMS-LPT) were designed for collecting and efficiently converting to photocurrent the optical energy deflected from the blazed grating couplers. By forming a localized photoactive region in the mesa, a high photogain of 110 was measured in the uniform base EMS-LPT and of 68 in the double diffused EMS-LPT.