To date, applications of low temperature superconductors in optoelectronics have been very limited and have been primarily constrained to uses in infrared and microwave detectors. The primary reason for not utilizing superconducting electrodes and transmission lines in semiconductor based optoelectronics is because the incorporation of superconducting elements in such devices would require the operation of the devices at liquid helium temperatures. As those skilled in the art recognize, the other semiconducting elements necessary for operation of such optoelectronic devices usually do not work properly at these temperatures and further, the high cost of refrigeration does not make the incorporation of superconducting elements into semiconducting optoelectronic devices cost effective.
In contrast to low temperature superconductors, it has been documented that when a direct current which is near a superconducting material's critical current level, J.sub.c, is applied to a superconducting stripline, the superconducting stripline exhibits a local sensitivity to optical illumination. This reaction manifests itself as a local surface resistance. As reported in, "Microwave Detection and Mixing in Y-Ba-Cu-O Thin Films at Liquid-Nitrogen Temperatures," Journal of Applied Physical Letters, Vol. 53(9), August 1988, this response to optical illumination can be as fast as 40 picoseconds. To date, however, the use of high temperature superconductors has also been limited to applications in infrared and microwave detectors.
Further, it is documented that high temperature superconducting material, which is cooled to below its transition temperature, has also been utilized in several microstrip line applications due to its characteristic low surface impedance. Some examples of these applications of high temperature superconductors are further described in publications such as, "Picosecond Pulses on Superconducting Striplines," Kautz, Journal of Applied Physics, Vol. 49(1), 1978 and "Principles of Superconducting Devices and Circuits," Van Duzer et at, Elsevier Press, New York, 1981. Generally, the characteristic impedance and phase velocity of these high temperature superconductors may be described as a function of the stripline width for a given dielectric substrate thickness. The effect of this relation is such that the velocity of the carrier signal will decrease if the stripline is made wider and likewise, the velocity of the carrier signal will increase if the stripline is made narrower. As those skilled in the art readily recognize, this effect may translate into a myriad of different applications and uses.
The use of high temperature superconductors, however, has yet to have been disclosed in fully monolithic devices, i.e. where the entire optoelectronic element is made entirely of a high temperature superconductor. The present invention addresses such an application.