<title>Applications of high-Tc superconductors in optoelectronics</title>

Abstract

The discovery of high-temperature superconductors (HTS) has opened new opportunities for applications of superconductors in optoelectronics. The HTS perovskites represent a new class of solid-state materials, exhibiting many very interesting and potentially electronic, optical, and electro-optical properties. They also operate int he 30 - 80 K temperature range, where refrigeration is cheap and the parameters of semiconducting devices are optimal. A review of the substrate materials and deposition techniques suitable for fabrication of high-quality epitaxial HTS films for electronic and optoelectronic applications is given. Laser processing techniques of HTS films are presented, with a special emphasis put on the laser writing method. Two possible approaches for the development of a complete optoelectronic system with the elements based on the HTS films and operational at liquid- nitrogen temperatures are presented. The first approach consists of manufacturing the devices made of conventional electro-optic materials and containing HTS transmission lines and electrodes. Design and properties of ultrafast HTS interconnects are discussed, and a new concept of the Mach- Zehnder-type YBa2Cu3O7-y-on LiNbO3 optical modulator is introduced. The second, more futuristic, approach, is to exploit contrasting properties of the oxygen-poor and oxygen-rich HTS phases to fabricate novel, monolithic devices. Recent experiments are discussed which reveal intriguing optical properties of HTS films, and are most relevant for the development of all-HTS optoelectronic devices. Several practical devices, such as high- frequency modulators, ultrafast-pulse generators, and sensitive photodetectors, are presented.