Active superconductive devices.

Active superconductive devices having a variable conductive element in electromagnetic contact with a superconductor have been formed. In one embodiment, a variable ohmic conductive device (16) such as a photoconductor is placed adjacent to a superconductor (12). The variation of the optical radiation on the photoconductor has the effect of modifying the electromagnetic environment adjacent to the superconductor, and consequently the electrical properties. Superconducting can be made a band-stop filter (10, 12, 14), with a photoconductor forming a microwave switch. In another embodiment, a variable ohmic element (46) added to a delay line (46) forms a phase shifter.