Detection of Millimetre Wave Radiation by Y-Ba-Cu-O Thin Films at Liquid Nitrogen Temperatures

Detecting properties of Y-Ba-Cu-O granular thin film structures obtained by two differnt technological methods and using three different substrate materials have been studied at millimetre waves. The response to 25 and 100 GHz radiation is presented as the function of dc bias current for several temperatures around 77 K. For power levels below saturation the amplitudes of the recovered video signals were found to be proportional to the incident power. Sensitiviy obtained at 110 GHz is comparable to that of crystal point-contact detector. Preliminary results on mixing of two Ku-band sources for IF frequencies up to 5 GHz are presented, indicating that the response time of Y-Ba-Cu-O films is shorter than 40 ps. Due to pronounced quantum effects, which manifest themselves especially in narrow superconducting strips below 60 K, at present state of the technology the usefulness of investigated detectors is limited to liquid nitrogen temperatures.