High-Q LaAlO(3) dielectric resonator shielded byYBCO-films

• Published in: IEEE transactions on applied superconductivity Vol. 4; no. 3; pp. 143 - 148
• Main Authors: Tellmann, N, Glein, N, Dahne, U, Scholen, A, Schulz, H, Chaloupka, H
• Format: Journal Article
• Language: English
• Published: 01-09-1994
• ISSN: 1051-8223
• DOI: 10.1109/77.317829

We have investigated a dielectric resonator consisting of a single crystalline LaAlO(3)-cylinder shielded by a cylindrically shaped copper cavity with endplates made from epitaxial films of YBa(2)Cu(3)O(7) or niobium. For YBa(2 )Cu(3)O(7) films unloaded quality factors Q(0 ) of 4.5.10(5) at 10 K and 1.3.10(5) at 77 K were achieved at 11.6 GHz using a compact shielding cavity with a diameter of 15 mm and a height of 3.8 mm. The loss contributions of the dielectric resonator, the normal conducting cylinder wall, and the superconducting endplates, with one of them being separated by a small distance h from the dielectric cylinder, were calculated by modeling the electromagnetic fields of the TE(0numu)-modes. The dielectric loss tangent of the LaAlO (3)-cylinders was found to be 10(-6) at 4.3 K and f=11.6 GHz and to increase slightly with temperature. Moreover, the calculations indicate the tunability of the resonance frequency by changing h over a range of 1 GHz without significant degradation of Q (0). These resonators are considered to be useful devices for stable oscillators and narrowband filters