Daniel B. Laubacher

5 GHz high-temperature-superconductor resonators with high Q and low power dependence up to 90 K

The authors have fabricated high-temperature superconducting films made of TlBaCaCuO (2212) and YBaCuO

HTS sensors for NQR spectroscopy

Using a high temperature superconductor (HTS) sensor, we have detected a /sup 14/N nuclear quadrupole resonance (NQR) signal from a room temperature sodium nitrite (NaNO/sub 2/) sample. This demonstrates the feasibility of using such sensors for the NQR detection of contraband, e.g. explosives. The sensor is composed of two high Q-value, self-resonant HTS devices strongly coupled to each other that detect the induced magnetization of the target compound. We briefly describe our techniques for making, adjusting the resonant frequency and spoiling the Q-value of the HTS sensors.

High T/sub c/ superconductor and III-V solid state microwave hybrid circuits

Several high-temperature superconductor (HTS)/III-V solid-state hybrid microwave circuits were designed, fabricated, and tested. The I-V curves, S-parameters, and noise behavior for several solid-state devices at cryogenic temperatures were measured. Several high-electron-mobility transistor (HEMT) and heterojunction bipolar transistor (HBT) C-band low-noise amplifiers were fabricated and tested at cryogenic temperatures with an additional gain of 3 dB when compared to their room-temperature gain. These amplifiers were also used in low-phase-noise oscillators stabilized by a HTS lambda /2 microstrip line resonator with a loaded Q-value of 3*10/sup 3/ or a sapphire-HTS resonator with a loaded Q-value of 1.2*10/sup 6/, both measured at 80 K. Preliminary measurement at 70 K indicates that the phase noise of an oscillator stabilized with a sapphire-HTS resonator was below -125 dBc/Hz at 10-kHz offset and limited by the test setup.<<ETX>>

High T/sub c/ superconducting coplanar delay line with long delay and low insertion loss

Coplanar delay lines have been fabricated from TlBaCuCuO (2212) and YBaCuO

Fabrication And Performance Of KTP Optoelectronic Modulators

We have fabricated ion-exchanged potassium titanyl phosphate (KTP) Mach Zehnder and phase modulators operating at X = 1.3um and 0.633um. These devices were designed for very high frequency operation with a 3-db modulation bandwidth of greater than 12GHz. Device insertion losses were between 1.5db and 5db with switching voltages (D.C. ) of 10V. Thick (- 3μm) electroplated gold was used to produce low-loss 50Q impedance coplanar strip electrodes. High optical power operation at 0.633um ( -100μW) produced no optical damage effects. Further results such as device stability will be presented at the conference.

Hybrid HTS and III-V Microwave Oscillators

Low-noise oscillators operating as pure microwave frequency sources have many critical real world uses in modern radar, communications, and information processing applications. One such application would be as a local oscillator in an advanced microwave front-end receiver. Hybrid oscillators consisting of III-V FETs and high temperature superconducting (HTS) passive microwave devices have been fabricated and tested at cryogenic temperatures at Du Pont. Initial devices operating in the C-band at 4.7 GHz have utilized commercially available High Electron Mobility Transistor (HEMT) unpackaged chips. Wide band amplifiers with bandwidth from 2 to 8 GHz were fabricated and tested at 77 K show 17 dB gain. This is 3 dB higher than amplifiers operating at room temperature. Hybrid oscillators were fabricated using these wide-band amplifiers with feed back provided by a Tl2Ba2CaCu2O8 microstrip resonators. Resonators were fabricated from two-side coated HTS films on LaAlO3 substrates and had loaded Qs of 5000 with insertion loss of -6 dB. Oscillators show phase noise of less than -106 dBc (1 Hz) at 10 KHz offset from operating frequency of 4.7 GHz.

HTS/III-V Hybrid Microwave Circuits

Application of high temperature superconductor (HTS) thin films in microwave systems may require a range of microwave devices and the hybrid integration of these devices with III-V semiconductors. To demonstrate the utility of HTS microwave technology, we have developed several prototype HTS/III-V hybrid devices including wide band amplifiers, narow band amplifiers, and very low phase noise oscillators. C-band amplifiers designed to function at cryogenic temperatures show a 3 dB gain over those at room temperature. Low phase noise oscillators stabilized by HTS half wavelength resonators with loaded Q value of 3 × 103 or a sapphire loaded HTS resonator cavity with a loaded Q value of 1.2 × 106 at 80 K have been fabricated and tested. The phase noise at 70 K of the sapphire loaded HTS resonator cavity was below -125 dBc/Hz at 10 kHz off-set and limited by the test equipment This is the lowest phase noise yet reported for such an HTS stabilized oscillator.