Yuji Kintaka

Surface resistance of screen-printed Bi2223 thick films on Ag and dielectric ceramic substrates

Surface resistance R/sub s/ of screen-printed (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thick films on Ag, MgO, and Ba(Sn,Mg,Ta)O/sub 3/ substrates was measured at 10.7 GHz in the temperature range between 20 and 130 K using a dielectric resonator method. For thick films on Ag substrates, it becomes lower than that for a Cu plate as temperature decreases below 100 K, and reaches 1.7 m/spl Omega/ at 77 K and 0.3 m/spl Omega/ at 30 K. The use of MgO or Ba(Sn,Mg,Ta)O/sub 3/ dielectric substrate for film fabrication causes some degradation in the value of R/sub s/, while still being superior to that for a Cu plate below 80 K. From a practical point of view, the (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ thick films were screen-printed on both sides of Ba(Sn,Mg,Ta)O/sub 3/ disk to serve as superconducting electrodes for the dielectric resonator. The unloaded quality factor Q/sub n/ for the resonator at 2.1 GHz on a TM/sub 010/ mode is superior to the same dielectric resonator with Cu electrodes below 90 K. It is 3 times higher than the value for the resonator with Cu electrodes at 70 K and also 5 times higher at 30 K.

Femtosecond mode-locked Nd(3+)-doped Ba(Zr,Mg,Ta)O(3) ceramic laser.

We have demonstrated continuous wave (CW) laser operation and the first, to the best of our knowledge, sub-200 fs mode-locked laser operation of Nd(3+)-doped Ba(Zr,Mg,Ta)O(3) ceramic. Its disordered crystalline nature exhibits a broad gain bandwidth of 30 nm with a high-emission cross section. It also has higher thermal and mechanical properties than Nd:glass. In CW operation, a maximum output power of 1.5 W under 6.2 W of absorbed pump power was obtained. In mode-locked operation, a pulse duration of 196 fs with an average power of 60 mW was successfully achieved. The laser spectrum straddled both fluorescence peaks of A-site and B-site Nd(3+) ions.

Development on highly transparent ceramics

Transparent dielectric ceramics were developed originating from dielectric ceramics of which development was conducted by Dr. Wakino for microwave applications. A Ba(Mg, Ta)O3 based transparent ceramics shows high transparency and various optical properties depending on the composition. Based on the knowledge obtained from the study of Ba(Mg, Ta)O3 based transparent ceramics, we also developed other transparent ceramics such as LaAlO3-Sr(Al, Ta)O3 solid solution. The Ba(Mg, Ta)O3 based transparent ceramics was commercially utilized as high-refractive-index lens for slim digital camera applications, where the refractive indices reduced the focal length of optical lens modules.

Femtosecond Mode-Locked Nd3+-doped Ba(Zr,Mg,Ta)O3 Ceramic Laser

We report efficient CW laser operation and first femtosecond mode-locked laser operation of transparent Nd3+:Ba(Zr,Mg,Ta)O3 ceramic. The disordered crystalline system exhibits the characteristic broadband absorption and fluorescence spectra suitable for ultrashort pulse lasers.

Diode-pumped mode-locked Nd 3+ -doped Ba(Zr,Mg,Ta)O 3 ceramic laser

Nd³⁺-doped Ba(Zr,Mg,Ta)O<inf>3</inf> ceramic laser is reported. The broadband fluorescence profile can be tailored by the “disordered” perovskite structure and is suitable for ultrashort pulse lasers. Mode-locked laser operation was demonstrated for the first time.

Microwave properties of screen-printed Bi2223 thick films on Ba(Sn, Mg, Ta)O3 dielectric disk

Abstract The TM 0 1 0 -mode microwave resonator was fabricated with Bi2223 thick films on a Ba(Sn,Mg,Ta)O3 dielectric disk with a relative dielectric constant of er=24. Bi2223 thick films were screen-printed on both sides of the dielectric disk and subjected to a twice repetition of cold isostatic pressing at 0.4 GPa and sintering at various temperatures. An increase of the sintering temperature from 820 to 840 °C raises the Bi2223 phase purity up to 98% on the surfaces of the thick films, but the high-temperature sintering above 830 °C causes a chemical reaction at the interface between Bi2223 thick film and the dielectric disk. An optimization of the sintering temperature to 830 °C gives the unloaded quality factors Qu as much as 74,000 at 70 K and 158,000 at 25 K, which correspond to surface resistances Rs of 0.34 and 0.14 m Ω for Bi2223 thick films, respectively. These are approximately 20 times higher than the values for the resonator using Ag electrodes with the same structure.

Fabrication and Microwave Operation of Dual-mode Ba(Sn,Mg,Ta)O3 Resonator with Bi2223 Thick Film as Superconductor Electrodes

The TM110 dual-mode microwave resonator was designed and fabricated with screen-printed (Bi,Pb)2Sr2Ca2Cu3Ox thick films and a 25mm-cubic Ba(Sn,Mg,Ta)O3 dielectric ceramic block of relative dielectric constant ɛr=24. The thick films were printed on every six surface of the dielectric block and served repetitive combination processes of cold isostatic pressing and sintering. The typical value of the unloaded quality factor was 40,000 at 1.8GHz, 70K, and the surface resistance of Bi2223 was estimated at 1mΩ.