Huo Yujing

Fabrication, characterization and welding of Bi(Pb)-Sr-Ca-Cu-O superconducting fibres

Superconducting fibres of Bi(Pb)-Sr-Ca-Cu-O high Tc superconducting materials have been prepared by means of the laser-heated pedestal growth (LHPG) method. The highest zero resistance temperature Tco reached is 114 K, and the highest critical current density Jc (77 K, 0 T) is greater than 5000 A cm-2. As-grown superconducting fibres were successfully fabricated without post-growth heat treatment. Amorphous materials were used for the first time to make high quality fibres. The strong textured structure and highly aligned morphology of the fibres were studied. The influence of growth conditions, thermal treatment and the composition of the fibres was also discussed.

Bi-based superconducting fibers prepared from amorphous materials

Bi-based superconducting fibers have been prepared from amorphous materials by the LHPG method. The onset transition temperature reached is 102 K, and the zero resistance temperature reached is 86 K. The critical current density Jc (77 K, O T) is greater than 5000 A/cm2. Structure analysis indicates that the superconducting fibers have highly aligned morphology with a-axis parallel to the growth direction.

Laser-Diode-Pumped Nd:YAP Single Crystal Fiber Laser

We have developed a Nd:YAP single crystal fiber laser with linearly polarised light output at 1.0795 ?m. The laser is 100 ?m in diameter and operated with a threshold of 6.65 m W. The slope efficiency is 12.9%.

Diode-Pumped Nanosecond Pulsed Laser with Pulse-Transmission-Mode Q-Switch

Q-switched pulses at 1.064 µm with a peak power of 5.02 kW and a pulse width of 2.8 ns were obtained which were pumped by a 1 W laser diode on the Nd:YVO4 microchip at the 1 kHz repetition rate. These values were achieved by combining the techniques of acousto-optic Q-switching and electro-optic pulse-transmission-mode Q-switching. The temporal characteristics of the pulses were analysed numerically. The experimental results are shown to be in good agreement with theoretical predictions.

Preparation, structure and properties of Bi-based superconducting fibers grown by laser-floating-zone-growth method

Abstract In this report, we describes investigation of the preparation, structure and properties of Bi-based superconducting fibers grown (polycrystalline, modifying-composition with self-flux and amorphous material) and varying growth condition have been used. We have got the polycrystalline and single-crystal(or called quasi-single crystal) fibers with Tc value of 83–110K and the most Jc vallue of more than 5200A / cm2. The fibers have a good texture structure i.e., its a-b plane is parallel to the growth direction and c-axis is perpendicular to the influence of growth direction. The growth condition, composition of the source materials and post—growth heat treatment have also been discussed.

Velocity Measurement Based on Laser Doppler Effect

A novel method for velocity measurement is presented. In this scheme, a parallel-linear-polarization dual-frequency laser is incident on the target and senses the target velocity with both the frequencies, which can increase the maximum measurable velocity significantly. The theoretical analysis and verification experiment of the novel method are presented, which show that high-velocity measurement can be achieved with high precision using this method.

Controllable Passively Q-Switched Laser

We present a novel kind of pulsed laser named controllable passively Q-switched laser (CPQL). A CPQL of Nd:YVO4 with Cr:YAG as saturable absorber was demonstrated and studied as an example of the kind of pulsed lasers. In CPQL, as the actively controlling signal, a diode laser beam was focused onto the saturable absorber in the resonant cavity of the passively Q-switched laser (PQL) and was absorbed by the absorber to realize the active control of the CPQL. The characters of the CPQL output laser pulses, such as generation time, repetition rate, pulse width, peak power and energy per pulse, can be controlled by the operator. The CPQLs possess the advantages of both passively Q-switched laser and actively Q-switched laser. Because of their compactness, low cost and controllability, the CPQLs will find wide applications in many fields.

Bi-BASED SUPERCONDUCTING FIBERS WITH HIGH CRITICAL PARAMETERS

Superconducting fibers of Bi(Pb)-Sr-Ca-Cu-O high Tc superconducting materials have been prepared by means of the laser-heated pedestal growth (LHPG) method. The highest zero resistance temperature T c0 reached is 114 K, and the highest critical current density J c (77 K, 0 T) is greater than 5000 A/cm 2 . As-grown superconducting fibers were successfully fabricated without post-growth heat treatment. Amorphous materials were used for the first time to make high quality fibers. The influence of growth conditions, thermal treatment and the composition of the fibers were discussed.

110K Superconducting Fibers of [Bi,Pb(Sb)] 2 Sr 2 Ca 2 Cu 2 O 10 + x

Superconducting fibers of [Bi,Pb(Sb)] 2 Sr 2 Ca 2 Cu 3 O 10 + x high T c superconducting materials have been prepared by means of the laser-heated pedestal growth method with T c 0= 110K and J c >10 3 A/cm 2 . Structure analysis showed that the a-b plane of the material prefers to align along the growth direction, though the post-growth heat treatment, which is still necessary at present stage, may destroy the texture structure in some extent.The existence of Pb is vital for stabilizing the 110K phase of the Bi-based fibers.

Preparation of the Bi-Sr-Ca-Cu-O superconducting fibers

Bi-Sr-Ca-Cu-O superconducting fibers have been successfully prepared by means of the laser-heated pedestal growth method. The superconductivity of the fiber sample is closely related to the composition of source material, the power of focused laser beams, the pull rate of growing fiber, and the condition of post-annealing. The typical size of samples is 150μm × 30mm. The onset of transition was 118K, and zero resistance was 85K. The majority phase in the fibers is the 85K (2-2-1-2) phase of the Bi-Sr-Ca-Cu-O materials. Samples are stable and reproduceable.