Jingzhong Xiao

Spectroscopic properties and diode end-pumped 2.79 μm laser performance of Er,Pr:GYSGG crystal

We demonstrate a 968 nm diode end-pumped Er,Pr:GYSGG (Gd₁.₁₇Y₁.₈₃Sc₂Ga₃O₁₂) laser at 2.79 μm operated in the pulse and continuous-wave (CW) modes. The lifetimes for the upper laser level ⁴I₁₁/ ₂ and lower level ⁴I₁₃/₂ are 0.52 and 0.60 ms, respectively. The laser produces 284 mW of power in the CW mode, corresponding to the optical-to-optical efficiency of 14.8% and slope efficiency of 17.4%. The maximum laser energy achieved is 2.4 mJ at a repetition rate of 50 Hz and pulse duration of 0.5 ms, corresponding to a peak power of 4.8 W and slope efficiency of 18.3%. These results suggest that doping deactivator Pr3+ ions can effectively decrease the lower-level lifetime and improve the laser efficiency.

Spectroscopic, diode-pumped laser properties and gamma irradiation effect on Yb, Er, Ho:GYSGG crystals

We demonstrate a diode end-pumped Yb, Er, Ho:Gd(1.17)Y(1.83)Sc(2)Ga(3)O(12) (GYSGG) laser operated at 2.79 μm in continuous-wave mode. Spectral analysis shows that Yb(3+) and Ho(3+) act as sensitizer and deactivator ions, respectively. Pumping with a 967 nm laser diode produces the maximum output power of 411 mW, corresponding to optical-optical conversion and slope efficiencies of 11.6% and 13.1%, respectively. The minimum laser threshold is only 81 mW because of Ho(3+) doping. The laser properties are only slightly influenced by 100 mrad gamma irradiation. The Yb, Er, Ho:GYSGG crystal possesses excellent radiation resistance and is a potential laser gain medium in radiant environments.

Czochralski growth and topographic study of tetragonal (La, Sr)(Al, Ta)O3 single crystals

Abstract Large tetragonal phase (La,Sr)(Al,Ta)O3 (LSAT) crystals used as substrates for growing functional thin-film materials were successfully grown by the Czochralski method using [0xa00xa01] LaAlO3 rod as seed. The crystal phase was determined by the method of powder X-ray diffraction analysis and the transmission spectrum indicates that the absorption edge of the crystal is at 270xa0nm while no apparent absorption peaks were found. Through the technique of environmental scanning electron microscopy and synchrotron radiation white-beam topography, the surface topography and defects were characterized, and clear and stable images of twins, micro-cracks, inclusions, grain boundaries, dislocation etch pits, and growth striations in the as-grown LSAT crystals were obtained.

Performances of a diode end-pumped GYSGG/Er,Pr:GYSGG composite laser crystal operated at 2.79 μm.

We demonstrate a comparative investigation on Er,Pr:GYSGG and GYSGG/Er,Pr:GYSGG composite crystals at 2.79 μm. Simulating results show the highest temperatures are 369 K and 318 K, respectively. A maximum output power of 825 mW with slope efficiency of 19.2% and maximum laser energy of 3.65 mJ with slope efficiency of 22.7% are obtained in the GYSGG/Er,Pr:GYSGG composite crystal, which have an obvious improvement than those of Er,Pr:GYSGG crystal. The thermal focal lengths are respectively 41 and 62 mm when the pump power is 2.5 W. All these results indicate that the GYSGG/Er,Pr:GYSGG composite crystal has great advantages in reducing the influence of thermal effects and improving laser performances.

Sol-gel derived morphotropic phase boundary 0.37BiScO3–0.63PbTiO3 thin films

Dielectric/ferroelectric properties of morphotropic phase boundary 0.37BiScO3–0.63PbTiO3 thin films with a PbTiO3 seed layer deposited on platinized silicon substrates by sol-gel are examined. Room temperature dielectric constant of >1600 and dielectric loss of 0.02 are achieved (100Hz). A well-defined hysteresis loop was observed with a Pr of ∼23μC∕cm2. In particular, the remarkable low Ec of ∼33kV∕cm of these films adds value to the potential application of BiScO3–PbTiO3 films in high temperature ferroelectric memories. The influence of PbTiO3 seed layer on the electric properties and the relation with the phase formation process, crystallinity, and microstructure of the films is discussed.

Observation of three-dimensional domain configurations in 0.92Pb(Zn1/3Nb2/3)O3-0.08PbTiO3 crystal by environmental scanning electron microscopy

The images of three-dimensional 180degrees and non-180degrees (90degrees) domain configurations on the unpolished and unpoled (111) face of 0.92PZN-0.08PT rhombohedral relaxor-ferroelectric crystal have been obtained by environmental scanning electron microscopy for the first time. The size of the 180degrees domains ranges from 10 to 50 Am, and that of the non-180degrees domains from 1 to 10 mum. The boundaries of the crossed three-dimensional non-180degrees domain bands are nonparallel and have a triangular shape. This unique non-180degrees domain architecture is different from the 109degrees or 71degrees domain structure in normal rhombohedral ferroelectric materials, and is helpful for completely relaxing the additional stresses due to domain deformation in 0.92PZN-0.08PT crystals.

Characterization of 0.92Pb(Zn1-3Nb2-3)O3–0.08PbTiO3 crystals grown from high-temperature solutions

Abstract Large 0.92Pb(Zn 1/3 Nb 2/3 )O 3 –0.08PbTiO 3 (0.92PZN–0.08PT) single crystals were grown successfully by the high-temperature solutions method using PbO as flux. The crystal was determined by powder X-ray analysis to have rhombohedral structure. The surface profile and topography of the crystals were investigated by atomic force microscopy and synchrotron radiation white-beam topography, through which defects such as scratches and inclusions were observed. The optical spectra show that the crystals’ absorption edge is 360xa0nm. The results of ferroelectric hysteresis loops experiments indicated that the ferroelectric parameters including saturation polarization, remnant polarization, and coercive field increased with the highest applied voltages. According to the differential thermal analysis curve, the melting point of 0.92PZN–0.08PT crystals can be found at approximately 1187°C.

In situ observation of ferroelectric domain configurations in unpoled 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 crystals by synchrotron radiation topography

Abstract In situ observation of ferroelectric domain structures and phase transition in unpoled 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 (PZN–8%PT) crystals has been successful performed by real time white-beam synchrotron radiation topography (WBSRT) with several aluminum foils for surrounding the sample. This novel topography method can be used to overcome the shortage of the common WBSRT for investigating lead-contained crystals. The complex and unique configurations and dynamic behaviors of ferroelectric domain walls in unpoled PZN–8%PT induced by temperature variation were revealed, which were believed to be meaningful for indicating the intrinsic nature of the phase transition and the origin of the strong piezoelectricity in relaxor ferroelectric materials.

Environmental SEM investigation on surface defects in 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3 single crystal

In this paper, the technique of environmental scanning electron microscopy (ESEM) has been employed to investigate the surface defects of the (111) appearing face in 0.92Pb(Zn1/3Nb2/3)O-3-0.08PbTiO(3) (PZN-8%PT) crystals. From the ESEM images, we succeeded in observing and studying the growth hillocks and etch pits, low-angle grain boundaries, and sub-grain boundaries in (111) face, which were related to the generation of dislocation and stacking faults, respectively. On the other hand, an image of a unique multi-layer lamellar structure and fine step structure obtained in the (111) face reveals that the dominant fast growth mechanism of PZN-8%PT crystal grown by the flux method is a sub-step mechanism, unlike the screw dislocation growth mechanism

Electrical properties of sol–gel derived MPB 0.37BiScO3–0.63PbTiO3 thin films deposited on iridium oxide electrodes

The characterization of sol–gel derived morphotropic phase boundary (MPB) 0.37BiScO3–0.63PbTiO3 (BSPT) thin films, deposited on IrO2/TiO2/SiO2/Si and Pt/TiO2/SiO2/Si substrates, was performed to identify the influence of the IrO2electrodes on the films microstructure and electrical properties. Though the ferroelectric behaviour of both films is similar, with remanent polarization values of 26 µC cm−2 and 23 µC cm−2, respectively, for IrO2 and Pt bottom electroded films, the leakage current density (JL) at room temperature markedly decreases from > 10−6 A cm−2 for BSPT on Pt to the order of ≤ 10−8 A cm−2 for BSPT on IrO2, under the maximum voltage of 4 V (∼80 kV cm−1). The formation of an interface layer between the film and the electrode, as observed by Rutherford Backscattering Spectroscopy, is proposed to have a space charge sink effect and, as a consequence, to account for the improvement of the leakage current behaviour of the IrO2 electroded films.