Haihe Jiang

2.79 μm high peak power LGS electro-optically Q-switched Cr,Er:YSGG laser

A flash lamp pumped Cr,Er:YSGG laser utilizing a langasite (LGS) crystal as an electro-optic Q-switch is proposed and demonstrated. It is proved that a LGS crystal with relatively high damage threshold can be used as the electro-optic Q-switch at 2.79 μm, and 216 mJ pulse energy with 14.36 ns pulse width is achieved. Its corresponding peak power of pulse can reach 15 MW, to our knowledge the best result at a 2.79 μm wavelength.

Electron crystallographic study of Bi2(Sr0.9La0.1)2CoOy

The superstructure in Bi-2(Sr0.9La0.1)(2)CoOy has been studied by the two-stage image-processing technique consisting of image deconvolution and phase extension; and based on the combination of high resolution electron microscopy and electron diffraction. All unoverlapped atoms including oxygen are resolved in the final projected potential map of resolution of about 1 Angstrom. The structure modulation is seen clearly. It is caused by the fluctuation of both atomic positions and occupancy

Mid-infrared ZGP-OPO with a high optical-to-optical conversion efficiency of 757%

We experimentally demonstrate a ZnGeP2 based optical parametric oscillator (ZGP-OPO) with a record of the optical-to-optical conversion efficiency. To improve the conversion efficiency, we design and construct a double-pass pumped high-gain OPO and a matched large-sized high-peak-power pump beam to suppress the spatial walk-off and conversion. Pulse energy of 19 mJ with pulse width of 27.8 ns at 5 Hz in the mid-infrared 3-5 μm waveband is obtained in the doubly resonated ZGP-OPO, the beam quality M2 is about 9.6, and the corresponding optical-to-optical conversion efficiency reaches up to 75.7%.

High peak power Q-switched Er:YAG laser with two polarizers and its ablation performance for hard dental tissues

An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.

Structural modulation in Bi2(Sr0.9La0.1)2Cu1−xCoxOy (x=0.2, 0.6, 1.0)

Abstract Three specimens of Bi 2 (Sr 0.9 La 0.1 ) 2 Cu 1− x Co x O y with x =0.2, 0.6, 1.0, respectively, were investigated by transmission electron microscopy to explore the influences of Co substitution for Cu on the structural modulation. They have in common orthorhombic modulated structures. But the modulation periodicity decreases gradually with the increase of Co content. Its ratio to the corresponding lattice parameter of basic structure equals 4.28 for x =0.2, 4.18 for x =0.6 and 4.00 for x =1.0. Consequently, the modulated structures of the former two phases are incommensurate, while it is commensurate for the last one. The stacking disorder due to the weak bonding connection between two adjacent Bi–O layers has been observed in the two incommensurate modulated phases.

Preparation, crystal structure, spectra and energy levels of the trivalent ytterbium ion doped into rare earth stannates

Yb³⁺-doped Rare Earth Stannates Ln₂Sn₂O₇(Ln=Y, Gd) with space group Fd3m were synthesized by co-precipitation technique. Their structures were determined by Rietveld refinement to their X-ray diffraction, and their atom coordinates, lattice parameters and temperature factors were given. From emission, absorption and excitation spectra, the energy levels of Yb³⁺ in Ln₂Sn₂O₇(Ln=Y, Gd) were assigned and the crystal field parameters were fitted to energy splitting of Yb³⁺-doped Ln₂Sn₂O₇ (Ln=Y, Gd).

Picoseconds pulse generation with a Nd:GGG laser operating on quasi-three-level transition

We presented the first demonstration of a mode-locked Nd:GGG laser on quasi-three-level transition. With a semiconductor saturable absorber mirror for passively mode-locking, 24.7 ps laser pulses had been obtained at the wavelength of 937.4 nm.

Structural variation in a (Y1−yCay)(Sr2−xBax)(Cu0.5B0.5)Cu2O7−δ system

The crystal structure of compounds (Y1−yCay)(Sr2−xBax)(Cu0.5B0.5)Cu2O7−δ has been studied by electron diffraction and high-resolution electron microscopy. The structure is tetragonal for the samples with x = 0.5, 1.0 and 1.5, y = 0.4. The incommensurate structural modulation is found in samples with y ≤ 0.3, and the average unit cell of modulated structure is tetragonal. The change of x or y induces the variation of modulation wave vector.

Λ* Resonance Model Calculation of K-p→ηΛ Reaction Near Threshold

A Lambda* resonance model for the eta - Lambda interaction near threshold is proposed. By assuming the Lambda* (1670) excitation dominates in the K- p --> eta Lambda reaction near threshold, the corresponding eta production cross section and the s-wave eta - Lambda scattering length are calculated. The obtained production cross section is consistent with the available experimental data, which indicates that the Lambda* (1670) excitation is dominant in the production reaction near threshold. The eta - Lambda interaction is found to be attractive.