Su Liangbi

Femtosecond Laser-Written Waveguides in a Bismuth Germanate Single Crystal

We demonstrate the fabrication of symmetric waveguides in a bismuth germanate (BGO) single crystal using a double line approach by an 800 nm femtosecond laser. The optical attenuation of the single mode waveguide is measured to be 4.2 dB/cm at 633 nm. The influence of pulse energy and focal depth on the end facet of the irradiated region is also studied. This technique is promising to fabricate buried BGO waveguide arrays used in positron emission tomography systems.

Passively mode-locked 2-μm Tm:YAP laser with a double-wall carbon nanotube absorber

We report on a diode-pumped passively continuous wave (cw) mode-locked Tm:YAP laser with a double-wall carbon nanotube (DWCNT) absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.

Crystal Growth and Characterization of the Rare-earth Orthoferrite Sm

利用光学浮区法生长Sm 0.8 Tb 0.2 FeO 3 单晶, 采用劳尔背衍射仪对样品质量进行检测并定向。测试了 c -切Sm 0.8 Tb 0.2 FeO 3 单晶在零场冷却模式的磁温曲线, 发现其自旋重取向温度范围为360~400 K。总结以前的工作发现Sm 1- x Tb x FeO 3 系列材料的自旋重取向温度随着稀土铽(Tb)含量的增加而线性减小, 这表明Sm 1- x Tb x FeO 3 系列材料中Fe 3+ -Re 3+ 之间的超交换作用发生变化。热膨胀测试结果发现Sm 0.8 Tb 0.2 FeO 3 存在三个温度转变区域: ~250 K、350~480 K和 ~700 K。250 K发生的不正常相变是由于铁离子弱铁磁矩诱导的稀土离子磁矩方向的改变造成的, 350~480 K是由于在这一温度范围发生铁离子自旋重取向, 而~700 K发生的相变是由于铁离子自旋由反铁磁有序到顺磁无序的磁转变。利用光学浮区法生长Sm 0.8 Tb 0.2 FeO 3 单晶, 采用劳尔背衍射仪对样品质量进行检测并定向。测试了 c -切Sm 0.8 Tb 0.2 FeO 3 单晶在零场冷却模式的磁温曲线, 发现其自旋重取向温度范围为360~400 K。总结以前的工作发现Sm 1- x Tb x FeO 3 系列材料的自旋重取向温度随着稀土铽(Tb)含量的增加而线性减小, 这表明Sm 1- x Tb x FeO 3 系列材料中Fe 3+ -Re 3+ 之间的超交换作用发生变化。热膨胀测试结果发现Sm 0.8 Tb 0.2 FeO 3 存在三个温度转变区域: ~250 K、350~480 K和 ~700 K。250 K发生的不正常相变是由于铁离子弱铁磁矩诱导的稀土离子磁矩方向的改变造成的, 350~480 K是由于在这一温度范围发生铁离子自旋重取向, 而~700 K发生的相变是由于铁离子自旋由反铁磁有序到顺磁无序的磁转变。

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Recently, α-Al2O3:C crystal with highly sensitive thermoluminescence (TL) and optically stimulated luminescence (OSL) has been successfully grown by the temperature gradient technique. This paper investigates the heating rate dependence of TL sensitivity, light-induced fading of TL signals and thermal stability of OSL of α-Al2O3:C crystals. As the heating rate increases, the integral TL response decreases and the dosimetric glow peak shifts to higher temperatures in α-Al2O3:C crystals. Light-induced fading of TL increases with the irradiation dose, and TL response decreases as the exposure time increases, especially in the first 15 minutes. With the increasing intensity of the exposure light, the TL fading of α-Al2O3:C crystal increases sharply. The OSL response of as-grown α-Al2O3:C crystal is quite stable below 373 K and decreases sharply for higher temperatures.

gt;0.8

Spectroscopic properties of Ce-doped yttrium orthoaluminate (Ce:YAlO3 or Ce:YAP) crystals grown by temperature gradient technique (TGT) were investigated, and the effects of the growth conditions on the properties were analyzed.. Methods of optical absorption (OA), photoluminescence (PL), photoluminescence decay (PLD), X-ray excited luminescence (XL) and cathodeluminescence (CL) were used in these investigations. The results showed that the absorption band peak at 202, 394 and 532 nm originated from F and F+ color center induced by the weak reducing growth atmosphere, green emission band near 500 ran derived from Ce3+ -Ce3+ pairs and band at 650 similar to 850 run from some unintentional impurity in crystals.

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Diode-pumped soliton and non-soliton mode-locked Yb:(Gd1−x Yx)2SiO5(x = 0.5) lasers are demonstrated. Pulses as short as 1.4 ps are generated for the soliton mode-locked operation, with a pair of SF10 prisms as the negative dispersion elements. The central wavelength is 1056 nm and the repetition rate is 48 MHz. For the non-soliton mode locking, the output power could achieve ~1.2 W, and the pulse width is about 20 ps. The critical pulse energy in the soliton-mode locked operation against the Q-switched mode locking is much lower than the critical pulse energy in the non-soliton mode-locked operation.

gt;Tb

采用坩埚下降法生长了系列共掺的Pr, Y: SrF 2 和Pr, Gd: SrF 2 晶体, 研究了调剂离子对Pr: SrF 2 晶体晶胞参数和光谱性能的影响规律。研究结果表明, 掺杂不同种类和浓度的调剂离子可以有效提高晶体的吸收截面和发射强度。同时, 调剂离子通过改变晶体内部的团簇构型和发光中心的局域配位结构, 使Pr, R 3+ : SrF 2 (R=Y, Gd)晶体各峰位的发光强度变化规律不一致: 绝大部分峰位发光强度先增加到峰值后减小, 极个别变化趋势相反或发光强度基本保持不变。结合晶胞参数和荧光寿命图谱也可以证明调剂离子对晶体内部团簇和局域结构的影响。总之, 掺入调剂离子后, Pr: SrF 2 晶体的光学性能更优, 尤其是共掺入6.0at%Y 3+ 或10.0at%Gd 3+ 后, 其光学性能达到最佳。

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By using a reflective graphene oxide as saturable absorber, a diode-pumped passively mode-locked Yb3+:Sc2SiO5 (Yb:SSO) laser has been demonstrated for the first time. Without extra negative dispersion compensation, the minimum pulse duration of 1.7 ps with a repetition rate of 94 MHz was obtained at the central wavelength of 1062.6 nm. The average output power amounts to 355mWunder the absorbed pump power of 15W. The maximum peak power of the mode-locking laser is up to 2.2 kW, and the single pulse energy is 3.8 nJ.

gt;0.2

The Er-single-doped and Er/Ce-codoped La3Ga5SiO14 polycrystalline powders are synthesized by the solid-phase synthesis method. The room-temperature luminescence spectra of the samples are investigated. The Near-infrared-region spectroscopic properties of Er3+ ions in the La3Ga5SiO14 systems are analysed with Judd-Ofelt theory and rate equations. The effective deactivating effect of Ce3+ ions on Er3+ ions is confirmed.

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Nd-doped PbWO4 crystals are grown by using the modified Bridgman method. The spectroscopic properties of the crystals are investigated. The changes of the absorption band at 350 nm are discussed for samples annealed at 740 °C and 1040 °C. The radiative lifetime of the 4F3/2 level is calculated by using the Judd-Ofelt theory according to the absorption spectrum of 0.5 at.% Nd-doped PbWO4 crystal. The spontaneous Raman scattering properties of the crystals are analysed.