The etching of a-plane GaN epilayers grown metal-organic chemical vapour deposition

Morphology of nonpolar （1120） a-plane GaN epilayers on r-plane （1102） sapphire substrate grown by low-pressure metal-organic vapour deposition was investigated after KOH solution etching. Many micron- and nano-meter columns on the a-plane GaN surface were observed by scanning electron microscopy. An etching mechanism model is proposed to interpret the origin of the peculiar etching morphology. The basal stacking fault in the a-plane GaN plays a very important role in the etching process.     

Improvement of the large aperture Ti：sapphire amplifiers in the petawatt femtosecond laser system at SIOM

We report the recent improvement on the petawatt (PW) femtosecond Ti:sapphire chirped pulse amplification (CPA) laser system at Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences. By enlarging the sizes of the pump and signal beams in the large aperture Ti:sapphire amplifiers and optimizing the whole laser system, the output laser energy before the pulse compressor is upgraded to 42.6 J. Accordingly, the peak power of the laser system exceeds 1 PW. The shot-to-shot instability of the output laser energy at about 40 J is less than ±5%.     

掺钛蓝宝石激光放大器中放大自发辐射效应研究

 给出了描述掺钛蓝宝石激光放大器的速率方程组，通过对放大介质内反转粒子数密度和放大自发辐射的时间和空间特性的数值计算与分析，提出可通过控制泵浦光脉冲和信号光之间的时间延迟来有效地抑制放大自发辐射对放大器增益的影响。     

LED泵浦蓝宝石光纤荧光温度传感器

采用激光加热基座法制备端部Cr3+离子掺杂的蓝宝石单晶光纤,得到一体型蓝宝石单晶光纤荧光温度传感头.对所制备的荧光温度传感头的荧光温度特性进行了实验研究.结果表明,随着温度升高Cr3+∶Al2O3单晶光纤荧光寿命单调下降,从温度为0 ℃的4.0 ms下降到450 ℃的0.2 ms.利用所制备的荧光温度传感头,用波长405 nm紫色LED作为泵浦光源,采用相关检测技术在线实时测量荧光寿命,研制成测温范围0 ℃～450 ℃一体型蓝宝石光纤荧光温度传感器.     

4.5MW小型化全固态腔倒空飞秒掺钛蓝宝石激光器

研制了国内首台腔倒空克尔透镜自锁模掺钛蓝宝石激光器,该激光采用二极管抽运的全固态连续波532nm激光抽运.在5.4W的抽运功率下,获得了峰值功率大于4.5MW、脉宽小于18fs的稳定锁模脉冲,其重复频率可低至20kHz,所占尺寸约53.5cm×20.5cm.据知,此结果是迄今重复率最低、结构最紧凑的声光腔倒空飞秒激光器件 关键词： 掺钛蓝宝石 腔倒空 飞秒脉冲 克尔透镜锁模     

高阻GaN的MOCVD外延生长

利用金属有机化合物气相沉积(MOCVD)在蓝宝石衬底上生长了高阻GaN薄膜。对GaN成核层生长的反应室压力、生长时间和载气类型对GaN缓冲层电学特性的影响进行了分析。实验结果表明,延长GaN成核层的生长时间,降低成核层生长时的反应室压力,载气由H₂换为N₂都会得到高阻的GaN缓冲层。样品的方块电阻R_s最高为2.49×10¹¹ Ω/□。以高阻GaN样品为衬底制备了AlGaN/AlN/GaN结构HEMT器件,迁移率最高达1 230 cm²/(V·s)。     

MW级峰值功率掺钛蓝宝石激光振荡器

在常规重复频率77 MHz掺钛蓝宝石飞秒激光器的基础上,通过腔内引入Herriott型多通望远镜系统增加总腔长及对腔内色散的深入分析和实验控制,实现了低重复频率、高脉冲能量飞秒激光振荡的稳定运行.在连续功率8.2 W的532 nm激光抽运下,得到了重复频率11 MHz、单脉冲能量达72.73 nJ、对应峰值功率MW量级的结果.相对80 MHz重复频率下6.25 nJ的单脉冲能量及150 kW的峰值功率,其输出能力提高了约一个量级. 关键词： 飞秒激光 掺钛蓝宝石激光器 低重复频率 MW     

Improvement of Test of Solar Neutrino Coherent Scattering with Torsion Pendulum

A torsion pendulum containing two sapphire crystals and two lead rings is used to test Weber＇s theory of enhanced solar neutrino coherent scattering. Our experiment gives a null result for the diurnal force with a noise level of 3.8 × 10^-14 N, which is 526 times smaller than the predicted value of Weber＇s theory, and directly rules out Weber＇s theory and the experimental result. This experiment also reveals a test of the weak equivalence principle with η （Al2O3, Pb） （0.8 ± 3.1） × 10^-10 for masses falling toward the Sun.     

Ti和蓝宝石的界面反应

在超高真空中用电子束蒸发在抛光的(1102)取向的蓝宝石(α-Al₂O₃)衬底上蒸镀500nm的Ti膜,在恒温炉中退火,然后用XRD(包括一般的和小角度的X射线衍射),AES(俄歇电子谱,包括深度剖面分布和通过界面的谱形分析)和SIMS(二次离子质谱)等表面分析技术详细研究了从室温至850℃,Ti与α-Al₂O₃的固相界面反应.结果表明室温及300℃,30min退火已有反应,Al₂O_{3< 关键词：}     

在蓝宝石上生长CeO2 缓冲层的原位双温工艺法及Tl-2212薄膜的技术改进

报道了在蓝宝石衬底上制备CeO₂缓冲层的原位双温工艺法及其对Tl₂Ｂa₂CaCu₂Ｏ₈（Tl-2212）薄膜超导特性的影响．XPS和AFM测试结果表明,采用原位双温工艺法制备缓冲层,具有工艺简单,薄膜表面光滑,衬底材料原子扩散量少等特点．在先驱膜的高温后退火过程中,40 nm厚的CeO₂薄膜就能有效地阻挡衬底材料对超导薄膜底层的扩散．随后制备厚度为530 nm的Tl-2212 关键词： Tl-2212超导薄膜 蓝宝石 氧化铈缓冲层 原位双温工艺法