Performance of laser-pumped quantum counters

Narrow-band quantum counters with less than unit internal quantum efficiency are analyzed. The pump power dependent expressions for the transient and steady-state quantum efficiencies are derived. These quanties are discussed for "typical" trivalent and divalent rare-earth-doped insulator crystals, and the performance of two specific systems is presented. It is shown that to achieve high quantum efficiency in trivalent rare-earth-doped quantum counter systems, the pump source must be highly nonblackbody in spectral character, i.e., a laser, and resonant with the transition between the relevant excited states. Performance limiting factors for laser-pumped quantum counters are pointed out.     

Spectroscopy and diode laser-pumped operation of Tm,Ho:YAG

Spectroscopic measurements and analysis of diode laser-pumped operation of Tm,Ho:YAG at 2.1 μm at room temperature have been performed. The peak effective stimulated emission cross section is measured to be 9×10^-21 cm² at 2.091 μm and the upper state lifetime is 8.5 ms. Under diode laser pumping, thresholds of 4.4 mW of absorbed power and slope efficiency of 19% have been demonstrated. Calculations of threshold power are performed based on the spectroscopic measurements. An energy transfer upconversion process is identified which leads to a sublinear rise in upper-state population with pump power     

Short-term stability of laser-pumped rubidium gas cell frequencystandard

The authors examine the influence of the light-shift effect on the frequency stability of a laser-pumped Rb gas cell standard for averaging time up to 10⁴ s. The measured stability at the flicker floor is 7×10^-14 for averaging times from 200 to 5000 s, providing that the laser frequency is properly set at the optical resonance frequency, and correcting for the variation of atmospheric pressure     

脉冲钛宝石激光器时间特性的研究

本文从四能级结构激光速率方程出发，对脉冲掺钛蓝宝石激光器的时间特性进行了理论研究。倍频调ＱＵｄ：ＹＡＣ激光器泵浦的掺钛蓝宝石激光器的输出脉宽和时间延时随泵浦能量、调谐波长和输出耦合率的变化而变化。所得的实验结果与理论结果相吻合。     

Cooling schemes for longitudinally diode laser-pumped Nd:YAG rods

Longitudinal diode laser pumping causes pronounced inhomogeneous heating of the laser material. The effect of the thermal load on the mechanical and optical properties is significantly influenced by the method used for cooling the pumped surface. Four methods for longitudinally pumped Nd:YAG rods were compared experimentally and with finite-element (FE) analysis. The pumped surface exposed to air or to flowing water, a sapphire plate pressed onto the pumped surface and composite rods, having an undoped pumped end, were investigated. The comparison includes temperature and stress distributions with the emphasis on thermal lensing. Careful validation of the FE code with experiments allowed to numerically comparing the cooling methods under identical conditions     

Mode-locking of diode laser-pumped Nd:YAG laser at 1.3 mu m

Reports on the development of a mode-locked AlGaAs diode laser pumped Nd:YAG laser operating at 1.3 mu m. The laser produces pulses of 47 ps duration with a time-bandwidth product of 0.42, which is close to the limit for Gaussian pulses.<>     

飞秒钛宝石激光器Kerr透镜锁模动态的特性研究

研究了Kerr透镜锁模钛宝石激光器中腔内群色散改变时脉冲的动态特性。实验研究了腔内群色散改变时输出脉冲的频谱、中心波长以及脉宽的变化规律;观测和解释了脉冲频谱的双峰结构;给出了脉冲宽度与腔内色散的具体关系式;获得了最短为14.6fs的自锁模脉冲     

Tunable te-CO2 laser-pumped formaldehyde far-infrared lasers: Offsets,assignment, and superfluorescence

Sixty and three absorption transitions in D₂CO and H₂CO, respectively, have produced a number of far infrared laser lines when they are pumped by an etalon-tuned TE-CO₂ laser. Almost all the absorption transitions pumped previously by a free runing TE-CO₂ laser have been efficiently pumped by the etalon tuned CO₂ laser and found to have offset within ±500 MHz from the line-center of the relevant CO₂ pump lines. 22 (1) absorption and 63 (4) emission lines of D₂CO (H₂CO) are assigned. Some of these lines have generated superfluorescence. In paticular, the D₂CO 319-μm line pumped by CO₂-9P(32) delivered an output energy of approximately one half that of the well-known D₂O 66-μm. It is shown that a large electric dipole moment and an appreciable amount of fractional population in the lower level of the pump transition of this line are responsible to the superfluorescence.     

连续钛宝石激光器波长调谐特性及斜效率的测量

采用四镜折叠驻波腔，以氩离子激光器的可见多谱线输出纵向激励，用国产钛宝石激光棒实现了连续激光运转。使用三套腔镜得到的波长调谐范围分别为６８０～７６０ｕｍ、７３０～８４０ｕｍ、９７０～１０１０ｎｍ，峰值波长约为７８０ｕｍ。当输出透射率为１１．７６％、泵浦功率约１０．０Ｗ时，获得７８０ｕｍ波长的激光最大输出功率约２．３５Ｗ，斜效率为３３．４９％。     

Modeling of laser-pumped Tm and Ho lasers accounting forupconversion and ground-state depletion

Models for numerical simulations of laser-pumped thulium- and thulium-holmium-doped lasers have been developed. In the models, upconversion losses and ground-state depletion in both thulium and holmium are accounted for, as well as spatial dependencies of the pump and resonator modes. The models apply to CW operation and to the build-up of population inversion prior to lasing in pulsed modes of operation. It is shown that upconversion losses in Tm:Ho:YAG significantly reduce the output from the laser in both CW and Q-switched mode. Simulations of CW lasers show good agreement with experimental results     

Interferometric measurement of low-frequency phase noise characteristics of diode laser-pumped Nd:YAG ring laser

Reports the interferometric measurement of the phase noise characteristics of a diode laser-pumped solid-state Nd:YAG 1.3 mu m laser based on a nonplanar ring cavity. Results show that the device has a low-frequency phase noise approximately three orders of magnitude lower than that observed with semiconductor diode lasers. The use of this source in fibre sensing applications is discussed.<>     

镀钛玻璃与PET之间的激光透射连接及其性能

激光透射连接具有生物相容性的异种材料在生物医学植入体及其封装中具有良好的应用前景。利用半导体激光器对镀钛玻璃与聚对苯二甲酸乙二酯(PET)进行激光透射连接试验,其中玻璃上镀钛薄膜是通过射频磁控溅射方法完成的镀膜。通过单因素工艺研究了主要工艺参数激光功率、扫描速度和镀钛薄膜的厚度对连接强度的影响,并探讨了玻璃基片的表面粗糙度对镀钛薄膜粗糙度以及其连接强度的影响。通过搭接剪切试验得到镀钛玻璃与PET之间的连接强度,采用真彩共聚焦材料显微镜对拉伸失效后的试样表面进行观测和失效分析,使用X射线光电子能谱(XPS)检测激光透射连接过程中镀钛玻璃与PET之间化学键的形成信息。结果表明:主要工艺参数激光功率、扫描速度对连接强度有着重要影响,增加玻璃基片的粗糙度和镀钛薄膜的厚度可以提高其连接强度,为激光透射连接镀钛玻璃与聚合物提供了参考。     

A laser-pumped temperature sensor using the fluorescent decay time of alexandrite

In this work a simple intensity-independent fiber-optic temperature sensor using alexandrite crystal was constructed. The sensor uses the change in the characteristics of the fluorescence of the material to sense the parameter required and operates using light from an electrooptically modulated He-Ne laser at 633 nm. Microprocessor control and signal processing is used to achieve an accuracy ofsim pm1degC with a 3-s response.     

Au/Ti/p型金刚石膜欧姆接触特性研究

在重掺杂硼金刚石膜上溅射沉积了Ti/Au接触 ,用CTLM测量了样品退火前后的I-V特性 ,并对大电流情况进行了讨论。就测试温度和光照强度对接触特性的影响进行了分析。定性给出了该接触的能带模型。样品接触电阻率 ρc 最低值达 1.2 3 6× 10 - 6 Ω·cm2 。     

基于钛相变边缘传感器的超导单光子探测器特性

研究了基于钛TES的超导单光子探测器的特性,器件尺寸范围为5 μm×5 μm到20 μm×20 μm,集成光学腔体后在1 550 nm波长实测的系统探测效率最高达到72%,最佳能量分辨率为0.26 eV。在此基础上,采用二流体模型提取了基于钛TES的超导单光子探测器的特性参数（包括温度灵敏度、电流灵敏度、热容等）,并模拟计算了基于钛TES的超导单光子探测器的响应时间和能量分辨率,与实验结果完全吻合。结果表明优化探测器尺寸和临界温度,可以同时达到高探测效率和高能量分辨率,实现光子数可分辨的高性能单光子探测器。     

n-GaN表面Ti/Al/Ti/Au电极的电学特性

实验研究了淀积在GaN上的Ti/Al/Ti/Au电极的电学和热学特性,绘制了不同退火温度下的I-V曲线,得到了最低的欧姆接触电阻率(ρs=1.2×10-4 Ω·cm2),并通过X射线衍射谱分析了GaN与Ti/Al/Ti/Au电极接触表面在退火过程中的固相反应.实验结果表明,在Ti/Al表面增加Ti/Au保护层能够保证Al层在高温时不发生球化和氧化,电极更稳定可靠能够进一步提高欧姆接触特性.     

准连续钛蓝宝石激光器动力学特性的研究

本文采用激光速率方程理论详细地研究了准连续钛蓝宝石激光器的动力特性。结果表明在固定腔参数下,泵浦脉冲能量是决定输出脉冲脉宽和形状的主要因素,而输出脉冲的时间延迟由泵浦脉冲能量和脉宽共同测定。数值计算结果和文献的实验结果相一致。     

Ti膜磁控溅射及光吸收特性研究

介绍了射频磁控溅射金属Ｔｉ膜工艺，对Ｔｉ膜光吸收特性进行了测试，用经典电子理论分析了光吸收机理。     

Ti/Ag/Cu活性焊料的封接特性

Ti／Ag／Cu活性焊料法广泛应用于陶瓷与金属的焊接中，但该焊料在陶瓷表面的浸润性较差，在金属表面易发生偏析的现象。本文对该焊料的流散特性进行了讨论，对陶瓷与金属的封接界面进行了分析，对封接机理进行了讨论，结果表明在封接界面生成Ti的氧化物主要是TiO2。