脉冲放电激励的钡蒸气激光的研究

设计和制作了新型结构的金属蒸气激光放电管.用钡为激光介质,通过纵向高频快脉冲放电激励,在国内首次实现波长为1.13μm和1.50μm的红外钡蒸气激光振荡,激光成分主要集中在1.50μm这条谱线上,激光输出功率和功率密度分别达1.2W和33.3mW/cm3.测量并讨论了各工作参量和激光输出特性之间的关系.     

用于LAGEOS测距的超短脉冲激光系统

本文报道一个Nd:YAG超短脉冲激光系统.该系统在1.06μm波长处的单脉冲输出能量大于100mJ.经倍频后获得0.53μm输出大于50mJ.该系统在上海天文台主镜为φ600mm的测距仪上使用,测到了激光地球动力卫星(LAGEOS),测距能力8000km,测距精度5cm左右.     

锶蒸气中原子激光与离子激光的同时振荡

通过锶蒸气中的高频脉冲放电,实现了锶原子6.45μm自终止跃迁激光和锶离子1.03μm/1.09μm自终止跃迁激光的同时振荡.其中6.45μm激光最大激光平均功率为273mW.在对比实验的基础上分析和讨论了主要工作参数对这两组激光输出影响的差异.     

锶蒸气中原子激光与离子激光的同时振荡

通过锶蒸气中的高频脉冲放电,实现了锶原子6.45*!μm自终止跃迁激光和锶离子1.03*!μm/1.09*!μm自终止跃迁激光的同时振荡.其中6.45*!μm激光最大激光平均功率为273*!mW.在对比实验的基础上分析和讨论了主要工作参数对这两组激光输出影响的差异.     

重复频率下飞秒激光驱动产生的X射线焦斑测量

为了获取强激光驱动产生的X射线光源焦斑尺寸和空间分辨率,设计了刃边及双网格方法,其中刃边厚度为0.2μm,双网格分别为400目铜网格和394lp/cm的镍网,利用X射线CCD作为探测元件。Ti宝石激光在能量1J、脉宽40fs、频率10 Hz、激光功率密度约为4.4×1018 W/cm2的条件下,重复频率加载圆盘Cu靶。在中国工程物理研究院25TW激光装置上首次获得了X射线的焦斑及网格图像,并推算了该装置的X射线焦斑尺寸为43μm,而网格空间分辨力为34μm。结果表明该刃边及双网格方法适合强激光驱动产生的X射线焦斑尺寸测定。     

脉冲放电激励的钡蒸气激光的研究

设计和制作了新型结构的金属蒸气激光放电管.用钡为激光介质,通过纵向高频快脉冲放电激励,在国内首次实现波长为113μm和150μm的红外钡蒸气激光振荡,激光成分主要集中在150μm这条谱线上,激光输出功率和功率密度分别达12W和333mWcm3.测量并讨论了各工作参量和激光输出特性之间的关系     

电泳式He-Sr+复合激光特性研究

设计制作了7 mm内径和38 cm有效激励长度的电泳式He-Sr 激光管,采用修饰Blumlein电路,通过纵向高重复率脉冲放电激励,实现了一价锶离子复合激光430.5 nm和R-M跃迁激光1.03μm的同时振荡,其中复合激光占主要成分.测量分析了复合激光输出功率与工作参量(脉冲频率,充电电源电压和氦压)的关系曲线.获得了最大激光功率819mW和56mW/cm3功率密度的实验结果.     

面向激光等离子体尾波加速的毛细管放电实验研究

具有合适径向密度分布的等离子体通道可以用于超短超强激光导引,这使得等离子体通道在激光尾波加速中有着重要的应用.本文介绍了在上海交通大学激光等离子体实验室开展的毛细管放电和光导引实验.通过光谱展宽法测量了充氦气的放电毛细管中的等离子体密度分布,在长度为3 cm、内径为300μm的毛细管中实现了轴向均匀,径向呈抛物线型的等离子体密度分布.通过改变放电延时和喷气时长,确定和优化了产生等离子体通道的参数区间,得到的最大通道深度为28μm,与实验中使用的激光焦斑半径匹配.在此基础之上,开展了不同能量的激光脉冲在放电等离子体通道中的导引研究,结果发现当通道深度与焦斑半径匹配时,激光可以不散焦地在通道中传输,实现激光导引.这项研究为未来的激光尾波级联加速和锁相加速等研究奠定了基础.     

大口径KDP晶体高效率倍频

本文报道了用一块3cm厚Ⅱ类KDP晶体,在φ42mm口径、功率密度为0.27GW/cm~2的1.06μm激光束作用下,0.53μm倍频激光外部能量转换效率达到 61.5％的实验结果。实验和理论计算值符合较好。     

超短脉冲激光在掺Er3+ 磷酸盐玻璃中制备光波导的实验研究

超短脉冲激光通过非线性吸收调制光学材料折射率提供了一种高效制备集成三维光子器件的途径.掺Er³⁺磷酸盐玻璃由于其优异的特性以及在1.55μm通信波段附近的发射光谱,成为了集成光学主动增益材料中的研究热点.实验采用重复频率1 kHz,中心波长800 nm,脉冲宽度120 fs的钛宝石飞秒激光放大系统作为制备波导的光源,系统研究了加工参数对激光写入形貌、波导形成及光学特性的影响.实验结果表明,在狭缝整形辅助短焦物镜横向刻写条件下,写入脉冲能量为1.8μJ时,光波导可以在写入速度为10μm/s-160μm的较宽范围内形成;写入速度为40μm/s时,光波导写入脉冲能量参数窗口为1.6μJ-2.0μJ;波导写入深度在125μm-200μm范围时,波导横截面对称性较好且折射率修改明显;近场强度测量结果显示所制备波导近场强度分布对称,导光特性良好.通过有限差分法反推波导区域折射率修改分布,结果显示最大折射率修改为Δn=6.6×10^-4.截断传输损耗测量结果显示所制备波导的传输损耗低至0.91 dB/cm.     

Design considerations and scaling laws for high power convective cooled CW CO2 lasers

Various criteria for designing high power convective cooled CO₂ lasers have been discussed. Considering the saturation intensity, optical damage threshold of the optical resonator components and the small-signal gain, the scaling laws for designing high power CW CO₂ lasers have been established. In transverse flow CO₂ lasers having discharge of square cross-section, the discharge lengthL and its widthW for a specific laser powerP (Watt) and gas flow velocityV (cm/s) can be given byL = 1.4 x 10⁴ p ^1/2 V ^-1 cms andW = 0.04P ^1/2 cms. The optimum transmitivity of the output coupler is found to be almost constant (about 60%), independent of the small signal gain and laser power. In fast axial flow CO₂ lasers the gas flow should be divided into several discharge tubes to maintain the flow velocity within sonic limit. The discharge length in this type of laser does not depend explicitly on the laser power, instead it depends on the input power density in the discharge and the gas flow velocity. Various considerations for ensuring better laser beam quality are also discussed.     

Performance studies of a pulsed HF laser with a sliding discharge plasma cathode

The plasma electrode design concept is applied for the first time to an HF laser. The discharge along the surface of a dielectric (sliding discharge) is used as a plasma cathode for the main laser discharge. The laser operates at atmospheric pressure with a gas mixture of He/SF₆/C₃H₈. Details are presented on the efficiency of energy transfer, the dependence of laser performance on circuit parameters, gas mixture, relative energy loading and time delay between the plasma electrode and main discharges. The F atom production rate is estimated from the linear dependence of the output energy on the electric charge passed through the discharge. Output energies of 600 mJ were obtained at 1.6% efficiency from a small active discharge of 108 cm₃ volume and 38 cm length, while the maximum specific input and output energies were 370 J/1 and 5.7 J/1, respectively. These values compare favourably with those reported in the literature for non-chain-reaction-type gas mixtures at 1 atm pressure and demonstrate that the plasma electrode design is a powerful scheme for developing gas-discharge lasers.     

A CW DCN waveguide laser of high volumetric efficiency

This paper describes a CW submillimeter waveguide laser operating on 190 and 195 μm DCN lines with high volumetric efficiency. The laser cavity is a 3.2 cm inner diameter, 70 cm long, Pyrex tube with plane reflectors (one of them is a copper mesh) against its ends. After optimization of various parameters (such as the N₂:CD₄:He gas mixture, the pressure and the discharge current, the wall temperature and the output coupling), this laser, with only 57 cm long active discharge, delivers 8.4 and 7.6 mW on the 190 and 195 μm lines, respectively, for the EH₁₁ mode. This represents volumetric powers of 75 and 65 μW cm^-3. The free space propagation of the EH₁₁ fundamental mode was found to be as for a gaussian beam, and the absorption of the laser beam in the atmosphere was also measured.     

Outlook for parameters of CW copper-vapor lasers

Results of numerical experiments performed for a CW copper-vapor laser are presented. Calculations give an output power of about 15 W and a laser efficiency of the order of 0.1% relative to the discharge power. Strictly specified ranges of the main initial parameters are determined in which CW lasing is possible:p _Cu=0.26–0.69 mm Hg,p _Ne=0.4–1.2 mm Hg,E=40–125 V/cm.     

A 5 cm single-discharge CO2 laser having high power output

A single-discharge self-sustained CO₂ laser has been constructed with a gap distance of 5 cm. The system has a very simple construction; it produces a very uniform discharge with an output power of 50 Joules per liter for a CO₂ : N₂ : He = 1 : 1 : 3 mixture. The efficiency can be as high as 19%.     

Generation of a uniform high-density microwave plasma for CO2 lasers using orthogonal electric fields

To realize a CO₂ laser using a fast-axial-flow high-output-power microwave discharge excitation, we devised a technology for making the microwave discharge uniform by varying the oscillation direction of an electric field with time. We also verified the effectiveness of this technology. As a result, we succeeded in increasing the discharge uniformity to 70% of the laser-tube cross-sectional area and realized a high laser output power and a high laser efficiency. In the case of a microwave input power of 1450 W, a maximum laser output power of 273 W and a laser efficiency of 18.8% were achieved; in the case of a microwave input power of 1070 W, a laser output power of 214 W and a laser efficiency of 20.0% were achieved. At the time of maximum output power, a high input power density of 280 W/cm³, which is approximately 20 times that in a dc discharge method, was achieved. Thus, a high-output-power microwave-discharge-excited CO₂ laser has become feasible. PACS 42.60.By; 52.80.Pi     

Parametric measurements on a doped CO2TEA laser

Parametric measurements have been performed on a CO₂TEA laser with a discharge volume of 6.5 × 6.5 × 45 cm³. The effect of a low ionization seed gas, tri-n-propylamine, upon amplification, power output and voltage-current characteristics has been measured. A small-signal gain of 4.8%/cm has been measured in a 1:1:3 mixture and a power output of 60J/? in a 3:11:21 mixture.     

A 10 cm aperture,high quality TEA CO2 laser

Experiments have been performed on a corona preionization type 10 cm aperture TEA CO₂ laser. For a CO₂:N₂:He=1: 1: 7: mixture an output energy of 34 joule per liter and for a 1 : 1 : 10 mixture 40 joule per liter could be obtained. The overall efficiency is about 18%. The time behaviour of the current and voltage of the system shows a delay of several hundreds of nanoseconds after the preionization peak, which indicates a relatively low initial electron-density level. Neverthe less, it proved to be high enough to obtain a very homogeneous discharge and reproducible output energy.     

电泳式He-Sr+复合激光特性研究

设计制作了7mm内径和38cm有效激励长度的电泳式He-Sr⁺激光管,采用修饰Blumlein电路,通过纵向高重复率脉冲放电激励,实现了一价锶离子复合激光430.5nm和R-M跃迁激光1.03μm的同时振荡,其中复合激光占主要成分.测量分析了复合激光输出功率与工作参量(脉冲频率,充电电源电压和氦压)的关系曲线.获得了最大激光功率819mW和56mW/cm³功率密度的实验结果. 关键词： 锶离子激光 电泳 脉冲放电