Advancement and problems of fullerene-oxygen-iodine laser

The methods of improving the efficiency of a fullerene-oxygen-iodine laser are investigated. In the course of this research, we developed new fullerene coatings that possess better mechanical and radiative hardness, as well as higher efficiency of singlet oxygen generation. We show that, by using these coatings, the energy yield per unit volume of the active medium can be increased to 9 J/l, which is almost two times higher than the previous result. The energy efficiency of the laser can also be increased by a factor of nearly two. At the same time, several problems were revealed that hinder the further improvement of the laser efficiency and its long-term operation with stable parameters of the output radiation. We outline principal approaches to further optimization of the laser design that would help to overcome the negative factors and make it possible to create a fullerene-oxygen-iodine laser with high and stable parameters of the output radiation.     

Modelling of a solar-pumped MHD excimer laser

An analytical model is applied to the concept of a solar-pumped MHD laser utilizing the CsXe excimer and Cs₂ dimerA-X laser transitions. The model predicts practical gain coefficients on the excimer band for supersonic flow of a 2000 K, 20 atmosphere cesium-xenon plasma across a ∼10 kG magnetic field.     

用于太阳光泵浦激光的抛物面环形阵列聚光器

为研制适用于太阳光直接泵浦激光器的聚能系统,在分析菲涅尔透镜聚光原理及缺陷的基础上,提出抛物面环形阵列聚光器的设计方法。完成了由抛物面环形阵列聚光器、菲涅尔透镜及复合抛物面聚光器（CPC）组成的太阳光泵浦激光器二级聚能方案,并与传统菲涅尔透镜方案进行了对比。光线追迹仿真分析表明:新型聚光器能够克服传统菲涅尔透镜的色散、小棱镜面像差及光线遮挡的缺陷,从而提高聚能效,使用抛物面环形阵列聚光器的多级聚能方案较传统菲涅尔透镜的多级聚能方案聚光比提高约18.5%,更适合于大相对孔径、高聚光比聚光场合的应用。     

Improvement in solar-pumped Nd:YAG laser beam brightness

Solar-pumped solid-state lasers are promising for renewable extreme-temperature material processing. Here we report a large improvement in solar laser beam brightness by pumping a thin Nd:YAG single crystal rod. A fused silica light guide of 14 mm×22 mm rectangular cross-section is used to both transmit and homogenize the concentrated solar radiation from the focal zone of a 2.88 m² parabolic mirror to the entrance aperture of a modified 2D-CPC flooded pump cavity, within which a 4 mm diameter rod is efficiently pumped. 2.2% slope efficiency is reached. Laser beam brightness figure of merit B is three times higher than that of the most recent solar-pumped Nd:YAG laser by a Fresnel lens. The introduction of the rectangular cross-section light guide has also ensured a much more stable laser emission than previous pumping schemes.     

用于太阳光泵浦激光器的菲涅耳透镜设计方法

建立并分析了太阳光点聚焦型菲涅耳透镜的理论模型。提出了适用于太阳光泵浦激光器的设计方法。综合考虑会聚总功率和功率密度提高倍数两个因素,合理设计了菲涅耳透镜口径,相对孔径以及环形小棱镜的宽度(环距)三个参数,获得了用于太阳光泵浦激光器的菲涅耳透镜。     

Lasing of iodine in the fullerene-oxygen-iodine system

The possibility of lasing in the fullerene-oxygen-iodine system with optical excitation of fullerene is studied. Laser radiation with an energy of 25 mJ and a pulse duration of 5–10 ms is obtained.     

Feasibility analysis of radiation balanced laser

An end-pumped slab laser model is analyzed to evaluate the feasibility of radiation balanced laser (RBL) when the laser crystal is chosen to be Yb:KGW. The ratio between fluorescence and stimulated photon number is first introduced to help estimate the output power of RBL. Through the analysis it turned out to be difficult to build high power RBL, but the idea of radiation balance can be used to reduce the waste heat for all laser design.     

Feasibility study of laser cooling of InF molecule

By employing ab initio quantum chemistry method, we investigate the feasibility of laser cooling InF molecule. Four low-lying electronic states (X¹Σ⁺, C¹Π, ³Π and 2³Π) of InF have been calculated using the multi-reference configuration interaction (MRCI) method. The spin-orbit coupling effects are also taken into account in the electronic structure computation at the MRCI level. The highly diagonal Franck-Condon factors for C¹Π → X¹Σ⁺ transitions are estimated. The radiative lifetime of the C¹Π (v′ = 0) state is about 2.22 ns, which is found to be enough short for rapid laser cooling. Though the cooling wavelength of InF is located in the short-wavelength ultraviolet light (UVC), a frequency quadrupled Ti: sapphire laser (189–235 nm) could be capable of generating laser transition wavelength of InF. Furthermore, the C¹Π → X¹Σ⁺ transitions perhaps can be followed by the B³Π₁ → X¹Σ⁺_0⁺ transitions to attain a lower Doppler temperature. Meanwhile, for achieving quasi-closed transition cycle of InF molecule, we investigate the hyperfine structure of the lowest state X¹Σ⁺. Overall, the present results indicate the possibility of laser cooling InF molecules.     

Feasibility of a laboratory X-ray laser pumped by ultrashort UV laser pulses

In order to allow widespread application of soft X-ray lasers there is a strong effort worldwide to use as small as possible pump lasers for plasma production. Short pulse lasers ( 1 ps), particularly in the UV, have attracted much interest, since extremely high intensities (up to 10¹⁸ W/cm²) can be achieved with a relatively high repetition rate. In this article we discuss their merit for soft X-ray laser pumping and possible solutions to the specific problems, for instance pulse front distortion, nonlinear absorption in window materials, plasma formation by short laser pulses and the relatively low total pump energy.     

Multimode-diode-pumped gas (alkali-vapor) laser

We report what we believe to be the first demonstration of a multimode-diode-pumped gas laser: Rb vapor operating on the 795 nm D1 resonance transition. Peak output of approximately 1 W was obtained using a volume-Bragg-grating stabilized pump diode array. The laser's output radiance exceeded the pump radiance by a factor greater than 2000. Power scaling (by pumping with larger diode arrays) is therefore possible.     

Filament-induced laser machining (FILM)

Laser filamentation provides high intensity plasma strings of micrometric diameters and lengths of tens of centimeters. We demonstrate that these filaments can be used for remotely drilling and cutting metals and biological materials such as flesh and bones. Since no tight focusing is needed, complex 3D shapes can be machined without any adjustment of the laser while processing.     

Chaotic (as the logistic map) laser cavity

A laser whose output is a train of short pulses of intensities given by the logistic map is described. The device can be achieved with Nd:YAG and dye laser amplifiers, and the experimental problems involved in attempting its realization are discussed. At a special alignment condition, the sequence of pulse intensities is given by a map of a new kind, of undefined universality class.     

X-ray laser research at the LULI (Palaiseau)

The X-ray laser program at Palaiseau is based on the recombination scheme in lithiumlike ions, which requires a moderate pump power and seems to be promising for the purpose of scaling to shorter wavelengths. In aluminum plasmas, peak gain values of 2-2.5 cm^-1 have been obtained at a wavelength of 105.7 Å corresponding to the 3d -5f transition, 6 ns after the top of a 2 ns laser pulse. The same transition in sulfur is emitted at 65.2 Å and has shown a gain of 1 cm^-1 in a preliminary time-integrated experiment. Simulations using a collisional-radiative model as the postprocessor of a hydrodynamic numerical code predict amplifications for the 3d-4f, 3d-5f, and 4d-5f transitions. A new experiment, in progress at the present time, has been designed to enhance the gain-length product up to 10-15 at 105.7 Å. The recently extended facilities of the LULI make it possible to produce a 6-cm-long plasma column, keeping the flux density at the same level as in the previous experiments     

实用型放电泵浦XeF(B-X)准分子激光器

 研制了一台实用型放电泵浦的351 nm XeF(B-X)准分子激光器,激光器采用新型开关电源、结构紧凑型张氏电极及放电火花预电离的激光腔结构,通过优化储能电容和放电电容量及比值,选取合理的工作气体压力和配比,优化了激光器性能,提高了激光器输出参数:单脉冲能量153 mJ,平均功率12.9 W,转换效率最高达到0.88%,重复频率1~80 Hz,能量不稳定度小于4%,近场光斑尺寸7 mm×22 mm。激光器已应用到常规抗蚀剂曝光的印刷电路板(PCB)激光投影成像照明系统的实验中。     

实用型放电泵浦XeF(B-X)准分子激光器

研制了一台实用型放电泵浦的351 nm XeF(B-X)准分子激光器,激光器采用新型开关电源、结构紧凑型张氏电极及放电火花预电离的激光腔结构,通过优化储能电容和放电电容量及比值,选取合理的工作气体压力和配比,优化了激光器性能,提高了激光器输出参数:单脉冲能量153 mJ,平均功率12.9 W,转换效率最高达到0.88%,重复频率1~80 Hz,能量不稳定度小于4%,近场光斑尺寸7 mm×22 mm。激光器已应用到常规抗蚀剂曝光的印刷电路板(PCB)激光投影成像照明系统的实验中。     

XeF(C-A)蓝绿激光线宽压缩技术

利用表面放电光泵浦XeF(C-A)蓝绿激光器开展了激光线宽压缩技术研究,分别采用谐振腔腔镜谱带重叠法和光栅谐振腔法实现了线宽小于10 nm的窄线宽激光输出。采用谐振腔腔镜谱带重叠法,激光输出线宽约7 nm,采用光栅谐振腔法可以将激光线宽压缩到约1 nm,并实现XeF(C-A)激光的可调谐输出,调谐范围为470～495 nm。     

A recombination laser from cooled hydrogen plasma (plasma dynamic laser)

Using our time-dependent model we calculate the inversion density and gain for a visible line (6563 Å) from hydrogen as a result of rapid cooling of a plasma. A visible plasma dynamic laser is shown to be possible under certain conditions.     

On the structure of the laser irradiated Si(111)-(1 × 1) surface

We have studied the geometric structure of the Si(111)-(1 × 1) surface, prepared from a Si(111)-(7 × 7) surface with a pulsed ruby laser. With the technique of medium energy ion scattering, in combination with channeling and blocking, we find that this surface has a structure very similar to the (7 × 7) surface. Our results are inconsistent with a simple relaxation model.