Interaction of IR laser radiation with liquids

The different laser radiation interaction mechanisms are briefly discussed together with the theoretical models which explain the thermoelastic regime. A general survey of experimental measurements includes optical techniques and acoustic methods.     

Interaction of intense laser radiation with weak electromagnetic waves in an evacuated section of a ring laser

A laboratory experiment for the study of nonlinear interaction of electromagnetic waves in vacuum is proposed. The basic idea of the experiment is as follows. If one separates a certain region of the circuit in a ring laser from the remaining part with gas-impenetrable partitions, evacuates it, and forms external electromagnetic fields there, the oscillation frequencies and the polarization states of the electromagnetic waves traveling in this ring laser in counter directions are different. A calculation is made for the oscillation frequencies of electromagnetic waves traveling in a ring laser in opposite directions in the case when they interact in an evacuated section of the ring laser circuit with intense laser radiation. It is shown that the effect can be observed in experiments using presently available pulsed lasers of ultrahigh power.     

Interaction of intense CO2 laser radiation with a dense laser produced carbon plasma

A high density laser produced carbon plasma is heated with the beam from a pulsed CO₂ laser. The evolution of the electron density profiles is studied by interferometry.     

Interaction of intense ultrashort laser pulse with shell target

Based on numerical PIC modeling and an analytical model, we analyze the interaction of a short high-intensity laser pulse with homo- and heterogeneous (two-layer) shell targets. We show that the shell target is capable of focusing ions in a narrow region. In this case, the ion energy exceeds the ion energy for a flat infinite target of the same thickness. We propose to use the effect of focusing and cumulation of ions to implement the collision of ionic beams that counterpropagate from opposite sides of the sphere and to increase the yield of ion-ion reactions. The constructed model makes it possible to calculate the energy of the ion and the number of ions in the region of focusing.     

Interaction of intense laser pulses with hydrogen atomic clusters

The interaction between intense femtosecond laser pulses and hydrogen atomic clusters is studied by a simplified Coulomb explosion model. The dependences of average proton kinetic energy on cluster size, pulse duration, laser intensity and wavelength are studied respectively. The calculated results indicate that the irradiation of a femtosecond laser of longer wavelength on hydrogen atomic clusters may be a simple, economical way to produce highly kinetic hydrogen ions. The phenomenon suggests that the irradiation of femtosecond laser of longer wavelength on deuterium atomic clusters may be easier than that of shorter wavelength to drive nuclear fusion reactions. The product of the laser intensity and the squared laser wavelength needed to make proton energy saturated as a function of the squared cluster radius is also investigated. The proton energy distribution calculated is also shown and compared with the experimental data. Our results are in agreement with the experimental results fairly well.     

类金刚石a-C:H膜的热释氢和红外吸收研究

本文利用热释氢和红外吸收研究了H在非晶态碳(a-C:H)膜中的含量和组态。实验结果表明,随着样品制备时衬底温度的增大:1)H在a-C:H膜中的组态从两相结构过渡为单相结构;2)H在a-C:H膜中的含量单调减少;3)a-C:H膜中sP³/sP²键合比例单调增大。 关键词：     

A new calorimeter for intense laser radiation

A new type of laser calorimeter has been developed which provides high measurement sensitivity and accuracy over several decades of input radiation intensity. The approach features a rapidly spinning liquid film as the calorimetric medium, and as such can accommodate a wide spectrum of incident laser radiation, through appropriate selection of the absorbing fluid. Because of the rapidly moving thin fluid technique utilized in the construction, the calorimeter exhibits fast response, even at high or low power levels. The design concept and method of fabrication make the device quite rugged and virtually burn-out proof.     

Lysine IR emission spectrum excited by moderately intense visible radiation

The excitation of IR emission is observed for thin films illuminated by continuous visible light in the absence of light absorption in the sample. The effect is demonstrated by the example of the lysine molecule and explained by the resonant combined action of optical photons with frequencies ω_i and ω_j, whose differences ω_i?ω_j=Ω coincide with the frequencies of the lysine vibrational modes.     

High-aspect-ratio microdrilling in polymeric materials with intense KrF laser radiation

UV laser microdrilling of high-aspect-ratio holes has been studied by using an intense beam with a low numerical aperture (KrF laser). The UV laser ablation produces a minimum of thermal or mechanical damage on the target. Under some particular experimental conditions (many high-fluence pulses), it is shown that long deep holes are obtained with reproducible aspect ratio (up to K/d길) in a variety of materials. Experiments with polymers (PMMA, PC, PET, PI, PS, PEEK) show that the more absorbing the polymer is, the better the resolution. However highly absorbing materials exhibit a low ablation rate. These promising results on laser microdrilling can be extended to new applications, for example, when the beam/target relative movement is computer driven. For instance this approach can be applied to cutting micro-objects with complicated shape or to machining fragile or brittle materials.     

强激光毁伤过程的热辐射谱测量

以热辐射谱的温度反演为例,介绍了光谱技术在强激光毁伤过程中的应用。利用自制的高速光谱测量系统,实时采集了毁伤过程中的辐射光谱,基于普朗克黑体辐射原理,反演了毁伤区的温度,并应用主成分回归算法,计算得到了毁伤区的温度分布,实现了强激光辐照靶材过程中瞬态温度和温度分布的测量。光谱测量区在200～1 000 nm时,所对应的温度反演为700～6 000℃。     

Theory of the interaction of intense laser radiation with magnetoactive plasma

Analytical expressions for the density of magnetoactive plasma perturbed by circularly polarized relativistically strong laser radiation are obtained.     

Ion-beam analysis of the structure and composition of nanocomposite nc-TiC/a-C:H coatings

The structure and composition of nanocomposite nc-TiC/a-C:H thin films prepared by closed-field unbalanced reactive magnetron sputtering in an argon-acetylene atmosphere have been investigated. The concentrations of carbon and heavier elements have been obtained by Rutherford backscattering and nuclear backscattering. The hydrogen concentration in the films has been determined by elastic recoil detection analysis. Based on the data obtained, a scheme has been proposed to evaluate the C:H matrix mass density and the sp ³ and sp ² fractions in the matrix.     

Interaction of CO2 laser radiation with glasses

An illustration of an interaction of pulsed multimode TEA CO₂ laser radiation, through or without a mask, as well as of a laser scanning process of a frequency Q-modulated cw CO₂ laser beam on glass surfaces has been shown. As an object of investigation glass articles with composition as a standard industrial potassium-boron silicate glass, we have used. A complex of investigations shows that the laser treatment leads to qualitative constant changes (well defined peeling structure) depending on the time surface treatment, defocusing and the pulse length of the laser output.     

Interaction of an intense laser field with a dielectric containing metallic nanoparticles

In order to understand the role played by nanodefects in optical breakdown of dielectrics, the interaction of an intense laser field with model dielectric samples containing metallic nanoparticles is studied both theoretically and experimentally. A theoretical study of the metal conduction electrons dynamics in the laser field predicts an efficient injection of carriers from the metallic inclusion to the conduction band of the dielectric, which leads to a strong local increase of the optical absorption in the initially transparent matrix. This prediction is tested experimentally by using time-resolved spectral interferometry to measure excitation densities as a function of the laser intensity in silica samples doped with gold nanoparticles, which are compared with similar measurements in pure silica. PACS 61.80.Ba; 42.70.-a; 78.47.+p     

Interaction of intense laser pulses with atomic clusters at different gas densities

The interaction of intense femtosecond laser pulses with rare gas clusters was studied experimentally,the time-of-flight spectra of ions from exploding clusters at different gas densities have been measured. It is found that while the relative components of ions inlow and high energy of the ion energy spectrum decrease with the increase of the gas density,the average ion energies are the same for different gas densities,which indicates that the effect of gas density on laser-cluster interaction is not important under our experimental conditions.     

Ionization of atoms and ions by intense laser radiation

The ionization of negative ions by ultrashort electromagnetic pulses, the multiphoton ionization of atoms beyond the perturbation theory taking into account the Coulomb interaction, and the relativistic theory of tunneling in application to the ionization problems have been analyzed. The main results have been obtained using the imaginary time method.     

Interaction of laser radiation with a low-density structured absorber

A theoretical model is proposed for computing simulations of laser radiation interaction with inhomogeneous foam materials doped with heavy elements and undoped materials. The model satisfactorily describes many experiments on the interaction of the first and third harmonics of a 200 J pulsed PALS iodine laser with low-density porous cellulose triacetate targets. The model can be used to analyze experimental data and estimate the reality of experimental results.