Polymer-coated hollow fiber for CO(2) laser delivery

Hollow fibers for CO(2) laser light have been fabricated with a cyclic olefin polymer as the inner dielectric. A film of cyclic olefin polymer was coated inside the glass capillary tubing by a simple liquid-flowing process. A polymer-coated fiber with a 700-microm bore showed a loss of 0.06 dB/m for CO(2) laser light because cyclic olefin polymer has low absorption at a 10.6-microm wavelength.     

Increase of the atomic phase density in a hollow laser waveguide

A study is made of the channeling of atoms in a narrowing hollow waveguide carrying on its inner surface a surface wave with positive detuning for the absorption line of an atom. The inelastic reflection of atoms from the surface light wave and the convergent geometry of the waveguide make it possible to decrease the temperature and increase the phase density of an ensemble of atoms introduced continuously into the hollow convergent waveguide from a magnetooptic trap, by a factor of 10⁵. It is suggested that such a waveguide be used to study collective phenomena in quantum-mechanical systems with a high density (Bose-Einstein condensate) and as a high-luminosity coherent source of cold atoms. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 10, 763–767 (25 May 1996)     

Two-Frequency waveguide CO2 laser for atmospheric pollution monitoring

The present paper suggests and discusses a method allowing one to produce a two-frequency switching mode between any two adjacent transitions of a CO₂ laser. Switching is achieved by means of simple modulation of the resonator length by a piezoelement. The use of conventional electronic circuits ensures the maintainance of a high power balance (10^–2–10^–1%) vs. switching rate) at the generation frequencies. The data of the two-frequency CO₂ laser with a waveguide resonator used for various systems, based on a differential absorption technique and designed to control the atmospheric pollutions, are presented.     

Fiber laser annealing of nanocrystalline PZT thick film prepared by aerosol deposition

Nanocrystalline PZT thick films (1 mm square and over 10 μm thick) directly deposited onto stainless-steel substrates (PZT/SUS) by aerosol deposition (AD) technique and then annealed using focused laser beam with a fiber laser to suppress thermal damage to the back sides of the PZT/SUS and substrate near the film edge and to retain the dielectric and/or ferroelectric properties of the PZT/SUS. Compared with CO₂ laser annealing, fiber laser annealing suppressed thermal damage to the substrate. Compared with PZT/SUS annealed at 600 °C using an electric furnace, PZT/SUS annealed at 600 °C using a fiber laser showed superior properties, namely, dielectric constant ? > 1200 at a frequency of 100 Hz, remanent polarization P_r > 30 μC/cm², and coercive field strength E_c < 50 kV/cm at a frequency of 10 Hz. Furthermore, the grain growth for the PZT/SUS formed by AD technique and annealed by fiber laser irradiation was occurred within the laser spot size.     

介质镀膜空芯光纤在THz频段的传输特性

理论分析了介质镀膜空芯光纤在THz频段的传输特性,得出了该光纤的特征方程及模式分布。利用射线光学原理计算了介质膜材料为聚酰亚胺、介质膜厚度为0.05 mm的光纤的衰减常数随介质膜内直径的变化情况。得出其主模在THz频段的衰减常数小于1 dB/m,该值远小于相同内径的金属圆波导在这一频段的衰减常数。模拟计算了介质膜厚度为0.05 mm、内径为1 mm,金属膜内径为1.05 mm的介质镀膜空芯光纤在0~1 THz的S参数,模拟结果显示该光纤在THz频段有很宽的通带,且在通带内衰减常数小于0.5 dB/m,可用于THz频段电磁波远距离传输。     

Conditions for single-line and single-mode tuning of a CO2 waveguide laser

Single-mode tuning over 500 MHz in 90 lines, and 700 MHz in 70 lines is reported for a pyrex waveguide CO₂ laser in long-pulse operation. The peak power exceeds 100 W in the strongest lines, and the beam profile is diffraction limited. These features make the laser well suited as pump source for optically pumped molecular lasers.Work supported by the Danish National Science Research Council under Grant No. 11-3389     

Measurement of rotational temperature in CO2 waveguide laser medium

A small-signal gain in CO₂ waveguide laser medium has been measured on rotational-vibrational transitions in the P-branch of the (0, 0, 1)-(0, 2⁰, 0) band. It has been found that the rotational temperature is well defined in the waveguide laser system where high excitation power is injected and a large amount of energy is flowing through vibrational, rotational, and translational degrees of freedom. The rotational temperature is slightly higher than the translational temperature.     

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.     

The structure of dielectric β-SiC thin films of hollow glass waveguide for CO2 laser power delivery

A novel type of hollow glass waveguide with β-SiC dielectric films was manufactured by a modified chemical vapor deposition method. FTIR absorption spectra and SEM results show that the change of film structure is responsible for the phenomena of the blue shift and the narrow width of the fundamental absorption band of β-SiC, and that the microfissures at the films provide the heterocrystallization centers for promoting the formation of β-SiC crystal. The influences of the concentration of hydrogen gas passed through the system and the reaction temperature are discussed with regard to the film structure.     

Novel technology and performance of a high-power CO2 waveguide laser

Several new techniques have been developed to solve the problems encountered in the design and construction of rugged, reliable, high-power, CO₂ waveguide lasers. High-power single transverse mode output requires long single- or multiple-folded waveguide paths to be created in a dense ceramic body. The limitations of extruded or drilled bores have been overcome by fabricating the waveguide in two halves which are subsequently bonded together with a glaze or by thermodiffusion to form a vacuum-tight assembly. Several lasers have been constructed by these methods, one such device giving over 10 W CW output is described. These techniques can be readily extended to larger, higher-power devices. Reliable seals between semiconductor optics and metals using pure In soldering have also been developed for clean “hard seal” assembly. Dissociation of the CO₂ gas can lead to rapid decline in output power. The effects can be reduced by attaching a reservoir to the laser, or more preferably by the incorporation of a catalyst to reverse the reaction. These techniques have been applied to sealed-off CO₂ waveguide lasers which have demonstrated 5 yr shelf life and up to 5000 h operating life.     

Dynamics of a waveguide pulsed-periodic CO2 laser with loss modulation

The nonlinear dynamics of a waveguide CO₂ laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the cavity's longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency is explained by the attendant modulation of the refractive index of the loss modulator. To whom correspondence should be addressed. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 471–478, July–August, 1999.     

Self-focussing of CO2 laser radiation in SF6

Self-focussing of high-power TEA CO₂ laser pulses for a number of 10 m P-band lines is reported in SF₆ molecular gas. Application of this effect to estimating the intensity-dependent refractive index of the gas is demonstrated.     

Active mode locking of a high pressure CW waveguide CO2 laser

In this paper, we report on a new concept for active mode locking of lasers. It has been successfully applied to a cw waveguide CO₂ laser and pulse widths as short as 2 ns have been obtained.     

液体薄膜靶在激光驱动辐射源和激光离子加速中的应用

流动的无支撑液体薄膜在各个领域有着广泛应用。超强激光作用在这样的薄膜上,可产生涵盖太赫兹到伽马射线的高亮度次级辐射及高能的离子,并具有高重频、低成本、可连续工作等显著优势。概述了液体薄膜靶的制备和表征方法,阐明了液体薄膜靶相对于传统靶材的特性和优势,并对其在激光驱动辐射源和激光离子加速中的应用做出了总结和展望。     

Parameter study of RF excited diffusively cooled all-metal slab waveguide CO2 laser

In this paper, we have investigated some parameters of a radio frequency (RF) excited diffusively cooled all-metal slab waveguide CO2 laser based on the modified Rigrod theory by introducing a waveguide coupling efficiency which designates the coupling between the waveguide and the resonator mirrors. The parameters of the laser small signal gain go, saturation intensity Is, and waveguide coupling efficiency η are studied theoretically and experimentally. In the experiments, three sets of output coupling flat mirrors with the different transitivities were used, and a maximum laser power output of 150 W was obtained from a gas discharge region of 2-mm height, 20-mm width, and 386-mm length coupled with a CASE-I optical waveguide resonator.