Strong amplified spontaneous emission and lasing from a narrow-gap RF-excited Ar-He-Xe gas mixture

The performance of a RF excited cw atomic xenon laser at wavelengths of 2.03 μm and 2.65 μm was studied theoretically and experimentally as a function of electrode distance. Results for inter-electrode distances from 2 to 0.25 mm are presented. A high pumping rate resulted in strong 40 mW cw amplified spontaneous emission at 2.65 μm wavelength from the configuration with the smallest distance of 0.25 mm between the electrodes. The maximum laser output of 2.7 W (0.24 W/cm³) was obtained with an active medium volume of 2×15×370 mm³ whereas the maximum specific output of 1.9 W/cm³ was received for an active medium volume of 0.25×2.25×370 mm³. A fluid model of the RF discharge was developed to analyze the laser behavior for different distances between the electrodes. Received: 30 November 1999 / Revised version: 21 April 2000 / Published online: 6 September 2000     

Prospects for improving energy parameters of radiation of a Cu laser excited by a transverse discharge

The production of copper vapors by an electric explosion and their excitation by a transverse discharge are considered. The results of the study are used for determining the optimal explosion regime for a copper conductor. Maximum specific parameters of a Cu laser are obtained. In an active volume of 0.5 cm³, a radiation energy of 0.92 mJ corresponding to an efficiencyη=0.25 % is obtained. For an active volume of 0.25 cm³, the specific radiation energy corresponded to 2.4 mJ/cm³. The specific power was equal to 120 kW/cm³ forη=0.16 %. An analysis of studies devoted to the given excitation method is performed that shows the possibility of further improvement of the efficiency of the laser under study.     

A copper iodide laser excited by transverse discharge

Operation of a copper iodide laser in a transverse-discharge configuration is reported. Oscillation occurs on both the 5106 and 5782 Å transitions of neutral copper over a wide range of discharge parameters, including buffer gas pressures up to one full atmosphere. Laser pulse energies of 5 μJ per cm³ of active volume (total active volume ≈ 100 cm³) have been obtained and preliminary investigations suggest that this type of device can be scaled to larger active volumes and greater output energies.     

Industrial sealed-off copper vapor lasers with improved efficiency and radiation power

Results of experiments aimed at improving the efficiency and radiation power of industrial repetitively pulsed copper vapor lasers are presented. Design and technological improvements are described which increase the efficiency of a laser oscillator up to 1–1.2% relative to the input power drawn from a rectifier and up to 1.4–1.6% relative to the power fed into an active element. The possibility of improving efficiency up to 1.8 and 2.9% respectively is demonstrated. For a laser amplifier, the efficiency is 1.2–1.3 times higher than for an oscillator. For a laser oscillator and a laser amplifier, the power drawn from the active element is 37 and 44 W respectively for a working volume of 250 cm³, 44 and 60 W for a volume of 350 cm³, and 55 and 70 W for a volume of 900 cm³.     

A gold-vapor laser using Ne-H2 as buffer gas

A small amount of hydrogen was added to neon buffer gas in a discharge-heated gold vapor laser. It was found that the output power and efficiency of the gold-vapor laser dramatically increased. The average output power and efficiency increased as much as 60%, when 0.5–1.0 Torr of hydrogen was added to neon. Maximum average power of 8 W was obtained using a plasma tube with 30 mm^00D8×100 cm active volume.     

Miniaturization of a thalliumiodide photodissociation laser

We report on the operation of a thallium photodissociation laser with an active medium in the form of a thin layer on a quartz wall. Laser emission has been obtained with layer thicknesses below 100 m. This gas laser seems to be feasible with an active volume as small as 10^–1 to 10^–2 mm³.     

High repetition-rate and quasi-cw operation of a waveguide CO2 TE laser

We report operation of a waveguide CO₂ TE laser at excitation pulse repetition frequencies as high as 40 kHz. Quasi-continuous laser output was obtained yielding an average output power of 1.5 W from an active volume of 0.1 cc. Details of laser construction and excitation circuitry are given.     

Some design limitations for large-aperture high-energy per pulse excimer lasers

Summary Some limitation problems for gas discharge excimer lasers, when scaled to a high pulsed energy output with high repetition rate are discussed. As an example, we present some experimental results obtained with an X-ray preionized (10×10×100) cm³ active volume, low-repetition-rate-operated gas discharge XeCl laser system. ENEA student. ENEA guest.     

Modelling of Tm3+-doped LiNbO3 Waveguide Lasers

In this work, CW laser operation of Tm³⁺-doped LiNbO₃ channel waveguides has been modelled. The model is based on time dependent laser rate equations coupled with the laser signal and pump photon flux equations. Steady state solutions for the population densities, pump and signal powers are obtained by using finite difference discretization of the active volume. The effects of spectroscopic parameters such as concentration dependent cross-relaxation and excess waveguide loss have been analyzed. We demonstrate good agreement with experimental data previously reported in Zn-diffused LiNbO₃:Tm³⁺ channel waveguide lasers. It is shown also that laser performance can be substantially improved by optimizing the cavity length.     

Miniature high-repetition-rate TEA CO2 laser with surface-wire-corona preionization

In this article, an experimental study of a miniature, sealed-off, high-repetition-rate transversely excited atmospheric-pressure (TEA) CO₂ laser with a kind of surface-wire-corona preionization (SWCP) is described. We have utilized an SWCP consisting of SiO₂ dielectric tube and a fine wire strained and attached to the dielectric surface. A BN ceramic material, which has an extremely low coefficient of thermal expansion of about 5 × 10⁻⁷/°C was employed as a supporter of the resonator. A measurement on emission spectra of SWCP has been reported. By applying SWCP to the TEA CO₂ laser, efficient laser operation at an overall efficiency of 9.8% with an output energy of 150 mJ has been achieved from a small discharge volume of 25 cm³ with an active length of 230 mm. At the pulse repetition frequency of 60 Hz, the TEM₀₀ mode of laser beam with pulse width of 60 ns was obtained.     

Rapidly tuning miniature TEA CO2 laser – rotating mirror and grating mechanism

In this research, directed toward using differential absorption lidar (DIAL) for measuring concentrations of pollutant gases, a device for rapidly tuning a transversely excited atmospheric-pressure (TEA) CO₂ laser is presented. It is shown that it is possible to utilize a rotating six-sided scanning mirror and a fixed diffraction grating to rapidly switch wavelength over randomly selected lasing transitions in the 9–11 μm region of the spectrum. The scanning mirror and an optical encoder are driven by a hysteresis synchronous motor at a speed of 1500 rpm. A surface-wire-corona preionization was utilized in a cavity. The laser system is highly automated with microprocessor-controlled laser line selection. Single-branch emission at two wavelengths with time interval ⩽10 ms has been obtained from a single cavity TEA CO₂ laser. An accurate line selection has been demonstrated in over 40 transitions at a pulse repetition frequency of up to 100 Hz. The laser energy at first-order couple output was up to 20 mJ per pulse and the pulse width is about 60 ns in an active volume of 36 cm³.     

Quasi-simultaneous ultraviolet and infrared emission from a plasma cathode TEA laser

Quasi-simultaneous laser action in the UV (0.337 μm) and the IR (10.6 μm) was observed from a pulsed laser with a sliding discharge plasma cathode. The laser operates at atmospheric pressure, with a gas mixture of CO₂/N₂/He, at a 0.26/0.50/4.0 lmin⁻¹ flow rate. Output energies of 30 mJ in the IR and 0.35 mJ in the UV were obtained, from a laser discharge volume of 38.0×1.0×2.8 cm³. The optimum gas mixtures have been determined and the temporal behavior of the discharge parameters, the performance characteristics of the laser and the beam spatial distributions were investigated.     

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     

Design and performance characteristics of a krypton chloride (λ = 222 nm) excimer laser

Development of a discharge-pumped krypton chloride (KrCl) laser operating at 222 nm wavelength is demonstrated. In this paper the design, successful realization and operating characteristics of KrCl excimer laser are reported. The laser is driven by a simple and efficient excitation technique using automatic UV pre-ionization with discharge-pumped self-sustained capacitor–capacitor (C–C) energy transfer circuit. The experimental investigations including output laser energy, temporal pulse parameters, emission spectra and beam profile of the KrCl laser were recorded. For high repetition rate operation, in-built, compact gas circulation system using tangential blower was incorporated. The laser was operated at 25 kV discharge voltage, gas mixture of 5 mbar HCl, 160 mbar kypton and neon as balance with a total gas pressure of ～2.5 bar. These experiments produced an efficient and reliable output energy of 25 mJ from an active volume of 60 cm³.     

Scalable concept for diode-pumped high-power solid-state lasers

A new, scalable concept for diode-pumped high-power solid-state lasers is presented. The basic idea of our approach is a very thin laser crystal disc with one face mounted on a heat sink. This allows very high pump power densities without high temperature rises within the crystal. Together with a flat-top pump-beam profile this geometry leads to an almost homogeneous and one-dimensional heat flux perpendicular to the surface. This design dramatically reduces thermal distortions compared to conventional cooling schemes and is particularly suited for quasi-three-level systems which need high pump power densities. Starting from the results obtained with a Ti:Sapphire-pumped Yb:YAG laser at various temperatures, the design was proved by operating a diode-pumped Yb:YAG laser with an output power of 4.4 W and a maximum slope efficiency of 68%. From these first results we predict an exctracted cw power of 100 W at 300 K (140 W at 200 K) with high beam quality from a single longitudinally pumped Yb: YAG crystal with an active volume of 2 mm³. Compact diode-pumped solid-state lasers in the kilowatt range seem to be possible by increasing the pump-beam diameter and/or by using several crystal discs.     

Output characteristics of a cataphoresis He–Sr recombination laser

A cataphoresis discharge tube of 7 mm inner diameter and 38 cm active length was designed and made for the He–Sr⁺ laser. The cataphoretic input of uniform distribution of strontium vapor concentrations along the active region was realized by the cataphoresis effect and the slow flowing (0.5 nl/h) of helium buffer gas. The strontium ionic recombination laser at 430.5 nm and the R–M transition laser at 1.03 μm were obtained with the modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The laser components are concentrated on the 430.5 nm wavelength. Dependences of working parameters such as the pulse frequency, the supply voltage, and the helium pressure on laser output characteristics were measured and discussed. The maximum laser output power of 819 mW and specific power of 56 mW/cm³ were obtained, respectively.     

Influence of the photoionization process on the fragmentation of laser desorbed polycyclic aromatic hydrocarbons

Characterization of polycyclic aromatic hydrocarbons (PAHs) samples has been performed by laser desorption combined with multi-photon ionization technique using two different geometries of the ionization laser beam. This comparative study evidences the strong influence of ionization laser fluence on PAH fragmentation. Through a ∼10³ enlargement of the ionization probe volume and 10⁴ reduction of laser fluence over previous studies, fragment free mass spectra are obtained with higher sensitivity and selectivity. The ability to measure fragment free PAH mass spectra is a very important step in the end goal of measuring complex unknown mixtures of PAH desorbed from solid surface such as soot samples.     

X-ray preionized CO2 laser

A short pulse (100 ns) high-energy x-ray source has been used to preionize a transversely excited carbon dioxide gas discharge laser of 600 cm³ active volume. The maximum output power of 60 MW in a 50 ns FWHM pulse was achieved from a CO₂–N₂–He–CO–Xe static gas mixture at 600 Torr pressure. The energy conversion efficiency was 6%.     

Photolytical XeF(C–A) laser amplifier of femtosecond optical pulses: gain measurements and pump efficiency

Gain characteristics of a photolytically driven XeF(C–A) laser amplifier are studied experimentally in the unsaturated amplification regime. The gaseous active medium is optically pumped by vacuum-ultraviolet (VUV) radiation from two large-area multichannel surface discharges initiated along opposite walls of the amplifier chamber. A total gain factor of 10² is obtained for the ultrashort optical pulses under multipass amplification in the active volume of 40?×?18?×?4 cm³ dimensions with a spatially homogeneous gain distribution. Spectral measurements reveal a good conservation of the seed pulse spectrum. Small-signal gain reaching 2×10^-3 cm^-1 is observed for the blue-green seed pulses of 150 fs duration, as well as for the continuous seed radiation at 488 nm. The obtained gain values, being compared with the gain calculated for the measured pumping radiation power, indicate that the quantum yield of the XeF(B) formation as a result of the XeF₂ photodissociation is high and approaches unity within the spectral band of the XeF₂ VUV photodissociation continuum.     

Photochemical xenon-oxide laser

Theoretical and experimental investigations are described, aimed at the develo pment, construction, and study of the features of a photochemical xenon-oxide laser whose action is based on the photodecomposition of nitrous oxide by vacuum ultraviolet radiation of an open hlgh-current discharge with formation of oxygen atoms followed by oxidation of the xenon. The theoretical problems connected with the determination of the mechanism and the calculation of the kinetics of the physicochemical processes in an XeO laser are considered. A numerical computation of the pumping is carried out, and the inversion and gain on the laser transition are calculated. The construction of the laser is described, as well as an experimental procedure for obtaining the optimal temperatures, composition, and pressure of the working-mixture components. The spectral composition of the laser radiation and the energy characteristics of the laser are investigated. The heat released in the course of the photolysis, the constants of the quenching rates of the upper laser state of XeO (2¹Σ⁺), and the vibrational relaxation of the lower state of XeO (1¹Σ⁺) are estimated. The internal losses in the active medium of the photochemical XeO laser are theoretically investigated. The possibility of increasing the volume of the active medium using a plane-parallel cavity is estimated.