A hollow cathode bismuth ion laser

cw laser oscillations of Bi II at 680.9, 660.0, and 571.9 nm have been achieved for the first time by using a bismuth hollow cathode discharge. In addition, laser oscillations of Bi I at 1.1711 m in the afterglow were observed. The ionic laser lines are excited by Penning ionization. The atomic line is produced by recombination of the bismuth ions and lowenergy electrons in the afterglow.     

Pulsed 469.4 nm hollow cathode He-Kr laser

Design principles, construction and operation characteristics of a pulsed 469.4 nm He-Kr laser are described. The laser was operated in a 20 cm active length transverse hollow cathode discharge and was excited by 50 Hz repetition rate 0.1–1 ms duration square wave current pulses. Cataphoresis of Kr ions was found to play an important role in forming the laser pulse shape. By increasing the voltage a considerable increase of peak laser power occurred, the maximum power obtained was 80 mW. The sealed-off laser was operated using 400 s, 4 A current pulses, pulsed laser power being 20 mW, average power 0.4 mW, respectively. The lifetime of the laser was 440 h, tube failure being due to gas cleanup caused by cathode sputtering.     

Numerical modeling of a He-Kr coil hollow cathode laser

A theoretical study of a He-Kr laser (KrII, 469.4 nm line) pumped by a helical hollow cathode discharge is presented. A detailed kinetic model of plasmachemical reactions and radiative processes including the influence of gas heating on the active medium is developed. In the process of numerical calculations the dependence of the plasma parameters (electron and gas temperature, electron and metastable density, upper and lower laser level density) and laser characteristics (output power and gain coefficient) on the variations of discharge pumping, gas-mixture partial pressures and geometry of the coil hollow cathode, are investigated. The results of the numerical calculations are in a good agreement with the experimental data.     

Numerical modeling of a He-Zn laser with helical hollow cathode

A kinetic model is proposed for a He-Zn laser with a helical hollow cathode oscillating on the Zn II 758.8 nm line: The dependence of the laser output power and gain on the active medium parameters, excitation pulse shape and cavity is investigated theoretically. The results from the numerical calculations are in a good agreement with the experimental data.     

On the excitation mechanism of the He-Ar hollow cathode laser

Investigations were carried out on the Ar-II 476.5 nm laser to obtain information on possible excitation mechanisms. The He-Ar hollow cathode discharge was excited by square wave current pulses. From the results of measurements it could be concluded that collisions of the second kind between He 2³ S metastable atoms and ground state Ar ions are dominant in the excitation of the upper laser level. This is also supported by results obtained in the case of the He-Kr hollow cathode laser, where the upper level of the Kr-II 469.4 nm laser is excited by a similar collision process.     

The effect of substituting metal vapour with metal halide vapour in a hollow cathode laser discharge

He−Zn and He−ZnCl₂ hollow cathode discharges were compared. The metal vapour concentration necessary for laser operation can be achieved at a lower temperature for the molecular substance. On the other hand, the efficiency decreases because part of the He ions necessary for the selective excitation of the upper laser level of the metal ion are lost in the dissociation process. This work was carried out under a contract with the Central Research Institute for Physics of the Hungarian Academy of Sciences.     

A hollow cathode tin laser

We have observed laser emission from five SnII transitions (579.9, 645.4, 719.1, 1061, 1074 nm) and four infra-red SnI transitions (1193, 1302, 1346, 1361 nm) in a tin hollow cathode in which the tin vapor was entirely created by discharge sputtering. Laser action occurs in the afterglow stage of the discharge with the exception of the 645.4 nm SnII line which operates in CW mode. The inversion in the afterglow is believed to be created by a recombination and population redistribution mechanism induced by collisions of the tin ions with low energy electrons.     

Laser action in a gallium hollow cathode discharge

cw laser action was observed for the 6335 and 7199 Å transitions of Ga II in a hollow cathode discharge. Charge exchange and radiative cascade processes are suggested to be responsible for the population of the upper laser levels.     

A high average power rotating hollow cylinder Nd : glass laser

The rotating hollow cylinder glass laser is one of the approaches for the generation of high average output powers scaling to kilowatt levels from solid-state laser materials. An analytical solution of the heat conduction equation is presented for a thin wall, infinitely long glass medium, with boundary conditions given by Newton's law of cooling. The theoretical result is applied to predict thermal effects of this geometry which ultimately limit the laser performance, and the design of such a laser. A flashlamp pumped rotating Nd-doped phosphate glass hollow cylinder laser has been demonstrated. An average power output of 300 W has been achieved at 3.8% slope efficiency and 2.6% overall efficiency. Our investigation shows that the development of a kilowatt average power rotating cylinder laser is feasible.     

Laser action in an indium hollow cathode discharge

Hollow cathode discharge excitation of indium is shown to produce laser action at 468.1, 689.2, 1342.8, and 1720nm. The cw468.1 nm and 1720 nm ionic lines are excited by charge exchange effect whereas the 689.2 nm cw ionic line is excited by a radiative cascade. The 1342.8 nm atomic line appears in the afterglow of the pulsed discharge and its population inversion is produced by recombination of the indium ions and the electrons. Shanghai Institute of Optics and Fine-Mechanics, Academia Sinica. Research Fellow 1979–1980 of the Alexander-von-Humboldt-Stiftung     

The spatial distribution of small signal gain in a segmented hollow cathode discharge laser

Received: 5 February 1997/Revised version: 30 April 1997     

CW HCN laser gain in a hollow dielectric rectangular cross-section discharge tube

This paper describes a 1 m-long CW HCN discharge laser with a hollow dielectric rectangular discharge tube of 5×20 cm² cross-section. For optimum working conditions, the characteristics of the amplifying medium have been made constant over the cross-section, by using an additional magnetic field. Then, the unsaturated gain for the 337 μm line is 6.8% m⁻¹. It is shown to be dependent on the smaller dimension of the cross-section rather than on the other dimension. By using the tube as a waveguide, laser output power of 1 Watt might be obtained with a discharge length of 4 m, instead of the 12m-long discharge required to get the same output power from a cylindrical waveguide laser.     

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 laser accelerator

We show that a laser can efficiently accelerate charged particles if a magnetic field is introduced to improve the coupling between the particle and the wave. Solving the relativistic equations of motion for an electron in a uniform magnetic field and superposed, circularly polarized electromagnetic wave, we find that in energy-position phase space an electron traces out a curtate cycloid: it alternately gains and loses energy. If, however, the parameters are chosen so that the electron's oscillations in the two fields are resonant, it will continually accelerate or decelerate depending on its initial position within a wavelength of light. A laboratory accelerator operating under these resonant conditions appears attractive: in a magnetic field of 10⁵ Gauss, and the fields of a 5×10¹² W, 10 μm wavelength laser, an optimally positioned electron would accelerate to 700 MeV in only 10m. Supported by NASA Grant NSG-7490     

Frequency tuned carbon monoxide waveguide laser with rf pumping

The results of the investigation of a rf-discharge-excited sealed-off CO waveguide laser with a selective resonator are reported. The operation on more than 40 vibration-rotation transitions of a CO molecule has been obtained in a laser having a square section (Al/BeO) waveguide with dimensions of 1.5×1.5×180 mm. Maximum frequency tuning of 550 MHz with output power of 0.5 W at line centre has been observed on theP _10–9(17) transition at –20°C ground electrode temperature at a pressure of 180 Torr.     

Carbon atom fluorescence and C2 emission detected in fuel-rich flames using a UV laser

Laser-induced fluorescence from carbon atoms, excited at the two-photon resonances around 280 nm, has been detected in fuel-rich hydrocarbon flames together with Swan band emission from the C₂ radical, which was non-resonantly excited at the same wavelengths. The emission from the C atom and from the C₂ molecule exhibited several similarities, indicating a possible common photo-chemical origin.     

Population densities and optical gain of VUV transitions of Cu II in Cu−He hollow cathode discharges

Population densities of excited Cu II-levels between 16 and 25 eV in Cu–He hollow cathode discharges were determined by emission spectroscopy. Population inversion was detected for several 6s-4p transitions. Investigation of the enhancement of Cu II vuv lines in He compared to Ne discharges showed that the excitation of the 6s levels by charge transfer is up to 100 times higher in He than in pure Ne discharges. Using the population densities and known transition probabilities, a single pass gain of 55% m^–1 at 780.8 nm and 1.2% m^–1 at 154.17 nm at a current density of 0.4 A cm^–2 was calculated.This paper is dedicated to Prof. Dr. H. Gobrecht on the occasion of his 75th birthday     

A double-wavelength nitrogen-laser-pumped dye laser

A narrow-band tunable double-wavelength dye laser with a bandwidth of 0.1 cm⁻¹ is described. The output at one of the wavelengths is found to be completely linearly polarized in the plane of incidence.     

Output characteristics of a hollow cathode He-Cd laser

Optimum discharge conditions, gain and oscillation linewidth were determined for the blue (4416 Å), green (5378, 5337 Å) and the red (6360, 6355 Å) transitions of a hollow cathode He-Cd laser. A total peak output power of 75 mW has been obtained at 5378 and 5337 Å. Mode investigations showed that the green and red transitions operate in a single axial mode, while the blue one does not.     

A cw uv copper hollow cathode laser in the 260 nm region

A cw uv copper hollow cathode laser is described, which could be operated for a longer time duration with an output power of 7 mW in the 260 nm region. A double-cathode configuration with a protection for the mirrors from metal-vapour deposition is presented. Characteristics of the laser output power, the spontaneous emission, and the ion densities in the negative glow were measured as depending on the discharge current, the neon gas pressure, and the size of the cathode slit. The observed saturation of the laser output power at high discharge current (1 A/cm²) and the optimum slot size are discussed.