Copper Halide Laser Research Articles

Comparison of the output power of copper halide lasers versus buffer gas pressure and frequency

In this work, an iodide copper vapor laser (CuI) has been designed and fabricated. The effect of different operational parameters such as frequency and buffer gas pressure on output power laser have been investigated to determine the optimal condition of frequency and neon gas pressure. Based on experimental results, the maximum output power of about 0.5W is obtained at 16 kHz of frequency and 30 torr of Ne gas pressure. Moreover the experimental results of CuI laser have been compared to the similar data for the other halide copper lasers such as CuBr and CuCl. The output power of CuI laser is less than that of others. The optimum frequency of lasers have different values, but the optimum gas pressures are the nearly same for three lasers, at the same conditions.

Acoustic effects of metal vapor lasers

Some fluctuations in the output power of a copper vapor laser with a 16 mm bore were recorded by varying the excitation frequency from 13 to 33 kHz. The effect arises from the laser tube, which performs both as an optical and an acoustic resonator at the acoustic resonant frequencies. It is shown that a similar effect occurs in other metal vapor and copper halide lasers as well.

Investigation on magnetic pulse compressor used for copper halide laser

In copper halide lasers, the excitation of copper atoms is produced through the discharge of a storage capacitor. Performances of it were essentially linked to the type of switch used and also to its mode of operation. Thyratrons are the most common switches. Nevertheless, their technological limitations do not allow a high repetition rate and high rate of rise of current. But these limitations can be surpassed by combining the thyratron to magnetic pulse compression (MPC). The MPC driver can improve the laser excitation pulse rise time and increase the repetition rate. A single stage MPC system for CuBr laser has been developed in this paper. With this MPC, the power of laser output was increased more than 20%. The mechanism of MPC performance was analyzed. The design advisements and parameter choices of MPC were presented particularly.

A microwave-excited copper halide laser

A microwave-excited copper halide laser

Characteristics of a copper bromide laser with flowing Ne-HBr buffer gas

The operating characteristics of a small self-heated copper halide laser (λ=510.6 and 578.2 nm) are described, where the copper lasant atoms are produced by electric-discharge dissociation of copper bromide that is generatedin situ by flowing Ne-HBr gas mixture over copper pieces in the laser tube. The excitation technique permits fast startup (<1 min to laser oscillation from cold), and rapid and simple control of the CuBr vapour pressure, simultaneously introducing H2 to increase the efficiency. Specific laser output energies and average powers of 12μJ cm−3 and 195 mW cm−3, respectively, are almost a factor of 2 higher than those previously reported in the literature for multi-kilohertz copper bromide lasers. A maximum power of 7.8 W was obtained from the 40 cm3 active region. At its highest efficiency (0.8%) the laser produced 6.1 W.

Time dependence of the electron density in the afterglow of copper halide lasers operating in the double-pulse excitation regime

The results are given of measurements of the electron density in the interval between dissociation and excitation pulses in CuBr and CuI lasers. The efficiencies of the different electron density relaxation mechanisms are analyzed. A comparison is made with similar results for a self-heating copper vapor laser.

Interpulse kinetics in copper and copper halide lasers

The various rate processes that govern the interpulse relaxation in metal vapor and metal halide vapor lasers are considered. Computer calculations indicate that the rapid metastable levels relaxation observed in copper and copper halide laser experiments requires the existence of a relatively small resonance in the cross section for metastable excitation or deexcitation near threshold. The accurate calculation of interpulse relaxation requires knowledge of rate constants presently not well known; this is especially so for metal halide lasers.

Copper halide laser pumped with vacuum-tube and thyratron oscillators

A copper halide laser was excited by vacuum-tube and thyratron oscillators. Several laser tubes were arranged in parallel and operated synchronously in order to increase the output power. It was found that not only the average but also the peak powers were additive. One laser tube produced output radiation of 18.5 W power, whereas three tubes arranged in parallel and focused at the same point produced 30 W.

Driving circuits for copper halide lasers-a parametric study

The influence of circuit inductance and current rise-time on the performance of a longitudinally excited copper halide laser was investigated for (a) double spark gap and (b) thyratron burst-mode driver circuits with low inductance configurations. The inductance of the circuit of the dissociation spark gap was not critical and the output of the laser increased as the inductance of the laser-pulse spark gap circuit was decreased to its minimum value. The effectiveness of the driver circuit was limited principally by the long extinction time of the dissociation spark gap, which restricted the interpulse delay time to values considerably in excess of the intrinsic delay for the laser itself. For the lowest inductance (about 65 nH) of the thyratron burst-mode circuit, the duration of the current pulse is limited by the finite speed of propagation of ionisation waves in the laser discharge tube rather than the inductance and the rate of rise of current in the thyratron significantly exceeds the tube rating. An L-C inverter circuit is described which removes the thyratron from the laser discharge circuit but it is found that the inversion time must be matched to the current growth in the laser tube and this requires the addition of inductance to the thyratron circuit. The most critical factor in determining the pulse energy available from the laser is the restriction on the rate of current rise for presently available thyratrons.

Rapid differential decay of metastable populations in a copper halide laser

The time dependences of the populations ofthe copper metastable levels ( 2D 5 2 , 2D 3 2 have been measured in a longitudinally-excited CuBr laser of tube diameter 12 mm at a dissociation energy density of 15 mJ cm -3. The metastable populations are created within 3 μs of the dissociation discharge pulse and thereafter decay to the ground level by electron collisions. The decay of the 2D 3 2 population is faster than that of the 2D 5 2 population and, in the case of CuBr, both decay rates are increased significantly by the decomposition products which arise from the presence of cupric oxybromide as an impurity. Decay times for the 2D 5 2 , 2D 3 2 populations as short as 4, 1.8 μs respectively have been observed under optimum laser conditions. The increase in the relative intensity of the 578.2 nm line at the shortest interpulse delays (ca 10 μs) is due to the more rapid decay of the 2D 3 2 population. At times up to the several microseconds after the dissociation current pulse the gas in the laser tube remains highly conducting. The rise-time of the pumping pulse is then determined by the external circuit rather than by the transit time of an ionization wave. The controlled effect of the cupric oxyhalide impurity in both CuBr and CuCl lasers offers the prospect of more efficient operation of copper halide lasers at repetition rates in excess of 20 kHz.

The pumping efficiency of copper halide lasers

A simple relation between the copper halide laser output and the densities of ground state ( 2S) and metastable state ( 2D) copper atoms was found. This relation was used to analyze the experimental results of Nerheim. In all the analyzed systems it was found that about four percent of the ground state copper atoms take part in the lasing process. This may have implications for the efficiency of copper halide lasers.

A continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit

Experimental characteristics of a continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit are reported. Quartz laser tubes 1 m in length and 1.5 and 2.5 cm in diameter were employed to study the effects of the electrical circuit, lasant, and buffer gas on laser performance. Measured properties of the Blumlein circuit are compared with an analytic solution for an idealized circuit. Both CuCl and CuBr with neon and helium buffer gas were studied. A maximum average power of 12.5 W was obtained with a 1.5 nF capacitor charged to 8 kV and discharged at 31 kHz with CuCl and neon buffer gas at 0.7 kPa in a 2.5-cm-diam tube. A maximum efficiency of 0.72 percent was obtained at 9 W average power. Measurements of the radial distribution of the power in the laser beam and the variation of laser power at 510.6 and 578.2 nm with halide vapor density are also reported. Double and continuously pulsed laser characteristics are compared, and the role of copper metastable level atoms in limiting the laser pulse energy density is discussed.

A transversely excited copper halide laser with large active volume

Operation of a pulsed copper halide laser excited by transverse discharge and with an active volume of 250 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> is reported. Total laser output pulse energies (at λ5106 and 5782 Å combined) of 2.5 mJ per pulse and peak powers exceeding 100 kW have been achieved in the double-pulse mode with CuBr as the lasant.

Time dependence of copper-atom concentration in ground and metastable states in a pulsed CuCl laser

We have measured the time dependence of the concentration of copper atoms in the ground and metastable states in a pulsed CuCl laser by monitoring the absorption of atomic copper lines. We found that the ground-state population rises from a very small value at the end of the dissociation pulse to a maximum and decreases slowly after about 160 μsec. The metastable population reaches a maximum after about 40 μsec and then decreases relatively rapidly. We conclude that the minimum and optimum delay times in a double-pulse copper halide laser are determined primarily by the slow buildup of the copper-atom ground-state concentration. This concentration then decays by recombination.

Kinetic processes in continuously pulsed copper halide lasers

Absorption measurements in the afterglow of electrically excited copper halide laser mixtures are described. Ground state and metastable copper density decay rates determine the optimum delay for application of a second electrical pulse. Output energy densities of 45 μJ . cm-3have been observed for single-pulse conditions. Gas temperature increases limit the electrical pulse energy which can be applied on a continuous basis, and in this regime the output energy density is reduced to \sim 11 \mu J . cm-3due to the decreased pulse energy and cumulative population effects. Thermal gradients and radial cataphoresis are suggested as explanations for observed transient effects in the multipulse output envelope. Average 5106 A power levels of 1.34 W at 0.3 percent efficiency were observed within 18 kHz burst-mode pulses applied at low duty cycle.

Long-lived, sealed-off copper halide lasers

Long-lived, sealed-off copper halide lasers

High average power pulser design for copper halide laser systems

A circuit using two thyratrons is described which provides alternating polarity, high-current pulses at pulse repetition rates up to 20 kHz, suitable for operating copper halide lasers. The circuit is a modification of a Blumlein configuration in which two networks are charged in parallel and discharged in series, providing a voltage quadrupling effect when used with resonant charging. By triggering the thyratrons sequentially the current is reversed on alternate pulses, which greatly reduces axial cataphoretic effects and extends the laser tube operating lifetime. The circuit can deliver up to 5 kW average power at 15 kHz.

Relaxation processes in the discharge used in a copper halide laser

A spectrographic investigation was made of the radiation emitted from pulse discharges in mixtures of CuBr and CuI with Ne and He. The dependence of the relative intensity of the molecular spectrum on the discharge conditions and the time characteristics of the deexcitation of the resonance and laser lines of Cu I were determined. Prolonged afterglow due to the 3d10nx–3d10 4p2 P03/2,1/2 and 3d10nx–4s2 2D3/2,5/2 in Cu I was observed. The possibility that the discharge contraction was due to an increase in the importance of the dissociative recombination processes was considered. It was concluded that cooling of electrons played an important role in the deactivation of the metastable states of Cu I.

Axial cataphoresis effects in continuously pulsed copper halide lasers

It has been observed in a continuously pulsed copper halide laser that laser performance deteriorates rapidly due to axial cataphoresis effects. Dissociated copper ions are pumped cataphoretically toward the cathode by the applied electric field, causing nonuniform laser discharges and preferential copper condensation near the cathode. These effects can be eliminated experimentally by alternating the polarity of the applied voltage either mechanically or electronically. This improvement permits long-lived copper halide laser operating at average power levels in the 1–10-W range.

A hollow-cathode copper halide laser

We have successfully operated a CuCl laser in a metal tube in a hollow-cathode configuration. An average output of 400 mW was obtained with 0.06 percent "wall plug" efficiency. Excitation was by pulse burst with a repetition rate of 1-15 kHz within the burst. Despite the use of an unsealed vacuum system and cold windows the laser was operated for more than 300 h on a single charge of CuCl. The hollow-cathode configuration appears to offer significant improvement in mechanical strength and lasant conservation over Pyrex- or quartz-walled longitudinally pumped copper halide lasers.