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CuBr master oscillator-power amplifier (MOPA) laser system fitted with a generalized diffraction filtered resonator (GDFR) is reported to produce high-quality beam of throughout-pulse diffraction-limited laser emission at the repetition rate of /spl sim/19 kHz. The comparison with typical (stable and unstable) resonator configurations for CuBr lasers has featured out its high brightness accompanied by a very low beam divergence permanent within laser pulse. This intrinsic characteristic of GDFR-MOPA laser radiation makes it a perfect light source for fine laser applications.

High beam quality output has been demonstrated from a single medium-scale (2 cm dia. × 50 cm) CuBr laser with hydrogen additives. The addition of hydrogen leads to beam divergence reduction and laser power lift-up finally yielding 5-fold increase in laser power spatial intensity compared with the case of no hydrogen added. With a simple positive-branch unstable resonator practical (pulse-average) divergence of ∼80 μrad is achieved. The easy-feasible sealed-off version of CuBr laser makes it an attractive source for many high-quality laser beam applications.

A comparative study has been carried out of the output characteristics, electric parameters, and main kinetic plasma processes concerning CuBr laser performance during the excitation pulse. Four electric circuits were used for CuBr vapor laser excitation: WPC (without peaking capacitor); OC (ordinary circuit, i.e., with a peaking capacitor); IPC (interacting peaking circuits), and IC (interacting circuits). The calculated and experimental values are in very good agreement. The improvement of the CuBr laser performance from WPC- to IC-excitation (the laser power and efficiency increase three times) is mainly attributed to the increased physical laser efficiency, which concerns the electrooptic energy conversion with regard to plasma kinetic processes. >

Populations of CuI ground state, resonance, and metastable levels have been measured in CuBr laser with and without hydrogen additives. Temporal evolution and spatial distribution populations have been studied during the excitation pulse and also during the interpulse period of time. Addition of hydrogen results in a smaller rate of resonance and metastable levels excitation and smaller depopulation of the ground state during the excitation pulse. Repopulation of the ground state after the excitation pulse with hydrogen is much faster. CuBr molecules have been detected only in the periphery of the active zone. The density of the CuBr molecules had no noticeable change either during the excitation pulse or in the interpulse period. >

The IC-excitation that had been developed in our lab has been applied very successfully in the excitation of CuBr vapor laser.1 The power and efficiency of CuBr vapor lasers have been increased by a factor of 1.5-1.7. In the present work we present the examination of IC-excitation for Sr+ laser.

An average laser power of 6.7 W has been obtained from a small-bore CuBr laser with a constructive active volume of 4.77 cm/sup 3/, i.e., a record specific average power of 1.4 W/cm/sup 3/ for multikilohertz operation of copper vapor lasers has been achieved. It was found that the small-bore CuBr laser can operate with a neon buffer at atmospheric pressures. >

The development of high-power CuBr lasers for micromachining and other technology applications requires an investigation and control of the beam quality of these lasers. An important laser system property is the laser power density, Ps obtained after focusing the output radiation. It is equal to where Pout is the average laser output power, θ is the divergence of die laser output power and F is the focus length of the output focusing optical system. It is clear that Ps is proportional to the quantity Pout/θ2 which is an inherent property of the light emitted from a laser. This quantity represents the laser power spatial intensity because θ2 is actually the solid angle in which laser output is concentrated. This laser power spatial intensity can be quantified in W.mrad−2, for example. The inverse - square dependence of laser power spatial intensity on the divergence of laser output power means that higher laser power density can be more easily obtained by improving the beam divergence. Thus, a serious decrease in laser beam divergence should sharply' reduce the demand for too high laser output.

Copper bromide vapor laser (CuBrVL) as an alternative of the copper vapor laser (CVL) is successfully being developed. CuBrVL of an average output of up to 10W has already approved as a commercial vanant in the practice [1]. The effect of hydrogen in CuBrVL that increases more than twice its average power and efficiency [2], provided new opportunities for a high-power and efficient CuBrVL to be created.

The addition of 0.3 Torr hydrogen to a 15 Torr neon buffer in the CuCl- and CuBr-vapor lasers causes the output power and efficiency to increase as much as twice. This is another proof of the proposition that the improvement of the laser performance is due to processes taking place in the buffer plasma of the laser discharge.

A systematic investigation of the electric parameters of the CuBr laser plasma during the excitation pulse in their correlation to the laser output characteristics is presented. Based on the electric parameters, the temporal course is calculated of the electron density during the discharge. The authors offer a simple mechanism which generally explains how the hydrogen occurred in the copper vapor laser. The mechanism consists of shielding copper ionization by the process of electron detachment from negative hydrogen ions. >

Addition of small amounts of hydrogen to the neon buffer gas in a CuBr laser causes doubling of the average output power and laser efficiency. An efficiency of 1% is easily obtained. Electrical parameters of the pulsed discharge as functions of the hydrogen additive pressure are reported.

An innovation in CuBr laser excitation causes a significant increase of the output power and laser efficiency. The novel electrical circuitry consists of two interacting peaking circuits. A comparison of the operation parameters between an ordinary-circuitry (OC) excited CuBr laser and the novel-circuitry (interacting peaking circuits, IPC) excited CuBr laser is made. An efficiency of 1.45% at 17.4 W average output of the IPC CuBr laser is obtained.

The most likely reasons for the hydrogen effect on the CuBr laser performance are discussed. A novel electrical circuitry consisting of two interacting peaking circuits for the CuBr laser excitation is also described. Based on these innovations the output power and the efficiency of a typical CuBr laser tube (electrode separation of 50 cm and i.d. of 2cm) scale up, respectively, to 20 W and 1.5%.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An experimental examination of the lifetime limiting processes in a whole-heated sealed-off CuBr laser is performed. The influence of the CuBr expenditure, the pollution of the laser windows, the recombination processes and the change of the plasma composition, especially the bromine concentration increase is investigated. Considering the experimental results a sealed-off CuBr laser of not less than 500 h of operation is designed.

In our previous papers1,2 we have suggested two novel excitation circuits for CuBr vapor laser (IPC and IC circuits). The effect of these new circuits is an essential increase of the laser efficiency.

A low temperature copper vapor laser utilizing pure copper with an admixture of another metal chloride (BiCl3, FeCl2 or NaCl) is investigated. Best lasing characteristics are obtained when BiCl3 is used.