A brief review of the evolution of metal vapor lasers is given. A chronology of some of the important discoveries and developments is followed by a summary of excitation mechanisms and other processes relevant to metal vapors. Features of commercial metal vapor lasers, including those of the helium-cadmium laser and the copper vapor laser, are described. Directions for future research and development in this field are suggested.

The density of ground state copper atoms has been measured in an operating large-bore copper laser using hook spectroscopy. In this method, dispersion, due to the copper resonance lines at 327.4 nm and 324.7 nm, is measured by placing the copper laser tube in one arm of a Mach-Zehnder interferometer illuminated by a broad bandwidth UV source. The light source was a Nd:YAG-laser-pumped dye laser which was modified to have a 15 nm bandwidth and then frequency doubled in a 3 mm thick KDP crystal, resulting in a UV beam with an 8 nm bandwidth. The Nd:YAG laser was synchronized with the copper laser, allowing a time resolution of 8 ns. Copper density was measured both as a function of time and as a function of radial position across the bore of the tube. The radial resolution was about 2 mm. The space-dependent data gives information about the gas temperature distribution since the density is inversely proportional to the temperature. The gas temperature distribution found in this way agrees well with the predictions of a simple heat-conduction model which assumes uniform power deposition. The power deposition found in this way was compared to that found by calorimetry.

Time and spatial profiles of the density were directly measured for the lower level (²D_5/2) as well as the upper level (2P_3/2) of a copper vapor laser (CVL). A significant spatial dependent population of the lower level was observed. It was higher at the center than near the wall of a 42 mm diameter tube at just before discharge. On the other hand, a slight radial dependence was detected for the upper level. These radial dependent densities presumably resulted in the spatial dependent gain of the CVL.

Radial effects in small-bore CVL devices are investigated by direct measurement of upper and lower laser level population densities, with spatial and temporal resolution, using the hook method.

A large deplition of the copper ground state is found in CVL, following the excitation pulse. The recovery time of this level is longer than the pulse seperation in a self-heated CVL, and must influence its prf properties. It is suggested that the missing atomes are iorized.

Kinetics of population and depopulation of atomic copper ground state, resonance and metastable levels and also some higher laying levels were measured in active medium of copper vapor laser. A typical commercial sealed-off self-heated discharge tube was studied. Simultaneously at the same conditions of operation characteristics of excitation pulse and gain in active medium were measured. The measurements were made for the whole temperature interval of laser action.

In this paper we briefly describe the new room-temperature metal vapour laser in which a gas flow is used with a small sputtering cathode to produce a single shot, or low repetition rate, laser output on the CuI and AuI transitions. We summarise the results of studies made of the various aspects of the device physics including the sputtering and entrainment processes, the preionization of the metal vapour jet and the parametric dependences, and we discuss their implications for future development.

A 100W copper vapor laser is studied for use as an amplifier. The gain is measured with temporal and radial resolution throughout the gain period and the absorption is monitored throughout the interpulse period. Preliminary results are presented. Evidence of upper level coupling in an operating copper laser is also observed. A large population transfer between upper levels in an oven containing copper vapor is only observed in the presence of a very strong U.V. probe beam.

To obtain an efficient and high-repetition rate ultraviolet light, the 2553 nm second harmonic of a copper vapor laser was generated in barium borate, the excellent nonlinear crystal in ultraviolet region. High quality laser beam from an unstable resonator was focused in the crystal to achieve high power density. The conversion efficiency of 9 % was obtained at an average input power of 2.5W.

An active projection system with a copper vapor laser for LCD-TV pictures is constructed. The maximum size of the projected image is 1.6 m in diameter. Illuminance of the image is then 0.5 W/m². We estimated the image quality: resolving power of the system, fidelity of the gray levels, background noise and speckle.

Active mediume of pulsed copper bromide vapor laser with and without admixture of hydrogen was studied as brightness amplifier in laser projection microscope. Admixture of hydrogen improved the uniformity of gain across the active mediume and prolonged its duration. Due to that with this brightness amplifier it was possible to obtain good quality amplified images of objects located several meters from the amplifier. Influence of amplifier saturation on characteristics of projection system was also studied.

Brief review of the last results on laser brightness amplifiers for different optical systems is given. Nonlinear properties of these systems and some new effects connected with the saturation of active medium of amplifiers are discussed. Some possible applica-tions (processing of microobjects, projection on large screen, TV-projection ...) are described.

The first medical application for metal vapor lasers has been granted marketing approval by the FDA. This represents a major milestone for this technology. Metalaser Technologies recently received this approval for its Vasculase unit in the treatment of vascular lesions such as port wine stains, facial telangiectasia and strawberry hemangiomas.

The enhancement of selectivity of light influence on pathological tissues because of using new optical methods of forming of irradiative light beams was studied. In order to form such beams the specific properties of optical systems with image brightness amplifi-ers were used. Thermal destruction, photo-dynamic therapy and combination of these methods were investigated.

A variety of techniques for extending the wavelength capabilities of copper vapour laser systems upwards to the red and downwards to the ultraviolet are reviewed. Techniques discussed include CVL pumping of fixed-wavelength dye lasers, harmonic and sum-frequency generation from the CVL and CVL-pumped solid state lasers.

The gain of the optically pumped copper vapor laser (OP-CVL) has been measured using a tunable dye laser. A maximum gain of 2.96 cm^-1 was obtained for the green laser. This is more than ten times larger than the gain measured in a conventional longitudinal discharge copper vapor laser. It is found that the gains for the green and yellow lasers are both a linear function of temperature. Fine-structure mixing induced by collisions has been also studied and it affects the laser behavior considerably.

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%.

An efficient and simplified electrode design for the concentric cylindrical type hollow cathode structure of which the discharge length is as short as 19cm can perform the white light laser operation which employs three primary colors from 636.Onm (red), 537.8nm (green) and 441.6nm (blue) lines of CdII transitions. As a measure to quantify the trade-off between hollow cathode effect and Cd vapor diffusion, we consider the loss of cathode area defined by the ratio of total lost areas due to cathode holes to whole inner areas of the cathode cylinder. The cathode dimensions should be properly designed to have the optimum loss of cathode area of 8.0%. By this design, the white light laser operation was achieved with discharge length as short as 19cm, and the total white light output at maximum power was estimated to be more than 1mW.

We demonstrate a unique, efficient white light laser source realized by the He-Zn mixture with substantially short discharge length of 10 cm. The white laser light can be made up of only two wavelengths at simultaneous oscillation --- 492.4 nm (4f²Fo712_4d²D_5/2) and 610.2 nm (5d ²D 512 -5 2p0_3/2 The ideal white color region for human eyes lies just between these two wavelengths in the chromaticity diagram. Therefore, such a compact white light laser will be useful for some specific purposes such as a white color standard. Moreover, we have analyzed the proper relation between the electron energy and the discharge sustaining voltage which appears as a function of the Zn vapor pressure measured at the terminal of the tube, considering the Druyvesteyn distribution of electron energy. Then we succeeded to operate a He-Zn laser tube in white light with 10-cm discharge length. The derived output beam was estimated to be about 0.5 mW.

We have directly measured a comparably large isotope shifts in the CdI (10p³P°₀,₁,₂- 16s³S₁) line by a convenient method of detecting the absorption spectra using a 780 nm band GaAlAs laser diode. The estimated isotope shifts from the measurement were about 2 GHz be-tween the adjacent isotope spectra. Because the presently measured line involves a s-electron transition, such a large isotope shift should be acceptable from the spectroscopic viewpoint. Applying the numerical simulation using Voigt profile to the measured absorption profile, we have also estimated the pressure broadening factors in this spectral line. In addition, we also measured and simulated another absorption spectra of the 782.64 nm CdII (9d²D_5/2-5p"²P°_3/2) line and the results have confirmed the validity of our estimations.

Excimer lasers are recognized for their efficiency in the ultraviolet. Fully utilizing the capabilities of the excimer medium, however, has always been a challenging engineering problem. Ultraviolet waveguide lasers combine optical waveguiding concepts, microwave discharge excitation, and excimer laser technology to produce a family of compact lasers with novel operating parameters. These new uv sources find a wide variety of applications in direct-write photoablation, microsurgery, and fluorescence instrumentation. They also can serve as master oscillators in larger excimer systems.

Operation of a scaled, injection-controlled XeF(C→)A) laser is described. The output energy is 0.6 J per pulse from an extracted volume of 0.48 ℓ, which corresponds to an extraction energy density of 125 J/ℓ. The energy deposition in the gas is 105 J/ℓ and the intrinsic efficiency is therefore 1.2%. Also included is the first report of a repetitively-pulsed (1 Hz) electron-beam pumped XeF(C→)A) laser.

A wavelength and power survey of the 275 nm to 400 nm region has been made with commercial large-frame argon ion lasers operating at elevated discharge currents and various gas pressures. The UV output in the 300 nm to 386 nm region is separated into three groups of lines and used to pump several dyes giving single-frequency tunable outputs from a ring dye laser covering 364 nm to 524 nm. Intracavity frequency doubling with B-BaBA in the ring laser with the dye Stilbene 3 has produced milliwatt level single-frequency output tunable from 215 nm to 235 nm.

We constructed a quantitative theoretical model of an intracavity frequency doubled and passively mode-locked laser and efficiently extracted an ultraviolet femtosecond pulse train of milliwatt average power and 100 MHz repetition rate from a colliding pulse mode-locked dye laser by intracavity frequency doubling in KDP.The ultraviolet and visible outputs, which are comparable in power and pulse duration, are perfectly synchronized with each other. The major findings are that for second harmonic conversion efficiencies consistent with continuing laser operation 1) a stable mode-locking regime always exists, although it narrows somewhat with increasing conversion efficiency; 2) the duration of the fundamental pulses can always be preserved, even in the femtosecond time domain, by re-adjusting saturable gain and saturable loss parameters; 3) the energy of the fundamental pulses can also be preserved under the same conditions.

The requirements for practical self-heated Sr⁺ (λ430.5 nm) recombination lasers are reviewed, and the results of a continuing study of volume and pulse-repetition-frequency scaling of this type of laser are discussed in detail. Finally, consideration is given to the prospects for a high-power (5-10 W) Sr⁺ laser.

A brief review of some present techniques to obtain long-pulse laser action in excimer discharge devices will be presented. An attempt will be made to point out the strengths and weaknesses of these techniques.

This paper discusses the design and performance of a new excimer laser. The laser delivers output powers as high as 160 Watts on KrF with an efficiency of 4.5%, and has demonstrated gas lifetimes significantly better than any previously reported for high-power, commercial lasers. Details are given of an apparatus designed to determine the impurities which presently limit gas lifetime in excimer lasers.

Excimer lasers emitting more than 200 W output power are not commercially available. A significant increase requires new technological efforts with respect to both the gas circulation and the discharge system. A due research project has yielded a laser which emits 0.5 kW at 308 nm when being UV preionized and operated at a repetition rate of 300 Hz. The laser, which is capable of operating at 500 Hz, can be equipped with an X-ray preionization module. After completing this project 1 kW output power will be available.

The use of low peak power, long optical pulse duration excimer lasers to reduce catastrophic front surface damage to fibers as well as non-linear absorption and colour centre formation is described.

The design and performance of a XeC1 discharge pumped laser (A = 308 nm) using a wire ion plasma (WIP) X-ray gun for preionization are presented. The optimization of gas mixture and preionization level at high PRF (1 kHz) is discussed.

Gas. Immersion Laser Doping (GILD) is presented as a powerful process to fabricate emitter and base regions in narrow-base bipolar transistors. Characterization of maximum melt depth versus silicon surface melt time is performed. Results of this characterization demonstrate that surface melt time provides an accurate in-situ measurement of junction depth. The GILD process is then used to fabricate the emitter and active-base regions in simple bipolar transistors. Base widths ranging from 700Å to 1200Å are achieved. The transistors exhibit good electrical behavior with maximum forward current gains greater than 50.

Excimer lasers emit light energy, short optical pulses at ultraviolet wavelengths, that results in a unique laser tissue interaction. This has led to an increasing number of studies into medical applications of these lasers in fields such as ophthalmology, urology, cardiology and neurology.

Two photon pumping of alkali halide crystals is discussed as a possible UV laser source. An experimental characterization of NaI is presented including one and two photon excited luminescence spectra, temporal behavior of the excited state, and the measurement of the two photon absorption coefficient and 351 nm.

Plasma use as a lasing medium has many potential advantages over conventional techniques including increased power levels and greater wavelength ranges. The basic concept, first proposed by Gudzenko, is to heat and then rapidly cool a plasma forcing inversion through bottleneck creation between the recombination reaction populating a given energy level and the subsequent decay processes. Much effort has been devoted to plasmas heated by lasers and pinch devices. We are concerned here with electron beam heated plasmas focusing on the CIV 5g-4f transition occurring at 2530 Angstroms. These studies were initiated to provide theoretical support for experiments being performed at the University of Michigan using the Michigan Electron Long-Pulse Beam Accelerator (MELBA) The theoretical model is discussed first to provide necessary background. Studies are then presented which identify two types of plasma response dependent upon the heating rate. Finally implications of the general studies upon MELBA experiments are discussed.

Semiconductor compounds ZnS_Sei , and ZnO are used as an active medium for e-beam pumped semiconductor lasers (BBPSVIT The plates of these compouds of 2-3 cm in diameter and about 20-30 um thickness with covered mirrors surfaces form the optical cavity of a 2-D scannable laser. The e-beam energy being 75 keV, the maximum power reached 5 Watts at the wavelength λ = 375 nm (ZnO BBPSL). With the use of these compounds the generation in the range 330-400 nm has been obtained.