We have developed a high-power microwave discharge excited carbon-dioxide laser oscillator by using a newly developed method called the orthogonal electric fields method in which the vibration direction of an electric field changes over time for achievement of a homogeneously spread electric discharge. A homogeneously spread electric discharge with a high output power and a high laser efficiency has been generated. The relative discharge area of the electric discharge accounted for about 70% of the cross section of the laser tube. In the configuration of a single discharge area, we achieved a maximum laser output power of 273 W at 1450 W microwave input power, and a a maximum laser efficiency of 20.2% at 1070 W microwave input power. At the maximum laser output power, the input power density was high, at about 240 W/cm³, which is about 20 times that achieved using a dc discharge method. Furthermore, a demonstration model having five electric discharge areas in a laser tube showed a maximum laser output power of 609 W at 3590 W microwave input power, and a maximum laser efficiency of 22.7% at 1394 W microwave input power. This work demonstrates the possibility of fabrication of a high-power microwave discharge excited carbon-dioxide laser which could be widely used industrially.

A unique way of driving a multi-channel rf excited slab laser is presented. Resonant cavity techniques were employed to provide high power splitting and impedance transformation for the excitation of multiple discharge elements. Uniform and isolated power division was observed in 24 channels, stacked in a radial array referred to as the Zodiac geometry. Impedance matching networks were not necessary as the rf cavity splitter created a near ideal voltage source capable of driving any discharge impedance. With 24 channels driven, optical powers over 3 kW have been observed.

Transverse and longitudinal density disturbances in the discharge volume of a transversely excited atmospheric carbon-dioxide laser are measured using a laser schlieren method, and two-dimensional aerodynamic calculations qualitatively reproduce the temporal histories of the disturbances. Exponential decay of the transverse disturbance between the flattened electrodes lasts for several milliseconds. An efficient damping of the shock wave after discharge is confirmed using an acoustic attenuator based on the Helmholtz resonator design. Accumulated pressure disturbances in the volume due to successive laser shots induce a gradual decrease to the steady-state energy level in a pulse-periodic operation, and it is deduced that the modulational instability in the shot to shot pulse energy results from the longitudinal standing wave.

High power and high beam quality cw carbon-dioxide lasers using new resonators with a phase-unifying output coupler are presented. The phase-unifying output coupler has a circular partial-reflection region in the center surrounded by an antireflection region. The two laser beams that fall onto the two regions of the phase-unifying output coupler have a phase difference from each other when they pass through these regions. The phase difference is structurally canceled out by introducing a stepwise groove outside the phase-unifying output coupler. The new resonators operate in a large volume fundamental mode that is mainly determined by the phase-unifying output coupler. A 5 kW diffraction limited output beam that is promising for industrial laser application is obtained experimentally when the new resonators are applied to high power cw carbon-dioxide lasers. In laser materials processing, we can achieve a penetration depth of 5 mm at a speed of 5 m/min for high speed laser welding of stainless steel. Furthermore, we can cut 1 mm thick mild steel at a speed of 58 m/min and 0.5 mm thick mild steel at a speed of 95 m/min for high speed laser cutting.

A cw carbon-dioxide laser capable of being switched at a 30- Hz rate to different laser lines in the 9 - 11 micrometer spectral region has been developed as a single mode local oscillator for high-detection-sensitivity coherent lidar applications. Over sixty ¹²C¹⁶O₂ laser lines (fifty lines for a ¹³C¹⁶O₂ laser) with output power varying from 0.5 W to 5 W were obtained using a compact galvanometer controlled scanning mirror/fixed grating configuration; with a specially designed galvanometer-input voltage waveform digitially controlled through a 16-bit D/A converter, the laser frequency fluctuation was found using a heterodyne technique to have settled to about 0.3 MHz peak-to-peak in 25 ms following each line switching, which is adequate for our coherent lidar atmospheric sensing applications.

The Field Ladar Demonstration (FLD) program (also known as the Hi-Class-High Performance CO₂ Ladar Surveillance Sensor) which is building a high power, coherent, carbon- dioxide, multi-function laser radar at the Maui Space Surveillance Site (MSSS) facility on Mt. Haleakala, Maui has completed its Phase 2 testing. The Phase 2 effort has the primary objective of demonstrating that a subset of the final system components (oscillator, receiver, processor and beam director) provide the capability required for an operational hardbody and remote chemical detection sensor. The final major component, the power amplifier, will be added in Phase 3. The objectives for this phase include real-time satellite metric determination and demonstrations of range-Doppler imaging and long range, remote chemical species detection (lidar). Specifically, the Phase 2 testing will demonstrate: real-time (30 Hz) generation of satellite range and range rate; detection of return signals from 'uncooperative' satellites (having no retro-reflectors); wideband imaging; and measurement of path-integrated chemical species absorption at long range (18 km) using a coherent DIAL technique and the FLD, wavelength agile transceiver.

This paper presents investigations of the carbon-dioxide lasers excited using two techniques: e-beam controlled discharge and e-beam ignited discharge. The working mixtures were CO₂-N₂-He, CO₂-N₂ and CO₂-N₂He- H₂. We can change working mixture composition, its pressures, pumping power and the laser pulse duration from 50 ns to 10 microseconds. The operating time of a repetitive carbon-dioxide lasers excited by e-beam controlled discharge or e-beam ignited discharge in nonstop mode is determined by the lifetime of the foil separating the vacuum gap from the gas cell. The radiation energy of 3 kJ has been achieved in the active volume of 50 1 at pressure of 2 atm. When 12 1 active volume was used the energy deposited in to the CO₂:N₂:He equals 1:2:2 mixture was as high as 0.6 kJ/lXatm while the radiation energy was about order of magnitude 80 J/lXatm.

The design of mobile high power gas dynamic CO₂ laser complex for technological applications in the field conditions is presented.

Historical background and present status of excimer laser annealing of amorphous silicon for poly-TFTs fabrication are presented. Scanning and single shot systems are compared both on the physical and economical aspects. Process optimization and process control using real time spectroscopic ellipsometry are also presented. Finally, some perspectives in the development of very high power excimer laser are also given.

High repetition rate operation technology and spectral narrowing technology with compact excimer lasers whose cross-sectional dimensions are around 120 by 120 mm. High repetition rate operation over 1.5 kHz and spectral narrowing to 1 pm are reported. These technologies are essential to promising applications of ArF excimer lasers. High resolution pattern of 0.16 micrometer line and space is demonstrated by an optical laser lithography with the compact ArF excimer laser. The smallest ArF excimer laser specific to the photo-chemical surgery of cornea is also presented.

Performance of a 6 inch by 6 inch surface discharge that give integrated light intensities greater than 400 mJ/cm² is reported here. Light uniformity on the surface of high density alumina dielectric has been measured to show better than 5% across the entire discharge area. Detailed spectroscopic content of these discharges in different gases and gas mixtures are presented from 160 nm to 735 nm region.

This paper describes recent results achieved in the development of a compact 1 kW XeCl laser GEFEST - 4, intended for using in various technologies. The laser was designed to obtain various output combinations of pulse energy (epsilon) and pulse repetition rate (f) with the same average output power P equals epsilon times f approximately equals 1 kW. Different excitation system for discharges with various cross sections are considered. Using the excitation system with UV preionization on the base of creeping discharge on dielectric surface we obtained an average output power of 1 kW at a pulse repetition rate of 100 Hz and 150 Hz (10 J multiplied by 100 Hz and 6.6 J multiplied by 150 Hz) with an efficiency of 1.65%. To obtain the combination of parameters 3.3 J multiplied by 300 Hz a spiker-sustained excitation system is developed which ensures in monopulse mode a pulse energy of 3.6 J with an efficiency of 3.6%. For this system the influence of macro- and micro-instabilities in discharge on energy and duration of the laser pulse is investigated. Capability of obtaining other combinations of epsilon and f at the epsilon multiplied by f approximately equals 1 kW is briefly considered.

Investigations on creation of a high-power and high- efficiency copper bromide vapor laser (CuBrVL) (lambda510.6, 578.2 nm) are reported. Laser generation of 100 W output power was achieved at 3% efficiency (based on stored energy). These output power and efficiency figures are record values for copper bromide lasers. The device produced maximum output power at a PRF of 17.5 kHz. Laser operating characteristics and electrical parameters are described.

In this paper, a theoretical random walk model for the metal-vapor segregator of metal-vapor laser is presented. The proposed model was verified qualitatively by experiment. Based on this model, a new type of segregator was proposed. Its principle is as follows: several metal pieces of high metal vapor condensation coefficients were used to adsorb the random walking metal-vapor particles that collide upon them, as a result, a protection of laser windows from the metal-vapor pollution was achieved. A Monte Carlo Simulation showed that the ability of antipollution for this new type segregator was much higher than that of the common segregator.

A variety of infrared rotational Raman lasers developed at RIKEN for the purpose of molecular laser isotope separation are described. One of the major advances is that annular pump beams from an unstable resonator of a TEA CO₂ power oscillator can be efficiently converted to Stokes beams in a multiple pass cell, which results in an increase in the total efficiency of the para-H₂ Raman laser system. The annular pump beams are used to generate second Stokes waves in ortho-D₂, which provide a number of lines different from those of first Stokes waves in para-H₂ in the 13 - 18 micrometer spectral range. First Stokes generation using the S(2) transition of ortho-D₂ at room temperature is also described.

The DLR successfully operates a supersonic chemical oxygen iodine laser (COIL) at power levels of up to 8 kW. We address substantial discrepancies between the measured oxygen yield and its theoretically deduced value. This major issue cannot be resolved by using the well-known heuristic model for COIL performance evaluation. Therefore, a new approach derived from a comprehensive enthalpy flow model is presented and validated. We conclude that the experimental yield value is consistent with the new model whereas the theoretical yield is largely overestimated.

The high frequency temporal structure of probe and phase conjugation (PC) signals under degenerate four-wave mixing (DFWM) of long pulse carbon-dioxide and carbon laser radiation in their inverted media has been studied experimentally with nanosecond resolution over the full pulse length. The multiline and single spectral line pulses of electron-beam controlled discharge (EBCD) carbon-dioxide and carbon lasers with pulse length of approximately 10 - 20 microseconds and approximately 200 - 300 microseconds, accordingly, are characterized by complicated temporal behavior with a periodic structure (approximately 100 ns) on account of mode beating with a depth of modulation up to 100%. On the round-trip period carbon-dioxide and carbon laser pulse consists of several spikes (for free-running mode) or a single spike in case of mode locking with pulse length of approximately 10 ns. A plasma mirror is used for carbon-dioxide laser to operate in the latter mode of operation. The time history of PC signal has a complicated behavior and structure differed from that of probe laser signal on large (greater than or equal to 100 ns) and small (approximately 10 - 100 ns) temporal scale. A relative influence of amplitude and phase mechanisms of creating diffraction gratings inside active medium, and also the influence of small scale and large scale gratings and spike synchronism conditions on the PC signal is discussed.

To overcome the difficulty that the operating pressure range of usual mass-spectrometers does not meet the pressure ranges of gas lasers, the authors have improved the M.S technique by the following four procedures: (1) Making an ultramini-flow valve which can sample the laser mixture and take mass-spectrum only by a little amount of gases; (2) Creating a high pressure ultramini-flow valve possessing pressure-linearity up to 1000 times 133 Pa, especially suitable to M S analysis of TEA carbon-dioxide lasers; (3) Investigating the time-delay and giving an evaluate method to correct them; (4) Proposing a method, the sample gas bottle method, to overcome the sensitivity-fluctuation of the M S tube through comparison.

Two new techniques have been proposed for outgassing the metal parts of helium cadmium lasers of the positive column type. The first method, double-way exhausting method, is mainly for cadmium outgassing; the second one, auxiliary anode method, is especially for cathode cylinder outgassing.

In this paper, we think that in rf discharge carbon-dioxide lasers there are only cathode space and quasi-Faraday dark region but not plasma area. The electron motive equation in the cathode space and quasi-Faraday region of the rf discharge space are given. We use the ponder motive force to calculate the electron energy in these spaces as well as the size of the quasi-Faraday dark region. At last, some problems of the high power carbon-dioxide laser are discussed.

In this paper, some phenomena which lead to the failure of the domestic helium cadmium lasers of the positive column type were given. The related mechanisms were discussed. In addition, some improvement ideas as well as repairing techniques also were given.

The improved mass-spectrometric technique for gas lasers has been used to perform a lifetime study for a high repetition- rate TEA carbon-dioxide laser. The laser has Chang's electrode with a blower inside. Some procedures have been adopted to improve the accuracy of the mass-spectra taken. The results were rather complex and a brief discussion is given.

In order to study the discharge characteristics of carbon- dioxide laser tube with distributing gold rings, a comparison experiment has been carried out with two carbon- dioxide laser tubes -- one was typical, the other was improved by putting a series of gold rings in the discharge capillary. Two kinds of gases -- helium and neon have been used in the experiment. The results showed that both the breakdown voltage and the terminal voltage of the laser tube having gold rings are increasing significantly in comparison with the tube without gold rings.

Our original pumping system for the gas-discharge TE carbon- dioxide laser was tested in the 5 kW laser. It includes crossed electrodes (20 anodes, 5 cathodes), thyristor invertor (2.5 kHz), system of unballast connections of sections to the invertor. The preionizer placed upstream realizes the 100 kHz discharge through dielectric electrodes. On the basis of the principle of minimum of energy dissipation high efficiency of current distribution over crossings (20 by 5) with a small number of sections (20 plus 5) is shown. It provides a stable dc discharge at average power input to 4W/cm³ due to influence of upstream discharges upon the downstream ones. The active medium of the laser was studied by method of IR luminescence at the wavelength 2 - 8 micrometer in 'switched on' and 'switched off' resonator. The luminescence intensity in the band 4.3 micrometer gives the particular information about the active medium. The 2D model of a discharge segmented along the gas flow was constructed to describe the distribution of electrical, gas-dynamic and kinetic characteristics. It was shown that in the most volume of chamber the discharge burns in the recombining plasma at reduced E/n, thus favoring high excitation efficiency.

Over the last several years, Rocketdyne has conducted a number of experiments on advanced jet generators. Both cross flow jet generator and counter flow jet generators have been tested. We have made laser power measurements at our Continuous Wave Chemical Laser Facility (CWLL) and at the Air Force Phillips Laboratory RADICL test facility. A test there resulted in a measured chemical efficiency of 29.6%. This is the highest efficiency reported for a supersonic oxygen-iodine chemical laser.

The chemical oxygen-iodine laser derives its energy from the reaction of basic hydrogen peroxide with chlorine. The traditional oxygen-iodine laser uses an 'open loop' cycle, in which fresh reactants are furnished in bulk form. This approach is not suitable for a continuously operating laser because supplying fresh reactants and disposing of reaction products are expensive and require significant logistics. This work describes a new concept for continuous in-situ regeneration of chlorine and basic hydrogen peroxide.

A jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was studied including singlet delta oxygen, O₂(¹(Delta) _g), and residual chlorine concentration measurements. The investigation was intended mainly for a water vapor measurement in gas effluent of generator in dependence on properties of liquid jets: a chemical composition and temperature of the input liquid (alkaline solution of hydrogen peroxide), a liquid jets diameter and their geometrical arrangement. Effects of these parameters on output power of a small-scale supersonic laser were studied as well. Possible approaches to a chemical fuels management in a chemical oxygen-iodine laser for industrial applications are considered. An 'open loop' cycle with a possible use of sodium hydroxide, and a 'closed loop' cycle with a regeneration of both potassium hydroxide and hydrogen peroxide are discussed.