This PDF file contains the front matter associated with SPIE Proceedings Volume 7915, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Experiments and modeling have led to a continuing evolution of the Electric Oxygen-Iodine Laser (ElectricOIL) system. A new concentric discharge geometry has led to improvements in O2(a) production and efficiency and permits higher pressure operation of the discharge at high flow rate. A new heat exchanger design reduces the O2(a) loss and thereby increases the O2(a) delivered into the gain region for a negligible change in flow temperature. These changes have led to an increase in laser cavity gain from 0.26% cm^-1 to 0.30% cm^-1. New modeling with BLAZE-V shows that an iodine pre-dissociator can have a dramatic impact upon gain and laser performance. As understanding of the ElectricOIL system continues to improve, the design of the laser systematically evolves.

The chemistry of electric discharge driven oxygen iodine lasers (EOIL) has long been believed to have O₂(a¹▵g) as the sole energy carrier for excitation of the lasing state I(²P_1/2), and O(³P) as the primary quencher of this state. In many sets of experimental measurements over a wide range of conditions, we have observed persistent evidence to the contrary. In this paper, we review our experimental data base in both room-temperature discharge-flow measurements and EOIL reactor results, in comparison to model predictions and kinetics analysis, to identify the missing production and loss terms in the EOIL reaction mechanism. The analysis points to a significantly higher level of understanding of this energetic chemical system, which can support advanced concepts in power scaling investigations.

We are investigating catalytically enhanced production of singlet oxygen, O₂(a1▵g), observed by reaction of O₂/He discharge effluents over an iodine oxide film surface in a microwave discharge-flow reactor at 320 K. We have previously reported a two-fold increase in the O₂(a) yields by this process, and corresponding enhancement of I(2P1/2) excitation and small-signal gain upon injection of I₂ and NO₂. In this paper we review observed I* excitation behavior and correlations of the catalytically generated O₂(a) with atomic oxygen over a large range of discharge-flow conditions to develop a conceptual reaction mechanism for the phenomena. We describe a first-generation catalytic module for the PSI supersonic MIDJet/EOIL reactor, and tests with this module for catalyst coating deposition and enhancement of the small-signal gain observed in the supersonic flow. The results present compelling evidence for catalytic production of vibrationally excited O₂(X,v) and its participation in the I* excitation process. The observed catalytic effects could significantly benefit the development of high-power electrically driven oxygen-iodine laser systems.

Kinetic data obtained in the last decade has resulted in revisions of some mechanisms of excitation and deactivation of excited states in the chemical oxygen-iodine laser (COIL) medium. This review considers new kinetic data and presents analyses of the mechanisms of pumping and quenching of electronically and vibrationally excited states in the oxygen-iodine laser media. An effective three-level model of I₂ molecule excitation and relaxation has been developed. The calculated effective rate constants for deactivation of I₂(X,11&leνle;24) by O₂, N₂, He and CO₂ are presented. A simplified kinetic package for the COIL active medium is recommended. This model consists of a 30-reaction set with 14 species. The results of calculations utilizing simplified model are in good agreement with the experimental data.

This paper presents a first demonstration of a diode pumped Potassium laser. Two narrowband laser diode arrays with a linewidth about 10 GHz operating at 766.7 nm were used to pump Potassium vapor buffered by Helium gas at 600 torr. A stable laser cavity with longitudinal pumping and orthogonal polarizations of the pump and laser beams was used in this experiment. A slope efficiency about 25% was obtained.

A blue alkali laser operating by direct optical excitation of the 7²P_3/2 state of cesium is demonstrated. A mixture of cesium vapor and various buffer gases (⁴He, CH₄, C₂H₆) were pumped with the output of a pulsed dye laser in a heated glass cell. The spin-orbit mixing and fluorescence quenching cross sections were calculated for each buffer gas using the time-dependent D1 (459 nm) side fluorescence. At certain temperatures and buffer gas pressures, a spatially coherent blue beam is produced in the forward direction. An analysis of the spectrum shows this beam contains both D₁ amplified spontaneous emission (ASE) and Stimulated Raman Scattering (SRS).

In this paper we describe a platform for small signal gain measurements for alkali atom laser systems based on the DPAL excitation method. We present initial results that clearly show the transition from absorption on the alkali atom D1 lines in Cs and Rb to optical transparency and positive gain. The achievement of optical gain is critically dependent upon alkali cell conditions and collision partners. We also present the first spatially resolved gain measurements in a DPAL system. The small signal gain methods described will be valuable tools for power scaling of these laser systems.

We report on the results from our transversely pumped alkali laser. This system uses an Alexandrite laser to pump a stainless steel laser head. The system uses methane and helium as buffer gasses. Using rubidium, the system produced up to 40 mJ of output energy when pumped with 63 mJ. Slope efficiency was 75%. Using potassium as the lasing species the system produced 32 mJ and a 53% slope efficiency.

Rubidium dimers were formed by thermal vaporization of the metal followed by continuous co-expansion with argon through a small pinhole into a vacuum chamber. The dimers were detected by laser-induced fluorescence (LIF). Vibrationally resolved excitation spectra were recorded for two new band systems in the wavelength regions around 394 nm and 353 nm. The well known D-X system near 430 nm was also observed. All three band systems exhibited long vibrational progressions, indicative of substantial changes in the equilibrium bond lengths on electronic excitation. Isotope splittings between the bands of ⁸⁵Rb₂ and ⁸⁵Rb⁸⁷Rb were resolved for the band system centered at 353 nm. Vibrational analyses were carried out, and the upper state vibrational constants are reported. Possible assignments of the electronic configurations for the newly observed states are considered.

The exciplex pumped alkali laser (XPAL) system has been demonstrated in mixtures of Cs vapor, Ar, with and without ethane, by pumping Cs-Ar atomic collision pairs and subsequent dissociation of diatomic, electronically-excited CsAr molecules (exciplexes or excimers). The blue satellites of the alkali D2 lines provide an advantageous pathway for optically pumping atomic alkali lasers on the principal series (resonance) transitions with broad linewidth (>2 nm) semiconductor diode lasers. Because of the addition of atomic collision pairs and exciplex states, modeling of the XPAL system is more complicated than classic diode pumped alkali laser (DPAL) modeling. The BLAZE-V model is utilized for high-fidelity simulations. BLAZE-V is a time-dependent finite-volume model including transport, thermal, and kinetic effects appropriate for the simulation of a cylindrical closed cell XPAL system. The model is also regularly used for flowing gas laser simulations and is easily adapted for DPAL. High fidelity calculations of pulsed XPAL operation as a function of temperature and pressure are presented along with a theoretical analysis of requirements for optical transparency in XPAL systems. The detailed modeling predicts higher XPAL performance as the rare gas pressure increases, and that higher output powers are obtainable with higher temperature. The theoretical model indicates that the choice of alkali and rare gas mixture can significantly impact the required intensities for optical transparency.

The possibility of using rare gas atoms as the active species in an optically pumped laser is considered. Rg(np⁵(n+1)s) metastable states may be produced using low-power electrical discharges. The potential then exits for optical pumping and laser action on the np⁵(n+1)p↔np⁵(n+1)s transitions. Knowledge of the rate constants for collisional energy transfer and deactivation of the np⁵(n+1)p states is required to evaluate the laser potential for various Rg + buffer gas combinations. In the present study we have characterized energy transfer processes for Ne (2p⁵3p) + He for the six lowest energy states of the multiplet. Deactivation of the lowest energy level of Kr (4p⁵5p) by He, Ne and Kr has also been characterized. Preliminary results suggest that Kr (4p⁵5p) + Ne mixtures may be the best suited for optically pumped laser applications.

The technical solution of a CO laser facility for industrial separation of uranium used in the production of fuel for nuclear power plants is proposed. There has been used a method of laser isotope separation of uranium, employing condensation repression in a free jet. The laser operation with nanosecond pulse irradiation can provide acceptable efficiency in the separating unit and the high effective coefficient of the laser with the wavelength of 5.3 μm. Receiving a uniform RF discharge under medium pressure and high Mach numbers in the gas stream solves the problem of an electron beam and cryogenic cooler of CO lasers. The laser active medium is being cooled while it's expanding in the nozzle; a low-current RF discharge is similar to a non-self-sustained discharge. In the present work we have developed a calculation model of optimization and have defined the parameters of a mode-locked CO laser with a RF discharge in the supersonic stream. The CO laser average power of 3 kW is sufficient for efficient industrial isotope separation of uranium at one facility.

We have developed an autocorrelator utilizing multiphoton ionization of rare gases as a nonlinear medium to evaluate the pulse width of a femtosecond Ti:Sapphire laser at 882 nm. The autocorrelation width of 171 fs (FWHM) was evaluated by the autocorrelator utilizing nine-photon ionization of Ar. By using the ninth-order correlation factor of 1.06, the actual pulse width of 161 fs (FWHM) was determined, which was consistent to that of 165 fs (FWHM) measured with a two-photon autocorrelator. The autocorrelation measurement utilizing the multiphoton ionization of Ar should be applied to vacuum ultraviolet (VUV) ultrashort pulses at 126 nm, since neutral Ar atoms will be ionized by two-photon absorption. This method has a potential to become a versatile autocorrelator that characterizes femtosecond laser pulse widths in the wide spectral range between IR and VUV.