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(2P1/2), 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 72P3/2 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
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.