This PDF file contains the front matter associated with SPIE
Proceedings Volume 7196, including the Title Page, Copyright
information, Table of Contents, Introduction (if any), and the
Conference Committee listing
Generation of singlet oxygen and atomic iodine for operation of the chemical or discharge oxygen-iodine laser
(COIL/DOIL) is described, employing novel methods and device configurations proposed in our laboratory. A
centrifugal spray generator of singlet oxygen was developed, based on the conventional reaction between chlorine and
basic hydrogen peroxide. Recent results of theoretical and experimental investigation of the generator parameters are
presented. A new conception of the discharge generator of singlet oxygen was initiated, based on a combined DC arc jet
and RF discharge techniques. Principle of the generator currently developed and constructed is described. A new device
configuration was designed for the alternative method of atomic iodine generation using a radiofrequency discharge
decomposition of iodine compounds like CH3I or CF3I. Some recent experimental results of this research are also
Recent investigations of an Electric Oxygen-Iodine Laser system have shown that computational modeling over-predicts
the laser power output measured in experiments for similar gain conditions. To help resolve this
discrepancy, detailed 2-axis mapping of gain and gain recovery measurements downstream of an operating laser
cavity were performed. Modeling and analyses of the gain recovery experiments indicate that when the pumping rate
of I(2P1/2) by O2(a1Δ) is reduced by an effective factor of approximately 4 as a result of an unknown competing
reaction, the calculations are well matched to the experimental gain recovery measurements. The agreement
between the measured and modeled laser power extraction also significantly improves when the reduced effective
pumping rate is used. The results suggest that there may be a competing reaction that effectively reduces the
forward pumping rate as compared to the classical chemical oxygen-iodine laser kinetics rates. Understanding of
this kinetic process should enable us to accommodate or eliminate its impact on ElectricOIL performance.
Pulsed discharge is effective means to achieve high-peak lasing in COIL. Numerical model is developed for simulation
of pulsed discharge in gas stream from the singlet oxygen generator mixed with CF3I. The model comprises a system of
kinetic equations for neutral and charged species, electric circuit equation, and gas thermal balance equation. Sources of
iodine atoms under discharge and post-discharge conditions are analyzed. The dominant source in the discharge is
electron-impact dissociation of CF3I molecules. In post-discharge phase chemical reactions are identified giving notable
input into I production. Deformation of laser pulse waveform observed experimentally is explained by influence of these
Enhanced production of singlet oxygen, O2(a1Δg), was observed by reaction of O2/He discharge effluents on an iodine
oxide film surface in a microwave discharge flow reactor at 320 K. We observed a two-fold increase in the O2(a) yields in
excess of discharge-generated amounts for non-catalytic conditions. The iodine oxide surface appears to catalyze the
heterogeneous reaction to form O2(a) with high collision efficiency. Injection of molecular iodine into the catalytically
enriched active-oxygen flow resulted in excitation of the I(2P1/2) state approaching optical transparency at 1315 nm. Addition
of NO2 resulted in positive small-signal gain in the 320 K subsonic flow. The observed catalytic effect could significantly
benefit the development of electrically driven oxygen-iodine laser systems.
Herein the authors report on the demonstration of gain and a continuous-wave laser on the 1315 nm transition of atomic
iodine using the energy transferred to I(2P1/2) from O2(a1Δ) produced by both radio-frequency and microwave electric
discharges sustained in a dry air-He-NO gas mixture. Active oxygen and nitrogen species were observed downstream of
the discharge region. Downstream of the discharge, cold gas injection was employed to raise the gas density and lower
the temperature of the continuous gas flow. Gain of 0.0062 %/cm was obtained and the laser output power was 32 mW
in a supersonic flow cavity.
Electra is an electron beam pumped laser being developed at the Naval Research Laboratory as an inertial
confinement fusion (ICF) driver. Two opposing 500 kV, 100 kA electron beams pump the main amplifier, which
achieves energies of 730 J over a 100 ns pulse at 248 nm when run in an oscillator configuration. KrF lasers have been
shown to have intrinsic efficiencies of greater than 12% and, based on that, wall plug efficiencies of >7% are projected
for an IFE system based on our established improvements in laser physics and pulsed power technologies. The Electra
main amp has run at rep-rates of 1 Hz, 2.5 Hz, and 5 Hz in runs exceeding 10,000 shots.
This paper will present an overview of the Electra accomplishments and highlight recent research, including
integrating Electra's amplifiers into a durable full laser system, interferometric measurements of the near field spatial
distortions in the amplifiers and their effect on the far field profile, and spatially and temporally resolved temperature
measurements of the electron beam transmission foil.
High energy excimer lasers lend maximum flexibility to laser microprocessing, since virtually every
material is amenable to accurate, high resolution material ablation without subsequent post treatment. Due
to the UV photons provided with no up-conversion required as direct output by excimer lasers, output
powers of many hundred watts are easily achievable and are key to high throughput, and up-scaling
capability of manufacturing processes. In particular, the large flat-top excimer laser profile is well-suited
for most efficient parallel processing of two and three dimensional microstructures. Compact
micromachining concepts particularly suited for material ablation and surface activation will be
Parametric study of a slab first-overtone carbon monoxide laser was performed. The compact slab first-overtone CO
laser with active volume 3x30x250 mm3 was excited by a repetitively pulsed capacitive RF discharge (81 MHz or
60 MHz) with pulse repetition rate 100-500 Hz. The laser electrodes were cooled down to 120 K. Gas mixtures
CO:O2:N2:He with different component contents at gas pressures 15-22 Torr were used. Two laser resonator mirrors
sets were used in the experiments on multiline lasing. More than 100 spectral lines within the spectral range ~2.5-4.0
μm with maximum single line average output power 12 mW were observed. Total output power of the slab firstovertone
CO laser came up to 0.3 W, with maximum laser efficiency 0.5%. Special details of long time output laser
power behavior are discussed.
When it comes to highest power laser applications CO2-lasers are one of the most prominent choices. In most applications the raw laser beam which exhibits a Gaussian or Gaussian-like shape is employed. In contrast, homogeneous top hat profiles or customized beam shapes offer several application-specific advantages. Up to now the possibilities of beam shaping for CO2-lasers were very limited based on traditional approaches only. To make the advantages of homogeneous beam profiles also accessible for CO2 sources LIMO has expanded its range of production capabilities for the manufacturing of ZnSe micro-optics. LIMO's proprietary production technology is based on computer-aided design and no etching technique is involved at all. A Gaussian-to-top-hat converter made of ZnSe is demonstrated. The properties of the micro-lens surface, the generated beam profile with a CO2-laser as well as first application results are shown.
Studies were performed using self-channeled femtosecond laser pulses (filaments) interacting with various materials at a
distance of 30 meters. Using time resolved optical shadowgraphy, the filament interaction with the target is observed.
Shockwaves in both the target and the surrounding atmosphere are observed and their velocities measured. Estimations
of the shockwave energy are made from these observations. In transparent targets, optical coupling into the target
material is observed. This coupling results in optical damage lines in the material. Results of the filament interactions
will be discussed along with supporting modeling.
Lasing on the 62P1/2→62S1/2(D1) resonance transition of atomic Cs at 894.3 nm has been demonstrated in mixtures
of Ar, ethane, and Cs vapor by the photoexcitation of ground state Cs-Ar collision pairs and subsequent dissociation
of diatomic, electronically-excited CsAr molecules (exciplexes or excimers). The blue satellites of the alkali D2 lines
provide a pathway for optically pumping atomic alkali lasers on the principal series (resonance) transitions with
broad linewidth (>2 nm) semiconductor diode lasers. In this paper we discuss different variations of this new laser
system and the experiments of the initial demonstration.
We report on the results of our diode pumped alkali laser experiments. Using volume bragg gratings, we have produced
a 1.28 kW diode stack with a 0.35 nm bandwidth and ~70% of the power contained in the peak. We use two of these stacks to pump a 23 mm rubidium cell. We achieve 29 W of average output power at a 14% duty factor.
Scaling of alkali lasers to higher powers requires combining beams of multiple diode laser pump sources. For
longitudinal pumping this can be very complicated if more than four beams are to be combined. In this paper we report a
first demonstration of a transversely pumped Cs laser with fifteen laser diode arrays. The LDA pump beams were
individually collimated with a beam size of about 1 x 4 cm as measured at a 1 m distance from the diodes. All these
beams were incident on a cylindrical lens to be focused and coupled through the side slit of a hollow, cylindrical diffuse
reflector which contained the Cs vapor cell. We measured the output power and efficiency of the Cs laser for pump
powers up to 200 W at different cell temperatures. Although the values of output power and slope efficiency obtained for
this laser system were less than those for a longitudinally pumped alkali laser, these recent results can be significantly
improved by using a more optimal laser cavity design. The demonstrated operation of Cs laser with transverse pumping
opens new possibilities in power scaling of alkali lasers.
We describe a series of measurements of absorption and laser induced fluorescence using cells that contained cesium and
rubidium and krypton as a bath gas. These studies showed strong blue wing absorption to the short wavelength side of
the alkali atom D2 lines due to collisionally formed Cs-Kr or Rb-Kr excimers. These studies indicate that these species
may be appropriate candidates for optically excited Rb and Cs atomic lasers.
Alkali vapor lasers pumped by diode lasers are currently being investigated in several laboratories. One
problem with this type of device is the poor matching of the broad linewidth of the pump source with the
narrow absorption lines of the alkali atoms. A possible means for overcoming this difficulty is to use far-wing
line broadening effects that are associated with alkali - metal rare gas interactions. This concept has
recently been demonstrated for optical excitation of Cs-Ar dimers and collision pairs. Accurate data
concerning the upper and lower state potential energy curves of M-Rg pairs are needed to evaluate the
scaling possibilities for alkali metal rare gas dimer lasers. In addition to determining the details of the dimer
absorption spectra, knowledge of the ground state potential also permits calculation of the number density
of dimer pairs that will contribute to the absorption at a specific wavelength. In the present study we have
used theoretical potential energy curves to predict equilibrium constants for the M + Rg ↔ MRg systems
with M=Rb and Cs, and Rg=Ar, Kr and Xe. Excited state potential energy curves have been calculated for
CsAr, and these data have been used to investigate the ability of first-principles calculations to predict the
spectral properties of the Cs-Ar dimer.
We report on the first experimental demonstration of high order harmonic generation in rare gases directly
from a high power Ytterbium doped fiber chirped pulse amplification system. The laser delivers 270 fs pulses
in the 30-100 μJ energy range at repetition rate varying from 100 kHz to 1 MHz. A proper focalization allows
reaching several 1013W/cm2 in the gas jet. We have been able to produce and detect harmonics up to order 31
in Ar, Kr, and Xe at 100kHz repetition rate. Harmonic generation at 1 MHz is also demonstrated in Xe up to
We have demonstrated an argon excimer vacuum ultraviolet (VUV) amplifier at 126 nm by using the optical-field induced ionization (OFI) of argon. The gain-length product of 5.6 was achieved as a result of the optical feedback inside the amplifier with a VUV mirror. Plasma self-channeling caused by the high-intensity pump laser was simultaneously observed when the maximum gain-length product was observed. We have also optimized the output power of a subpicosecond VUV seed beam at 126 nm produced in low-pressure
rare-gases as a result of the seventh harmonic nonlinear wavelength conversion of a Ti:Sapphire laser at 882 nm.