The Department of Navy has been pursuing a technology development program for advanced, all-fiber, Ultra Short
Pulsed Laser (USPL) systems via Small Business Innovative Research (SBIR) programs. Multiple topics have been
published to promote and fund research that encompasses every critical component of a standard USPL system and
enable the demonstration of mJ/pulse class systems with an all fiber architecture. This presentation will summarize
published topics and funded programs.
The use of lasers for Electronic Warfare applications will be discussed and reviewed. Specific examples of deployed
EW systems which include lasers will be presented along with a discussion of their most salient features.
Forty years after the publication from Shank and Ippen on the generation of subpicosecond laser pulses we are witnessing an explosion in the number of applications for ultrashort pulsed lasers (USPL).1 While some technologies are invented and applied in industry without delay, there has been a significant delay in the deployment of femtosecond lasers. Ultrashort pulsed lasers used to require a laboratory environment and in many cases included flowing laser dye solutions that made them extremely impractical. The development of chirped pulse amplification for solid state and fiber lasers2,3 has changed the landscape and has made available intense USPL sources that can be operated outside the laboratory. This in turn has opened numerous applications in the materials processing and medical devices markets. In this special section we present a collection of papers that is representative of some of the advancements and applications in USPL design and applications.
KEYWORDS: iodine lasers, Chlorine, Chemical species, Fluorine, Iodine, Energy transfer, Chemical oxygen iodine lasers, Combustion, Absorption, Chemical lasers
The measurement of positive small signal gain on the 1.315 micron spin orbit transition of atomic iodine following energy transfer from chemically generated NCl(a1Δ) is reported. Previous instances of gain produced by energy transfer from NCl(a1Δ) used DC discharges to generate F and Cl atoms; this report describes recent progress towards a true chemical laser device which uses a high temperature chemical combustor and a supersonic reactor to generate NCl(a1Δ). These improvements represent a significant step towards the development and demonstration of a scalable All Gas-phase Iodine Laser (AGIL) device.
KEYWORDS: iodine lasers, Temperature metrology, 3D modeling, Chemistry, Process modeling, Chemical reactions, Computer simulations, Chemical species, Chlorine, Optical simulations
This work revisits the finite-rate chemistry mechanism for AGIL in light of recent rate measurements for kinetic processes. The effect of temperature dependence of kinetic processes measured only at room temperature conditions is explored by assuming a square-root dependence upon temperature in line with kinetic theory. A sensitivity study is performed to elucidate the relative impact of each chemical kinetic process modeled with respect to the larger set of modeled chemical kinetic processes. And reactant mixing is examined, with documentation of the effects of the reactant mixing predictions upon recent multi-watt power extraction experiments.
The demonstration and characterization of a multiwatt All Gas-phase Iodine Laser (AGIL) are described. A 20-cm subsonic reactor was used to produce NCl(a1Δ) for a series parametric studies of the I*(2P1/2) - I(2P3/2) small signal gain and extracted power dependence on reactant flow rates and reaction time. A reduction in the flow channel height led to improved performance. The highest measured gain was 4.2 x 10-4 cm-1 and the highest power observed was 31 W.
The uncertainty in both the fluorine atom concentration and the gain length has inhibited the development of accurate and device independent models of HF overtone lasers. Furthermore, previous methods of measuring the small signal gain were cumbersome and could not easily generate spatial maps of the gain in the cavity. Experimental techniques have been developed to directly measure the concentration of fluorine atoms, the gain length and the small signal gain in a hydrogen fluoride 5 cm slit nozzle laser. A gas phase titration technique was utilized to measure the fluorine atom concentration using HCl as the titrant. The gain length was measured using a pitot probe to locate the interface of the primary flow with the high Mach number shroud flows. A tunable diode laser was utilized to perform small signal gain measurements on HF overtone (ν=2→0) transitions.
KEYWORDS: Hydrogen fluoride lasers, Chemical species, 3D modeling, Energy transfer, Turbulence, Fluorine, Laser systems engineering, Chemical reactions, Molecules, Laser resonators
The small signal gain of a small-scale HF overtone laser was measured using a sub-Doppler tunable diode laser system. The spatially resolved, two-dimensional small signal gain maps that were generated show a highly inhomogeneous gain medium indicating the dominant role played by mixing of the H2 and F streams in HF laser performance. The measured gain data were analyzed with the aid of a two-dimensional computational fluid dynamics model. The results show that reactant mixing mechanisms have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms, including reaction rate constants and reactant concentration, have a greater effect on the maximum system gain.
A review of recent advances in chemical laser technology is presented. New technology and concepts related to the Chemical Oxygen Iodine Laser (COIL), All Gas-phase Iodine Laser (AGIL), and HF Overtone Laser are discussed.
The demonstration and characterization of a multiwatt All Gas-phase Iodine Laser (AGIL) are described. A 20-cm subsonic reactor was used to produce NCl(a1Δ) for a series parametric studies of the I*(2P1/2) - I(2P3/2) small signal gain and extracted power dependence on reactant flow rates and reaction time. A reduction in the flow channel height led to improved performance. The highest measured gain was 4.2 x 10-4 cm-1 and the highest power observed was 31 W.
Overtone small signal gain data measured while operating a small-scale HF laser saturated on the fundamental transitions are compared with fundamental lasing output spectra and spontaneous overtone emission spectra measured orthogonal to the lasing axis. In all cases, the data are consistent with an equilibrium rotational distribution. These results are discussed in terms of their applicability to the question of rotational nonequilibrium in cw HF lasers.
KEYWORDS: Hydrogen fluoride lasers, Chemical species, Diffusion, Data modeling, Fluorine, Laser systems engineering, Turbulence, 3D modeling, Chemical reactions, Computer simulations
The small signal gain of a small-scale HF overtone laser was measured using a sub-Doppler tunable diode laser system. Measurements of reactant concentration, flow velocity and gain length were also made. The spatially resolved, two-dimensional small signal gain and temperature maps that were generated show a highly inhomogeneous gain medium indicating the dominant role played by mixing of the H2 and F streams in HF laser performance. The measured gain and temperature data were analyzed with the aid of a two-dimensional computational fluid dynamics model. The results show that reactant mixing mechanisms have a large effect on the gain averaged over a vertical profile while kinetic rate mechanisms, including reaction rate constants and reactant concentration, have a greater effect on the maximum system gain.
We present preliminary results of an effort to develop an ultra-sensitive, diode laser-based diagnostic for NCl(X), an important species in the all gas phase iodine laser. This system uses a narrow band, tunable diode laser to probe transitions within the (0,0) band of the NCl(b - X) system near 662 nm. We provide a description of our detection and calibration strategies and present initial calibration results.
The demonstration and characterization of a multi-watt All Gas-phase Iodine Laser (AGIL) are described. A 20-cm subsonic reactor was used to produce NCl(a1Δ) for a series of parametric studies of the I*(2P1/2)-I(2P3/2) small signal gain and extracted power dependence on reactant flow rates and reaction time. The highest measured gain was 2.5x10-4 cm-1 and the highest power observed was 18 W.
A tunable diode laser was used to probe the overtone gain medium of a small-scale HF laser. Two-dimensional, spatially resolved small signal gain and temperature maps were generated for the P(3) ro-vibrational transition in the first HF overtone band.
KEYWORDS: Hydrogen fluoride lasers, Molecules, Energy transfer, Chemical species, Temperature metrology, Laser systems engineering, Fluid dynamics, Computational fluid dynamics, Data modeling, Fluorine
An abbreviated review of rate coefficients relevant to HF laser kinetics modeling is presented. The literature has been surveyed from the last published review in 1983 to the present. Updated HF Einstein emission coefficients are tabulated. This brief summary of a more detailed review addresses rate coefficients relevant to HF generation, reactive quenching, self-relaxation, and vibrational relaxation by a selection of atoms and molecules. In addition, a review of recent experiments and theoretical calculations relevant to the role of rotational non- equilibrium in HF lasers is presented. A list of recommended temperature dependent expressions for critical reaction rate coefficients is given.
A tunable diode laser was used to probe the overtone gain medium of a small-scale HF laser. 2D, spatially resolved small signal gain and temperature maps were generated for the P(3) ro-vibrational transition in the first HF overtone band.
The rate constants for H atom reactions with Cl2 and F2 have been measured by monitoring the loss rate of hydrogen atoms in the presence of excess [Cl2] and [F2] via time-resolved, laser-induced Lyman-a fluorescence. The rate constants for H + F2 and H + Cl2 were found to be 2.4 +/- 0.4 X 10-12 and 2.52 +/- 0.18 X 10-11 cm3 molecules-1 s-1, respectively. The result for H + F2 is consistent with the recommendation of Baulch et. al. (J. Phys. Chem. Ref. Data 10 (suppl. 1) (1981)) and our k(H + Cl2) value is consistent with the majority of previous measurements.
CW laser action has been demonstrated on the electronic I* (2P1/2) ? I (2P3/2) transition of atomic iodine at 1 .3 15 ?m from the NC! (a1Æ) + I (2P 3/2) energy transfer reaction. The stimulated emission was generated in a transverse subsonic flow device when hydrogen azide, HN3, was injected into a flow of iodine and chlorine atoms. The measured laser output power was 180 mW.
CW laser action has been demonstrated on the electronic I* (2P1/2) yields I(2P3/2) transition of atomic iodine at 1.315 micrometer from the NCl (a1(Delta) ) + I(2P3/2) energy transfer reaction. The stimulated emission was generated in a transverse subsonic flow device when hydrogen azide, HN3 was injected into a flow of iodine and chlorine atoms. The measured laser output power was 180 mW.
Metastable NCl(a1(Delta) ) is a promising energy carrier for use in chemically driven iodine lasers. The present studies of NCl(a) kinetics and demonstration of a non- intrusive method for detecting NCl(X) were conducted in support of efforts to develop an NCl(a)/I laser system. Photolysis of ClN3 by O2, H2, HCl, Cl2 and ClN3 were determined. The result were consistent with recent measurements made in a discharge flow system. NCl(X) was detected via transient absorption of the b-(chi) system. A CW ring dye laser was used to record a high-resolution spectrum of the origin band. Time resolved absorption measurements were used to examine the kinetics of NCl(X) formation and decay.
KEYWORDS: Chlorine, Molecules, Chemical species, Temperature metrology, Micro optical fluidics, Chemical lasers, Chemical oxygen iodine lasers, Halogens, Hydrogen, Human-computer interaction
The rate constant for Cl + HN3 over the temperature range 300-480 K has been studied in a flow reactor. Based on the rate of loss of HN3 and the rate of NCL(a1(Delta) ) generation, the temperature dependence of this reaction is described by the collision theory expression 1.2 +/- 0.3 X 10-11 T0.5 exp(-1514 +/- 93/T), with E0 equals 3.0 +/- 0.2 kcal mol-1 or an Arrhenius fit k(T) equals 2.0 +/- 1.0 X 10-10 exp(-1452 +/- 150/T) with Ea equals 2.9 +/- 0.2 kcal mol-1.
A direct measurement of gain on the electronic I (2P3/2) - I*(2Pi/2) transition of atomic iodine at 1.315 jam using tunable diode laser is demonstrated. The population inversion results from the efficient energy transfer between NCI (alA) metastables and I (2P3/2) atoms. Ground state iodine atoms and NCI (a1 A) metastables are produced in a transverse subsonic flow device from the stepwise reaction of Cl atoms with HI followed by the reaction of Cl with azide (N3) radicals, respectively. Under current experimental conditions, a gain of 0.020%/cm is obtained and appears to be limited by reagent number density. A kinetic model was constructed to simulate the experimental gain profile using a mechanism consisting of fully coupled finite rate chemistry and 1-D fluid dynamics. Good agreement with experimental and theoretical calculations are obtained. Keywords: Gain, population inversion, atomic iodine, NCI (a*A) metastables, azides, energy transfer
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