IR scene generators are devices that simulate the IR radiation seen by heat seeking devices and IR detectors. Since the tracking accuracy is essential to heat seeking operation, a realistic high-resolution image is required. Current thermal RI scene generators use resistor array technology to generate an image whose size is on the order of 25mm square. We are building a 600mm X 600mm IR display systems with a scanned laser heating system for devices requiring a larger image size. Three high-powered CO2 lasers are raster-scanned over a thin kapton screen. Rapid modulation of the laser coordinated with the scanning produces a pixilated heated image that emits IR energy. The system is composed of a background heating system with two laser each scanning a 128 X 64 array and a hotspot heating system with one laser scanning a 40 X 40 array. The background system is fixed over the entire screen and simulates environmental IR while the hotspot system can be scanned anywhere on the screen and simulates a target. Convective cooling is used to increase spatial resolution and temporal response. An IR camera provides closed loop optical feedback for the system.
Theoretical investigation has been made to describe the discharge in CO2 lasers excited by high frequency magnetic-confined discharge. The distribution of the electron energy was considered to be a Maxwellian and the most important collision cross sections were considered, the energy balance equation for electron can be put up under the influence of the magnetic field. The evaluation of the present model was performed for gas mixtures of CO2, N2, and He, the influence of the electron energy on the intensity of the magnetic field and the spatial distributions of the electron density and electric field were presented in this paper.
We reported a discharge configuration for the slab CO2 laser excited by switching power, and the frequency of the power sources is about 300 kHz. The discharge was confined between two water-cooled narrow gap anodized aluminum plates. The uniform stable discharge was obtained in the volume of 4 X 30 X 400 mm3, the input power density is about 25W/cm3. The measurements of gain in the discharge show that this configuration is suitable for the high power CO2 laser.
For developing a new laser for laser cutting, which has the advantage of good beam quality, small size and low cost, we have proposed a round-metal-resonator CO2 laser with blow-in discharge and spiral flow. In this paper, investigations have been made on the resonator and beam quality of this laser. At first the ideal of the new laser is introduced in this paper. And secondly, the new structure for carbon dioxide laser is explained. Thirdly, investigations have been made on the resonator and the output beam quality of the carbon dioxide laser. The resonator parameters are determined by the matrix optics calculations and by considering the size of experimental structure and the basic design principles of resonator. The output laser intensity spacial distribution of the laser resonator with gain spacial distribution inside is obtained by solving the diffraction integral equations through iteration method. The results indicate that from the new structure laser, the quasi-fundamental mode laser beam can be obtained with a higher efficiency. The ideas to improve the gain distribution in the lasing channel, and then the quality of the mode of the output beam arise from these calculations.
Laser processing of metallic surfaces using a fs pulse laser has bene shown to produce novel effects. We demonstrate nanoscaled surface texturing effects of aluminum alloy 2024 using femtosecond pulse laser irradiation. The laser source is a 248-nm excimer laser with a pulse width of 500fs delivering a laser output fluence in a range from 0.02 to 10 J/cm2. The micrographs of the scanning electron microscopy have been characterized as a function of incident laser fluence. Results indicate that the surface futures, ranging from nanoscale to microns, can be developed through variation in fluence intensities. Advantages of femtosecond pulse laser for precise metal microstructuring and physical mechanisms for ultrashort pulse laser ablation have been discussed.
Energy, temporal and spectral characteristics of HF-laser pumped by non-chain chemical reaction initiated by radially converging e-beam, planar e-beam and non-self-sustained discharge have been investigated. The major channels of vibrationally excited HF molecules formation have been analyzed. It has been confirmed that the high efficiency of non-chain HF laser can be reached only by simultaneous atomic and molecular fluorine formation under the action of e-beam and molecular fluorine participation in the inversion releasing process. It is shown that the laser pulse has a complex spectral-temporal structure caused by consecutive generation of the P-lines and overlapping of the rotary lines of the same oscillatory band and separate oscillatory lines during a pulse of radiation. With e-beam pumping of a 30 1 active volume laser, the output energy as high as 115 J and efficiency with respect to e-beam energy deposited into gas mixture up to 8 percent were demonstrated. The optimal gas mixture SF6: H2 equals 8:1 under pressure of 0.45 atm has been obtained. At pressure 1.1 atm and non-uniform output distribution, total laser energy and efficiency with respect to e-beam energy deposited into gas were found to be up to 200 J and 11 percent respectively. E-beam initiated low pressure pulsed discharge for excitation HF molecules leads to increase of radiation energy in 2.8 times.
A large progress was achieved during the 34 years period of development of the lasers on self-terminating transitions (STT) from the upper resonant to the lower metastable levels. The number of obtained laser lines on STT in atomic and ionic spectra is not less than 44. The parameters of the lasers are also impressive. An average power of 201 W with efficiency of 1.9 percent was achieved in the Cu-vapor of the so-called HyBrID laser. At the same time no effective lasers on STT in the blue spectra were developed. In the combination with the green Cu-vapor and the red Au-vapor lasers an effective blue laser can be useful to the elaboration of the color optical projection system that amplifies the brightness of images. The Bi-vapor and the Fe- vapor blue lasers tested until now do not satisfy the average power and efficiency requirements. We have suggested the titanium atom to obtain laser oscillation o several STT in the blue-green spectral region that fully satisfy the Gould criteria for efficient lasers on STT. An additional stimulus was that the laser oscillation on the above- mentioned transitions was achieved by N2-laser pumping of the titanium vapor. We provided the calculations of the kinetics of excitation and ionization of titanium atoms in saturated power approximation which clearly shows the population inversion at least on two TiI STT. The extremely low pressure of the saturated Ti vapor at acceptable temperatures strongly prevents the practical use of pure Ti vapor for the STT laser. To solve the problem of Ti laser on STT we had to undertake three different methods to obtain Ti atoms in the discharge: a) the principal experiments with exposed Ti-wire might answer on the question of perspective of Ti atom for the STT laser; b) the experiments including the process known as 'iodine method of rectification'; c) the cathode sputtering of titanium cathode in the hollow- cathode discharge. Nevertheless, lasing action had not yet been achieved but all the three methods are now in progress to elaborate the blue Ti-vapor laser on STT.
The results of the Singlet Oxygen Generator with Twisted Aerosol flow (TA-SOG) investigations are presented. The experimental results demonstrate TA-SOG output values exceed those of other types SOGs known from publications. TA-SOG outflow is aerosol-free all over the broadly ranged parameters even at a gas pressure over 100 Torr and velocity 100 m/sec. The maximal chemical efficiency was obtained as 70 percent. The reactor cross-sectional electronic energy flux exceeds 1.5 kW/cm2. Measured Singlet Oxygen (SO) yield was approximately 60 percent at the pressure 12- Torr at the measurement point distant by more than 10 cm of reactor outlet. Chlorine utilization exceeds 90 percent. All the listed parameters were obtained without any buffer at its outlet. It is directly connected to COIL supersonic nozzle not fearing BHP carryover. So, TA-SOG output and nozzle input pressures are almost equal without additional ejectors. TA-SOG model created provides atmospheric pressure of the spent solution at SOG outlet, which simplifies sufficiently the re-circulation system design.
The developed supersonic COIL with 5 cm gain length was driven by Verti Jet SOG having 0.28 liter of working volume. The oxygen was diluted by the primary nitrogen downstream from the JSOG. Two types of nozzles were tested: single throat nozzle with 10 mm throat height and double throat height 15 mm. The COIL with single throat nozzle operated at the primary nitrogen dilution O2:N2 equals 1:1 and the chlorine flow rate less than 40 mmole/s to maintain the designed gas flow conditions in the reactor of JSOG. The maximum power 765 W has been achieved at 39 mmole/s of the chlorine molar flow rate. The using of double throat nozzle allowed to increase chlorine moral flow rate up to 75 mmole/s. In this case the maximum power 1.4 kW has been reached for primary nitrogen ratio O2:N2 equals 1:1.28. The specific performance so f 5 kW per 1 liter of the reactor volume, of 100 W/cm2 per unit of the stream cross section are in the cavity and of 2,7W of the pump capacity were obtained.
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.
In a chemical oxygen-iodine laser (COIL), chemically prepared, gaseous gain medium at 3-10 Torr pressure is drawn through the laser cavity by vacuum suction. Multiple-stage vacuum pumps such as Roots blowers or steam ejectors are typically used to receive and compress the gas flowing from the laser and exhaust it to the atmosphere. The size and weight of such vacuum pumps present a significant challenge to engineering and packaging a transportable COIL system.
The chemical oxygen-iodine laser (COIL) uses a reaction of gaseous chorine and aqueous solution of basic oxygen peroxide (BHP) to produce oxygen singlet delta molecules, O2(1(Delta) ). Quenching of O2(1(Delta) ) during its extraction from the BHP solution and quenching of excited atomic iodine I* by water vapor from the O2(1(Delta) ) production process are well-known parasitic effects in COIL. This paper shows that both of these effects can be significantly reduced by replacing the hydrogen 1H1 isotope atoms in BHP by the 1H2 isotope atoms. In addition to restoring laser power lost to parasitic quenching, use of basic deuterium peroxide (BDP) rather than BHP is expected to allow generation of O2(1(Delta) ) at elevated temperature. This approach promises to save refrigerant, reduce the risk of BDP freezing, and delay precipitation of salt form BDP solution. Methods for producing BDP are outlined.
The possibility to produce high concentrations of singlet delta oxygen, enough to operate oxygen-iodine laser, using discharge techniques without dangerous chemicals was investigated. The results of study of singlet oxygen yield in the vortex-flow glow discharge in pure oxygen are presented. The discharge in the vortex flow is used because it permits to have extremely stable CW discharge with very high power load at high pressures.
Powerful electron and beams of nanosecond and microsecond length produced by diode electron guns with explosion- and self-emission cathodes are widely used in high-density energy physics. Analytical and experimental investigations of the relativistic electron beam propagation in a heavy gas mixture are presented in this paper.
High-pressure subsonic mode operation of chemical oxygen- iodine laser (COIL) is studied. In this mode, the singlet oxygen generated by the liquid-jet singlet oxygen generator (SOG) is directly utilized in the optical cavity without supersonic expansion. Drastic reduction of the required vacuum pump capacity, and iodine consumption was obtained. We have demonstrated a 25.0 percent of chemical efficiency with a small-scale device. The scale-up version of the COIL is developed and initial tests are conducted. The device is so designed that it will operate for 2 hours at 1kW laser output. Due to the inadequate heat exchanger of basic hydrogen peroxide (BHP), performance of the system was not yet satisfactory. However, a 30-minute continuous operation o the counter-flow type jet SOG with recirculation of BHP was demonstrated for the first time.
An advanced mixing nozzle concept has been developed for high chemical efficiency, high pressure recovery chemical oxygen-iodine laser applications. This concept incorporates the use of mixing tabs mounted at the nozzle exit plane for generating structured streamwise vorticity for mixing enhancement. The tab vortex generators produce strong streamwise vortices for mixing entrainment of highly compressible mixing layers. The optimal tab configuration, dimension, ramp angle relative to the flow direction, and tab spacing were determined by CFD analyses. The CFD computations show the entrainment and mixing produced by these mixing tabs are very efficient. The predicted mixing effectiveness of this nozzle configuration has been validated by experimental Pitot pressure scans of a three- blade nozzle hardware assembly.
A spontaneous Raman scattering system has been developed which can monitor the yield of a COIL singlet oxygen generator performance in real time. This approach permits one to directly measure [O2(a1(Delta) )] and [O2((Chi) 3(Sigma) )] simultaneously by monitoring their Raman spectra on the same ICCD array. This technique is reviewed and the major sources of error discussed and analyzed. The uncertainty in the Raman cross section limits the accuracy of the measurement technique. With the current uncertainty of the Raman cross section, this technique gives an accuracy of better than 2.5 percent in the yield measurement at 50 percent yield.
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.
The dismantlement of obsolete nuclear facilities is a major challenge for both the US Department of Energy and nuclear power utilities. Recent demonstrations have shown that lasers can be highly effective for size reduction cutting, especially for the efficient storage and recycling of materials. However, the full benefits of lasers can only be realized with high average power beams that can be conveniently delivered, via fiber optics, to remote and/or confined areas. Industrial lasers that can meet these requirements are not available now or for the foreseeable future. However, a military weapon laser, a Chemical Oxygen Iodine Laser (COIL), which has been demonstrated at over a hundred kilo Watts, could be adapted to meet these needs and enable entirely new industrial applications. An 'industrialized' COIL would enable rapid sectioning of thick and complex structures, such as glove boxes, reactor vessels, and steam generators, accelerating dismantlement schedules and reducing worker hazards. The full advantages of lasers in dismantlement could finally be realized with a portable COIL which is integrated with sophisticated robotics. It could be built and deployed in less than two years, breaking the paradigm of labor-intensive dismantlement operations and cutting processing times and costs dramatically.
We discuss recent progress in the development of sensitive, diode laser based diagnostics for chemical oxygen iodine lasers. These diagnostics have been developed to the point where multiple species, temperature, and velocity in the flow can be determined. This paper focuses on measurement of collisional broadening parameters that are needed to extract the transnational temperature from the flow. We report the temperature dependance of collisional broadening coefficients for the (3,4) hyperfine transition with helium and oxygen bath gases.
Water vapor measurements at DLRs supersonic chemical oxygen iodine laser (COIL) have been carried out applying a tunable diode laser system. During a typical hot flow of 8 s, the water molar flow rate increases from 35 mmol/s to 85 mmol/s. Simultaneous measurements in the subsonic and supersonic region showed that about 10 percent of water in front of the expansion nozzle is lost. Standard mathematical expressions for water vapor pressure have been used to estimate the water partial pressure over basic hydrogen peroxide from the gas temperature measured by thermocouples at the exit of the singlet oxygen generator. A second tunable laser diode system was used to measure the iodine small signal gain for different iodine flow rates. Gain values were found at 1.2 percent/cm. From the recorded iodine atom absorption profiles the temperatures were calculated to be 190-220 K. The high starting temperatures are in accordance with the water measurements and a temperature increase due to water condensation.
Stimulated Brillouin scattering (SBS) and wave front phase conjugation of CO2 laser radiation in compressed xenon placed into low Q resonator of this same laser has been demonstrated experimentally for the first time. The action on nonlinear medium was carried out by opposing focused beams of multimode radiation. The difference in resonator longitudinal mode frequencies was set equal to the frequency of the acoustic wave excited by the radiation with 9.584 micrometers wavelength at SBS. Radiation pulse duration was close to acoustic phonon lifetime. In experiments the SBS excitation was manifested longitudinal mode synchronizing, power and energy rise and also in increasing laser radiation oscillation duration and in decreasing divergence to diffraction limit.
In our work we investigate the dependence of the CPT canyon width and depth on the radiation fields intensities fields intensities and detunings, the magnetic fields strength and the relaxation constants. We solve the problem of population dynamics for the system of 6P½ 6P3/2 and 7S½ levels of tallium, interacting with two linear polarized monochromatic laser fields and magnetic field, which is perpendicular to the laser propagation direction. Chosen configuration of E- and H-vectors permit us to separate three-level (Lambda) -type system of magnetic sublevels which is uncoupled by radiation fields with the other sublevels. The full set of density matrix equations is solved by a computer. We find the parameters values for which the canyon width is minimal and the depth is maximal. We show that the magnetic field breaks the conditions of equality of laser fields frequencies detunings for CPT. We observe the decreasing of canyon width and depth with increasing of the magnetic field.
The theory of interaction of intense bichromatic field of laser radiation with multilevel atomic system in the external magnetic field is considered. The magnitudes of interaction are much larger than the width of atomic levels. The vector-potential of radiation field consisting of two monochromatic components with the frequencies resonant to adjacent transitions is taken in electric dipole approximation. The eigenvalues and eigenstates of the Hamiltonian, including spin-orbit interaction and interactions with laser radiation and external magnetic fields, are found without perturbation theory using resonant approximation. When the effects of resonantly excited radiation are considered the Hamiltonian of interaction with the weak field of scattered radiation is included also. Its eigenfunctions are found with the help of perturbation theory. We consider tow types of effects: polarization effects and effects of resonantly excited radiation. As the atomic system is multilevel we use the numerical methods. The influence of the magnetic field on coherent population trapping effect for multilevel systems is considered. Some of our theoretical results coincide with known experimental ones.
The evolution of laser technology is one of the most significant events in modern science. Beginning in 1960, laser technology has advanced from an elementary form of maser technology to the highly complex output power laser system. The purpose of this research is to determine the dependence of the output power laser on temperature, gas mixture pressures, input power and the brewster angle. In addition, the researcher calculated the molecular properties of CO2. The researcher established procedures to measure the changes of gas mixture pressures, input power and brewster angle. In addition, the researcher examined the temperature as a function of gas mixture pressure, output power as a function of temperature, gas mixture pressure, input power and the brewster angle. In order to calculate the molecular properties of CO2, the researcher used CNDO and MOPAC.
A calibrated piston source of light, which simulates a cylindrical-volume source, has bene used to measure the absolute concentration of O2(a1(Delta) ). It is proved that this Piston Source Method is one of the simplest and most convenient ways to measure the O2(a1(Delta) ) concentration in a singlet oxygen generator, especially in real time measurements.
New fits to the molecular iodine dissociation rate data of Heidner et al. Were obtained with the goals of achieving a better overall representation of the experimental data and determining a set of rate constants compatible with the assumption that the dissociation intermediate I2dagger is vibrationally excited I2. Improved rate constants were obtained that are significantly different from those used in current computational models of COIL systems. While the new rate constants provided a better representation of the experimental dat, troubling discrepancies remain. New reactions involving electronically excited iodine (I2*) were then added to the model in an attempt to resolve these discrepancies. Preliminary calculations indicate that I2* kinetics provide only a minor path to dissociation and that these model deficiencies will not be resolved by adding electronically excited iodine channels.
The IR free-electron laser (IR FEL) at Jefferson Laboratory has achieved steady-state 3 micron lasing at a power level of 1.7 kW. Efforts to upgrade this device to 10 kW operation over the next three year are underway. As a result of this success and recent technology advances, free-electron lasers (FEL) should be considered a serious option for high-power, commercial material processing and military applications. The discriminating attributes of FELs are their wide-band tunability, their implicit potential for very high-power operation due to the vacuum lasing medium, and the intrinsic picosecond pulse structure that promises superior performance in certain material processing applications. Applications spanning high-value-added micromachining to low-value-added, high-power, high-throughput surface processing of metals and polymers are identified. The projected economics and market insertion point for a potential commercial application in polymer processing is described. Concepts for compact high-power FEL systems based upon superconducting RF accelerometers with energy recovery are defined. Key technology issues on the path to commercial deployment, such as the demonstration of reliable, high- current photo-cathode injectors, are identified and discussed. It is concluded that the first commercial material processing FEL beta units could be coming on line in about five years.
Mirror heating in a high power FEL can alter the optical mode and affect the gain of the laser. This can lead to a large reduction of the laser power from ideal values. Measurements of the power and mode size in the Jefferson Lab IR Demo laser have shown clear evidence of mirror distortion at high average power loading. The measurements and comparisons with modeling will be presented. Both steady state and transient analyses and measurements are considered.
An estimate for the mass of a nominal high-energy laser system envisioned for space applications is presented. The approach features a diode pumped solid state Yb:YAG laser. The laser specifications are10 MW average output power, and periods of up to 100 seconds continuous, full-power operation without refueling. The system is powered by lithium ion batteries, which are recharged by a solar array. The power requirements for this system dominate over any fixed structural features, so the critical issues in scaling a DPSSL to high power are made transparent. When based on currently available space qualified batteries, the design mass is about 500 metric tons. Therefore, innovations are required before high power electrical lasers will be serious contenders for use in space systems. The necessary innovations must improve the rate at which lithium ion batteries can output power. Masses for systems based on batteries that should be available in the near future are presented. This analysis also finds that heating of the solid state lasing material, cooling of the diode pump lasers and duty cycle are critical issues. Features dominating the thermal control requirements are the heat capacity of garnet, the operational temperature range of the system, and the required cooling time between periods of full operation. The duty cycle is a critical factor in determining both the mass of the diode array needed, and the mass of the power supply system.
Techniques for autonomous alignment of beam control systems have been developed for a number of technologies including laser resonators, telescopes, and optical components. These techniques have been designed to perform remote autonomous alignment on space-based optical systems. This paper present an alignment procedure based on a modified Downhill Simplex optimization algorithm using the attributes of the optical system's far-field image as a figure of merit. Investigations using numerical simulations have demonstrated that this methodology is robust and viable as an approach for alignment of the wide field-of-view three-mirror beam expander developed under the Advanced Beam Control System (ABCS) program. Following computer simulations, we conducted laboratory experiments to validate the far-field optimization concept using the ABCS brassboard optical system. The potential utility of far-field optimization to the alignment of other optical systems such as Space-Based Laser is briefly discussed.
After successful testing at the Raytheon facility in Danbury, Connecticut, the completed SAAO adaptive optical system has been shipped to the AEOS site on Haleakala, Maui, Hawaii. The system is undergoing final integration with the AEOS observatory. This paper describes the adaptive optics system design, including an overview of al major subsystems, the electronics, and the software. We discuss the design trades and system engineering that led to the final configuration. Also included is a review of opto-mechanical aspects of the system.
This paper describes a set of detailed modes, set up in frequency domain and in time domain, that were used to support the analysis, design, test and performance verification phases of the SAAO Adaptive Optics (AO) System, which is being installed atop the 10000 ft Haleakala on the island of Maui in Hawaii. The AO system consists of a 941 actuator deformable mirror, a state-of-the-art 32 by 32 channel wavefront sensor and high speed reconstructor and control electronics, a high bandwidth fast steering mirror and sensor for tracking and jitter control, and the various other optical elements that are essential to close the AO loops. The high fidelity of the mode, which includes details such as the optical misregistrations, timing latencies, wave optics and atmospherics, allows us to tune it to match test results. Thus anchored, the mode is then sued to make performance predictions. The model provides a valuable tool in understanding and testing such highly complex electro- optic systems.
This paper describes laboratory evaluations of the SAAO Adaptive Optics (AO) System, which is installed at the Air Force AEOS facility at Haleakala on the island of Maui in Hawaii. The AO system includes a 32 by 32 channel wavefront sensor, a high-speed wavefront reconstructor, a 941-actuator deformable mirror, a high-bandwidth steering mirror, and a tracking sensor for tilt control. The performance metrics discussed include track bandwidth, track jitter vs. target brightness, AO system temporal response, and the resulting Strehl ratios and MTF for a range of target brightness. Test methods and results are described.
A beam control system capable of jitter stabilization and rapid slew angles for a 30 cm diameter clear aperture laser radar (LADAR) was developed and tested. It has achieved greater that 40dB error rejection at low frequencies and also attained low jitter levels. These attributes will enable the LADAR system pointing jitter error to achieve sub 10 (mu) rad levels in flight tested. Additionally, the fast slew rates will allow targets to be acquired quickly such that LADAR data collection can commence in a very short time following initial acquisition.
The operation of various designs of a Faraday isolator with different orientation of a magneto-optical crystal is studied theoretically. It is shown that for different configuration of the isolator, different crystal orientations may be optimal. An original technique was used to measure thermo-optic constants for a terbium gallium garnet crystal which characterize the photoelastic effect. Measurements were made for different orientations of crystallographic axes: (001), (110), (111), as well as for crystals grown by different producers. The results are compared with theoretical estimation. Values of the constants are presented, allowing one to choose such crystal orientation which is optimal from the point of view of isolation at high average power.