A CO2 electric discharge simulation program has evolved over the past twenty years, and has success-fully been used in the analysis, design, and post-test rationalization of a variety of systems, both industrial and military, CW and pulsed, operating over a wide range of conditions. Laser kinetics are accurately modelled by using the best-available measured rates and by simultaneously solving four integro-differential state equations, the overall energy equation, and the laser photon conservation equations(s). Discharge pumping rates have been correlated from Boltzmann code predictions. The model is described, important dimensionless parameters are identified, and results for small-signal gain and extracted power are presented and interpreted. The conditions have been specifically selected to show the most significant trends with pressure level, gas mixture, and other major independent design variables.
A transverse-flow, cross-discharge cw-C02 laser with an auxiliary glow-DC-discharge was developed. The maximum input power increased twice to four times as large as that without the auxiliary discharge. A single-path resonator with 65 mm-aperture and a Z-path resonator with 45 mm-aperture were set up. The output power exceeding 3 kW was obtained for both type resonators with 40 cm-long-discharge area. We deduced an equation which gave the output power for the Z-path resonator. The calculated results agreed with the measured output power.
A description of a reliable industrial repetitively pulsed high-power CO2 laser is presented. The laser is capable of continuous operation at variable repetition rates (between 1 and 10 Hz) and variable energy per pulse (100 to 1400 joules per pulse) resulting in a large range in average power (i.e. between 100 watts and 14 kilowatts). The system is modular and includes the laser, power supplies (sustainer and E-beam pulse power systems) cooling systems and optics.
rave optics codes are Physical optics models based on the scalar wave approximation to Maxwell's equations. These codes model the propagating wave front as a complex field of amplitude and phase. The Teledyne Brown Aero Optics Quality Code is am extension of the Systems Optical Quality (SOW code developed for the Air Force 'Weapons Laboratory as a, C02 gas dynamic laser resonator design tool. Aero Optics enhancements make appropriate modifications to the electromagnetic wave front as it propagates through turbulent aerodynamic flow fields. The turbulent effects are represented by a density calculated using computational fluid dynamics and integrated along the optical path between the propagation steps. Propagation steps are modeled using a, fast -fowler transform routine and the result is a complete specification of intensity and phase profile at any instant, of time, after any particular component in the optical system. Applications of this code include modeling of CO2 laser range finders, active laser discriminators and resonator design for gas dynamic laser systems. This paper describes the Aero Optic Code and presents results validating the calculations.
The absence of an applications led design philosophy has compromised both the development of laser source technology and its effective implementation into manufacturing technology in particular. For example, CO2 lasers are still incapable of processing classes of refractory and non-ferrous metals. Whilst the scope of this paper is restricted to high power CO2 lasers; the design methodology reported herein is applicable to source technology in general, which when exploited, will effect an expansion of applications. The CO2 laser operational envelope should not only be expanded to incorporate high damage threshold materials but also offer a greater degree of controllability. By a combination of modelling and experimentation the requisite beam characteristics, at the workpiece, were determined then utilised to design the Laser Manufacturing System. The design of sub-system elements was achieved by a combination of experimentation and simulation which benefited from a comprehensive set of software tools. By linking these tools the physical processes in the laser - electron processes in the plasma, the history of photons in the resonator, etc. - can be related, in a detailed model, to the heating mechanisms in the workpiece.
Increasing interest is being shown towards using CO2 lasers for a variety of military applications. These applications include rangefinders, lasers radars, lhser beamrider missile guidance, and laser communications. The requirements on laser performance parameters generated by each of these potential applications are reviewed. Requirements are determined for laser output power (or pulse energy), lasing wavelength, pulse duration, pulse repetition frequency, beam divergence (beam quality), and laser frequency stability.
This paper outlines recent advances in the technology of CO2 waveguide lasers and the relevance of this within the context of the increasing number of ground based and aerospace applications in the 10 micron wavelength region.
CO2 TEA lasers have been extensively developed at Hughes for a number of important military applications, including chemical defense, long range rangefinders, and uplink guidance control of projectiles. The devices are characterized by highly compact geometries using hermetically sealed, closed cycle gas flow with catalysts. Repetition rates are on the order of 200 Hz and output energies range from 100 mJ to to 300 mJ per pulse. Total prototype laser package volume and weight at the higher output energies is on the order of 1.5 ft3 and 40 pounds, respectively, and includes all components, requiring only an external source of 28 VDC. shot lifetimes have been achieved in closed cycle operation with room temperature catalysts for both the normal and 13C1602 isotopes. Wavelength tunability over 60 lines in the R and P branches of the 9.4 and 10.6 μm bands has been shown with emphasis on the 9P(42) line (of interest in chemical defense) where 170 mJ was obtained in multi-mode output. Rapid switching among lines at 10 Hz was achieved and extension in this rate by at least an order of magnitude is in progress.
Chirp measurements have been conducted on the pulsed output of an unstable resonator oscillating on the P20 line of the 10.6 micron band of an e-beam sustained CO2 gain medium. A heterodyne method was used, mixing the oscillator signal with a cw laser operating on the same line. The mode volume was approximately 5 liters at a pressure between 1/3 and 1/2 atm. The measurements were conducted at pulse lengths of the order of 20 microseconds and are useful in characterizing the device for use in radar applications. Chirp values of less than 1 MHz are observed during the first 10 μ sec, in the remainder of the pulse, values of several MHz are observed, with decreasing frequency.
A single-pulse closed volume discharge has been used to characterize the amplification properties of 12C1602 and 13C1602 laser gas mixes. Small signal gain data were obtained from vibrational fluorescence measurements of standard and isotopic laser mixtures under identical pulsed pumping conditions. The variation of the peak gain and post-pump decay rate with CO2 partial pressure and pulse length is discussed. The experimental measurements are compared with the predictions of a kinetics model of the excitation and deactivation processes in a CO2 laser. For both 12CO2 and 13CO2, the calculated decay rates are found to be in good agreement with the experimental values. The modeling results also predict a crossover point from g(13CO2) > g(12CO2) to g(13CO2) < g(12CO2) at pulse lengths near 60 microseconds for a pressure of 1 atm and a 7.7He:2N2:1CO2 gas mixture. The effects of total pressure and gas mixture composition on the crossover point and on energy extraction are discussed.
A scheme for weapon guidance, using a coded laser beam which can replace currently used wire or similar link for transmitting guidance commands from ground station (launcher), has been proposed. The guidance unit consists of target acquisition and tracking system, CW laser and laser beam encoding mechanism. The target acquisition and laser beam modulator are mounted together on a two axes gimbal. The laser is mounted on another gimbal which also has two degrees of freedom. The steering commands of latter gimbal are derived from the former one so that the laser beam follows the axis of the acquisition system with time delay depending on the mission requirement. The transmitted laser beam is spatially and temporally coded with the help of optical modulator and a rotating neutral density filter respectively. The coded laser beam is received by an electro-optical sensor on board the weapon to generate the signals for weapon control. Angular resolution of the guidance unit depends on modulator's linear resolution and focal length of the collimating lens. The characteristics of the optical modulator, to achieve ks 0.1 mrad resolution, have been discussed. The transmitted power for Nd YAG and CO2 lasers for a typical scenerio has been calculated.
In laser cutting, kerfs are made through the removal of molten material. For effective material removal, an off-axial gas jet is used. Clearing molten material with a jet makes the molten layer thin and reduces the amount of the laser beam energy diverted to heat the molten layer to its evaporation temperature. The use of an off-axial jet introduces additional parameters such as reservoir pressure, nozzle-workpiece distance, jet targeting point, and jet attack angle. The effects of these jet parameters on the cutting depth are investigated theoretically and experimentally. An optimal Set of conditions in order for the jet parameters to achieve maximum cutting depth is found.
Furniture with inlays is rather expensive. This is so on two accounts: Firstly, furniture with inlays is generally manufactured with solid wood.Secondly,wood carving and figure cutting are both time consuming and they produce a high rate of rejections. To add to it all the cutting and carving of minute figures requires an outstanding craftmanship. In fact the craftman is in most instance the artist and also the manufacturer. While desiring that the high artistic level is maintained in the industry the search for new method to produce inlays for furniture in not son expensive materials and to produce them in a repetitive and flexible way laser cutting of plywood was found to be quite suitable. This paper presents the charts for CO2 laser cutting of both positive and negatives in several types of plywood. The main problem is not so much the cutting of the positive and negatives pieces but to be able to cut the piece in a way that the fitting is done without any problems caused by the ever present charring effect, which takes palce at the edges of the cut pieces. To minimise this aspect positive and negative pieces have to be cut under stringent focusing conditions and with slight different scales. The condittions for our machine are presented.
Remote sensing of gaseous constituents in the atmosphere is possible with a single laser system operating at high (more than 100 Hz) pulse tuning rates so as to minimize the effects of atmospheric turbulence. This paper investigates the possibility of using a galvanometric scanner as a rapid tuning device for both pulsed and continuous wave CO2 lasers. When used with a TEA laser, the galvanometer was able to switch lines as fast as 140 Hz.
With these prophetic words towards the end of the nineteenth century, Wells created a vision of high power lasers and their awesome capability of delivering energy at a distance. One might even argue that he was talking about a gas laser, and perhaps he had the notion of carbon dioxide lasers. Be that as it may, 1989 marks the 25th anniversary of the discovery of laser action on the vibrational rotational transitions of a molecule (Patel, 1964a). And since the first publication of the paper on the CO2 laser over 10,000 papers have appeared on either the science or technology of CO2 or other molecular vibrational-rotational transition lasers or their applications. Several books too have appeared. In light of this, to go through the detailed description of the molecular lasers would be superfluous. Nonetheless, a description based on my first-hand experience may provide some additional insights.