共查询到20条相似文献,搜索用时 343 毫秒
1.
Various forms of CO2 lasers have achieved CW powers in the 60-kW range, operating efficiencies approaching 30 percent, pulse energies of approximately 2000 J, pulsewidths less than 1 ns, peak pulse powers in excess of 109W, a frequency stability of a few parts in 1012, and sealed-off tube lifetimes of many thousands of hours. In addition, the laser can be easily Q-switched as well as gain-switched and has been electrically, optically, gas-dynamically, and chemically pumped. In addition to all these attributes, the CO2 laser output wavelength lies within one of the best atmospheric windows. It should be no surprise then that during the last eight years, the CO2 laser has firmly established itself as a candidate for recognition as the most important among the numerous laser devices presently known. Depending on the gas pressure, gas flow rate, pumping mechanisms, gas mixture, etc., CO2 lasers can exhibit a wide range of noise, bandwidth, gain, and power saturation characteristics. This flexibility enables a designer to optimize the performance of CO2 laser stable-frequency master oscillators; power oscillators; low-noise high-gain preamplifiers; intermediate-power or high-power amplifiers. As a result, CO2 laser oscillator-amplifier chains can be designed utilizing guidelines similar to those which have been extensively applied in the design of transmitters in the RF and microwave region of the electromagnetic spectrum. 相似文献
2.
Application of dc electric field to a gaseous system destroys the basic inversion symmetry and allows three-wave mixing processes to occur. A theoretical derivation of this effect under conditions of resonantly enhanced nonlinearities is given for a three-level system. Calculations are presented for mixing of a CO2 laser with 4-GHz microwaves in the molecule NH2 D, producing single lower sideband radiation. 相似文献
3.
The operational characteristics of a continuously tunable DF → CO2 transfer laser optically pumped with radiation from a pulsed DF laser are experimentally and theoretically studied. The pump radiation is absorbed by DF in a high-pressure DF/CO2 /He gas mixture, and subsequent V-V energy transfer to the CO2 ν3 mode provides the CO2 laser population inversion. Continuous tuning of the CO2 laser frequency between five CO2 line centers from 29.14 to 29.30 THz has been demonstrated, using a 12 atm gas mixture. The maximum pulse energy was about 0.8 mJ. In experiments with a two-mirror CO2 laser resonator, pulse energies up to 6 mJ and 35 percent slope quantum efficiency have been obtained at 10 atm gas pressure. The gas mixture typically contained 0.5 percent DF, 5 percent CO2 , and 94.5 percent He, but this was not critical. Computer simulations based on a rate equation model of the laser have given results which are in reasonable agreement with those obtained experimentally. 相似文献
4.
Measurements of UV photoionization parameters for TEA CO2 gas lasers are presented. Electron density and ionization decay times are given as a function of pressure for several gases and gas mixtures. Penetration depth of ionizing radiation in the gases is determined. The effect of selected additives on photoionization is demonstrated. The results show that a significant enhancement in electron density can be achieved. TheX -band microwave interferometer data provide additional insight into the mechanisms involved and further substantiate the effectiveness of the technique in high-powered CO2 laser design. 相似文献
5.
A technique is demonstrated for reducing the rapid intensity fluctuations in the beam of a single frequency, polarized CO2 laser tuned to theP(20) transition at 10.6 μm. The method uses a Stark-tunable absorption line in NH2 D to compensate for the fluctuations of the laser output. Substantial reductions in laser beam intensity noise have been obtained. The method may be applied to other lines of the CO2 laser and indeed to other types of lasers. 相似文献
6.
An experimental investigation of the conversion efficiency of a high pressure CO2 laser pumped CH3 F Raman laser is reported. We show that resonance absorption of the CO2 laser radiation in the CH3 F gas can lead to a severe limitation of the efficiency. At CO2 laser frequencies where the stimulated Raman action is strongest, a quantum efficiency for conversion of CO2 laser radiation into far infrared radiation of the order of 0.1 is observed. 相似文献
7.
This paper reports a technique by which repetitively pulsed outputs may be obtained from some continuously excited gas lasers by supplying the resonator with pulses of excited gas. The technique is applied to a CO2 laser in which 14 kW, 1 ms (FWHM) pulses are produced at a repetition frequency of 200 Hz. 相似文献
8.
Experiments on internal frequency modulation (FM) of a CO2 laser showed no limitation of FM by the linewidth. However, distortions in the form of strong enhancement of sideband amplitude arise for frequencies equal to the cavity resonant frequencies, most pronounced if the modulator is positioned near a cavity mirror. 相似文献
9.
Optical pumping of a submillimeter wave (SMMW) laser with a relatively compact RF-excited CW CO2 laser is described. The increased frequency tunability of the waveguide pump laser has resulted in new low threshold SMMW emissions in C2 H2 F2 , CDF3 , and CD2 F2 by pumping into absorption lines which are beyond the tuning range of a conventional CO2 laser. Frequency offsets and some assignments obtained with the aid of a tunable diode laser heterodyne spectrometer are reported. 相似文献
10.
A proof of principle experiment to demonstrate the physics of a radiatively pumped laser has been carried out. For the first time, a blackbody cavity has optically pumped a CW CO2 laser. Results are presented from a series of experiments using mixtures of CO2 , He, and Ar in which maximum output power was obtained with a 20 percent CO2 - 15 percent He-65 percent AR mixture. The dependence of the output power on the blackbody temperature and the cooling gas flow rate is also discussed. By appropriately varying these parameters, continuous output powers of 8-10 mW have been achieved. 相似文献
11.
A compact CO2 -NH3 FIR laser system, with an NH3 laser cavity inserted in the pump CO2 laser cavity, was designed. Temporally smooth and reproducible single mode NH3 laser pulses with an energy of 5 mJ (20 kW peak power) were obtained at the 152 μm line when optically pumped by the injection-locked single-mode CO2 laser with a pulse energy of 0.3 J. 相似文献
12.
Small-signal gain of flowing gas CO2 laser amplifiers at 10.6 microns has been optimized for media including pure CO2 CO2 : N2 , CO2 : He, CO2 : CO, CO2 : O2 , CO2 : N2 : He, CO2 : CO : He, and CO2 : CO : N2 . Optimum gain of all flowing gas systems studied increases monotonically with increasing gas flow rate. In the low CO2 flow rate region, 10 < RCO 2 : < 50 cm3/min, gas flow enhances the gain most for systems containing N2 . Results provide strong evidence that the rapid increase in gain with flow rate in CO2 : N2 mixtures is due to removal by convection of the dissociated product CO. For 50 < RCO 2 < 200 cm3/min, a slow linear increase in gain of all gas mixtures with increasing flow rate occurs and is attributed to the cooling of gas temprature by convection. A stronger dependence of gainG on amplifier boreD , viz.,G propto I/D , was obtained for flowing gas media relative to that previously observed for nonflowing gas mixtures which is consistent with the proposed mechanism of gas cooling by convection. Highest gain values obtained were 7.8 and 6.2 dB/m with the flowing gas mixtures CO2 : N2 : He and CO2 : CO : He, respectively, in a 12 mm bore water-cooled amplifier tube. Similarities between CO2 : N2 and CO2 : CO systems suggest that pumping of the CO2 laser by resonant transfer from CO* (upsilon = 1 ) can be significant. 相似文献
13.
The envelope of the sidebands of a CO2 laser digitally frequency modulated at a cavity resonance frequency has been studied. Both theory and experiment yield that rise time is determined by the photon lifetime in the optical resonator. Using a conventional CO2 laser, exponential transient behavior with rise times of some 50 ns has been observed. 相似文献
14.
We have developed an accurate method of determining vibrational temperatures and populations in CO2 laser discharges. Our technique involves the use of both the regular 00 ° 1 and sequence 00 ° 2 laser transitions as probes of a CO2 laser amplifier. We have been able to separately investigate the quantitative effects of gas heating, dissociation, and ν3 mode excitation efficiency on the small-signal gain in typical CW CO2 lasers. In general we find that the maximum gain attained in a typical flowing gas CW CO2 laser is limited by dissociation of CO2 at high discharge currents. To investigate the more fundamental limitations on the gain, we used a short discharge tube with fast flow rates. Contrary to many previous results, we find that thermal effects play a somewhat secondary role in the discharge dynamics, and that the lower laser level populations are small under all discharge conditions. Our results show that the chief limitation on gain in CW CO2 lasers is the "saturation" of the ν3 mode vibrational temperature T3 at high discharge currents. This saturation effect is observed for a wide range of gas mixtures and pressures, and has been studied in detail. Gain coefficients as high as 3.3 percent/cm have been obtained in a conventional 1-cm bore CW discharge tube. We also report preliminary results of an experiment which uses a tunable diode laser to measure gain on a large variety of transitions in a CO2 discharge. The diode laser measurements give a striking confirmation of the results described above, and provide the first direct experimental evidence that a Boltzmann distribution exists in the vibrational modes of discharge excited CO2 . 相似文献
15.
Antropov E. Silin-Bekchurin I. Sobolev N. Sokovikov V. 《Quantum Electronics, IEEE Journal of》1968,4(11):790-796
In order to examine the CO2 laser oscillation mechanism, a measurement was made of the unsaturated gain of CO2 laser radiation in an active medium of gas discharge containing CO2 , N2 , and He. A two-beam optical balance method was used to measure the gain in an amplifier; the accuracy of the measurement was approximately 10 percent. The output of a CO2 -N2 -He laser was used as the radiation source. The absolute power of the probing beam, which has a diameter of approximately 5 mm, was maintained at approximately 15 mW. Saturation was not observed at probing signal levels up to 80 mW. Amplifier tubes with diameters of 55, 34, 12, and 5 mm were used. The dependence of the amplifier gain on the current density, pressure, composition of the gas mixture, and tube diameter was measured. Comparison was also made of the calculated and measured values for the laser population inversion. 相似文献
16.
《Quantum Electronics, IEEE Journal of》1977,13(10):871-875
Improvements in a 16-μm radiation source based upon the combined effects of stimulated rotational Raman scattering and resonantly enhanced four-wave mixing in parahydrogen gas are described. For this source, the input waves of which are provided by temporally and spatially coincident pulsed beams from a ruby and CO2 TEA laser, it was found that cooling the parahydrogen gas from 300 K to <100 K, at constant molecular density, increased the output at 16 μm by roughly a factor 4. The maximum output was measured to besim 40 mu J/pulse, which is near the theoretical limit for the 2.5 MW CO2 laser intensities that were applied. 相似文献
17.
For the pulse pumped CO2 laser we used Q-switching to investigate inversion kinetics. The pump was synchronized with the Q-switching mirror. It was possible to obtain the Q-switch pulses at any phase of the pump pulse. The repetition rate was 50 Hz and the pump pulse duration was 4 or 10 ms. It was found that there is an optimum delay in switching the cavity Q-factor after the discharge started. The giant pulse intensity increased several times after the discharge was switched from CW to pulses. The inversion rise time was 1-2 ms and its lifetime was strongly dependent on the discharge current, due to plasma heating during the current pulse. Increasing the helium percentage in the discharge prolonged the inversion lifetime because of high thermal conductivity of helium gas. Gaseous BCl3 was chosen to obtain the CO2 laser giant pulses with bleachable filter. The vibronic frequency V3 of the B11Cl3 molecules coincides with theP lines of the CO2 laser. Rarer B10Cl3 corresponds to less activeR lines. Pure BCl3 did not give the giant pulses. Adding helium to the BCl3 cell gave the pulses. The best results came from adding very small amounts of ammonia NH3 because of the effective vibrational energy transfer between colliding BCl3 and NH3 molecules. 相似文献
18.
Relaxation time of the 0001 upper and 1000 lower CO2 laser levels as a function of H2 O, CO, and Xe gas pressure has been measured using the afterglow pulse-gain technique. Lifetime data for these gas mixtures and also for mixtures of CO2 , CO2 -H2 , CO2 -He, and CO2 -N2 , obtained previously, are analyzed and compared with available ultrasonic and fluorescence data. Results indicate that the 1000 and 0110 levels of CO2 are strongly coupled and depletion of the lower laser level population is essentially limited by the relaxation rate of the 0110 level. Other processes involving energy exchange between CO2 and foreign gases are detailed. 相似文献
19.
An interferometric method is described for measuring the phase shifts caused by anomalous dispersion in laser active media under actual oscillating conditions. In addition, some data are presented which show how this method can be used to measure dispersion in a single-frequency 10.6-micron CO2 laser plasma. The application of an interferometer of this kind to laser frequency stabilization is also discussed, and an absolute frequency stabilization scheme for CO2 lasers is suggested. Because the phase shift observed is an antisymmetrical function about the center of the molecular resonance, it can be used directly as an absolute frequency control discriminant. The resulting frequency control system requires neither amplitude nor frequency modulation of the laser. A modification of a Mach-Zehnder interferometer for the measurement of dispersion in laser amplifiers is also described. This modified interferometer was used to measure phase shift as a function of frequency in an unsaturated traveling-wave CO2 amplifier. The oscillographic data resulting from these measurements are shown. 相似文献
20.
Gain coefficient measurements of a MAGPIE (magnetically stabilized, photoinitiated, impulse-enhanced, electrically excited) coaxial CO2 laser discharge are presented. The effects of gas composition, input power, pulser ionization, and magnetic field on gain are examined. Measurements of the radial gain profile and saturation intensity are also discussed. A maximum small-signal gain of 0.30 m-1is observed, along with a saturation intensity of 190 W/cm2. 相似文献