共查询到20条相似文献,搜索用时 31 毫秒
1.
Single-pass gain at 10.6 microns has been studied parametrically in nonflowing CO2 or buffered CO2 amplifying media. The gain profile across the amplifier diameter and integrated gain both were determined. Parameters varied included buffer gas type, mixture ratio, gas pressure, amplifier bore, discharge current, and wall temperature. Tube bores of 12, 22, and 34 mm and buffer gases of H2 , He, Ne, A, and N2 were studied. Optimum gain is relatively independent of current density, but decreases with increasing wall temperature. The pressure-diameter relationshipP_{CO_{2}} cdot D sim 4 torr-cm was found to hold for CO2 , CO2 :He, and CO2 :N2 amplifying media at optimum gain. The gain depends strongly on the CO2 partial pressure and is relatively insensitive to the buffer gas pressure except for the case of H2 . The maximum gain decreased slowly with increasing amplifier diameter. The highest gain, 1.7 dB/meter, was achieved with a helium buffer gas in amplifiers with a diameter of 22 mm or less. No gain saturation was detected for a 30-dB range of input signal power, from a milliwatt to a few watts. Spectrograms showed that the principal spontaneous emission from CO2 :He amplifiers in the 2000-7000-Å range consisted of CO bands; no CO2 bands or He line spectra were observed. 相似文献
2.
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
3.
Nagai H. Hishii M. Shibayama K. Nagai A. Akiba T. 《Quantum Electronics, IEEE Journal of》1982,18(3):416-422
Discharge stabilization, long-term operation, output power characteristics, and efficiency of the high-pressure CW CO2 laser have been investigated under sealed conditions. A comparison is made with low-pressure CW CO2 lasers. Two types of electrode structures suitable for operations in the pressure range 100-760 torr are presented. Effects of O2 and CO on the discharge stability and unsaturated gain are described. By using molecular sieve3A as an adsorbent of water vapor, which was the most detrimental impurity, sealed operation with no decrease in output power was achieved at 0.5-1.5 kW for more than 150 h elapsed time including about 30 h of discharge time. It has been demonstrated that high efficiency can be obtained in spite of high-pressure and sealed operation. The efficiency was improved by reducing the cavity loss due to the absorption of intracavity radiation by CO2 molecules in the unexcited region, and by finding the optimum of gas mixture. A maximum efficiency of 19 percent was obtained at a 1 kW power level for a 100 torr gas mixture of either CO2 -CO-N2 -He = 2-1-19-19 or CO2 -CO-N2 -He-Ar = 2-1-18-10-10. The effects of Ar and N2 proportion on the unsaturated gain and saturation parameter are discussed. 相似文献
4.
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
5.
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
6.
The gain of CO2 waveguide lasers was measured for a wide range of He:CO2 ratios and total gas pressures. It was found that maximum gain occurs at relatively low pressures. To minimize laser discharge length it is advantageous to operate in this high gain, low pressure regime even at the expense of a reduction in saturation intensity which falls off quadratically with gas pressure. 相似文献
7.
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
8.
Using a simple rate equation approach we examine the gas kinetic and discharge properties of waveguide CO2 lasers. We calculate the dependence of the population inversion and laser small-signal gain on gas pressure, gas mixture, pumping rate (discharge current), tube bore diameter, and wall temperature. The results indicate, for example, that at a pressure of 50 torr and a tube-bore diameter of 0.125 cm, the gain is optimized with a gas mixture in the ratio CO2 :N2 :He of 1:0.75: 1.5. At higher pressures the gain is optimized by using more helium-rich mixtures. We also calculate the dependence of laser tunability on the gas kinetic properties and cavity losses. We find that for low-loss cavities the laser tunability may substantially exceed the molecular full width at half-maximum. Furthermore, the more helium-rich gas mixtures give greater tunability when cavity losses are small, and less tunability when cavity losses are large. The roles of the various gases in the waveguide CO2 laser are the same as those in conventional devices. By contrast with conventional lasers, however, the waveguide laser transition is homogeneously broadened. Thus the dependence of gain on gas pressure and other kinetic properties differs substantially from that predicted by scaling results from conventional low-pressure lasers. 相似文献
9.
Measurements of the small signal gain and saturation intensity of a CO2 -N2 -He laser are made as a function of gas flow velocity over the range fromsim 0-10 m/s. The small signal gain increases and the saturation intensity decreases with increased gas velocity. For intermediate flow velocities with a gas transit time in the laser of a second, the gain also depends on the direction of propagation of the amplified beam with respect to the gas flow. The directional dependence is due to an axial gradient in the saturation intensity. The transit time of the gas in the 2.5-m amplifier spans the time required for appreciable generation of CO by dissociation of the CO2 and the variation of the laser gain with velocity is attributed to the effects of CO on the inversion of the laser medium. 相似文献
10.
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
11.
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
12.
Single-pass gain has been measured for flowing CO2 , CO2 -N2 , CO2 -He, CO2 -N2 -He, and CO2 -N2 -H2 mixes. The gain for CO2 -N2 mixes varies as d-0.9, whered is the tube diameter. The diameter dependence of the gain is less pronounced for CO2 - N2 -He mixes; a peak gain of 4.7 dB/m was obtained in a 1/2 in diam tube. Fluorescence data indicate that the upper laser level population is saturated at 100 mA in all cases. The addition of He, H2 , or O2 depopulates the lower laser level; helium further increases the population of the upper laser level. The addition of CO increases the population of the upper laser level, probably by resonant transfer from the excited vibrational states of CO. 相似文献
13.
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
14.
In a sealed-off CO2 laser, deposits are formed from the gas mixture. The removal of the gas in this way limits the lifetime of the laser. Fragments of these deposits are analyzed mass spectrometrically and their possible composition is given. After the discharge tube was pumped down, the gases released from the walls were analyzed. CO2 was observed and it was apparently trapped at the walls. 相似文献
15.
An amplifier for 10.6-μ radiation of a CO2 laser has been constructed using the negative glow of a hollow-cathode discharge. The single-pass gain of 10 percent per meter reported here from such a discharge in a CO2 -He mixture is less than that realizable in the positive column of a glow discharge used for CO2 lasers under comparable conditions. The addition of N2 , CO, or O2 was not found to increase the gain. 相似文献
16.
Measurements made of the small-signal gain and time-resolved spectral output of a flash-initiated D2 -F2 /CO2 chemical transfer laser system are reported. Small-signal gain measurements indicate a possible lack of rotational equilibration among the rotational levels of the CO2 during the DF-CO2 V-V energy transfer process. Time-resolved spectral output of this system, operated as a laser oscillator, is presented as verification of the small-signal gain results. 相似文献
17.
In this investigation the degraded gas mixture in a sealed TE CO2 laser discharge was analyzed gas-chromatographically, which enabled us to determine the concentration of CO accurately, even in the presence of large quantities of N2 . According to the reversible decomposition reaction 2CO2 rightleftharpoons 2CO + O2 , [CO]/2[O2 ], which should be unity, was found to be noticeably more than unity. The deviation of the O2 concentration from that needed to satisfy the CO2 decomposition equation was more than 26 percent. No oxides of nitrogen were detected and the missing oxygen was recovered when the degraded gas mixture was heated to the dissociation temperature of ozone. 相似文献
18.
The factors which limit the small-signal gain of TE CO2 laser amplifiers are investigated with a novel technique based on gain measurements of the sequence, hot, and regular CO2 laser bands. This new technique enables us, for the first time, to determine accurately and independently the rotational and vibrational temperatures characterizing the CO2 laser system. The gain ratio of the sequence band (00° 2) to the regular band (00° 1) provides a simple and accurate determination of the ν3 mode vibrational temperature. It is found experimentally that the ν3 mode vibrational temperature saturates at a high input discharge energy. This saturation sets an upper limitation to the gain attainable in TE CO2 laser amplifiers. As we can measure all the characteristic temperatures relevant to the gain medium, a detailed comparison between the calculated and experimental gain can be carried out with no variable parameters. The result of such a direct comparison confirms both the validity of the conventional "mode temperature" model for CO2 laser dynamics and the validity of our measurement technique for vibrational temperatures. 相似文献
19.
The design of a new type of atmospheric pressure CO2 -N2 -He laser capable of producing 1.2-J infrared light pulses with a peak power of 0.5 MW is described. An investigation of the laser output dependence on gas flow, gas mixture, capacitor voltage, output coupling reflectivity, and electrode spacing was made. It is shown that even greater energies and powers should be possible at higher voltages and larger electrode gaps. 相似文献
20.
A pulsed excitation was used to study high peak power generation in CO2 and CO2 -mixture flowing gas lasers. A rotating mirror was used as aQ switch with a variable delay between excitation pulse and mirror alignment. A variation of the time delay and multiple-exposure photographs can permit a measure of the population inversion versus time to be photographed. High-voltage pulses were used with higher than usual gas pressures to generate peak powers of about 30 kW. Peak power was shown to be primarily dependent on CO2 partial pressure in CO2 -He and CO2 -N2 mixtures. 相似文献