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1.
Sixty-one new CW laser lines with wavelengths between 0.1 and 1.5 mm have been observed with a waveguide laser optically pumped by a CO2 laser. 相似文献
2.
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
3.
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
4.
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
5.
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
6.
We present a new and more efficient method of calculating the losses of a waveguide laser resonator consisting of a hollow circular dielectric waveguide and flat mirrors, taking into account the effects of waveguide modes up to order HE13 . Both symmetric and asymmetric cavities are considered. We show that low cavity losses, only slightly exceeding the HE11 waveguiding losses, are predicted to be possible for much larger mirror distances than had previously been suspected, provided that an optimum total cavity length is chosen. The low losses arise when the HE11 and HE12 modes emerge from the guide with relative amplitudes and phases such that the returning diffraction patterns interfere to produce a narrow beam with low aperture losses. The theoretical predictions were checked experimentally for CO2 lasers having various waveguide dimensions. Good qualitative agreement was found, but the optimum total cavity lengths were typically 3-5 percent longer than predicted. Possible explanations of this discrepancy are discussed. We also predicted and experimentally verified that variations of the cavity length over a few centimeters can exert a coarse wavelength selectivity sufficient to determine the band and branch on which a CO2 laser oscillates; conversely, that for a grating tuned laser, the cavity length must be varied by a similar amount as the wavelength is tuned in order to maintain low cavity losses over the entire wavelength range. 相似文献
7.
The present paper describes AM mode locking for homogeneously broadened systems, a procedure for measuring linewidths under laser conditions, and finally, experimental results for a 1-atm CO2 laser. Working in the frequency domain, analytic solutions are given for the pulse bandwidth and pulse shape as a function of frequency detuning. We arrive at a simple expression for the maximum positional shift of the mirror distance. It turns out that the linewidth is inversely proportional to the maximum frequency shift and can be obtained independent of the modulation parameters and time constant of the pulse-signal detector. Applying this analysis to an amplitude-modulated CO2 laser the pulsewidth and linewidth have been measured as a function of gas composition and modulation depth. In contrast to predictions deduced from absorption measurements under neutral conditions we find the striking result that under laser-discharge conditions the linewidth increases and the pulsewidth decreases with increasing helium percentage. 相似文献
8.
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
9.
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
10.
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
11.
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
12.
To improve understanding of multiple-photon absorption by polyatomic molecules, we have performed a series of experiments wherein a pulsed CO2 laser irradiated 0.02-0.08 torr samples of SF6 at 145 K. A CW probe laser monitored the time response of the induced absorption or transmission at many CO2 laser lines that are in or near the ν3 absorption band of SF6 . The experiments covered a 40-fold fluence range and probe times out to 4 ms. We conclude that the absorbed laser radiation produces a nonthermal vibrational-energy distribution and that intermolecular vibrational-energy transfer is important at early times in redistributing the absorbed energy. We also discuss the influence of other processes on the induced spectrum. 相似文献
13.
Eleven new far-infrared (FIR) laser lines have been observed from CH3 OH pumped by a CO2 laser. These lines are ranged from 78 to 694 μm and are obtained by using a copper waveguide cavity. 相似文献
14.
Henningsen J. Inguscio M. Moretti A. Strumia F. 《Quantum Electronics, IEEE Journal of》1982,18(6):1004-1008
Four new FIR laser lines at 62.98, 48.77, 224.53, and 190.65 μm are reported from CH3 OH, optically pumped by the 10R34 and 9R10 lines of a waveguide CO2 laser. Measurements performed by several techniques confirm that the pump offsets are outside the tuning range of conventional CO2 lasers. Two of the lines are assigned as highJ transitions within the torsional ground state of the CO stretch. 相似文献
15.
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
16.
17.
The multiline behavior of a ballast resistance helical TEA CO2 laser incorporating hot CO2 as an intracavity absorber has been studied. Simultaneous laser oscillation onP(16), P(18) , andP(20) lines of 10.6 μm has been obtained reliably. A rate equation model has been developed for the hot CO2 absorber and is incorporated with the model for the multiline TEA CO2 laser for calculating laser intensities onP(16), P(18), P(20) , andP(22) lines of the 10.6 μm band in the presence of the absorber. The theoretical calculations agree quite well with the experimental observations. These studies show that a hot CO2 column of Proper length and temperature inside a TEA CO2 laser cavity can produce simultaneous laser oscillation on at least three rotational linesP(16), P(18) , andP(20) of the 10.6 μm band with almost equal intensity. 相似文献
18.
26 new FIR laser lines have been observed in CO2 laser pumped CH3 OH, and together with some previously observed lines their wavelengths have been measured with a relative accuracy of3 times 10^{-4} by using the FIR resonator as a scanning Fabry-Perot interferometer. Based on the internal consistency of the data, it is suggested that a number of the lines originate from combination bands involving simultaneous excitation of the CO stretch mode and a different vibrational mode. 相似文献
19.
A transverse gas flow configuration has been developed utilizing RF discharge waveguide technology for several infrared lasers. Two potential applications have been identified: pulsed chemical laser and CW CO2 laser. In the 3.8 μm DF laser, the flowing gas device provides rapid gas replenishment to maintain high electrical efficiency at high repetition rates. An average power of 0.6 W was achieved at 1 kHz. An order of magnitude power improvement can potentially be developed in a closed cycle system. In the CW CO2 laser, the flowing gas provides efficient cooling so that high output power per unit gain length can be achieved. A 16 W output in a 20 cm gain length device, corresponding to a record 0.8 W/cm output has been demonstrated. This system can be developed into a 20-60 W laser with a 20-50 cm gain length. 相似文献
20.
Electrical plasma parameters of the CO2 laser were investigated by probe and high-frequency techniques. The electron energy distribution function was measured by the second derivative method. The relatively high-pressure effect on the electron probe current was taken into account when analyzing the experimental curves. The influence of the addition of N2 , He, Xe and the influence of CO2 dissociation on the plasma discharge properties were studied. Calculations of the pumping rates to vibrational levels taking part in creating inversion show that the influence on output power of a CO2 laser usually observed with the addition of N2 and He cannot be explained by a changing of the electron component of the plasma. The increase of output power and efficiency with addition of Xe to the CO2 laser is connected with an essential changing of plasma parameters of the electron component. 相似文献