PassivelyQ-switched N2O laser

Freon 12 and SF6have been used to passivelyQswitch laser transitions fromR(17)toP(36)in the00deg1-10deg0N2O band. Pulses having a half-intensity width of 0.75 μs with peak powers 10-20 times the CW power were observed.     

A TE duolaser providing simultaneous lasing on CO2and N2O transitions

Simultaneous laser action on CO2and N2O transitions has been achieved in a helical resistor-pin-type transversely excited (TE) laser. The laser emits typically a power of 10-100 kW in a 700-ns-long pulse which consists basically of two overlapping pulses, the peaks of which do not coincide, and which can be associated with the CO2and N2O emission, respectively. The conditions of optimal operation are described and the effects of some parameter changes are indicated.     

A 500 MHz tunable CO2waveguide laser for optical pumping

A long-pulse CO2waveguide laser is described, which can be single frequency tuned over 500 MHz in about 80 lines. A peak power reaching 125 W at line center and 85 W at the tuning edge in the strongest lines makes the laser ideally suited for optically pumped FIR lasers. New FIR lines have been observed by pumping CH3OH in absorptions located up to 268 MHz from the CO2line center. FIR wavelengths have been measured, identified, and compared to calculations at a level of relative accuracy of5 cdot 10^{-5}.     

Direct optical pumping of high-pressure CO2and N2O lasers with a pulsed HF pump laser

Pulsed HF laser radiation has been used for direct optical excitation of CO2and N2O lasers at 10 and 5 atm gas pressures, respectively, which are the pressures required for continuous laser frequency tuning between the line centers in these gases. The maximum demonstrated quantum efficiency is about 14 percent, which seems to be limited by the formation of pressure waves in the gas, in addition to losses in the resonator optics. We find that quantum efficiencies close to unity are theoretically feasible with a low-loss resonator, and by using a sufficiently short pump pulse to avoid a serious influence from pressure waves. The excitation scheme can be used with any of the CO2and N2O laser isotopes.     

Pulsed N2O molecular laser studies

The afterglow pulse-gain technique was used to measure the relaxation of the 00°1 upper laser level in N2O from 300 to 700°K. The rate constantk_{N_{2}O}(torr^-1s^-1) varies with temperature aslog10k_{N_{2}O} = 4.53 - 10.9T^{-1/3}. Measurements of the relaxation time at 300°K agree with the fluorescence technique results of Yardley [1]. Gain studies were also made with gas mixtures in a nonflowing system. Single-pulsed N2O + CO + He mixtures at 300°K showed considerable peak gain. However, subsequent pulses of these mixtures show that the gain is reduced because of the chemical reaction forming CO2. Measurements of this transformation from one molecular laser mixture to another are discussed.     

Lasing in N2O and CO2isotope mixtures pumped by blackbody radiation

The use of N2O and CO2isotopes as active species for a blackbody radiation pumped laser has been experimentally demonstrated and theoretically analyzed. The results obtained for mixtures containing N2O,¹³C¹⁶O2, and¹²C¹⁸O2are presented. For the first time, continuous lasing action with blackbody radiation pumping has been obtained for this species. Two active species mixtures were tested, obtaining up to a 100 percent increase in output power due toupsilon-upsilontransfer. A simple model was developed and gain calculations are presented.     

Third-harmonic generation in a mixture of DBr and N2O

Third-harmonic generation of CO2P(24) 10.6 mum laser radiation was achieved in a mixture of DBr and N2O. The ratio of DBr and N2O used was 29:1. A frequency tripled signal was observed up to a total pressure of 4 atm.     

A stacked Blumlein N2laser

A novel device for producing fast-rise-time, large-volume electrical-discharge excitation of gas lasers is described. Some operating characteristics of an N2ultraviolet (UV) laser are presented.     

The N2+waveguide laser experiment and theory

The operation of an N+2ion waveguide laser (4278 Å) excited by charge transfer from He+2created in a capacitively coupled self-sustained discharge is described. In addition, the results of an experimental diagnostic program and a computer modeling program, conducted to explain the general operations of the discharge pumped He-N2system, are presented. The results of this program indicate upper laser level electron quenching and lower level pumping may be seriously limiting the achievable laser efficiency of this system. During the course of this study, it was found necessary to measure the pressure broadening coefficient of the N+2(B) rightarrowN+2(X) emission" by He. The value of this coefficient was found to be 3.5 MHz/torr ± 0.7 MHz.     

A 6.5-J flashlamp-pumped Ti:Al2O3 laser

A flashlamp-pumped Ti:A₂O₃ oscillator has delivered 6.5 J per pulse at 800 nm under long-pulse extraction conditions. The device was designed for efficient short-pulse (2-3 ns) amplification to the multijoule energy level. To date, a peak stored energy in excess of 5 J has been obtained and is available for short-pulse extraction studies. The design and resulting characterization of this laser are discussed. The results show that the energy available for short-pulse extraction is limited by the flashlamp pumping time     

Near single-line operation of a free-burning CS2/O2/N2O flame laser with a nondispersive optical cavity

The CS2/O2/N2O flame laser has been operated for the first time under conditions in which the spectral output is nearly single line. This transition is theP_{10-9}(17) of CO at 5.4265 μm, the same transition which was observed to oscillate in single-line fashion by Hirose et al. in an electrically initiated CO chemical laser. It is suggested that the unique behavior of this line may be due to its close proximity to aPbranch transition in an adjacent band, namely theP_{9-8}(23) line, such that the gain profiles of the two lines overlap. Calculations suggest that at the conditions of these experiments, the separation of the line centers for this pair is about 0.3 Å or less. TheP_{10-9}(17) transition was also found to be totally absent under certain conditions of high multiline power, particulary at low O2and N2O flows. This may be due to absorption by a high-bandRbranch transition at 5.4266 μm, namely theR_{15-16}(32) line.     

Improved operation of N2O TE lasers

The operation of a transversely excited N2O laser is improved by the addition of H2or CO to the discharge. The improvement is due to the effective nullification of the dissociative electron attachment reaction with N2O.     

Photopreionization of the 3371-Å pulsed N2laser

Photopreionization of the 3371-Å pulsed N2laser by use of a seed gas of low ionization threshold and flashlamp excitation is observed to result in increased laser output and reproducibility. Preionization also increases the range of permissible operating pressures, enabling operation with atmospheric-pressure mixtures of N2and He without reduced intensity.     

Laser action from atmospheric-pressure H2-F2mixtures made at 300K

Thirty-five photons (lambda = 3 mum) per photolytic F atom have been obtained from a 40-cm³photochemical laser filled with 400 torr of F2, 100 torr of H2, and minor amounts of Ar and O2mixed at 300 K. With 0.035-percent dissociation of the F2, 0.83-J 250-ns full width at half maximum (FWHM) pulses were observed.     

Laser parameters for the 10.8-µ N2O molecular laser

Measurements were made of the radiative lifetime for the 001-100 transition in N2O, the absolute population densities of the laser levels, and the saturation parameter in a typical flowing N2O-N2-He laser. These numbers are compared with the corresponding parameters in the CO2-N2-He system to explain the difference in their performance characteristics. In addition, dissociation of N2O in a discharge and power enhancement in the N2ON2-He laser by adding CO are discussed.     

Gas dynamic CO2-He-(N2) laser investigations

Experiments on IR laser action and gain measurements are reported for a CO2-containing gas mixture flow that cools as a result of expansion. The mixture is preheated by a reflected shock wave, and the gas is expanded into a vacuum through a slit. Laser action is obtained in a CO2-He mixture, while the addition of nitrogen increases the gain. The gain was found to depend on the distance from the slit and the gas pressure before the slit.     

A study of the spontaneous emission from CO2-N2-He-H2laser discharges C3πu-B3πgemission bands of N2

Results of spectroscopic investigations of the spontaneous emission of CO2lasers are presented. The band head emission in the Second Positive System (C^{3}pi_{u}- B^{3}pi_{g}) of N2is studied as a function of discharge current and laser output power. The observed changes of the band head intensities are described in terms of the vibrational energy distribution in theC^{3}pi_{u}electronic state of N2. A simple model is developed by which the influence of the laser process can be understood. The excitation properties of theC^{3}pi_{u}state are in reasonable qualitative agreement with the predictions of this model.     

Pulsed discharge initiated chemical lasers -- Part II: HF laser emission from NF3and N2F4systems

A transverse, multiple-arc pulsed discharge has produced laser emission in NF3and N2F4mixed with H2, CH4, C2H6, HCl, HBr, and natural gas.P_{10}, P_{21}, P_{32}, and P43HF transitions were observed. The peak powers measured ranged from ∼8.5 to 25 kW with typical pulsewidths ofsim0.3 mus.     

CO2laser annealing of Si3N4, Nb2O5, and Ta2O5thin-film optical waveguides to achieve scattering loss reduction

Significant reductions in the optical scattering losses of Si3N4, Nb2O5, and Ta2O5waveguides fabricated on SiO2/Si substrates have been measured following CO2laser annealing. The largest improvements were observed for Si3N4waveguides, where waveguide attenuation values of about 6.0 dB/cm before laser annealing were reduced to as low as 0.1 dB/cm afterwards. An improvement of more than an order of magnitude was obtained for a Nb2O5waveguide upon laser annealing, the attenuation coefficient decreasing from 7.4 to 0.6 dB/cm. In the case of one Nb2O5waveguide no improvement was obtained upon laser annealing. The attenuation coefficient of a reactively sputtered Ta2O5waveguide was found to decrease from 1.3 dB/cm before laser annealing to 0.4 dB/cm afterwards. In the case of a thermally oxidized Ta2O5waveguide a small initial improvement in waveguide attenuation was followed by degradation upon further laser annealing.     

Optical pumping by CO2and N2O lasers: New CW FIR emissions in 1,1-difluoroethane

53 new CW FIR laser lines are reported in 1,1-difluoroethane optically pumped near 10 μm by CO2and N2O lasers. The emission spectrum initially reported in the literature consisted of four lines between 770 and 458 μm and has now been extended to the 2.39 mm- 319 μm region. The reason for this extension, especially to the long wavelengths, is analyzed.