A radiatively pumped CW CO2laser

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 CO2laser. 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.     

FIR laser lines of CH3OH pumped by CO2laser sequence lines

We report on the utilization of a sequence band CO2laser as the pumping source for new FIR laser lines of CH3OH.     

Far infrared optically pumped SO2laser

CO2laser pumping of the SO2molecule has produced far infrared (FIR) lasing on three rotational lines in the ν1excited state. Complete line assignments have been derived for all of the observed transitions.     

Additional CW far infrared laser lines from CO2laser pumped cis 1,2 C2H2F2

Six new CW far infrared laser lines are reported for the cis 1, 2 C2H2F2molecule optically pumped by a CO2laser. Of these, two have high conversion efficiencies in the 1-2 percent range.     

Analysis of CH3OH far infrared laser lines optically pumped by sequence band and isotopic CO2lasers

Assignments are presented for seven far infrared (FIR) laser lines of CH3OH pumped by theS-9P(31),18-10R(24),13-9R(26), and13-9P(16)CO2laser lines, plus an interesting speculation for the FIR line pumped by the18-9P(12)CO2line. Frequencies have been deduced to a substantially improved accuracy of ±0.001 cm^-1from IR and FIR spectroscopic combination differences for most of the assigned lines as well as three other predicted transitions. In addition, accurate frequencies are given for 13 predicted FIR laser transitions which are expected from the IR spectrum to be pumped by three¹⁶O¹²C¹⁸O laser lines.     

Compact, high-power FIR NH3laser pumped in a CO2laser cavity

A compact CO2-NH3FIR laser system, with an NH3laser cavity inserted in the pump CO2laser cavity, was designed. Temporally smooth and reproducible single mode NH3laser 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 CO2laser with a pulse energy of 0.3 J.     

Efficiency of a high pressure CO2laser pumped CH3F Raman laser

An experimental investigation of the conversion efficiency of a high pressure CO2laser pumped CH3F Raman laser is reported. We show that resonance absorption of the CO2laser radiation in the CH3F gas can lead to a severe limitation of the efficiency. At CO2laser frequencies where the stimulated Raman action is strongest, a quantum efficiency for conversion of CO2laser radiation into far infrared radiation of the order of 0.1 is observed.     

Numerical analysis of a CW RF pumped CO2waveguide laser

A fully two-dimensional analysis of a steady-state RF excited rectangular bore waveguide laser, without adjustable parameters, is presented. The effects of the gas temperature, diffusion, and electron density on the laser gain are accounted for. Comparisons of predicted small-signal gain and output laser power with experimental results are given. The agreement is quite satisfactory.     

Second-harmonic generation in proustite with a CW CO2laser

The possibilities for nonlinear optics in proustite have been explored in a wavelength region previously indicated as having low absorption. We used a 10-W CW CO2laser oscillating on a single transition at 9.2-μ wavelength. The observed values for nonlinearity and absorption are, respectivley,(7.9 pm 2.0) times 10^{-23}in MKS units and 0.29 cm^-1.     

New far infrared CW optically pumped cis-C2H2F2laser

Lasing on 6 FIR lines is reported for the new laser molecule cis-C2H2F2with high conversion efficiencies up to 7 percent of the maximum theoretical limit. A set of molecular selection criteria was used to predict efficient FIR lasing from this molecule, and analysis of the laser performance has increased the basic understanding of the molecular parameter contribution to high conversion efficiency. From this work a refined set of selection criteria has evolved that may be used to predict additional efficient laser molecules.     

High-pressure sealed CW CO2laser with high efficiency

Discharge stabilization, long-term operation, output power characteristics, and efficiency of the high-pressure CW CO2laser have been investigated under sealed conditions. A comparison is made with low-pressure CW CO2lasers. Two types of electrode structures suitable for operations in the pressure range 100-760 torr are presented. Effects of O2and CO on the discharge stability and unsaturated gain are described. By using molecular sieve3Aas 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 CO2molecules 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 N2proportion on the unsaturated gain and saturation parameter are discussed.     

Gain characteristics of an atmospheric sealed CW CO2laser

Experimental and analytical investigations have been made on unsaturated gain g0of a CO2electric-discharge convection laser, in which discharge current flow, gas flow, and the optical axis are mutually perpendicular. Stable glow discharges in sealed gas mixtures of CO2, CO, N2, and He were maintained at pressures up to 780 torr with an input power density of about 90 W/cm³. The ratio of electric field to neutral particle densityE/Nwas1.7 times 10^{-16}V . cm²and was independent of the total gas pressureP. The electron density in a positive column of the glow discharge was about4 times 10^{10}cm^-3. Detailed spatial distributions of g0at a wavelength near 10.6 μm were measured in the pressure range from 100 to 780 torr. Measurements were also made on the current dependence of g0and on the change in gowith discharge time. The g0distributions along the gas flow direction were found to agree with those calculated from the electron density distribution and the relaxation rate constant of the upper laser level on the basis of continuity equations for a two-level model. The integrated value of g0along the flow direction was proportional to P^-0.8whenE/N, electron density, and gas temperature were held constant. A maximum value of the g0distribution, which was proportional to P^-0.3, was 0.14 percent/cm at 780 torr.     

Whispering-gallery CO2laser

The design and operation of a CW CO2laser based on the whispering-gallery principle is reported. The optical cavity consists of a portion of the equatorial region of a torus terminated by two flat mirrors. In agreement with theoretical expectations, the output beam is found to be TE polarized, and to consist of low-order Airy-Hermite-Gaussian modes.     

A long-pulse high-energy CO2laser pumped by an ultraviolet-sustained electric discharge

A UV-sustained electric-discharge CO2laser has demonstrated optical energy-density extraction and long-pulse performance competitive with currente-beam sustained devices. Atmospheric-pressure CO2-N2-He mixtures seeded with tri-n-propylamine are volumetrically photoionized using the 1200-1700-Å radiation from a spark-array source. Laser pulse lengths up to 37 μs have been achieved with a specific energy of 47 J/1.atm. The best specific energy demonstrated was 60 J/1.atm in a 23-μs pulse.     

4B2--Pulsed and steady-state infrared emission studies of CO2laser systems

Transient and steady-state infrared emission at 2.5 to 15 μ from low-lying vibrational-rotational levels of CO2has been studied using a dc discharge. The time-dependent behaviors of several levels important for laser excitation and relaxation were examined following a pulsed discharge. The decays were, in general, different and were not simple exponentials. Relaxation of vibrational energy of CO2appears to occur by collisions involving vibration-vibration exchange between different vibrational modes and vibration-translation relaxation of the bending mode. The rate of transfer of vibrational excitation from N2to various vibrational modes of CO2was investigated as a function of CO2pressure. The addition of He reduced the emission from the lower laser levels with respect to that from the upper laser level and increased the nonradiative decay rate of the lower vibrational levels by CO2-He collisions. Under pulsed excitation, in addition to CO2laser action nearly coincident with the pulse, a weaker, delayed output was observed.     

Q-switched CO2laser

Experimental studies of a rotating-mirrorQ-switched CO2laser have been undertaken to obtain high peak powers at 10.6-μ wavelength. TheQ-switched pulse has a temporal structure consisting of two intensity peaks and is similar to the temporal behavior of a slowQ-switched CO2laser. Based on the gas pressure dependence it appears that the pulse structure and duration are influenced by collision-induced relaxations of the laser medium. Using an oscillator-amplifier system peak powers of 120 kW with pulsewidths of 200 ns have been obtained.     

Suppression of transverse modes of a CW CO2laser by cavity length control

The described technique of transverse mode control makes use of the small transition linewidths of the CW CO2laser. The laser medium itself is used for spectral discrimination. The method was tested and found to be superior to the usual technique of using an intracavity iris.     

CW 10.6-µ CO2laser pumped by the chemical reaction of nitric oxide with nitrogen atoms

The operation of a CW CO2laser pumped by vibrationally excited nitrogen generated by the reaction of nitric oxide with atomic nitrogen is reported. 15-mW output power at an overall chemical efficiency of 1 percent has been obtained. The population inversion density of the system has been determined from gain measurements.