Investigation of D2O-laser emission at 50, 66, 83, 111, and 116 µm

A D2O laser oscillator axially pumped by a TEA CO2laser operating on the9P(32)line has been investigated. The laser emits five FIR lines whose emission characteristics are presented. For the three strongest lines (66, 111, and 116 μm) and an oscillator of length 45 cm, a single axial mode can be made to dominate. Special attention is drawn to the newly discovered and identified 111 μm line.     

Dispersion in a laser-pumped molecular laser

The dispersion equations are derived for two laser fields of arbitrary intensity interacting with a homogeneously broadened, three-level molecular system. The results obtained apply to laser-pumped molecular lasers and may be used to analyze frequency pulling of the emitting laser and self-focusing or defocusing of the pump laser. The laser fields are allowed to be of arbitrary intensity and to be on or off resonance. The dispersion function for the emitting laserchi'(omega_{s})is evaluated in various limits. The present theory is applied to analyze previous experimental data for cavity frequency pulling in CO2laser-pumped molecular lasers, including a 385-μm D2O laser and a 496-μm CH3F laser. Good agreement is found between theory and experiment.     

A 16-µm source for laser isotope enrichment

A potentially efficient, high-energy 16-μm source is proposed based on stimulated rotational Raman scattering in H2or D2using a TEA CO2laser source. The calculated pump energy threshold for rotational Raman scattering on theS(0) 354.33 cm^-1Raman line of H2at 77 K and 1 atm pressure is 3.1 J.     

The optically pumped hydrazine FIR laser: Assignments and new laser lines

Strong far-infrared (FIR) lasing action has been observed in hydrazine optically pumped with isotopic CO2lasers and the N2O laser. The wavelengths of 13 new laser lines have been determined. The results of a recent infrared-microwave double resonance study of hydrazine have been used to assign the transitions involved in the production of five of these new lines and nine of the previously observed laser lines.     

Vibrational energy transfer in CO2under laser conditions with and without water vapor

It is shown that in the case of a dry 1.5-torr CO2gas fill the upper laser level is indirectly excited by vibrationally excited CO produced during the discharge, whereas in the case of a 1.5-torr CO2and 0.2-torr H2O mixture the upper laser level is directly excited by the electrons in the discharge. The collision relaxation times measured under laser conditions for the symmetric valence vibration of CO2in a CO2-H2O mixture and in a CO2-CO mixture as produced during a discharge of an initially pure CO2fill were 19 and 73 μs, respectively. If the reasonable assumption was taken that half of the CO2was dissociated into CO then this result shows that H2O was 14 times more effective in depopulating the lower laser level than CO. The growth in laser intensity for the dry fill was shown to be due to the CO (nu = 1) transfer of energy to the asymmetric vibration of CO2(00°1) with a characteristic increase that was exponential strictly only for a time short compared with the relaxation time of the symmetric vibration. The characteristic transfer time for excitation of the asymmetric vibration was dependent upon the fraction of CO present. If we make the assumption of 50 percent dissociation, the intermolecular energy transfer time between CO and CO2was found to be 40 torr-μs. Results obtained with N2and He added to the laser mixture indicated that He was not more effective in relaxing the lower laser level than N2or CO and was less effective than H2O.     

Observation and assignment of large offset farinfrared laser lines in CH3OH optically pumped by a CO2waveguide laser

Four new FIR laser lines at 62.98, 48.77, 224.53, and 190.65 μm are reported from CH3OH, optically pumped by the 10R34 and 9R10 lines of a waveguide CO2laser. Measurements performed by several techniques confirm that the pump offsets are outside the tuning range of conventional CO2lasers. Two of the lines are assigned as highJtransitions within the torsional ground state of the CO stretch.     

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.     

A study of the CW 28-µm water-vapor laser

The low signal gain of a CW water-vapor laser at 28 μm was measured as a function of the discharge current and pressure. Together with the measurement of other quantities such as the axial electric field and the concentration of OH, a partial interpretation of the mechanisms involved in pumping the 28-μm transition was possible. Thermal equilibrium between the ν0,2nu_{2}, and ν3vibrational levels will result in a large absorption at the elevated gas temperatures observed (800-1000 K). The strong dependence of gain on the electron temperature strongly suggests that the vibrational excitation proceeds through electron-impact excitation. Only the electron-impact excitation of H2O is quantitatively capable of overcoming the large thermally induced absorption. Although vibrational-excitation transfer from H2to H2O seems insufficient, by itself, to overcome this absorption, it may provide appreciable additional gain. Pumping of the 28-μm line through electron-ion recombination and by reactions involving OH can be ruled out.     

Pulsed high-power far-infrared gas lasers: Performance and spectral survey

We describe the practical performance of a pulsed mirrorless far-infrared gas laser pumped by a TEA CO2laser. The system is designed to serve as a high-power source for experiments in far-infrared nonlinear optics and saturation spectroscopy of solids. Out of numerous candidates, 11 gases were selected for a careful survey: CH3F,¹³CH3F, NH3, D2O, D2¹⁸O, D2S, HDS, CH3Cl, CH3Br, CH3I, and CH3CN. With an available pump energy of up to 10 J, a total of 203 far-infrared lines with pulse energies up to 12 mJ were found, covering the wavelength range from 42 μm to 1.2 mm. 78 of these lines had not been observed before. The position of further 39 lines is at variance with former literature reports.     

New frequency measurements and laser lines of optically pumped12CH3OH

The frequencies of 70 optically pumped CW FIR¹²CH3OH laser lines have been measured relative to stabilized CO2lasers. Fifteen new laser lines together with the relative output powers and polarizations for most of the 104 known lines pumped by laser lines in the normal 9 and 10 μm bands of¹²C¹⁶O2are also reported.     

SMMW laser emission and frequency measurements in doubly-deuterated methyl fluoride (CHD2F)

Submillimeter wave laser action is reported in CHD2F on 17 "parent" transitions plus three cascade lines. Accurate heterodyne frequency measurements are reported for nine lines. Useful output powers of greater than 1 mW were observed for several lines. The strongest line, which is at 384.3 μm, is particularly significant because of its potential as a local oscillator for the 385 μm D2O laser.     

Stimulated Raman emission in infrared excited gases

Using the pressure dependence of absorption, absorption coefficients and detunings were measured for CO2pump lines and the strong fat infrared emission in optically pumped D2O. The P (32) CO2line was found to be detuned ∼1.5 GHz from the ν2band transitions6_{6}, 6_{5} rightarrow 5_{5}, 5_{4}. The resulting emission lines at 50.3 μm and 66 μm were found to be detuned from their respective transitions by about the same amount. On the basis of these measurements and gain estimates for the far infrared, the resulting emission lines are identified as stimulated Raman emission.     

Pulsed high-power mid-infrared gas lasers

We present a survey in the spectral region of 200-700 cm^-1(14-50 mum) of pulsed mirrorless gas lasers pumped by a TEA CO2laser. 55 lines are found covering the wavelength range 15.8-57 cm^-1in the gases NH3,¹⁵NH3, D2O, CH3OH, CD3OH, and CD3OD. Most of these lines are reported for the first time. One of the strongest lines (26.4 μm in NH3) emits a considerable pulse energy of 100 mJ. No lines were found in C2H5OH and C3H6O.     

New pulsed far infared laser lines in D2O

Eleven new far infrared (FIR) laser transitions were obtained by pumping a D2O oscillator with the 9P(12), 9P(18), 9P(44), and 10R(22) line radiation of a TEA-CO2-laser. The efficiency of at least two of the new lines is comparable to that of the strongest known lines in D2O.     

Efficient and practical hydrogen vacuum ultraviolet laser

Investigations of the hydrogen vacuum ultraviolet (VUV) laser carried out in the Institute of Spectroscopy of the USSR Academy of Sciences are reviewed. Data for VUV TEA H2and D2lasers at gas pressure up to 2 atm and for low-pressure high-repetition rate hydrogen lasers axe presented. The upper limit quantum system efficiency for both gas dischaxge ande-beam excitation of H2lasers is discussed. The possibility of obtaining CW operation of the H2-VUV laser is also discussed.     

Observation of new FIR superradiant lines from optically pumped D2O

Four new laser lines from optically pumped D2O vapor are reported at wavelengths of 235 μm, 280 μm, 97 μm, and 98 μm, the latter having a quantum conversion efficiency of 38 percent.     

Millimeter and submillimeter-wave laser action in symmetric top molecules optically pumped via perpendicular absorption bands

Ninety-nine new far infrared (FIR) laser lines from 227 μm to 1.965 mm have been observed in CH3CN, CH3CCH, CH3Cl, CH3Br,and CH3I by optically pumping these gases with CO2-laser pulses of 150-μs duration.     

New CW FIR laser action by Stark tuning from optically pumped CH3OH and CH3OD

Fifteen new CW FIR laser lines are reported from Stark tuned CO2optically pumped CH3OH and CH3OD. Four new CW laser lines have also been observed from zero field optically pumped CH3OD, three with a CO2laser, and one with an N2O laser.     

Backward and foreward FIR emmission characteristics drom D2O in both Raman and laser regimes

Laser emission spectra for the 66 and 116 μ D2O lines pumped by the 9.66 μP32CO2line in both backward and forward directions have been obtained. Forward spectra are predominantly Raman dominated, except for a narrow pressure region near 2 torr where the 116 μ line is laser-like. Backward spectra appear to be entirely laser-like showing narrower bandwidths and constant frequency. The shape of the pulse outlines in different directions and pressures confirm the findings of the emission spectra. Total FIR energy emission is also asymetric, being significantly greater in the forward direction.     

Efficient operation of a low-impedance Blumlein discharge initiated HF/DF chemical laser

A study is described on the efficient operation of an HF/DF chemical laser initiated by a low-impedance Blumlein discharge. Some combinations of 0.33 and 0.66-Ω flat-plate Blumlein lines with simple discharge chambers of various active volumes were investigated. For an SF6/H2mixture, an HF laser gave a maximum efficiency of 6.3 percent, and 5 J/1 was extracted. Substitution of D2for H2gave a DF laser output energy as high as 80 percent of the HF chemical laser output.