New CH2F2 FIR laser lines pumped by a tunable WG CO2 laser

8 new large offset FIR laser lines of CH₂F₂ have been discovered by pumping with a high tunability waveguide CW CO₂ laser. Optoacoustic measurements of CH₂F₂ have also been performed and the pump offsets of the new and of previously known lines have been measured and checked. Some assignments are proposed and a few assignments found in literature are checked     

Frequencies of cw FIR laser lines from optically pumped CH2F2

The frequencies of 48 optically pumped cw FIR CH₂F₂ laser lines have been measured relative to stabilized CO₂ lasers. Uncertainties are estimated to be about 5 parts in 10⁷.     

Tuning characteristics of a high pressure CO2 laser pumped CH3F Raman laser

Conclusion We described a CH₃F Raman laser pumped by a two stage 20 atmospheres CO₂ laser. The emission spectrum of the CH₃F laser at 11 Torr extends from 23 cm^–1 to 45 cm^–1 when the CO₂ laser is scanned over the 9R emission branch at a fixed pump power of 180 mJ. The emission spectrum shows a strong structure with large parts where the FIR energy decreases to zero. This fact makes the use of such a laser for spectroscopic scanning experiments in the FIR difficult. The laser is, however, very suited for working at fixed but adjustable FIR frequencies. The pulse energy in the maxima of the emission characteristics at a pump energy of 180 mJ exceeds 300 J, which corresponds a photon conversion coefficient of more than 6%.     

New CW laser lines from CO2-laser pumped CH3OD

New laser wavelenghts have been observed from CW CO₂-laser optically pumped CH₃OD.     

Optically pumped cw CH2DOH fir laser: New lines and frequency measurements

We have measured the output powers and relative polarizations of 66 cw FIR laser lines from CH₂DOH (including 50 not previously reported), which were optically pumped by a CO₂ laser. The frequencies of 43 of these lines were measured relative to stabilized CO₂ lasers.     

FIR gain measurements in cw laser pumped CH3OD

Direct measurements of small signal and saturated gain in cw laser pumped CH₃OD are reported for three lasing transitions of 57 m, 82 m and 103 m. The 57 m transition has a measured gain of 0.6/m, the strongest gain in methanol reported so far. Moreover small gain saturation of this line makes it to be one of the strongest known cw FIR laser lines.     

Multiple submillimeter emissions of difluoromethane pumped by cw 9R(6) laser line of 12C16O2

Pumped by the 9R(6) ¹²C¹⁶O₂ laser lines, CH₂F₂ produces five SMM emissions. Levels involved in this process are identified with the help of a Fourier transform spectrum. Among these emissions we find cascade and intervibrational transitions allowed by Coriolis resonance between v₉ and v₃.     

Infrared-microwave double resonance as an aid in assignment of optically pumped submillimetre laser lines: CH2CF2, CH2F2, and CH3OH

Infrared-microwave double resonance has been used to confirm recent assignments of optically pumped submillimeter wave laser lines in CH₂CF₂ and CH₃OH, as well as a tentative assignment of a line in CF₂H₂. Intracavity double resonance signals have also been obtained in CF₂CH₂ using a circular copper waveguide laser.     

Single line high efficiency tunable fir generation by resonant four-wave mixing in CH3 pumped by a multiatmosphere tunable CO2 laser

By pumping CH₃F with a high pressure tunable TE-CO₂ laser, the resonant four-wave mixing process (RFWM) generates a very efficient tunable single line FIR emission at the Raman frequency. This result is strictly related to the spectroscopic structure of the CH₃F molecule. By means of this process, a tunable FIR emission on a 0.1 cm^–1 bandwidth 150 kW (8 mJ) single line, is obtained which can be used for many FIR multiphoton applications.     

Optically pumped NH3 laser using a continuously tunable CO2 laser

The use of a continuously tunable CO₂ laser to optically pump the NH₃ laser via previously inaccessible absorption lines is described. Efficient laser action has thus been achieved in the 11–13 μm region on transitions formerly only obtained in buffered mixtures.     

CO2/CO2 isotopic ratio measurements with a continuous-wave quantum cascade laser in exhaled breath

A laser spectrometer based on a continuous-wave thermoelectrically-cooled distributed feedback quantum cascade laser at ∼2308 cm⁻¹ has been evaluated for measurement of ¹³CO₂/¹²CO₂ isotopic ratio (δ¹³C) changes in exhaled breath samples and in CO₂ gas flows in the concentration range 1-5%. Mid-infrared CO₂ absorption spectra were measured in a 54.2-cm long optical cell using balanced detection whereby the beam passing through the cell was ratioed against a reference beam split-off from the main beam before the cell. Signal-to-noise ratios (SNR) were estimated for CO₂ concentration measurements determined from either absorption peak amplitude or absorption peak area. The highest SNR were achieved in the measurements based upon a fitted absorption peak area. Typical short-term δ¹³C precisions of 1.1⁰/₀₀ (1-s integration time) and 0.5⁰/₀₀ (8-12-s integration time) were estimated from the two-sample (Allan) variance plots of data recorded in the optical cell at a pressure of 20 Torr and with no active temperature stabilization of the cell and gas flow. The best precision of 0.12⁰/₀₀ was achieved for averaging 80 successive 1-s integration time measurements.     

Opto-voltaic representation of a gain profile in a cw CO2 laser

An opto-voltaic signal is investigated experimentally in a cw CO₂ laser equipped with a coupling-out hole mirror. It is shown that the opto-voltaic signal and the output laser power can be uncorrelated.     

Optically pumped submillimeter laser lines from CH2F2 and CD2Cl2 using a12C18O2 CW laser

Thirty-nine new submillimetre laser lines in CH₂F₂ and twelve in CD₂Cl₂ have been obtained in a Fabry-Perot FIR resonator by optically pumping with a CW¹²C¹⁸O₂ laser. The wavelength range obtained for CH₂F₂ is 126m to 1091m and for CD₂Cl₂ 212m to 774m. The wavelength measurements are accurate to within 5.10^–3. The relative polarisations of the pump laser and the FIR laser output were also determined. Tentative assignments of the IR and FIR transitions were made using existing microwave data.     

Far infrared emissions in NH3 using “forbidden” transitions pumped by a CO2 laser

In this paper it is shown that the use of Stark effect on ammonia gives the possibility to use pump transitions which are forbidden ones in the absence of an electric field. New far infrared emission lines are reported which cannot be obtained using the usual allowed pump transitions.     

Photodissociation of N2F4 by a nanosecond CO2 laser pulse

Photodissociation of N₂F₄ by a strong nanosecond CO₂ laser pulse was studied by probing the interaction volume with both UV and IR beams. Up to 20% of the molecules were found to be dissociated into NF₂ during the first few nanoseconds following the passage of the pulse.     

High power performances of a CW optically pumped 117 μm/184 μm CH2F2 laser with uniform coupling

This paper reports on power performances, laser gain measurements and pressure behavior of the CH₂F₂ laser operating on the intense lines at 117.7 μm and 184.3 μm. The optimum laser coupling rates are determined for these two transitions. 150 mW output power at 184.3 μm is obtained with a uniform coupling of the FIR cavity. To our knowledge this is the best result obtained in such a condition.     

Absolute frequencies of CO2 laser transitions by multiplication of CO2 laser difference frequencies

Frequencies of CO₂ laser transitions have been compared to the Cs standard by a four-step frequency chain using difference-frequencies from five CO₂ isotope lasers. A tungsten-nickel diode generates the differences and their harmonics. Measurement of the 10.71 μm R(6) transition of ¹³C¹⁸O₂ is described. The absolute frequency was found to be 27 979 469.512(65) MHz. Simultaneously, the four other CO₂ frequencies in the chain were also determined.     

N2F4 as saturable absorber of CO2 laser radiation

Tetrafluorohydrazine induces passive Q switching in a continuous-wave CO₂ laser in both the P and R branches of the 10.4 μ system, showing comparable effectiveness on all the accessible lines. At higher pressures, this gas forces the laser to oscillate in the 9.3 μ system in non frequency-selective cavities.     

Activation and cleaning of oxide surfaces by a cw CO2 laser

Silica, alumina, and zinc oxide surfaces have been dehydroxylated by a cw CO₂ laser. Three to seven W/cm² produce the same surfaces spectroscopically as does heating at 400–1000°C. Varying the laser power while keeping the total number of photons constant shows that this is not a linear photochemical process and may be purely thermal desorption. Laser heating has a number of practical advantages over traditional heating methods which have been used for surface cleaning and activation.