Acoustooptic extension of the frequency tunability of CW CO2 lasers: New FIR lasers emissions from CH3OH and13CH3OH

We have increased the frequency tunability of our CW waveguide CO₂ lasers by means of an acoustooptic amplitude modulator, operating at the fixed frequency of 90 MHz. The up-shifted, or down-shifted, laser optical sideband can be generated independently by adjusting the orientation of the modulator. The efficiency is larger than 50%. The frequency tunability of the CO₂ laser around each laser line is thus increased by 180 MHz. To demonstrate the possibilities of this method, a source composed of the above modulator and of a CW, 300 MHz tunable waveguide CO₂ laser has been used for the search of new large offset FIR laser lines from optically pumped CH₃OH and¹³CH₃OH molecules. As a result 15 and 10 new large offset laser lines were discovered respectively. New assignments of some laser lines are also proposed. We have also measured the Stark effect, the offset, and the polarization of other already known lines. In particular a Stark effect frequency tuning of about 1 GHz is demonstrated for a laser line at 208.399 m.     

Optical pumping by CO2 and N2O lasers: New cw FIR emissions in vinyl cyanide

A systematical study of optical pumping by CO₂ and N₂O lasers using a FIR metallic waveguide has been undertaken in vinyl cyanide. 97 new FIR laser lines are reported in the wavelength range 400 m–1,5 mm.Unité associée au CNRS (UA 836).     

Infrared Optoacoustic Spectroscopy of CHD2OH Around 10R and 10P CO2 Laser Lines

In this work we present results of an investigation on Doppler limited infrared absorbing transitions of CHD₂OH by optoacoustic detection. It is an alternative and attractive technique to be applied to this methanol isotopomer, in comparison to Fourier transform spectroscopy. Using a waveguide CO₂ laser of 290 MHz tunability on each line, we were able to observe 60 IR absorptions, most of them of large offset. The data will be useful in the theoretical analysis of this molecule, as well as in the generation of far-infrared (FIR) laser radiation in optically pumped molecular lasers.     

Multiple beams from Rogowski- profile solid electrode TEA CO2 lasers

Three and five beams were observed to emerge with angular symmetry from Rogowski- profile solid electrode TEA CO₂ lasers. A simple geometrical optics theory of the external reflection guided-modes within the rectangular cavity formed by the laser mirrors and electrodes has successfully accounted for the number and angular separation of these multiple beams, and has established criteria for their elimination.     

Mode structure in wideband waveguide radiofrequency CO2 lasers

We have analysed the mode structure of a wideband radiofrequency excited waveguide CO₂ laser by using different waveguide diameters and optical cavities. In particular we have observed the phase shift of some linear polarized waveguide modes in the transition region between the guided and the free Gaussian propagation.     

Slab CO2 lasers excited by switching power

In this paper we present a new discharge technique to excite slab CO₂ lasers. A uniform stable glow discharge has been obtained in a volume of 3 × 30 × 446 mm³. Output power is 10 W, and a gain of 0.26% cm⁻¹ has been obtained.     

Infrared optoacoustic spectroscopy of13CD3OD around the 10R and 10P CO2 laser lines

In this work we present the results of an investigation about Doppler limited infrared absorbing transitions of the C-O stretching vibrational mode of¹³CD₃OD by means of optoacoustic detection. This technique is an alternative, more sensitive and of higher resolution than the Fourier transform spectroscopy which is applied to this methanol isotopomer, due to the contamination problem associated with the fast exchange of OD by OH in the molecule. Using a waveguide CO₂ laser of 290 MHz tunability on each line we were able to observe 69 absorptions, most of then of large offset. The data will be useful in theoretical analysis of this sample, as well as a guide in the search for new FIR laser lines.     

Various techniques for multiline operation of TEA CO2 lasers

The various techniques used for multiline operation of TEA CO₂ lasers are reviewed with particular reference to the multiline laser parameters of interest in laser applications.     

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.     

Cold-cathode, glow-discharge, electron-beam gun pumped short pulse CO2 lasers

A pulsed cold-cathode glow-discharge electron beam gun emitting an electron-beam of 150 keV energy and 45 cm² cross-sectional area has been used to pump a short pulse CO₂ laser. A fast discharge capacitor bank was used to help make the design simpler than that employed in liquid coaxial lines. The system developed is capable of producing a CO₂ laser pulse of 1 J for about 200 ns duration.     

Advanced CO2 laser rangefinders

Factors affecting the design of compact heterodyne- and direct-detection systems are contrasted. Recent UK achievements are placed in context: a TEA laser direct-detection rangefinder and a chirp-pulse-comparison rangefinder-velocimeter are described.     

Application of CO2 lasers in mechanical engineering technology in the USSR

Lasers are finding many applications in mechanical engineering in the USSR. The various types of lasers in use are investigated and the main properties of laser welding and cutting are studied and compared with other forms of these processes. Methods of surface treatment and heat hardening are also investigated.     

Theoretical study of hybrid TEA–CO2 lasers

Temporal and spatial analysis of dynamics of hybrid transversely excited atmospheric pressure (TEA)–CO₂ lasers is studied using two different models with four and eight energy levels. These models are used for simulation of the laser and computing the output energy. Effects of several parameters such as input energies and gas mixture concentrations (especially presence of CO molecules) are also studied.     

Current CO2 laser surgery

With the development of suitable instrumentation, human-engineered to fulfil the requirements of the clinical surgeon and designed to fit in with the physical conditions prevailing in the operating theatre, laser surgery has advanced rapidly in the past few years. It shows signs of even more rapid progress and general acceptance as its application and advantages in more and more fields of surgery are demonstrated.     

Diffusion of excited state molecules in FIR- and CO2-lasers

Both standing waves in laser oscillators and spatially inhomogenous cross sections of laser beam and pumprate cause a non-uniform distribution of excited state molecules in longitudinal and transversal direction, respectively. This spatial hole burning however is smoothed by diffusion of the excited molecules. The effect of diffusion is investigated theoretically for an optically pumped far infrared laser as well as the corresponding CO₂ pump laser. It is found, that the remaining spatial hole burning in the direction of wave propagation is negligible within CO₂ lasers but not within FIR lasers. Concerning the transversal direction it can be shown that in the FIR laser diffusion takes no effect, whereas the transversal distribution of the excited molecules in the CO₂ laser is significantly influenced by diffusion.FIR ring lasers avoid longitudinal spatial hole burning, which leads to the common assumption that they use the active medium more efficient than conventional standing wave lasers, hence delivering higher output powers. This expected advantage is levelled out to a great extent by diffusion.     

New CW FIR laser lines obtained in ammonia pumped by a CO2 laser, using the Stark tuning method

We report fifty seven CW FIR emissions observed in NH₃, by resonant pumping with a CO₂ laser. Exact coincidences between IR absorption lines of the gas and emission lines of the CO₂ laser have been carried out by Stark tuning. IR frequency shifts, up to 30 GHz, have allowed the pumping of forty three NH₃ transitions.These FIR emissions correspond to thirty one different wavelengths in the 50–400 m range; eighteen ones of them are new emitted wavelengths by pumping with the CO₂ laser.     

CO2 laser welding of copper slabs

For the first time it has been possible to laser weld copper sheets up to 3 mm thick with a 2 kW cw CO₂ laser. The main questions arising from the process are indicated.     

Submillimeter emission lines from CD2Cl2 optically pumped lasers

Fifty-five new submillimeter laser lines from optically pumped CD₂Cl₂, have been obtained in a FIR metallic waveguide resonator. Twenty-seven lines, ranging from 184 m to 1387 m, and twenty-eight lines, from 219 m to 888 m, have been observed when using CW CO₂ laser and CW N₂O laser optical pumping, respectively. The accuracy of wavelength measurements are of the order of 3.10^–3.     

Compact, high power FIR NH3 laser pumped in a three mirror CO2 laser cavity

A compact CO₂–NH₃ FIR laser system where an NH₃ laser cavity was inserted in pump, three mirror CO₂ laser cavity was designed. The total length of this system was about 1.8 m. Output energy of about 1 mJ (10 KW pea power) was obtained at the 152 m and 90 m lines in NH₃. Power conversion efficiency of 1.7 percent was obtained at the 90 m line.     

Optically pumped CW CF3BR FIR laser. New emission lines and tentative assignments

Eight new CW FIR lines from the CF₃Br molecules pumped by a¹²C¹⁶O₂ laser are reported. Tentative assignments have allowed to assign eight among the ten lines reported.