Reinvestigation of far-infrared laser emissions from hydrazine and deuterated isotopes of difluoromethane and methanol

Hydrazine (N₂H₄) and the deuterated isotopes of difluoromethane (CD₂F₂) and methanol (CH₃OD and CD₃OH) have been reinvestigated as sources of far-infrared (FIR) laser emissions using an optically pumped molecular laser system designed for wavelengths below 150 microns. With this system, seven FIR laser emissions from optically pumped N₂H₄, CH₃OD and CD₃OH were discovered with wavelengths ranging from 54.0 to 185.0 m. In addition, the polarizations of eight previously observed laser emissions from optically pumped N₂H₄, CH₃OD and CD₂F₂ were measured for the first time. All laser emissions are reported with their operating pressures, relative polarizations and wavelengths, measured to ±0.5 m. The effectiveness of this particular system in generating short-wavelength laser emissions has been further demonstrated by the improvement in output power observed from nine known FIR laser emissions. PACS 07.57.Hm; 42.55.Lt     

Short-wavelength far-infrared laser cavity yielding new laser emissions in CD3OH

A significantly improved far-infrared laser has been used to generate optically pumped laser emissions from 26 to 150 μm for CD₃OH. Using an X–V-pumping geometry, several new laser emissions have been found for CD₃OH. In addition, an increase in power, by factors from 10 to 1000, for many of the previously known shorter-wavelength laser lines, below 100 μm, has been observed. Frequency measurements for several lines have also been performed and have been reported to a fractional uncertainty up to ±2×10^-7, permitting the spectroscopic assignment of the laser transition. One of the frequency-measured lines, 44.256 μm observed using the 10R34 pump, has confirmed the assignment of the previously reported FIR emission (n,K;J)=(1,7;20)?(0,8;20)A in the ground vibrational state. Received: 26 October 2000 / Published online: 7 February 2001     

Laser frequency measurements and spectroscopic assignments of optically pumped 13CH3OH

A three-laser heterodyne system was used to measure the frequencies of twelve optically pumped laser emissions from ¹³CH₃OH in the far-infrared (FIR) region. These emissions, ranging from 54 to 142 μm, are reported with fractional uncertainties up to ±2×10^-7 along with their polarization relative to the CO₂ pump. Using the 9P32 and 10R14 CO₂ lines, complete spectroscopic assignments for two laser systems were confirmed. Received: 31 May 2001 / Published online: 19 September 2001     

Frequency Measurements of Optically Pumped Laser Emissions from the CHD2OH Methanol Isotope

A threelaser heterodyne system was used to measure the frequencies of eleven optically pumped laser emissions from CHD₂OH in the farinfrared (FIR) region. These frequencies, reported with fractional uncertainties of the order ± 2 × 10^–7, are for emissions ranging from 102.9 to 212.4 m. To our knowledge, these measurements are the first reported FIR laser frequencies for the CHD₂OH methanol isotope when used as an optically pumped laser medium.     

Discovery and frequency measurement of short-wavelength far-infrared laser emissions from optically pumped <Superscript>13</Superscript>CD<Subscript>3</Subscript>OH and CHD<Subscript>2</Subscript>OH

A three-laser heterodyne system was used to measure the frequencies of twelve previously observed far-infrared laser emissions from the partially deuterated methanol isotopologues ¹³CD₃OH and CHD₂OH. Two laser emissions, a 53.773 μm line from ¹³CD₃OH and a 74.939 μm line from CHD₂OH, have also been discovered and frequency measured. The CO₂ pump laser offset frequency was measured with respect to its center frequency for twenty-four FIR laser emissions from CH₃OH, ¹³CD₃OH and CHD₂OH. PACS 07.57.Hm; 42.55.Lt; 42.62.Eh     

Discovery and frequency measurement of far-infrared laser emissions generated by optically pumped CH2DOH

A recently improved three-laser heterodyne system was used to frequency measure ten previously observed optically pumped far-infrared (FIR) laser emissions from the partially deuterated methanol isotopologue CH₂DOH. Also, a 64.0 μm FIR emission generated by the 9P32 line of the carbon dioxide (CO₂) laser was discovered and frequency measured. These newly measured frequencies have fractional uncertainties on the order of ±2×10^-7 and correspond to laser wavelengths ranging from 42.6 to 152.7 μm. The offset frequency for the CO₂ pump laser was measured for twenty-two CH₂DOH FIR laser emissions. PACS 07.57.Hm; 42.55Lt; 42.62.Eh     

Discovery and measurement of optically pumped far-infrared laser emissions in 13CD3OH

We report the discovery of four laser emissions from the partially deuterated C-13 methanol isotope ¹³CD₃OH when optically pumped with a cw carbon dioxide (CO₂) laser. The wavelengths of these lines, ranging from 45.3 to 108.9 m, are reported along with their polarizations relative to the CO₂ pump laser, operating pressure, and relative intensity. A three-laser heterodyne system was then used to measure the frequencies of eight optically pumped laser emissions from this methanol isotope. These emissions range from 53.4 to 126.1 m and are reported with fractional uncertainties up to ±2×10^-7. PACS 07.57.Hm; 42.55.Lt     

Frequencies of cw FIR laser lines for use in laser magnetic resonance spectroscopy

A transversely pumped far-infrared laser cavity has been used to discover two optically pumped laser lines: the 357.7 μm line from H₂C=CF₂ and the 242.3 μm line from CH₃OH. Using heterodyne techniques, the frequencies of fourteen far-infrared laser emissions have been measured, six for the first time. PACS  07.57.Hm; 42.55.Lt; 42.62.Eh     

CW and pulsed FIR-CO2 hybrid laser with improved efficiency and amplitude stability at short FIR wavelengths

For the first time stable cw output of a FIR-CO₂ hybrid laser has been achieved at wavelengths shorter than 300 m. Due to the saturable absorber characteristic of the FIR laser gas, cw or pulsed emission is observed on both, the CO₂ and the FIR laser output, depending on the operating conditions. Results are reported on different resonant lines in CH₃OH and the 67 m Raman line in NH₃. The good efficiency of this laser is also demonstrated by the excitation of two new emission lines in CH₃OH, namely 49 and 56 m, pumped by 9R(22) and 9R(24), respectively.On leave from the Institute of Physics, University of Beograd YU-11000, Beograd, Yugoslavia     

Frequency measurements of far infrared cw lasing lines in optically pumped CHCl2F

The wavelengths, frequencies, and relative polarizations of 15 FIR cw lasing lines obtained by optically pumping CHCl₂F with a cw CO₂ laser have been measured. The lines are in the wavelength range from 340.3 to 905.4 m and were pumped by P- and R-branch laser lines in the 9 m band of CO₂.Supported in part by a joint grant with the U. S. National Science Foundation grant # INT80-19014 and the Brazilian Consellio Nacional de Pesquisas (CNPq)Contribution of the U. S. Government, not subject to copyright.     

Controlled two-pulse generation in Q-switch mode from a single laser using Q-modulator with frustrated total internal reflection

In this work a cavity design for double-pulse generation in Q-switched mode from a single laser is proposed, based on the construction of a second laser channel using a FTIR (frustrated total internal reflection) Q-modulator. A time interval between the two pulses from 500 ns to 120 μs is obtained in a Nd:YAG laser. A comparison with other methods and cavity designs for double-pulse generation is presented. The case when this technique is applied on a tunable laser with metastable upper laser level (Cr:LiCAF, Cr:LiSAF, Alexandrite, Co:MgF₂ or other) is also considered. Even though the method presented in the paper does not rely only on the cavity configuration proposed, some advantages can be obtained – both polarization and wavelength-independent tuning without polarization and wavelength restrictions in combination with the possibility of different wavelengths and polarizations in each pulse. Moreover, by using an active medium generating wavelengths around and up to 3 μm, the Pockels-cell-Q-switch optical transmission problems can be avoided. Received: 9 May 2001 / Revised version: 2 August 2001 / Published online: 15 October 2001     

Investigation of 13CH3OH methanol: new laser lines and assignments

We have reinvestigated ¹³CH₃OH as a source of far-infrared (FIR) laser emission using a CO₂ laser as a pumping source. Thirty new FIR laser lines in the range 36.5 μm to 202.6 μm were observed and characterized. Five of them have wavelengths between 36.5 and 75 μm and have sufficient intensity to be used in LMR spectroscopy. Using Fourier-transform spectroscopic data in the infrared (IR) and FIR regions we have determined the assignment for 10 FIR laser transitions and predict nine frequencies for laser lines which have yet to be observed. Received: 17 July 2000 / Published online: 6 December 2000     

A review of optically pumped far-infrared laser lines from methanol isotopes

The technique of optical pumping in polar molecules is the most efficient for Far-Infrared (FIR) laser generation, providing also a versatile and powerful tool for molecular spectroscopy in this spectral region. Methanol (CH₃OH) and its isotopic varieties are the best media for optically pumped FIR laser, with over thousand lines observed, and the most widely used for investigations and applications. In this sense, it is important organize and make available catalogues of FIR laser lines as complete as possible. Since the last critical reviews of 1984 [1] on methanol and its isotopic varieties [2,3,4], over hundred papers have been published dealing with hundreds of new FIR laser lines. In 1992 a review of FIR laser lines from CH₃OH was presented [5]. In this communication we extend this work to the other methanol isotopes, namely CH₃OD, CD₃OH, CD₃OD,¹³CH₃OH,¹³CD₃OH,¹³CD₃OD, CH₃ ¹⁸OH, CH₂DOH, CHD₂OH and CH₂DOD.Work supported by FAPESP, CNPq, FAEP-Brasil, and CNR-Italia     

New FIR Laser Lines from CD3OH

Fourteen new optically pumped far-infrared (FIR) laser lines in the range 46.8 m to 172.6 m were discovered in optically pumped CD₃OH. The pump sources include both the CO₂ laser and the N₂O laser. Two theoretically predicted laser lines were observed in this study.     

Stark effect on CH3OH and CH3F FIR lasers: Large frequency tuning and resolved structures

The operation of a cw FIR laser in the presence of a strong electric field is described. A hybrid metal-dielectric waveguide is used and the cavity length is scanned to study how the frequency and power of the laser depend on the field strength. The results have also been checked by heterodyning with a conventional reference laser. We report the results obtained for the 496 μm line of CH₃F and the 70.5 μm and 119 μm lines of CH₃OH. A large frequency tunability of almost ±40 MHz is obtained in the best case with power levels in the mW range. A very simple theoretical model accounts for the experimental results. We also report the appearance of a new FIR line at about 204 μm when CH₃OH is pumped by the 9 μmP(34) of CO₂ in the presence of an electric field larger than 1.2 KV/cm.     

Infrared laser emission in two-photon pumped sodium vapour

We report infrared laser emission in the region of 3 to 5 μm from sodium vapour optically pumped by a pulsed dye laser with wavelengths ranging from 585 to 610nm. Twophoton excitation processes are believed to be responsible for the primary excitation. Both molecular transitions (4 to 5 μm) between high lying states, and atomic transitions (5² S _1/2−4² P _3/2,1/2 at 3.41 μm) have been identified.     

Frequency measurement of optically pumped FIR laser emissions from the CH3OD methanol isotope

A three-laser heterodyne system has been used to measure the frequencies of seven previously observed optically pumped FIR laser emissions generated by the CH₃OD methanol isotope. The frequencies, measured for the first time, are reported with fractional uncertainties up to ±2×10^-7 for laser emissions ranging in wavelength from 80.1 to 183.3 m. A previously measured FIR laser emission from CH₃OD, observed at 57.2 m, was also re-measured in this work. PACS 07.57.Hm; 42.55Lt; 42.62.Eh     

New laser lines from CHD2OH methanol deuterated isotope

Through the optical pump technique we have reinvestigated the CHD₂OH molecule as a source of far-infrared (FIR) laser lines using for the first time a CO₂ laser lasing on regular, hot, and sequence bands. As a consequence, we present here spectroscopic data of 16 new FIR laser transitions from this molecule. Furthermore, we also present a catalogue of all FIR laser lines generated from CHD₂OH. Received: 13 July 2001 / Revised version: 25 October 2001 / Published online: 14 May 2002     

Operating parameter optimization of optically pumped CH3OH far-infrared laser

By solving the density matrix equations of a quantum system, the output power intensity of an optically pumped CH₃OH FIR laser (CH₃OH-OPFIRL) was calculated by means of iteration method, and the spectral characteristics were got. Base on the calculation, optimization of operating parameters including operating gas pressure, pumped power and output coupling coefficient of the CH₃OH cavity laser were systematically studied. Experimental, a series of FIR emissions of the CH₃OH cavity laser pumped by TEA-CO₂ laser with 9P(16) line were measured. The experimental results were in good agreement with theoretical calculations. The project was supported by the Special Research Foundation of Doctorate Station in University of P.R.C.     

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.