New short-wavelength laser emissions from partially deuterated methanol isotopes

The partially deuterated isotopes of methanol, CH₂DOH and CHD₂OH, have been reinvestigated as sources of far-infrared (FIR) laser emissions using an optically pumped molecular laser (OPML) system recently designed for wavelengths below 150 μm. With this system, 10 new FIR laser emissions from these isotopes ranging from 32.8 to 174.6 μm have been discovered. This includes the shortest known OPML emission from CHD₂OH, at 32.8 μm. These lines are reported with their operating pressure, polarizations relative to the CO₂ pump laser and wavelengths, measured to ±0.5 μm. In addition, polarizations for three previously observed FIR laser lines from CHD₂OH were measured for the first time. This paper is dedicated to the memory of Dr. K.M. Evenson, a pioneer in the field for his role in the development of optically pumped molecular lasers and their use in laser frequency measurements and the laser magnetic resonance technique. His scientific expertise, guidance, mentoring and friendship will be greatly missed. Received: 27 March 2002 / Published online: 8 May 2002     

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     

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 and efficiency measurements on FIR laser lines close to the N+ 3 P 2−3 P 1 transition

FIR laser lines close to the N^{+ 3} P ₂–³ P ₁ transition at 122 m can be used as a local oscillator for heterodyne detectors. The frequencies of some candidate laser lines from CH₂F₂,¹³CH₃OH, CD₃OD, and CD₃OH have been measured and the output power of the most interesting lines has been optimized.     

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     

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     

New large offset far-infrared laser lines from CD3OH

The CD₃OH molecule has been investigated for new far-infrared laser lines by optically pumping with a cw waveguide CO₂ laser. The increased tunability (300 MHz) with respect to a conventional CO₂ laser permits to pump many new CD₃OH lines. As a consequence 108 new laser lines have been discovered, ranging from 42.9 to 1155 m in wavelength. On some lines the effect of an electric Stark field has been investigated demonstrating a laser frequency tuning. The total number of known FIR laser lines from CD₃OH is increased to about 340 making this molecule the most prolific together with CH₃OH.     

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     

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     

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     

CH<Subscript>3</Subscript>OH optically pumped by a <Superscript>13</Superscript>CO<Subscript>2</Subscript> laser: new laser lines and assignments

We report 12 new THz (far-infrared) laser lines from methanol (CH₃OH), ranging from 58.1 μm (5.2 THz) to 624.6 μm (0.5 THz). A ¹³CO₂ laser of wide tunability (110 MHz) has been used for optical pumping, allowing access to previously unexplored spectral regions. Optoacoustic absorption spectra were used as a guide to search for new THz laser lines, which have been characterized in wavelength, polarization, offset, relative intensity, and optimum operation pressure. For 20 laser lines previously observed, we have measured the absorption offset with respect to the ¹³CO₂ laser line center. PACS 33.20.Ea; 33.20.Vq; 33.80.-b     

Optically pumped 13CD3I: new TeraHertz laser transitions

We investigated the ¹³CD₃I isotopomer of methyl iodide as a source of TeraHertz laser radiation using the optical pumping technique. We used a pulsed waveguide CO₂ laser as the pump laser and an open Fabry–Pérot cavity for new laser line generation. We discovered 18 new laser lines with wavelengths ranging from 308.4 to 1132.7 μm, plus two lines previously assigned to ¹²CD₃I. All of the lines were characterized in wavelength, pump frequency offset, optimum pressure of operation, and relative polarization and intensity.     

Large offset far infrared laser lines generation from the C-O stretching Q-branch of 13CD3OD

2 laser of wide tunability to pump ¹³CD₃OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength, polarisation, optimum pressure of operation and precise offset measurements. Received: 17 September 1996/Revised version: 18 November 1996     

New FIR laser lines from an optically pumped far-infrared laser with isotopic 13C16O2 pumping

A ¹³C¹⁶O₂ laser optically pumping a FIR laser has resulted in 17 new FIR cw emissions from 78.5 μm to 917 μm. The FIR media were: CD₃OD, CH₃OD, CD₃OH, NH₃ and ¹⁵NH₃. Interesting effects have been observed with a combination of NH₃ and CD₃OD resulting in a new FIR emission. Two new FIR emissions at 181.5 μm and 355.5 μm have been observed with a ¹²C¹⁶O₂ laser optically pumping CD₃OD.     

Far infrared laser lines produced by methanol and its isotopic species: A review

Methanol (CH₃OH) is considered today one of the most important active media for the generation of laser radiation in the far-infrared (FIR) spectral region. Together with ten of its other isotopic species, it is responsible for the major part of the laser lines generated by the optical pumping technique. Due to the extreme importance of those molecules as laser generators, we understood that there was a necessity of a comprehensive work which would include as much pratical information as possible about each line.Chang et al⁽¹⁾ early recognized methanol as a source of strong FIR laser lines. Since then, more than 100 papers were published containing information about new laser emission. Recently, Moruzzi et al⁽¹¹⁴⁾ presented a review of 575 lines produced by¹²CH₃OH. In the present paper, we have extended the review to the various isotopic modifications of this molecule (namely¹³CH₃OH, CD₃OH,¹³CD₃OH, CD₃OD,¹³CD₃OD, CH₃OD, CH ₃ ¹⁸ OH, CH₂DOH, CH₂DOD and CHD₂OH), a total of nearly 2000 lines with wavelengths ranging from 19µm to 3030µm.     

IR and FIR spectroscopy of 13CD3OH around the 10P(22) and 10P(24) CO2 laser lines: New FIR laser emissions,frequency measurements and assignments

By using high resolution infrared Fourier transform data on ¹³CD₃OH and the 10P(22) and 10P(24) lines of a waveguide CO₂ laser to optically pump this methanol isotope, eight new FIR laser lines were observed. The frequencies of five laser lines were directly measured by heterodyne detection with already known laser lines. Particularly interesting are the lines pumped by the 10P(24) line, since a triade of emissions could be completely assigned.     

Multiwatt, tunable, diode-pumped CW Yb:GdCOB laser

We demonstrate that Yb-doped Ca₄GdO(BO₃)₃ (GdCOB) crystals are suitable for the development of high-power diode-pumped lasers emitting at around 1.04 μm. A 15%-doped Yb:GdCOB crystal was longitudinally pumped with a cw fiber-coupled diode emitting 10 W at 976 nm. While 5.2 W of diode power was absorbed, we obtained 3.2 W of 1043-μm laser light, with a beam quality factor M² equal to 3, and 2.5 W in a diffraction-limited beam. Furthermore, the laser is continuously tunable between 1018 and 1086 nm. Thermal effects have been investigated with a Shack–Hartmann wavefront analyser: although thermal lensing is not negligible, it does not affect the performance of the laser with the resonator design we used. Received: 1 August 2000 / Revised version: 18 September 2000 / Published online: 21 February 2001     

Radio frequency excited waveguide CO2 lasers on sequence-band transitions

2 lasers based on either a quartz or an alumina waveguide were studied on the 00°2 - [10°1,02°1]_I,II sequence bands. A compact multisegment RF excitation with capacitive coupling was used for pumping the gain section of the laser waveguide. The use of a separate intracavity hot CO₂ waveguide suppresses the regular-band transitions. The quartz waveguide laser has a total of 62 lines lasing on both the 9.4 and 10.4 μm sequence bands. The alumina waveguide laser has 40 lines lasing on the 10.4 μm sequence band. These lasers can be either pulsed or continuous-wave (CW) operated on the selected line without a line jumping problem. Received: 29 September 1997/Revised version: 2 December 1997     

High power pulsed fir laser lines from CD3OH

Sixteen FIR laser lines have been observed by optical pumping of CD₃OH with a tunable single-mode TEA CO₂ laser. Particularly large outputs are observed at 70.6 μm (10 P20 pump), 69.9 μm (10 R22), 42.3 μm (10 R6), and 105.3 μm and 41.7 μm (10 R8).     

Assignment of Fir Laser Lines of Fully Deuterated Dichloromethane

We have recently reported 16 new far-infrared laser emissions of CD₂Cl₂. While the overwhelming majority of the previously known FIR laser emissions of this molecule were polarized parallel to the polarization of the pump CO₂ line, 13 of our 16 new lines are polarized perpendicularly to the exciting CO₂ radiation. In principle, the presence of perpendicular/parallel emission pairs is extremely important for the assignment of laser transitions. In the present work we discuss the possible assignments of 16 far-infrared (FIR) laser emission pairs of CD₂Cl₂.