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.     

Far infrared frequency synthesis with stabilized CO2lasers: Accurate measurements of the water vapor and methyl alcohol laser frequencies

A far infrared (FIR) frequency synthesis technique using saturated-absorption stabilized CO2lasers and a point-contact diode has been used to measure frequencies of a number of strong CW H2O, D2O, and CH3OH laser lines. The first frequency measurements of the 79-μm H2O, the 73- and 108-μm D2O, and 11 CO2-pumped CW¹²CH2¹⁶OH laser lines are reported. This measurement is the first demonstration of the general usefulness of CO2lasers for accurate synthesis of FIR frequencies.     

Far-infrared laser emission by microwave-infrared-far-infrared three-photon interaction in NH3

We report low threshold Raman and hyper-Raman far-infrared laser emission associated with the¹⁴NH3,nu_{2}, sQ(5, 4)infrared transition. Using a circular metallic waveguide FIR resonator, which also acts as a microwave resonator, threshold pump powers were 50 W CO2-laser radiation and 150 W CO2, 15 W microwave for Raman and hyper-Raman emission, respectively. The hyper-Raman process is suitable to generate frequency-tunable FIR radiation.     

New efficient CW far-infrared optically pumped CH2F2laser

Far-infrared laser action is reported for the first time from the optically pumped CH2F2molecule. Lasing on twelve FIR transitions was produced by pumping with six emission lines in theRbranch of the 9.6 μm band of the CW CO2laser. High conversion efficiencies of up to 20 percent of the quantum limit have been obtained with the stronger FIR laser lines.     

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.     

New far-infrared laser lines from CO2-laser-pumped CH3OH gas by using a copper waveguide cavity

Eleven new far-infrared (FIR) laser lines have been observed from CH3OH pumped by a CO2laser. These lines are ranged from 78 to 694 μm and are obtained by using a copper waveguide cavity.     

New FIR laser lines from optically pumped CH3OH: Measurements and assignments

26 new FIR laser lines have been observed in CO2laser pumped CH3OH, and together with some previously observed lines their wavelengths have been measured with a relative accuracy of3 times 10^{-4}by using the FIR resonator as a scanning Fabry-Perot interferometer. Based on the internal consistency of the data, it is suggested that a number of the lines originate from combination bands involving simultaneous excitation of the CO stretch mode and a different vibrational mode.     

Narrow-band CO2-TEA laser for efficient FIR laser pumping

To reduce the linewidth mismatch between the emission lines of a CO2-TEA laser and the absorption lines of a low-pressure FIR gain medium a tiltable Ge etalon has been introduced into the TEA resonator. The resulting spectral compression and tunability increase the energy conversion efficiency in a TEA laser pumped CH3OH laser by as much as a factor of 37 and has led to the observation of 14 new FIR laser lines.     

Far-infrared CW Raman and laser gain of14NH3

The FIR Raman and laser gain properties of¹⁴NH3optically pumped by the CO29R(30)and the N2O10P(13)laser lines, respectively, have been measured and calculated using the quantum mechanical theory of three-level systems. The laser gain is about two orders of magnitude higher than for usual FIR laser transitions. The Raman gain shows two features characteristic for the two-photon process: extremely high saturation intensity and high pressure maximum. Very satisfactory agreement between theoretically calculated and experimentally measured gain properties is found.     

A powerful new optically pumped FIR laser--Formylfluoride

Intense FIR laser action is reported in formylfluoride (HFCO) with 7 lines of the normal CO2laser and 4 lines of the C¹⁸O2laser.     

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.     

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.     

A tunable far infrared laser

A continuously tunable far infrared (FIR) laser has been demonstrated; experimental results are presented. A high-pressure (10-12 atm) continuously tunable CO2TE laser is used to pump Raman transitions in CH3F; the generation of continuously tunable radiation in the250-300 mum wavelength range is reported. Accurate frequency and bandwidth measurements have been made and the FIR bandwidth in superradiant emission isapprox4-5GHz. Consequently, the generation of frequency tunable, subnanosecond pulses in the FIR appears feasible. The generation of tunable laser radiation from 150 to 1000 μm by stimulated Raman scattering should be possible using higher pump intensity and/or other gases.     

Far-infrared raman laser with high intensity laser pumping

Theoretical and experimental results are presented for a pulsed far-infrared (FIR) molecular gas laser with high intensity laser pumping. In these FIR lasers, high intensity pumping is found to produce stimulated Raman emission at very large offsets (up to 30 GHz) from resonance with the intermediate state. A theoretical, density matrix model is developed for these lasers to account for simultaneous Raman emission on rotational levels in the ground and excited vibrational states (double Raman resonance). This theoretical approach is necessary in the case of off-resonant, high intensity pumping. Theory predicts the FIR emission frequency, the FIR laser gain, and the pump threshold intensity as a function of pump laser frequency. Experimental results are obtained onP-,Q-, andR-branch transitions in¹²CH3F and¹³CH3F using a single-mode, grating tuned CO2TEA pump laser with an intensity of up to 40 MW/cm². Good agreement is obtained between theory and experiment for the observed values of FIR emission frequency and pump threshold intensity. These results indicate that a widely tunable (150-1200 mum), pulsed FIR CH3F laser could be constructed with a tunable, multiatmospheric CO2pump laser of modest power (about 2-5 MW).     

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.     

On the assignment of weak FIR laser lines in optically pumped CH3OH

The rotational-torsional-vibrational quantum numbers of the methanol states involved in the FIR laser action for 9P(22) and 9P(32) CO2pumping are derived. The pumping of weak FIR lines occurs through hot-band and weakly allowed IR lines.     

FIR laser lines of CH3OH pumped by CO2laser sequence lines

We report on the utilization of a sequence band CO2laser as the pumping source for new FIR laser lines of CH3OH.     

A broadly tunable NH3Raman FIR laser

The generation of broadly tunable FIR laser emission by pumping Raman transitions in NH3with 300 mJ, 50 ns duration pulses from a continuously tunable CO2laser is reported. FIR laser outputs up to 4 mJ and a photon conversion efficiency as high as 16 percent have been obtained.     

Far infrared laser emission from15NH3optically pumped by a CW sequence band CO2laser

Two new coincidences between theP(31) andP(35) CO210.6 μm sequence band emission lines and the¹⁵NH3absorption lines have been found to produce far infrared (FIR) emission lines atlambda = 111.9and 218 μm. In addition, the known coincidence between the regularR(42) 10.6 μm band CO2emission line and theasR     

High-power operation and scaling behavior of CW optically pumped FIR waveguide lasers

High-power far infrared (FIR) laser operation at the 10- 100 mW level is described for wavelengths throughout the 40 μm-1.22 mm spectral region. These data correspond to order of magnitude improvements in converting CO2laser energy into FIR laser output. This improved FIR laser performance is attributed to a waveguide laser geometry with reduced losses for the CO2pump and also to a new method of output coupling. The basic design concept of the efficient laser resonator is discussed as well as the prospect for further increases in laser performance through improved efficiency and sealing.