Tunable far-infrared spectroscopy extended to 9.1THz.

We synthesized tunable far-infrared radiation at frequencies higher than 9 THz (300 cm (-1)) by mixing CO(2) laser, (15)NH(3) laser, and microwave radiation in a W-Co metal-insulator-metal diode. We used this farinfrared radiation to accurately measure torsion-rotation transitions of CH(3)OH in the 8-9-THz region. We also measured the frequency of the aP(7, 3) (15)NH(3) laser transition.

Extension of tunable far-infrared spectroscopy to 7.9THz.

We generated tunable far-infrared radiation by mixing CO(2) -laser,(15)NH(3) -laser, and microwave radiations in a W-Co metal-insulator-metal diode. We used this far-infrared radiation to measure accurately the torsion-rotation transitions of CH(3)OH in the 6-8-THz region.

Far-infrared continuous-wave laser emission from H2O and from NH(3) optically pumped by a CO laser.

We report what we believe is the first observation of continuous-wave far-infrared laser emission from water vapor and from ammonia optically pumped by a CO laser.

Sequential optical pumping of a far-infrared ammonia laser.

We present a novel technique for resonantly pumping a continuous-wave far-infrared NH(3) laser with a linetunable mid-infrared NH(3) laser that is optically pumped by a CO(2) laser. In this two-step process we first convert 10-microm CO(2) laser photons into 11-13-microm NH(3) laser photons, which are then converted into 60-400-microm photons in a far-infrared NH(3) laser. Continuous-wave laser action on 10 far-infrared lines of (15)NH(3), including four new ones, has been obtained with a single CO(2) laser pump line.

Short-wavelength far-infrared laser cavity yielding new lines in methanol.

We report 16 new laser lines generated in a short-wavelength far-infrared Fabry-Perot laser cavity. The CO(2) pump laser is coupled into the far-infrared laser outside the far-infrared laser mode, and the cavity uses a 45 degrees adjustable output coupling mirror; this combination results in a low-loss Fabry-Perot cavity for wavelengths below 150 microm. The new lines are of medium and strong intensity and have wavelengths in the region 26.2-125.7 microm.

Sub-Doppler tunable far-infrared spectroscopy.

The first experimental observations to our knowledge of sub-Doppler linewidths in a cell made using tunable far-infrared radiation are reported. A double-resonance scheme has been used, combining CO(2)-laser infrared radiation with tunable far-infrared radiation to observe a sub-Doppler line shape in an excited vibrational state of CH(3)OH.

Pressure effects on the frequency of continuous-wave optically pumped far-infrared lasers.

The frequency of the 170.6-microm cw CH(3)OH optically pumped laser emission has been remeasured at different pressures without observing the pressure shift observed by Lawandy and Koepf [Opt. Lett. 5, 383 (1980)]. The far-infrared frequency was synthesized with two stabilized CO(2) lasers. No measurable pressure shift over the operating pressure range of the laser was observed, and the frequency was confirmed to be 1 757 526.3 MHz. However, competing lasing lines were found to produce spurious effects on the frequency. These effects may explain the apparent shifts.

Direct frequency measurements of transitions at 520 THz (576 nm) in iodine and 260 THz (1.15 microm) in neon.

The o hyperfine component of the (127)I(2) 17-1 P(62) transition at 520 THz (576 nm) in iodine was measured with respect to the CH(4)-stabilized 88-THz He-Ne laser. A 26-THz CO(2) laser, a color-center laser at 130 THz, and a He-Ne laser at 260 THz were used as transfer oscillators. The measured I(2) frequency was 520 206 808.547 MHz with a total fractional uncertainty of 1.6 x 10(-10). The 1.15-microm (20)Ne Lamb-dip-stabilized laser frequency was 260 103 249.26 MHz with a total fractional uncertainty of 3.1 x 10(-10).

Direct frequency measurement of the I(2)-stabilized He-Ne 473-THz (633-nm) laser.

The absolute frequency of the 473-THz He-Ne laser (633 nm), stabilized on the g or i hyperfine component of the (127)I(2) 11-5 R(127) transition, was measured by comparing its frequency with a known frequency synthesized by summing the radiation from three lasers in a He-Ne plasma. The three lasers were (1) the 88-THz CH(4)-stabilized He-Ne laser (3.39 microm), (2) a 125-THz color-center laser (2.39 microm) with its frequency referenced to the R(II)(26) (13)C(18)O(2)laser, and (3) the 260-THz He-Ne laser (1.15 microm) referenced to an I(2)-stabilized dye laser at 520 THz (576 nm). The measured frequencies are 473 612 340.492 and 473 612 214.789 MHz for the g and i hyperfine components, respectively, with a total uncertainty of 1.6 parts in 10(10). The frequency of the i component adjusted to the operating conditions recommended by the Bureau International des Poids et Mesures is 473 612 214.830 +/- 0.074 MHz.

Frequency measurement of the 260-THz (1.15-microm) He-Ne laser.

Absolute infrared frequency measurement has been extended to 260 THz with the measurement of the strong 1.15-microm laser line in (20)Ne. The frequency was synthesized in nonlinear crystals of CdGeAs(2) and Ag(3)AsS(3) from stabilized CO(2) lasers and the 1.5-microm laser line in (20)Ne. The measured frequency is nu(20)Ne, 1.15 microm = 260.103 284(30) THz.

Extension of absolute-frequency measurements to the visible: frequencies of ten hyperfine components of iodine.

Direct-frequency measurements have been extended into the visible region of the electromagnetic spectrum. The visible frequencies were synthesized by generating the second harmonic of the recently measured 260-THz (20)Ne, 1.15-microm laser with a LiNbO(3) crystal. The absolute frequencies of ten hyperfine components of (127)I(2) near 520 THz are reported.

Additional cw FIR laser lines from optically pumped CH(2)F(2).

Twenty-five new, cw, FIR lines from CH(2)F(2), optically pumped by a CO(2) laser, have been found, using a variablecoupling, open-structure resonator. Accurate wavelength measurements have been made on the 47 known CH(2)F(2) lines. The new lines are fairly uniformly distributed over a wide range, from 105 to 1448 microm.