Stimulated Raman emission at 9.2 μm from hydrogen gas

Light at 1.06 μm from a mode-locked Nd:YAG laser has been successfully down-converted by two vibrational stimulated Raman shifts in H₂ gas. Approximately 1 MW of power was produced at second-Stokes wavelength, 9.20 μm. Many other rational and vibrational shifts were observed, up to the seventh anti-Stokes at 260 nm.     

Infrared and far-infrared laser emissions from a TE CO2 laser pumped NH3 gas

In this paper, infrared (IR) and far-infrared (FIR) laser emissions from a TE CO₂ laser pumped NH₃ gas are reported. 8 IR laser emissions near the wavelength of 12 μm were observed by using 4 different CO₂ laser lines for the pumping. 3 IR laser emissions in P-branch of vibrational-rotational band (ν₂ → G) oscillated simultaneously in two pumping cases, i.e. pumping with the R(30) or R(16) line of 9.4 μm band from the CO₂ laser. 26 FIR laser emissions (26.45 μm ～ 281.0 μm) were observed by using 12 different CO₂ laser lines, and the 10 FIR emissions of them may be new laser emissions as far as we know.     

Non-collinear phase matched 4-wave mixing of CO2 and NH3 laser radiation in germanium

4-wave mixing has been demonstrated in room temperature germanium using a TEA CO₂ laser (9.3 μm) and an optically pumped NH₃ laser (12.8 μm) as radiation sources. Non-collinear phase matched emission near 7 μm has been observed with a mixing efficiency close to the calculated value. The extension of this mixing process to generate wavelengths in the important region near 16 μm is discussed.     

Infrared multi-line NH3 laser and its application for pumping an InSb laser

In this paper, infrared (IR) emissions from a TE CO₂ laser pumped NH₃ laser are reported. 38 IR laser lines were obtained from a CO₂ 9R(30) line pumped NH₃ : N₂ mixture by cooling a NH₃ laser tube, and 13 lines of them were new emission lines as far as we known. Four Q-branch lines were included and the others belonged to P-branch transitions. The 12.078 μm line, which was the strongest line in this experiment, was used to pump an InSb spin-fip Raman (SFR) laser which could be tuned from 13.35 to 13.55 μm.     

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).     

Tuneable laser operation of F+2 and (F+2)A centers in OH- and SH- doped alkali halides

Stabilization and tuneable laser operation of F⁺₂ and (F⁺₂)_A centers using OH^- and SH^- doped alkali halide crystals are reported. The new stabilization technique improves previously described laser systems and produced a new F⁺₂(KBr) laser (1.72–2 μm), covering an important gap around 2 μm. All crystals can easily be reactivated for laser operation after extended periods of storage at room temperature.     

A monochromatic and frequency stabilized cw source in the 5 μm region obtained by doubling the frequencies of a cw laser in tellurium

In this paper we describe the construction of a monochromatic and frequency stabilized continuous wave (cw) source in the 5 μm region. It is built up by a cw single line, single-mode frequency and amplitude stabilized CO₂ laser. This primary CO₂ laser source is then frequency-doubled in a tellurium crystal using second harmonic generation (SHG). The obtained emission is monochromatic (half-width 50 kHz). The frequency can be varied discreetly from 4.6 μm to 5.5 μ depending on the CO₂ laser line chosen.     

Stimulated Raman conversion of radiation from a YAG:Nd laser with wavelengths of 1.319, 1.338, and 1.357 µm in a barium nitrate crystal

We have studied stimulated Raman (SRS) conversion to the first Stokes component of multimode (M₂ = 8) radiation from a YAG:Nd laser with lasing wavelengths of 1.319 μm, 1.338 μm, and 1.357 μm in a barium nitrate crystal. We have obtained pulses of converted radiation with energies up to 120 mJ. We have achieved conversion efficiencies greater than 40% for each of the three Raman laser wavelengths of 1.530 μm, 1.556 μm, and 1.582 μm with divergence of the beams of converted radiation close to the diffraction-limited value (M₂ < 1.5). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 330–334, May–June, 2006.     

Generation of picosecond UV pulses by stimulated anti-Stokes Raman scattering

Picosecond stimulated anti-Stokes Raman scattering of hydrogen gas in the ultraviolet region has been studied, using the second harmonic of a modelocked Nd³⁺: YAG laser as an incident pulse (25 ps, 532 nm, 10 mJ). Good conversion efficiency for higher-order anti-Stokes lines has been realized, yielding 2 μJ (200 kW, 10 ps) output for the 8th one at 192 nm. Some features of transient stimulated Raman scattering have been examined and discussed.     

High power performances of a CW optically pumped 117 μm/184 μm CH2F2 laser with uniform coupling

This paper reports on power performances, laser gain measurements and pressure behavior of the CH₂F₂ laser operating on the intense lines at 117.7 μm and 184.3 μm. The optimum laser coupling rates are determined for these two transitions. 150 mW output power at 184.3 μm is obtained with a uniform coupling of the FIR cavity. To our knowledge this is the best result obtained in such a condition.     

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.     

One watt,far infrared CH3OH laser

Peak powers near 1 watt have been observed on the CH₃OH laser line at 570.5 μm as well as on each of three new CH₃OH laser lines produced by pumping a far infrared guided wave cavity with a 0.5 MW helical CO₂-TEA laser. The new lines have wavelengths of 58.1, 65.1 and 451.9 μm. For all four lines the optimum CH₃OH pressure was between 2.3 and 3 torr, and laser action at 65.1 μm persisted up to a pressure in excess of 9 torr.     

Single-mode optical pumping and superradiant emission in D2O and CH3F

Superradiant FIR emission in both D₂O and CH₃F has been investigated using a tunable single-mode CO₂ TEA laser as optical pump, and results compared with multimode pumping. The frequency offset of the absorbing transitions has been measured and compared to other work. Estimates of the dipole transition moments were also obtained from saturation broadening data. Fine structure of the CH₃F (Q12, K) lines have been resolved and compared with theory. High quantum conversion efficiencies were observed for several lines in D₂O: 38% (99 μm), 20% (385 μm) and 12.5% (121 μm) and in CH₃F 21% (496 μm).     

Frequency measurement of the 496 μm line of a CH3F FIR laser

A direct frequency measurement of the 496 μm, K = 2 line from a CH₃F laser is reported. Our laser is a metallic wave-guide device pumped by a frequency stabilized CO₂ laser; its output is mixed in a CaAs-Au Schottky barrier diode with a 100 GHz klystron and the beat note is observed on a spectrum analyzer. The result is f_CH3F(496 μm, K = 2) = 604 297.5 ± 0.2 MHz.     

Anti-stokes fluorescence of polymethine dyes excited by a titanium-sapphire laser

Fluorescence of symmetric polymethine dye solutions (λ _abs ^max ≈ 700 nm) upon anti-Stokes excitation by cw radiation of a titanium-sapphire laser (781 nm) is first investigated. A series of six compounds with analogous composition and spectral and luminescent properties is investigated. It is demonstrated that in addition to the anti-Stokes component, the Stokes component with a maximum at 820 nm (referred to the H-aggregates of initial dyes) is observed in the fluorescence spectra of solutions of the examined molecules when dye concentration increases to 10⁻³ M. Dependences of the anti-Stokes and Stokes component intensities on the exciting radiation power are obtained that confirm a linear excitation character. On examples of xanthene and polymethine dyes, the use of organic fluorophors for anti-Stokes laser cooling and some other possible applications of the anti-Stokes fluorescence are discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 63–70, March, 2007.     

Tunable UV-radiation by stimulated Raman scattering in hydrogen

We observed tunable UV radiation down to 175 nm by SRS of the output of a frequency-doubled dye laser in H₂. The high power output of the 4th anti-Stokes to 5th Stokes line generated by the frequency doubled dye laser and the 8th anti-Stokes to 3rd Stokes line generated by the undoubled dye laser represents a broadly tunable coherent radiation source between 189 nm and 2064 nm.     

Far-infrared two-photon intraband transitions in n-InSb

Two-photon cyclotron resonance and two-photon shallow donor transitions have been excited by a high power pulsed D₂O laser emitting λ = 119 μm and 66 μm laser lines at the same time. Transitions involving the absorption of two 119 μm photons or simultaneously one 119 μm and one 66 μm photon were observed. Two-photon selection rules are discussed by a rigorous treatment of the symmetry of the free electron Hamiltonian.     

Long-wave IR emission in CH3I pumped by a continuously tunable,narrowed-line,CO2 laser

About 150 FIR lines are produced in CH₃I by pumping with a narrowed-line continuously tunable CO₂ laser the 2ν₃ P, Q bands at 9.6 μm. We have obtained in the 330–1560 μm wavelength range, up to 2 μJ pulsed energies by pumping some of the K-sublevels of the P (16≤J≤46) and R (16≤J≤60) absorption lines.     

Tunable infrared generation in KTA and applications

Noncollinear difference frequency mixing of dye laser and Nd:YAG second harmonic (fundamental) radiation from a commercial laser system is employed for the generation of 2.7–5.3 μm (1.6–1.7 μm) radiations in a flux-grown KTiOAsO₁ crystal. The generated radiation is used to scan the methane absorption in the fundamental (v ₃) and its first overtone (2v ₃) band at pressure 90 torr in a laboratory made single pass gas cell of length 33 cm.     

Raman scattering from tuneable hot phonons and polaritons

We report the observation of Stokes and anti-Stokes Raman scattering from angular tuneable hot phonons and polaritons which have been pumped in uniaxial RbClO₃ crystals by a Q-switched CO₂ laser and probed with a c.w. argon ion laser.