New CW far-infrared lasing in14NH3using Stark tuning

New CW far-infrared lasing lines have been obtained in¹⁴NH3using either CO2or N2O pump lasers. Except for two of them, all of the lines have been obtained using the Stark effect to tune the infrared laser line and the infrared ammonia transition into frequency coincidence. Electric fields up to 18 kV/cm have been used with pressures of 20 millitorr.     

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.     

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     

Coherent Raman gain spectroscopy using CW laser sources

The recent demonstration of stimulated Raman gain (loss) spectroscopy (SRS) using CW laser sources introduces a powerful tool to coherent Raman spectroscopy. In this paper we undertake an experimental and analytical evaluation of several variations of SRS using CW laser sources including (1) direct stimulated Raman gain (loss) measurements, (2) optically heterodyned polarization interferometry, and (3) two-beam nonlinear interferometry. The results show CW SRS to be a convenient and effective means of obtaining direct Raman spectra in applications where background fluorescence precludes the use of conventional Raman techniques. Sensitivities comparable to or exceeding those obtained by coherent anti-Stokes Raman spectroscopy (CARS) are demonstrated. Ultimate sensitivities exceeding those achieved by spontaneous Raman spectroscopy are expected for high-resolution applications in gaseous media.     

8B7--Energy transfer and CW laser action in Ho3+:Er2O3

Er2O3: Ho³⁺is an unusual laser material in that the host crystal itself provides the dominant pumping mechanism by means of energy transfer. The additional pumping bands due to Er³⁺and the consequent efficient transfer of energy to the Ho³⁺laser ion lead to relatively low threshold laser operation: 5 joules pulsed and 200W CW for a 12mm long crystal at 77°K. The emission waveleng this 2.121μ, a region of good atmospheric transmission. Additional laser experiments were carried out at 145°K. Excitation and fluorescence spectra are discussed.     

Spiking oscillations in diode-pumped NdP5O14and NdAl3(BO3)4lasers

Using quasi-CW sinusoidally modulated excitation from a 0.8-μm-wavelength laser diode, we have obtained driven spiking oscillations in miniature, high-Nd-concentration room-temperature lasers of NdP5O14, and NdAl3(BO3)4. With modulation indices of 0.25 or less, peak-power enhancements of 11 (at 35 kHz) and 7 (at 124 kHz), respectively, have been observed for these materials. Theoretical calculations of these and other characteristics of the driven oscillations are in good agreement with experiment.     

Stimulated Raman scattering of XeF* laser radiation in H2

Stimulated Raman scattering (SRS) experiments have been performed using an ∼2 J,sim0.4 mus pulsewidth XeF* laser as the pump and high-pressure molecular hydrogen as the Raman-active medium. The SRS conversion efficiency and spectral distribution have been characterized as functions of H2pressure and pump laser focal parameters. Energy conversion efficiencies of >60 percent have been obtained, with the converted energy in first and second Stokes radiation, at 414 nm and 500 nm, respectively.     

New far-infrared laser lines in N15H3

Several isotopes of NH3have been studied as laser candidates, including ND2H, NH2D, ND3, and N¹⁵H3. Lasing was observed in N¹⁵H3at 15.08 and 15.91 μ. Tentative assignments of transitions to the2nu_{2} rightarrow nu_{2}vibrational levels have been made. Enhanced energy output was observed in N¹⁴H3with the addition of helium.     

Broad-band gain in optically pumped S2

TheB^{3} Sigma-_{u} rightarrow X^{3}Sigma-_{g}system of S2has many of the characteristics required of a tunable laser: a broad fluorescence spectrum and a Franck-Condon shift between theBandXstates. In this paper, theupsilon' = 4level of theB^{3} Sigma-_{u} rightarrow X^{3}Sigma-_{g}system of S2is pumped by the absorption of the 308 nm XeCl excimer radiation. Rare gas-S2collisions redistribute the population among theupsilon'levels, and the subsequent emission contains intense bands throughout much of the neat UV and visible region of the spectrum. Broad-band gain is reported on two blue-green bands (2,17) and (3,18) populated by rare gas relaxation. Absorption is reported on the near UV bandsupsilon' = 0 rightarrow upsilon" rightarrow 6,7,8where the lower levels are filled by the transient population cascading down theXstate manifold. A fluorescence study is presented which examines the potential advantages and limitations of this system.     

ScBO3:Cr--A room temperature near-infrared tunable laser

We report the first room temperature tunable laser in a borate single crystal. A tuning range of 787-892 nm has been demonstrated in a ScBO3: Cr laser. The laser loss is estimated to be 1.3 percent/cm from our preliminary laser results. Spectroscopic measurements indicate that the material is clear of absorption loss in the lasing spectral region, and the relative fluorescence efficiency for the entire Cr absorption band in the visible region is nearly unity. ScBO3:Cr holds promise as a high efficiency near-infrared tunable laser.     

New wavelengths of the YAlO3: Er laser

In addition to the 1.662 μm laser transition, stimulated emission at three new wavelengths at 1.677, 1.706, and 1.729μm have been observed at 300 K in the YAlO3:Er crystal with an activator concentration of 1.25 weight percent.     

Optical gain and saturation intensity in a transverse-flow CW CO2 laser

Simple expressions for the small-signal gain and the saturation intensity in a transverse-flow CW CO₂ laser have been derived considering the effect of gas flow and the finite time required for N ₂ molecule to transfer its energy to CO₂ molecules. These expressions provide estimates of these parameters fairly close to the experimentally measured values in high-power transverse-flow CW CO₂ lasers     

Far-infrared laser gain resulting from rotational perturbations

A simplified model is used to calculate the unsaturated gains of far-infrared rotational and vibrational-rotational laser transitions that are caused by rotational perturbations. Inversions are derived from the perturbation of an initial Boltzmann distribution of rotational populations, permitting the calculation of laser gains in terms of the perturbation parameters and the vibrational populations. The gain equations are applied to the three perturbations of H2O¹⁶that result in the largest number of laser lines. Numerical gain values in good qualitative agreement with experimental results are obtained.     

Submillimeter laser action of CW optically pumped CD2Cl2, CH2DOH, and CHD2OH

More than 30 laser lines, several of them with an intensity in the order of mW have been obtained in the submillimeter wavelength range from 100 to 900 μm by optically pumping the deuterated molecules of dichloromethane (CD2Cl2) and methanol (CD2HOH, CH2DOH) with a step tunable CO2laser.     

Small-signal gain and time-resolved spectroscopy of the D2-F2/CO2pulsed chemical transfer laser system

Measurements made of the small-signal gain and time-resolved spectral output of a flash-initiated D2-F2/CO2chemical transfer laser system are reported. Small-signal gain measurements indicate a possible lack of rotational equilibration among the rotational levels of the CO2during the DF-CO2V-V energy transfer process. Time-resolved spectral output of this system, operated as a laser oscillator, is presented as verification of the small-signal gain results.     

Additional CW far infrared laser lines from CO2laser pumped cis 1,2 C2H2F2

Six new CW far infrared laser lines are reported for the cis 1, 2 C2H2F2molecule optically pumped by a CO2laser. Of these, two have high conversion efficiencies in the 1-2 percent range.     

横流CO_2激光器的二维增益分布

用一维气流、准二维放电模型算出垂直于电极平面的等增益线二维分布。研究了放电区气体流速、放电参数以及气体成分等对小信号增益沿流动方向变化规律的影响。对于每一气体压力,有与最佳增益曲线对应的流速范围。将计算结果与实验结果进行了比较。     

Electronic- and phonon-terminated laser emission from Ho3+in BaY2F8

Infrared spontaneous and stimulated emission from Ho³⁺in BaY2F8is reported. In addition to the familiar⁵I_{7} rightarrow⁵I8transition at 2 μ,⁵F_{5} rightarrow⁵I5emission at 2.4μ and⁵I_{6} rightarrow⁵I7emission at 2.9μ are discussed. There are several unusual features of the 2-μ laser emission. At room temperature, phonon-terminated laser emission is observed at 2.171 μ. At 77 K a complex CW laser output is observed in a wavelength interval lying on the shoulder of a fluorescence line. The complex output is attributed to oscillation in transverse modes of the resonator. Oscillation is not observed in the strongest emission line, despite a large terminal state splitting of 310 cm^-1. These results are explained on the basis of a theory developed earlier for transition metal ion lasers. The validity of the model is supported by demonstrating the tunability through loss modulation predicted by theory. The observation of these effects is made possible by the very low internal scattering loss in the crystals. The⁵F_{5} rightarrow⁵I5laser lines near 2.4 μ represent relatively low gain transitions with pulse durations limited by accumulation in a longer lived terminal state. The dynamics of laser emission indicate the possible absence of thermal equilibrium in the excited state. For the 2.9-μ transition the bottleneck posed by a longer lived terminal state may be eliminated by the addition of Eu³⁺or Pr³⁺, but laser emission could not be obtained.     

Stimulated rotational Raman scattering in CO2-pumped para-H2

Stimulated rotational Raman scattering in a 300 K multipass cell filled with para-H2with a single-mode CO2pump laser was studied using a single-mode OPO as a probe laser at the Stokes frequency for the So(0) transition. Amplification and pump depletion are examined as a function of incident pump energy. For an incident CO2pump laser energy of 1.5 J, a photon conversion efficiency of 47 percent is observed.