CO2pulsed laser radiation tellurium detectors

Subnanosecond detectors and beam monitors for pulsed CO2laser radiation using the photon drag and optical rectification effects in tellurium are presented. Tellurium devices at 10.6 μ have a response of the order of 80 μV/kW . cm^-2with an NEP of8 times 10^{-4}W . Hz^1/2andD*of 500 cm . Hz^1/2/W which is superior to commercially available photon drag detectors and monitors. It is also expected and experimentally demonstrated that the responsivities of large area monitors can be multiplied by cutting the original area into multi-element strips and electrically connecting them in series.     

Gas dynamic CO2-He-(N2) laser investigations

Experiments on IR laser action and gain measurements are reported for a CO2-containing gas mixture flow that cools as a result of expansion. The mixture is preheated by a reflected shock wave, and the gas is expanded into a vacuum through a slit. Laser action is obtained in a CO2-He mixture, while the addition of nitrogen increases the gain. The gain was found to depend on the distance from the slit and the gas pressure before the slit.     

Results of the time-dependent gain with a high-current electron-beam sustained discharge in CO2

A large-aperture cold-cathode electron beam with 150 kV and 0.4 A/cm²has been used to sustain 1-μs discharges in a CO2-laser mixture of 3/(1/2)/1. The electron density produced in the gas was approximately3.9 times 10^{13}cm^-3and thus for 1 atm a discharge power density of 150 J/1μs was achieved at 5.4 kV/cm for the sustainer electric field. The time-dependent gain for the 001-100 transition has been measured. Taking the experimental values of the discharge power, the gain has also been calculated using a kinetics program and a solution of the Boltzmann equation for the fractional power transfer. The good agreement between the experimental and calculated results gives confidence that the performance of cold-cathode electron-beam sustained-discharge CO2lasers can be predicted.     

Small-signal gain of a CO2laser amplifier utilizing a white optical reflector design

A small-signal gain of 39 dB in a nonresonant multi-path CO2laser amplifier with a discharge length of 65 cm is reported. The multipath system employed is a modified White optical reflector design. An unsaturated gain of 39 dB was observed for signals smaller than 10^-5watt. No noise component, due to the amplifier, was detected for signals as small as5 times 10^{-8}watt.     

Experiment on cross relaxation in CO2

The details of the hole-burning process are studied experimentally and theoretically in a Doppler-broadened gain or absorption line in pure CO2and in CO2-N2mixtures contained in a test cell. The change of absorption or gain of the test cell when irradiated by a saturating laser in aPtransition is probed with another laser operating in one of manyRtransitions. In this way one may determine the rate of velocity cross relaxation within a single rotational-vibrational level and the rate of cross relaxation between different rotational levels of the upper and lower vibrational states. When the probing laser shares a common upper or lower level with the saturating laser, a pip is observed in the differential absorption or gain profile at total pressures of less than 0.5 torr. At higher pressures the relaxation across the velocity profile eliminates the pip. An analysis is presented of the population distribution in the multilevel system of CO2. Three of the relaxation rates (describing the relaxation across the velocity profile of a single level, the relaxation among rotational levels of the vibrational state, and the phenomenological relaxation rate of entry into and departure from the upper and lower vibrational states) are determined. The last of the three rates is found to be dominated by diffusion at the pressures used in the experiment.     

High power far-infrared emission from CO2laser-pumped D2S and HDS

Intense superfluorescent emission in the far infrared has been produced for the first time at wavelengths oflambda = 135.7 mum andlambda = 90.1 mum from D2S pumped with a CO2TEA laser. The pump and emission lines have been assigned to molecular transitions in the ν2vibrational mode. An additional strong line atlambda = 183.2 mum has been attributed to the HDS molecule.     

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.     

Transition selection with adjustable outcoupling for a laser device applied to CO2

In this paper we discuss the possibilities and realization in high-power systems of a narrow-band reflector with adjustable high reflectivity and with continuous tuning over a large frequency region. We describe a design for both low- and high-gain systems. For the experimental realization of a low-gain system we used a CO2laser and studied a continuous range of 65 transitions of the00deg1-02deg0and 13 transitions of the 01¹1-11¹0 vibrational band. With a cavity containing a dc discharge 130 cm long, for each band we found a continuous range of single oscillating transitions with output powers up to 15 W. Finally, we propose an experimental solution for continuous tuning of a high-gain system as, for instance, the central part of the00deg1-10deg0vibrational band of CO2.     

Collisionless self-focusing of CO210 µm P(20) laser light in SF6

We develop a simple intuitive picture of the vibration-rotation structure of the SF6molecule such that the molecular susceptibility responsible for self-focusing can be calculated. We treat the propagation dynamics by generalizing the standard steady-state Gaussian propagation equations to include the important effect of absorption in the wings of the spatial profile. By calibrating the model to absorption data at CO210 μmP(2)we find good agreement with beam waist data at the same wavelength. Absorption in the wings is dominant at low laser fluences, and the real part of the susceptibility is responsible for the defocusing-to-focusing turnover in the beam waist near 100 mJ/cm², consistent with the interpretation of Nowak and Ham [6].     

The LEKKO VIII CO2gas laser system

The eight-beam CO2laser system, LEKKO VIII, producing 10 kJ for the inertial confinement fusion (ICF) research, has been completed. Advanced techniques developed with the LEKKO II 1 kJ laser have been fully implemented; such as a new type of laser gas, suppression of parasitic oscillation, and automatic operation of the system. A concept for a 100 kJ laser is examined as a feasible module design for a 1 MJ system.     

Gain-optimized CO2waveguide laser

The gain of CO2waveguide lasers was measured for a wide range of He:CO2ratios and total gas pressures. It was found that maximum gain occurs at relatively low pressures. To minimize laser discharge length it is advantageous to operate in this high gain, low pressure regime even at the expense of a reduction in saturation intensity which falls off quadratically with gas pressure.     

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.     

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.     

Experimental studies of the O/O2/CS2CW CO chemical laser

Experimental studies of a CW transverse-flow chemical laser are reported. These studies include investigation of gas flow and mixing lengths, densities of chemical species in the reacting flow stream, and gas-additive effects on laser emission. This device has yielded the highest performance yet observed for CO chemical lasers with a specific output power of 65.5 J/g (29.7 kJ/1b) and a minimum chemical efficiency of 21 percent. It was found that additional chemical species are present in the flow stream beyond those predicted by a simple three-reaction model of the chemical kinetics. Gas additives have been found to give increases in total output power, and can also be used to enhance either high or low bands in the output spectrum.     

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.     

连续波化学氧碘激光器的小信号增益和腔内损耗

本文用变耦合率方法和平行板转动最大损耗法分别测出小信号增益为1.60×10~(-3)cm~(-1)和1.75×10~(-3)cm~(-1),腔内损耗为12.0％,获得了饱和参量为3.00kw/cm~2,并将所得结果与其它报道作了比较。     

Status of CO2isotope lasers and their applications in tunable laser spectroscopy

The use of CO2isotopes can provide a manifold expansion of the usable frequency range of sealed-off CO2lasers. Determination of the frequency, gain, and saturation parameter of the various CO2isotopic laser transitions will be discussed. Design considerations for constructing CO2isotopic lasers and selected applications will be presented.     

Radial gain profiles in CO2laser discharges

Measurements of the gain of the P(20), 10.6 μ, transition of CO2have been made in a flowing He, N2, CO2amplifier. Both small-signal and saturated gain conditions were investigated as a function of radial position. At low discharge currents, the radial small-signal gain profile followed a J0Bessel function distribution as predicted from the electron density distribution, while at higher currents, the gain was nearly constant across the tube diameter. Further increases in the current produced a lower gain on the tube axis than near the tube wall. This spatial behavior of the small-signal gain with discharge current can be understood following the theoretical models of Gordietz et al. or more recently of Wiegand et al. The theory indicates the small-signal gain behavior is largely explained by the increase of axial gas temperature with discharge current. Gain measurements at signal levels high enough to cause gain saturation indicate the gain is harder to saturate on the tube axis than near the tube wall. An analysis of the experimental data shows that the gain-saturation parameter increases with current density.