Production of electronically excited iodine atoms, I(2P1/2), following injection of HI into a flow of discharge oxygen

The emission from the transition I*(5²P_{1/2}) rightarrowI(5²P_{3/2}) at 1.315 μm following injection of HI into a microwave-discharged He/O2flow has been studied. Relative I*(5²P_{1/2}) emission intensities have been recorded as a function of HI and O²flow rates and as a function of time after injection. Pulsed gain measurements using an iodine photodissociation laser as a source show that the ratio,N_{I}*/ (N_{I} +N_{I}*,) approx 0.15-0.25, is less than that required for population inversion. This observation will be discussed in terms of known chemical processes involving O(³P), HI, O2(¹Δg), and iodine atoms.     

Gain versus time in the CF3I iodine photodissociation laser

A late-time rise in gain for the CF3I iodine photodissociation laser has been reported by other investigators. Within experimental error no rise in gain after the initial photolytic flash was observed in the present experiment.     

Note on near-infrared operating characteristics of the mercury ion laser

Additional excitation mechanisms, apparently overlooked in [1], but previously reported to be responsible for the selective excitation of the Hg II7p²P_{3/2}upper state of the 6150-Å laser line in mercury-helium lasers, are referenced and discussed. It is pointed out that asymmetric charge transfer and Penning-type ionization reactions can also account for the selective excitation of the Hg II7p²P_{3/2}state as well as direct electron impact excitation from the Hg I ground state.     

Diffraction limited CW optically pumped lasers

The far infrared spectral characteristics of inductive metal mesh dielectric hybrid mirrors were investigated. From experimental and theoretical studies, the mirrors were found to exhibit etalon effects due to the finite Si substrate thickness and to have two separate diffraction conditions. With grid spacinggand substrate index of refractionn, forn^{-1} < g/lambda < 1the mirrors diffract in transmission while forg/lambda > 1the mirrors diffract both in transmission and reflection. Using both inductive and capacitive mesh mirrors, EH11outputs have been obtained at the milliwatt level in the range 70 μm to 1.2 mm. Powers in excess of 10 mW were obtained from CH3OH at 96 and 118 μm, HCOOH at 393 μm, CH3I at 447 μm, and CH3F at 496μm.     

Kinetic model of photolytic O2(1Δ) generation

Kinetic analysis of photolysis of O3:O2:He mixtures by UV light has been studied. Dependence of O2(¹Δ) yield on partial pressures, flashlamp intensity, and duration was investigated. Results indicate sufficient O2(¹Δ) yield for operation of a high-power atomic iodine laser on the I*(²P_{1/2})underrightarrow{1.31 mu}m I(²p_{3/2}) transition.     

Efficient V-V energy transfer in a multiphoton excited mixture of SF6and CF4

Spectral and temporal measurements of infrared fluorescence (IRF) in SF6, CF4, and mixtures of SF6and CF4gases excited by a pulsed CO2laser are reported. Using the 944.2 cm^-1[P(20)] laser line for excitation and measuring the IRF spectra between 700 and 1500 cm^-1, a strong red shifted IRF peak of the ν3mode in pure SF6was found. No IRF was observed under these conditions in pure CF4. In a 13:10 mixture of SF6and CF4, two strong IRF peaks of the ν3modes, shifted to the red relative to the room-temperature fundamentals at 948 cm^-1and 1283.2 cm^-1, were observed. The peaks are almost equal in height and since both molecules have almost the same ν3band intensity, the present result suggests that efficient intermolecularV-Venergy transfer occurs from excited SF6to cold CF4molecules. The temporal behavior of the IRF signals under high excitation (langlenrangle approx 6) in pure SF6exhibits two relaxation times, one of bulk cooling withtau_{1} approx 1ms and the other of aV-Tnature withPtau_{2} approx 20 mus . torr. In the mixture, an additional relaxation of the intermolecularV-Venergy transfer process is observed withPtau_{3} approx 10 mus . torr. The red shift dependence of the IRF peaks on the degree of excitation was also measured and used to examine population distributions, specific IRF transitions, and anharmonicity parameters.     

Characteristics of the electron beam pumped iodine monofluoride laser

Electron beam pumping of Ar/CF3I/NF3mixtures yields optical pulse lengthssim0.5 mus from iodine monofluoride. Laser efficiency in this system is ∼0.04 percent. Laser performance is limited by the formation of molecular iodine. The formation of molecular iodine in the excited state (I*2) reduces the number of iodine atoms available to form IF*. In the ground state, molecular iodine (I2) absorbs the IF* laser emission at 485 and 491 nm.     

7B4--Absorption and emission properties of optically pumped ruby

Several experiments on optically excited ruby are described. First, absorption transitions initiated from the metastable states,tmin{2}max{3}²Eandtmin{2}max{3}²T1, are investigated in the photon energy range from 5500 to 45 000 cm^-1. The absorption spectrum of these excited states is determined in bothpi-and σ-polarizations and assignments for the observed absorption bands are achieved. Obtained results are compared with other experiments reported in the literature. Next, emission properties of pink ruby are studied in the region near theRlines. The emission spectrum is determined point by point by means of intense flash excitation. The observed weak bands are ascribed to theR'and phonon assistedRtransitions. Laser actions in these bands are discussed and experimental results on phonon terminated laser amplification are presented. An experiment using a giant pulse as an excitation source reveals that the transition time fromtmin{2}max{3}²Etotmin{2}max{3}²T1is shorter than a fraction of 1μs at room temperature.     

Line competition in the neutral argon laser

Uncertainties in transition assignments for the neutral argon laser lines at 1.792 and 2.208 μm have been resolved by operation of a CW neutral argon laser with several simultaneous output wavelengths. The observed competition effects have established the correct transition for the 1.792-μm line to be3d(1/2)_{1}deg -4p(3/2)_{2}and for the 2.208-μm line to be3d(1/2)_{1}deg -4p'(3/2)_{2}.     

Sensitivity of Pr+3: LaCl3infrared quantum counter

The NEPλand response time of the Pr³⁺:LaCl3Infra-red Quantum Counter have been measured for the wavelengths 1.48 μ, 1.58 μ, 2.03 μ and 2.33 μ at the nominal temperatures of 300°K, 77°K, and 4.2°K. The experimental arrangement is described and suggestions for improvement are made. The best results obtained are anNEP_{2.03_mu} = 2 times 10^{-5}watts(c/s)^{-1/2}and a temperature independent response time of 20-30 ms.     

New room temperature CW laser transitions in YAlG:Nd

Using a dispersive prism, the room temperature YAlG : Nd laser has been made to oscillate CW on a total of seven⁴F_{3/2} rightarrow⁴I_{11/2}transitions ranging in wavelength from 1.0519 μm to 1.1226 μm and a single⁴F_{3/2} rightarrow⁴I_{13/2}transition at 1.319 μm.     

The Mg atomic frequency standard

Recent advances towards the realization of an absolute frequency standard in the submillimeter region are reported. The³p1-³P_{0} Delta m_{j} = 0fine structure transition in the metastable triplet of²⁴Mg has been observed in an atomic beam with both Rabi and Ramsey interrogation techniques. Experimental results and theoretical predictions are compared and discussed in view of an Mg frequency standard.     

Near single-line operation of a free-burning CS2/O2/N2O flame laser with a nondispersive optical cavity

The CS2/O2/N2O flame laser has been operated for the first time under conditions in which the spectral output is nearly single line. This transition is theP_{10-9}(17) of CO at 5.4265 μm, the same transition which was observed to oscillate in single-line fashion by Hirose et al. in an electrically initiated CO chemical laser. It is suggested that the unique behavior of this line may be due to its close proximity to aPbranch transition in an adjacent band, namely theP_{9-8}(23) line, such that the gain profiles of the two lines overlap. Calculations suggest that at the conditions of these experiments, the separation of the line centers for this pair is about 0.3 Å or less. TheP_{10-9}(17) transition was also found to be totally absent under certain conditions of high multiline power, particulary at low O2and N2O flows. This may be due to absorption by a high-bandRbranch transition at 5.4266 μm, namely theR_{15-16}(32) line.     

Study of the duration and birefringence of self-trapped filaments in CS2

Small-scale optically trapped filaments in liquid CS2were studied by side illumination and crossed polarizers using the second-harmonic radiation of a mode-locked Nd³⁺: glass laser. Filaments produced by Nd³⁺laser radiation (1.06 μ) exhibited birefringence of magnitude(2 pm 1) times 10^{-3}and duration times< 10^{-11}second.     

Planar, buried, ion-exchanged glass waveguides: Diffusion characteristics

A detailed theoretical and experimental study of Ag+-Na+ exchange in soda-lime silicate glasses in a molten bath containing a mixture of NaNO3and Ag+ is presented. With no applied field, concentration profilesC(x, t)(and therefore, the index profiles for low concentrations) are given by complementary error function. The estimated value for the self-diffusion coefficientDof Ag+ is 0.133 μm²/min for low concentrations and it monotonically increases with the surface concentration C0until it saturates at about 0.3 μm²/min forC_{0} geq 10^{-3}MF. However, square root dependence of diffusion depth with time seems to be independent of the C0. Presence of an external fieldEcauses the effective depth of diffusion to increase. In fact, for largeEfields, the profile can accurately be described byC/C_{0} = frac{1}{2} erfc(x' - r)wherer = mu Et/sqrt{2Dt}where μ is the ionic mobility of Ag⁺in glass. We define a new diffusion depthWas the distance from the surface to the1/econcentration point, and for large fields,Wvaries linearly withEandt. Experimental results yielded a value of 15.55 μm²/Vmin forμ. As before, square root dependence ofWwithtand the linear variation ofWversus C0forC_{0} leq 10^{-3}MF, withWsaturating forC_{0} > 10^{-3}MF, were observed in the case of field assisted diffusion. A two-step process, where a surface waveguide formed in the first step with eitherEequal to zero or some finite value, is modified by performing a second diffusion in pure sodium nitrate to produce a buried, symmetrical fiber-like profile. This process is also studied in detail.     

Nonlinear refractive index and "DC" kerr constant of liquid CS2at 10.6 µm

The "dc" Kerr constant of CS2has been measured at 10.6 μm and found to be(2.9 pm 0.8) times 10^{-8}statvolt^-2cm. This yields a value of(2.1 pm 0.7) times 10^{-11}statvolt^-2cm²for the nonlinear refractive index.     

Application of laserQswitching for infrared spectroscopy

PassiveQswitching of IR lasers (N2O as well as CO2) has been applied for the detection of coincidences within a few 100 MHz between laser lines (νL) and molecular transitions (νM). Polar (¹²CH3F,¹³CH3F, C2H5OH, and C6H5CH3) as well as nonpolar molecules (SiH4, GeH4, CCl4, C2H4, C3H4, and C6H6) have been studied. The phenomenon depends strongly on the frequency mismatchDeltanu = nu_{M} - nu_{L}. 81combinations between laser lines and molecular absorption lines were found to produce theQ-switch effect.     

Atomic laser action in rare gas-SF6mixtures

Pulsed-laser action is described on a number of atomic transitions of ArI, one of which has not been reported previously. The addition of SF6to Ar shifts the laser action in the Ar from the3d'(3/2)min{1}max{0} - 4p'(1/2)_{1}transition to six ArI transitions originating from the three lowest states of the3p^{5}3delectron configuration. Significant enhancement of the intensity is observed over that resulting from a discharge in pure argon. In addition, when a small amount of SF6is added to a He discharge, laser oscillation results from FI at 0.7129 μm. Increased SF6pressure produces an unidentified oscillation at 2.639 μm. These last two transitions have been observed also in He-NF3, He-CF4, and He-PF3mixtures.     

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.     

Emission cross section and fluorescence efficiency of Nd-pentaphosphate

The room-temperature cross sections for the Nd³⁺⁴F_{3/2}levels to the⁴I_{11/2}and⁴I_{9/2}manifolds (lower laser state and ground state, respectively) in NdP5O14are measured by two spectroscopic methods. A value for the largest cross section ofsigma(R_{1} - Y_{2}) = 1.7 times 10^{-19}cm²is found. The highest effective cross section, resulting from superposition of two lines at 1.051 μm, gives a laser gain per Nd ion which is about 2/3 of the maximum gain in YAG:Nd. The relative branching ratio into the⁴I_{11/2}and⁴I_{9/2}manifolds is 0.65:0.35. Comparison of the integrated cross sections with the measured lifetime for 1-percent Nd in LaP5O14indicates a combined efficiency <0.1 for the remaining transitions, namely radiative decay into the⁴I_{13/2}and⁴I_{15/2}manifolds and multiphonon quenching. A measurement of temperature dependence of fluorescence lifetime supports this last result.