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.     

Atomic Sn, Sb, and Ge photodissociation lasers

Stimulated emission has been observed on the 380.1 nm line of atomic tin, the 326.7 nm line of atomic antimony, and the 326.9 nm line of atomic germanium following photodissociation of SnI2, SbI3, and GeI4molecular vapors. A 193 nm ArF laser was used as the excitation source. Bond energies for the dissociation of monoiodides were estimated. Output energies of 200, 80, and 75 μJ were obtained for 380.1, 326.7, and 326.9 nm transitions, respectively.     

Nonlinear optical processes in atoms and molecules using rare-gas halide lasers

The use of nonlinear optical processes expands the flexibility of excimer systems in the study of a wide range of atomic and molecular phenomena and materials. These mechanisms have already allowed for the selective excitation of states in the 10 to 20 eV range involving bound state excitation, ionization, and molecular dissociation. Specific examples involving the electronic excitation of H2, Kr, and Xe, the production of Xe⁺for the analysis of the molecular properties of XeF*, and nonlinear photodissociation of N2O and OCS are discussed.     

Repetitively pulsed, 70-J photolytic iodine laser with excellentoptical and long/reliable operation

The performance of a repetitively pulsed, 70 joule, closed cycle 1.3 μM photolytic atomic iodine laser with excellent beam quality (BQ=1.15) is presented. This BQ was exhibited in the fundamental mode from a M=3.1 confocal unstable resonator at a 0.5 Hz repetition rate. A closed cycle scrubber/laser fuel system consisting of a condensative-evaporative section, two Cu wool I₂ reactor regions, and an internal turbo-blower enabled the laser to operate very reliably with low maintenance. The fuel system provided C₃F ₇I gas at 10-60 torr absent of the photolytic quenching by-product I₂. Using a turbo-molecular blower longitudinal flow velocities greater than 10 m/s were achieved through the 150 cm long by 7.5×7.5 cm² cross sectional photolytic iodine gain region. In addition to the high laser output and excellent BQ, the resulting 8-12 μs laser pulse had a coherence length greater than 45 meters and polarization extinction ratio better than 100:1. Projections from this pulsed photolytic atomic iodine laser technology to larger energies, higher repetition rates, and variable pulse widths are discussed     

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.     

Stimulated-emission cross section and inversion lifetime in a three-atmosphere iodine photodissociation laser

An iodine photodissociation laser has been operated at three atmospheres by adding an inert gas to the laser medium. With three atmospheres of helium added a stimulated-emission cross section of2 times 10^{-19}cm²and an inversion half-life of 110 μs was observed.     

Long operating time CW atomic iodine probe laser at 1.315 µm

A photolytically pumped longitudinal flow CW atomic iodine laser at1.315 mum with virtually an unlimited operating time and easy operation is reported. Several weeks of continual operation is easily attainable. The prolonged lasing is achieved by employing a passive closed cycle flow system of the C3F7I laser fuel. A high pressure dc Hg arc lamp is used for the photolytic pumping. Peak CW powers of 38 mW have been obtained along with good stability (∼1 percent amplitude fluctuations) in the fundamental TEM00mode via the use of an internal lens.     

Gain and energy storage in holmium YLF

It is demonstrated that Q-switched holmium lasers are capable of high-gain and high-energy operation at 300 K. Small-signal gain coefficients of 0.50 and 0.12 cm/sup -1/ have been measured in YLF and YAG, respectively. Small-signal gains of 0.50 cm/sup -1/ are comparable to those achievable in Nd-YAG and are not typical of low-gain materials. This large gain in the Ho:YLF material is made possible by operating the amplifier in the ground state depletion mode. The amplifier performance data and associated analysis presented demonstrate that efficient energy storage is possible with very high excited state ion densities of the Ho /sup 5/I/sub 7/ upper laser level. This is an important result since upconversion can limit the /sup 5/I/sub 7/ population. Although upconversion was still present in this experiment, it was possible to achieve efficient energy storage, demonstrating that the problem is manageable even at high excitation densities in YLF.<>     

Compositionally tuned 0.94-μm lasers: a comparative lasermaterial study and demonstration of 100-mJ Q-switched lasing at 0.946and 0.9441 μm

A new and innovative composite laser material Nd:YAG_xYSAG_1-x has been developed with several objectives in mind; tunability, efficiency, and minimization of the deleterious effects of amplified spontaneous emission (ASE) in Q-switched operation. Wavelength tuning to the requisite wavelength 0.9441 μm was achieved by using the technique referred to as compositional tuning; that is, using nonstoichiometric laser materials to shift the wavelength for precise tuning. Laser efficiency was achieved by studying the physics of 0.94-μm transitions in nonstoichiometric materials; i.e., by examining the effects of the host on the linewidth and cross section of of 0.94 μm neodymium (Nd) transitions, ASE was minimized by choosing materials with a small ratio of 1.06- to 0.94-μm peak cross sections. A comparative study of six different Nd-doped mixed garnet laser material systems was performed to meet the objectives above. Within these six material systems, over 20 laser materials were spectroscopically analyzed. The optimal laser material was found to be Nd:YAG_xYSAG_1-x, which has been demonstrated to lase at the preselected wavelength of 0.9441 μm, an important wavelength for remote sensing of water vapor. Operating this laser on the ⁴F_3/2→⁴I_9/2 transition in Nd:YAG_0.18YSAG_0.82 at 0.9441 μm, has produced for the first time over 100 mT in the Q-switched mode. This represents one of the few lasers that have been designed to operate at a specific, user-preselected wavelength     

Iodine-atom laser emission in 2-2-2 trifluoroethyliodide

Lasing at 1.3 μ upon flash photolysis of 2-2-2 tri-fluoroethyliodide, CF3CH2I, has been observed on the²P_{1/2}-²P_{3/2}magnetic dipole allowed transition of atomic iodine. Using an 800-J flash, a maximum peak power output of approximately 108 W for 10-μs duration at half-maximum intensity was obtained with a pressure of 17 torr CF3CH2I.     

Tunable alexandrite lasers

Wavelength tunable laser operation has been obtained from the solid-state crystal alexandrite (BeAl2O4:Cr³⁺) over the continuous range from 701 to 818 nm. The tunable emission was observed at room temperature and above in a homogeneously broadened, vibronic, four-level mode of laser action. In this mode the laser gain cross section increases from7 times 10^{-21}cm²at 300K to2 times 10^{-20}cm²at 475K, which results in improved laser performance at elevated temperatures. Efficient 2.5 percent, low-threshold (10 J) operation has been obtained with xenon-flashlamp excitation of the 6 mm diameter × 76 mm length laser rods. Output pulses of greater than 5 J and average power outputs of 35 W have been demonstrated, limited by the available power supply. The emission is strongly polarizedEparallelb, with a gain that is 10 times that in the alternate polarization. The 262 μs, room-temperature fluorescence lifetime permits effective energy storage andQ-switched operation. TunableQ-switched pulses as large as 500 mJ have been obtained with pulsewidths ranging between 33 and 200 ns depending on the laser gain. Laser action has also been demonstrated on the high-gain (3 times 10^{-19}cm²emission cross section)Rline at 680.4 nm and is also polarizedEparallelb. This three-level mode is analogous to the lasing in ruby except that the stimulated emission cross section in alexandrite is ten times larger than for ruby.     

输出10MW、ns脉冲的光解碘原子激光振荡-放大系统

报道了一台小型实验室规模的光解碘原子激光振荡-二级放大系统,它可提供脉宽1ns～2μs、脉冲能量几十mJ～10J、峰值功率～10MW的单模输出.文中着重讨论了该系统的设计、各种选模、脉冲发生技术及其工作特性.     

Frequency tuning of a CW atomic iodine laser via the Zeeman effect

A continuously operating, C₃F₇I photolytic 1.315-μm atomic iodine laser has been used to make the first precise observations of frequency tuning of an atomic iodine laser by means of the Zeeman effect. Application of a uniform magnetic field to the gain region of the photolytic iodine laser causes the laser to operate at different frequencies as a function of the strength of the applied field and the polarization of the laser. With the light polarized perpendicular to the applied magnetic field by means of Brewster output windows, the laser could be tuned to frequencies near the 3-4, 2-2, and 3-3 zero-field transitions of the hyperfine spectrum of atomic iodine. With the light polarized parallel to the applied magnetic field the laser could be tuned to two frequencies bracketing the 3-4 zero-field transition and one frequency near the 2-2 transition. Measurements show close agreement between the observed frequency behavior and theoretical models     

Vacuum ultraviolet anti-Stokes Raman lasers

Anti-Stokes Raman laser schemes in atomic sulphur and selenium are studied, allowing conversion of laser lines out of the 350- 178 nm range into the 200-130 nm range. The necessary population inversion with respect to the atomic metastable¹S0levels is produced by photodissociation of the molecules COS and COSe with F2and ArF laser radiation, respectively. Anti-Stokes laser radiation at 167.5 and 158.7 nm for Se and at 182.0, 148.7, and 148.3 nm for S has been generated. Threshold pump energies of 0.1-20 μJ and output energies up to 5 μJ have been observed. At present, the systems are operated at low pump energies, just above threshold. It is expected that by the use of much higher pump energies and by further improvement of system parameters, output energies in the mJ range at MW peak powers will be possible for the VUV transitions.     

Application of laser photolysis to the study of reactive intermediates

Excimer laser flash photolysis in the study of diphenyl carbene (DPC) reveals the presence of at least three transient species produced by excitation of a precursor at 249 nm in isooctane solution at room temperature depending on the concentration of O2present. In an aerated solution, a fast first-order decay assigned to³DPC leads to the formation of an unassigned species which also decays by first order kinetics to produce the observed product Ph2CO. In degassed solution, the fast first-order decay of a species to produce³DPC which decays by second-order kinetics to produce the dimeric products observed.     

Measurement of the wavelength-dependent photoionization cross section of Se*(1S) in the spectral region of 170-175 nm

The photoionization cross section of excited atomic selenium, Se(¹S0), obtained by photodissociation of OCSe, has been measured in the wavelength region of 170-175 nm using a tunable xenon laser. A minimum value, at 172 nm, was found to be1.2 times 10^{-20}cm², approximately ten times less than a recently calculated value. The photodissociation cross section for OCSe, at the same wavelength, was found to be0.8 times 10^{-16}cm², in good agreement with published work. The effect of an election cooling buffer gas upon the electron production from excited selenium was also investigated.     

Atomic lead photodissociation laser

Stimulated emission has been observed on the 405.8, 368.3, and 364.0 nm lines of neutral atomic lead following photodissociation of lead dibromide and lead diiodide molecules with the 193 nm output of an ArF laser. Two-photon dissociation processes are involved in the excitation mechanism.     

Laser chemistry experiments with UF6

This paper summarizes the results of research in a number of different areas of the laser chemistry of UF6. These include: IR excitation and unimolecular dissociation; two color IR excitation; atom-molecule reactions; and UV photodissociation and photochemistry.     

Highly optimized tunable Er3+-doped single longitudinalmode fiber ring laser, experiment and model

A continuous wave (CW) tunable diode-pumped Er³⁺-doped fiber ring laser, pumped by diode laser at wavelengths around 1480 nm, is discussed. Wavelength tuning range of 42 nm, maximum slope efficiency of 48% and output power of 14.4 mW have been achieved. Single longitudinal mode lasing with a linewidth of 6 kHz has been measured. A fast model of erbium-doped fiber laser was developed and used to optimize output parameters of the laser