Flashpumped, Q-switched performance of Nd:YLF is reported in both single and multimode operation. Approximately 400mJ was extracted from a 1/4 x 3.0 inch Nd:YLF rod in a single, Q-switched pulse.

Stoichiometric crystals of TbP₅O₁₄, TbLiP₄O₁₂ , and TbAl₃ (BO₃₄)were obtained by fluxed growth techniques. The emission spectra of various transitions of Tb in these crystals were obtained at different temperatures. The gluorescence lifetimes of ⁵D₄ states were measured at various temperatures. The emission cross sections of ⁵D₄->⁷F₅ transition are reported.

This paper describes some of the recent progress in glass materials used to generate, control, and attenuate Nd:laser light. Technical and manufacturing developments for phos-phate laser glasses, large monolithic apodizers, high damage threshold AP treated glasses, filters, and other elements will be presented.

A direct method of determination of the valence-electron structure from its crystal structure has been presented by the writer at XIIth International Congress of Crystallography, at Ottawa, 1981. Here the method is applied to determine the valence-electron struc-tures of Y₃Aℓ₅0₁₂ (YAG) and Ak₂0₃, Cr203 (ruby) to see how certain properties of these laser materials are related to their valence-electron structures. The first point observed is the very strong, continuous, but zig-zag three-dimensional fractional covalent M-0 bond nets (M = Ak or Cr) being connected with the high melting points, the great resistance against the puncture by the strong laser beam. In the case of Nd-YAG, the distortion caused by the replacement of the Y atoms by almost the same size Nd atoms is small. On the other hand, because of the similarity of the valence-electron structures of oc-AZ203 and Cr203, the replacement of Ak atoms by the little larger size Cr atoms in small amount is easily understood. The large atomic spins of magnetic moment mg = 2.76 μb (= experiment value, the theoretical mB = 2.702 μg) of Cr atoms pointing paralell to the c axis of the hexagonal lattice, is found to be due to the direction of the spin situated in the space of lowest density space of the valence-electron cloud distribution. This agrees with the result of a-Fe disclosed in the paper "Electron theory of the magnetic moment structures of a-Fe, 6-Co, Ni from neutron diffraction experiments" presented at the Symposium on Neutron Scattering, Argonne National Laboratory, 1981. This will be found also true in many other oxides like a-Fe₂O₃, FeTiO₃, MnTiO₃ and so on.'

The optical properties of the Er³⁺ ion in Yttrium Orthoaluminate (YA10₃) are analyzed with a crystal-field Hamiltonian of C_s symmetry. Starting with the best-fit crystal field parameters, Bkm, the crystal field splitting schemes, the Judd-Ofelt intensity parameters, and multiplet-to-multiplet and line-to-line fluorescence branching ratios for Er³⁺ in YA10₃ have been predicted. The calculated energy levels and the Judd-Ofelt intensity parameters compare reasonably well with available experimental data. It is suggested that the present theory predicts the correct order of line-to-line intensities for the laser transitions emanating from the 453/2 manifold to ⁴I_j channels of Er³⁺ in YA1O3.

Organic dye molecules have fluorescent decay time constants of 4 to 5 nanoseconds. Fluorescence quenching (triplet state) also exists with a time constant of about 50 nano-seconds. The efficiency obtained in lasing dye is then very dependent on the rate in which it is excited. In order to obtain an advantage over laser pumping of dye cells, lamps that operate at high energy with fast rise times are very necessary. This is difficult to do with linear flashlamps because of the relatively high discharge circuit inductance.

Metal halide excimer lasers promise to be an efficient source of high power laser energy in the visible and near infrared. Based on extensive work on the HgBr laser we can expect that the nine lasers based on the group 2B metals (Zn, Cd, Hg) and the halides (Cℓ, Br, I) can each be tuned over a 1008 region. By using these lasers to pump hydrogen isotope Raman cells, a significant portion of the visible and near infrared can be accessed with practi-cal gas laser sources.

By illuminating a ground glass with a laser beam, a spatial field of speckles is created. These speckles are used as displacement gauging elements of curved 3-D objects whose surfaces are coated with photosensitive material. Equations are derived to show that all the three components of the surface displacement can be obtained from two specklegrams.

This paper reviews the frequency stabilization and selected applications of CO₂ lasers at M.I.T. Lincoln. Laboratory. Unsurpassed spectral purity and short-term stability was achieved. A long-term stabilization technique, which was used to line-center lock any regular or hot-band CO₂ isotope laser transition, is also described.

Transverse RF waveguide lasers have demonstrated an undesirable non-unizorm gas discharge related to the electrical transmission line oroperties of the optical waveguide structure. Laser efficiency has been increased over 4 times to 11% for a laser of electrical length in excess of 2/3 λ at 200 MHz by correcting the voltage standing wave pattern with oeriodic inductor shunts. Peak outputs of 8 Watts at 10% efficiency and peak efficiencies of 11% at 4.4 Watt output have been attained with sealed operation for a 21.6 cm device.

Detector structures for the 1-2 µm spectral region are briefly reviewed. Results from VPE InGaAs photodetectors are then described including 100 µm and 500 µm diameter devices for 1.0-1.7 µm, and thin cap 100 µm diameter devices for 0.5-1.7 µm response. High quantum efficiency, low leakage current and high reliability have been observed. Heterostructures for 2-3 µm response are also described.

A miniature Nd:YAG laser oscillator has been demonstrated which uses pulse-slice cavity dumping to achieve optical pulses of 425 ±50 picoseconds FWHM.

The ocular hazards associated with high peak power laser rangefinders can be avoided in systems which emit in the spectral range A λ⪆ 1.4μm. We describe the operation of a 1.73μm laser in erbium-doped lithium yttrium fluoride (Er^3+:YLF) and discuss two ranging systems which utilize this 1.73μm laser source.

The fundamental principles underlying the 3- and 4- level laser operation of alexandrite are discussed and recent performance highlights are given. Applications in the fields of hole drilling, semiconductor processing, photochemistry and lidar are described.

The advent of multifunctional CO₂ laser radars has led to the development of a variety of transmitter modules suitable for both coherent and noncoherent applications. Development trends in CO₂ TEA and modulated waveguide lasers, the principal laser radar transmitter technologies, are reviewed.

A slab geometry, with a zig-zag totally internally reflected optical path, significantly reduces thermal focusing, stress induced biaxial focusing and birefringence in a solid state laser host. We present results of a theoretical and experimental study of slab geometry Nd:Glass and Nd:YAG laser systems.

Neutrons from a pulsed Training Research Isotope Products General Atomics (TRIGA) research reactor are used to create nuclear reactions in a boron coating on the wall of an irradia-tiJn chamber that surrounds flowing oxygen. This generates high-energy ions that interact with the oxygen, producing the long-lived metastable, 02(1▵). Current experiments use 1 to 5 Torr of 02 in 100 to 200 Torr of Ar carrier gas. The 1.27-μm emission from 02(1▵) is monitored 8 meters from the excitation region and nearly 1 second after the reactor pulse (-10 msec wide). Results to date indicate 02;1M/02(3E) fractions obtained are well above the 17% required to invert iodine in a flowing transfer laser. The 0₂(1▵)-12 laser is of particular interest as a candidate driver for an inertial confinement fusion reactor. Since energy coupling between the pellet and driver occurs directly through neutrons, rela-tively high system efficiencies appear possible. Further, the long-lived 0₂(1▵) state provides the energy storage time (fractions of a second) needed between pellet implosions.