Abstract: A room temperature solid state laser for producing a laser emission at a wavelength of substantially 2 microns is disclosed. In a preferred embodiment, the laser comprises: a laser crystal having a host crystal material doped with an effective percent concentration of CR.sup.3+ sensitizer ions and with an effective percent concentraton of Tm.sup.3+ activator ions; and a flashpump for exciting the laser crystal to produce a laser emission at substantially 2 microns at a slope efficiency of at least 2 percent.

Abstract: A room temperature laser system for producing a CW laser emission at substially 2.3 microns is disclosed. In a preferred embodiment, the laser system comprises a laser diode source for producing a CW pump beam at a preselected wavelength; and a fiber laser doped with thulium activator ions sufficient to produce an output CW laser emission at a wavelength in the range of 2.2-2.5 microns when the fiber laser is pumped by the CW pump beam.

Abstract: A room-temperature, laser-pumped, Q-switched, thulium-doped, solid state laser for producing pulses of laser emission at substantially 2 microns is disclosed. In a preferred embodiment, the laser comprises: a laser cavity defined by first and second reflective elements opposing each other on a common axis to form a reflective path therebetween; a laser crystal disposed in the laser cavity, the laser crystal having a host material doped with an amount of thulium activator ions sufficient to produce a laser emission at substantially 2 microns from the .sup.3 F.sub.4 to .sup.3 H.sub.

Abstract: A method of achieving inversion in solid-state rare-earth materials for blue-green laser operation. A XeF excimer laser is used to pump a matching transition in divalent ytterbium in a host material. The host material is co-doped with a trivalent ion such as praseodymium (Pr.sup.3+) so that energy transfer to the trivalent ion will take place. Laser action is then from the Pr.sup.3+ ion. Alternative matching absorption transitions also occur in the trivalent rare-earth ions of Tb, Dy, Ho, and Nd.

Abstract: A solid-state laser operative in the mid infrared region (3-5 .mu.m) comprises a YLF laser including a trivalent terbium activator which is pumped by a resonant external laser source (Ho:YLF, 2.06 .mu.m laser) to directly populate the upper laser level which achieves inversion before non-radiative decay depletes the initial laser-level population. The initial laser manifold that is externally pumped is the .sup.7 F.sub.2 manifold. Inversion is then between the .sup.7 F.sub.3 and .sup.7 F.sub.5 manifolds and laser oscillation at 4.1 .mu.m is obtained.

Abstract: A new class of solid-state laser which employs self-pumping from internal laser transitions to achieve inversion in other transitions. A LiYF.sub.4 laser having an activator of trivalent holmium is pumped by a standard flashlamp or by a doubled Nd laser to populate the .sup.5 S.sub.2 manifold. Inversion is achieved between .sup.5 S.sub.2 and .sup.5 I.sub.5 at 1.4 .mu.m. Employing appropriate mirrors, inversion is then produced between .sup.5 I.sub.5 and .sup.5 I.sub.7 at 1.7 .mu.m. Finally inversion is obtained between .sup.5 I.sub.7 and .sup.5 I.sub.8 at 2.06 .mu.m.

Abstract: An efficient, four-level, blue-green, excimer-pumped laser which is opera at room temperature. The laser element includes a CaWO.sub.4 crystal which has been codoped with trivalent thulium activator ions and divalent ytterbium sensitizer ions. Energy is transferred from the absorbing Yb.sup.2+ ions to the Tm.sup.3+ ions and the laser transition is from the .sup.1 D.sub.2 multiplet to the ground .sup.3 F.sub.4 of the Tm.sup.3+ ion. This transition terminates on an excited state; therefore, the laser action is four-level.

Abstract: A method for determining the compensation density of narrow-gap semiconductors. Photo-excited carriers are generated by uniformily irradiating a sample with a laser pulse of a particular density and pulse width for a particular time length and at a low sample temperature. The laser wavelength is chosen with a photon energy sufficiently high that carriers are excited from the conduction band by normal intrinsic absorption (one-photon absorption). Subsequent to the laser pulse, conductivity-voltage measurements are taken as a function of time during the photo-electron decay. Such measurements are made for different applied source-detector connections on the same sample with identical pulse-time values for each different correction. The sample is then laser-pulsed as before with a magnetic field normal to the sample surface to obtain Hall-voltage measurements. The measurements are averaged for the same time duration and the average of all curves are used in the determination.

Abstract: Improvements in Praseodymium solid state YLF lasers operating in the blueeen spectral region at room temperature and providing short pulses useful for underwater communication and detection systems. A dye laser with a narrow spectral output matched to the absorption spectra of the solid state laser is provided as a laser pump. The Pr doped YLF crystal of the solid state laser is physically oriented so it can be longitudinally pumped by light polarized parallel to the c-axis of the crystal, and the solid state laser is equipped with special spectrally selective mirrors. The foregoing and other modifications of prior Pr solid state laser systems provide increased efficiency and power output.

Abstract: A method for determining in situ the thermal conductances of bonding layers of detectors in infrared detector arrays for quality selection of preferred detector arrays. Each detector of the array is heated successively by laser pulses of variable pulse width and the thermally-induced change in detector resistance is measured as a function of time after each laser pulse and converted directly to its corresponding temperature. Using measured values of detector resistance as a function of temperature for each detector, one can obtain the time-dependence of the detector temperature following each laser pulse for each detector of the array.

Abstract: A photoconductive detector comprising a thin film of photoconductive material deposited on a thin substrate of high thermal conductivity having a surface area that is large relative to the detector's absorbing surface area. The back surface of the substrate is metalized and soldered to a high-thermal-conductivity, large-thermal-mass heat buffer which is coupled to a heat sink. The resulting detector is hardened against damage resulting from laser irradiation.

Abstract: A method of determining thermal constants of bonding layers of an infrared ensor which comprises cooling a bonded layer sensor to 77.degree.K and then heating the sensor by a quick pulse of heat. The electrical resistance of the sensor is measured and the measurement continued to determine a thermal profile. The measured thermal profile is compared with a known profile to determine thickness of the bonding layers and the material layers.