USA As Represented by Secretary of the Navy

Roger E Allen

Leon Esterowitz

Filbert J Bartoli

Melvin R Kruer

Gregory J Kintz

Arrigo Addamiano

Philipp H Klein

Van O Nicolai

Arthur Linz

Lawrence S Goldberg

Hans P Jenssen

A continuous wave(CW) activator ion doped fiber laser is presented which lases at a normally self-terminating laser transition at a slope efficiency greater than that achieved by a self-terminating fiber laser. Two laser transitions, one corresponding to a self-terminating laser transition and the other to a transition out of the lower level of the self-terminating transition, are simultaneously stimulated in the activator ion doped fiber. Through simultaneous lasing of the two wavelengths corresponding to these transitions, the lower level of the self-terminating transition is sufficiently depopulated so that CW operation is achieved.

Rare earth ion doped CW cascade fiber laser

A room temperature laser system for producing a CW Laser emission at substantially 2.7 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 erbium activator ions to produce an output CW laser emission at a wavelength in the range of 2.71-2.78 microns when the fiber laser is pumped by the CW pump beam.

Erbium-doped fluorozirconate fiber laser pumped by a diode laser source

A laser system employing thulium and holmium in a trivalent state. The quantum levels of interest in the thulium and holmium are coupled so that one pumping photo absorbed by the thulium results in two photons emitted by the holmium, making for an unusually efficient laser system. The lower level is sufficiently depopulated at room temperature to allow laser operation without cryogenics. In preferred embodiments, the laser pump can be a laser diode, itself especially efficient, and whose output frequency is closely matched in photon energy to the thulium quantum state of interest, thus lending additional efficiency to the overall system. The thulium and the holmium exist in an yttrium-aluminum garnet crystal as lattice replacements for yttrium.

Method and apparatus for lasing

A laser and method for producing a laser emission at a wavelength of substantially 2.8 microns is disclosed. In a preferred embodiment of the invention, the laser comprises laser diode means for emitting a pump beam at a preselected wavelength; a crystal; and a laser cavity defined by first and second reflective elements at opposing ends of the crystal to form a reflective path therebetween; the crystal having a preselected host material doped with a predetermined percent concentration of erbium activator ions sufficient to produce a laser emission at substantially 2.8 microns when the crystal is pumped by the laser diode means, a portion of the laser emission at substantially 2.8 microns being outputted from one of the first and second reflective elements at a slope efficiency of at least 5 percent, but preferably 10 percent, when the crystal is pumped by the pump beam.

Laser diode pumped, erbium-doped, solid state laser with high slope

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.

Thulium-doped fluorozirconate fiber laser pumped by a diode laser source

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.

Excimer-pumped blue-green laser

A cubia, yttria stabilized halnia phosphor, doped with Ce.sup.3+, has been iscovered. The phosphor has a blue luminescence, peaking at about 4200 A, with a secondary peak in the 3800-4000 A region. The optimum composition is 3hfO.sub.2 :Y.sub.2 O.sub.3 :Ce.sup.3+ where the Ce.sup.3+ dopant ranges from 0.1-1.0 weight %.

Luminescent hafnia composition

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.

Excimer-pumped four level blue-green solid state laser

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. From the conductivity-voltage measurments and the Hall-voltage measurements, the mobility .mu., and carrier density n, can be determined. The time dependence of .mu. and n measured during the photo-electron decay yields values of mobility as a function of n. A mobility vs carrier density curve is then prepared and compared with previously prepared curves to obtain a match and thereby determine the quality of the sample. Thus characterization of n-type narrow-gap semiconductors can be made.

Method for determining the compensation density in n-type narrow-gap

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.

Praseodymium blue-green laser system

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.

Determination of thermal conductances of bonding layers in infrared

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.

Room-temperature, thin-film, PbS photoconductive detector hardened

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.

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Alexandria, VA, United States of America

Roger E Allen