Donald J. Reichle

High-energy Q-switched 0.946-µm solid-state diode pumped laser

Designing a high-energy Q-switched all-solid-state laser operating on the quasi-four-level 0.946-µm transition of Nd:YAG is quite challenging because of intense competition from the high-gain 1.064-µm transition. We have achieved such a laser by implementing an innovative resonator design, augmented by specialty coatings. Utilizing this approach, we obtained >75 mJ of Q-switched TEM00 mode energy in an all-solid-state diode pumped laser, a factor of 22 times more energy per pulse than any published data have reported.

Up conversion measurements in Er:YAG; comparison with 1.6 μm laser performance

Up conversion significantly affects Er:YAG lasers. Measurements performed here for low Er concentration are markedly different than reported high Er concentration. The results obtained here are used to predict laser performance and are compared with experimental results.

HIGH ENERGY DIODE SIDE-PUMPED Cr:LiSAF LASER

A diode side-pumped Cr:LiSAF laser has been demonstrated with a 30 mJ normal mode output energy, and an optical to optical eficiency of 17%. Improved optical quality laser material has been grown with several Cr concentrations. Optimum Cr concentration has been calculated and experimentally confirmed.

Dual-rod Cr: LiSAF oscillator/amplifier for remote sensing applications

A dual rod configuration is used to achieve 16W average power operation from a flashlamp-pumped Cr:LiSAF laser oscillator. A double-pass dual-rod amplifier configuration was used to amplify 141{mu}J pulses from a Q-switched diode-pumped LiSAF oscillator by a factor of {approximately}120. This experiment established a small signal gain of 13.4% per cm at 820 nm. Improved slope efficiency (7.4% electrical-to-light) and pulse repetition frequency (40Hz) were achieved with a single-rod oscillator using improved Cr:LiSAF material.

Measurement of Up Conversion in Er:YAG and Influence on Laser Performance

Up conversion significantly affects Er:YAG lasers, particularly when Q-switching. Measurements performed here using low Er concentration materials are significantly different than those reported using high Er concentrations. Analytical results are compared with experimental data and used to predict laser performance.

Line tunable visible and ultraviolet laser

A novel method of making a line tunable, visible and near ultraviolet, laser source is proposed and demonstrated. It requires only a single laser and 2 nonlinear crystals. It can produce outputs with wavelengths that cover much of the spectrum from 0.26 to 0.67 &mgr;m.

Diode-pumped laser amplifiers: application to 0.946 μm Nd:YAG

A diode-pumped laser amplifier model is derived from first principles and applied to a Nd:YAG amplifier operating on the 4F 3/2 to 4I 9/2 transition at 0.946 μm. The effects of amplified spontaneous emission are included in the model and the addition of this effect is shown to produce better agreement with the data. The amplifier model includes effects of the transverse and longitudinal variation of the pump beam, transverse and longitudinal variation of the probe beam, and multiple passes of the probe beam. Experimental results obtained with a quasi four-level Nd:YAG amplifier operating at 0.946 μm are used to validate the model. The amplifier was evaluated as a function of the pump energy, the probe energy, the probe beam radius, the pulse repetition frequency and the temperature. For all of the experimental conditions, the experimental results and the model agree.

1.88 µm InGaAsP pumped, room temperature Ho:LuAG laser

A room temperature, directly diode pumped Ho:LuAG laser oscillated for the first time. Direct pumping of the Ho upper laser manifold maximizes efficiency, minimizes heating, and eliminates Ho:Tm energy sharing. Design and performance are presented.

Asymmetric Time Constants

Time constants for population density rise and decay are often unequal. Asymmetric time constants result from: ground state depletion, up conversion, and amplified spontaneous emission. All these effects were modeled and Tm :germanate experiments support model.

Temperature dependence of lifetime and upconvereion in CrAiSrAIF/sub 6/ and Cr:LiSrGaF/sub 6/

Direct growth of semiconductor quantum dot structures can now be achieved in standard growth systems by use of lattice-mismatchinduced three-dimensional growth. Nevertheless, device applications of these self-organized quantum dots will become attractive only if important issues such as size fluctuation, area coverage, and wavelength tunability are controlled. The solution proposed by Ahopelto et al. is to use selective growth ofa heteroepitaxial InGaAs layer on top of nanoscale InP islands. In this quantum dot structure, the emission energy could be controlled by the InGaAs composition and thickness, and a better uniformity is achieved by selective growth of InGaAs on InP. Here we present the optical properties of the heterodots. The photoluminescence spectrum from these InGaAs heterodots exhibits a very bright peak at 1.387 eV with a full width at half maximum of 12 meV. This narrow linewidth might be due to the good uniformity of the InGaAs layer shape and thickness. Moreover, as expected from a schematic band diagram, the InGaAs layer provides type I recombinations for carriers with much shorter decay time than type I1 recombinations involving the InP islands. This behavior has been observed with time-resolved photoluminescence experiments. However, because of strain distribution in the InP islands, the energy of the type I1 transition is smaller than the energy of the type I transition. Therefore both processes are competing. Nevertheless time-resolved photoluminescence spectra exhibit very efficient relaxation processes from the wetting layer and from the surrounding GaAs to the InGaAs layer. Relaxation paths are currently being determined. Recent results have shown that intermixing between P and As could occur during the growth, producing very rough interfaces. Transmission electron microscopy is under investigation. It will finally give a full description of the heterodots system.