High Power Laser Action Research Articles

The density and compositional analysis of titanium doped sapphire single crystal grown by the Czocharlski method

Titanium doped sapphire (Ti:Al2O3) crystal has attracted attention not only as beautiful gemstones, but also due to their applications as high power laser action. It is very important crystal for tunable solid state laser. Ti:Al2O3 crystals have been success grown using the Czocharlski method with automatic diameter control (ADC) system. The crystals were grown with different pull rates. The structure of the crystal was characterized with X-Ray Diffraction (XRD). The density of the crystal was measurement based on the Archimedes principle and the chemical composition of the crystal was confirmed by the Energy Dispersive X-ray (EDX) Spectroscopy. The XRD patterns of crystals are showed single main peak with a high intensity. Its shows that the samples are single crystal. The Ti:Al2O3 grown with different pull rate will affect the distribution of the concentration of dopant Ti3+ and densities on the sapphire crystals boules as well on the crystal growth process. The increment of the pull rate will increase the percentage distribution of Ti3+ and on the densities of the Ti:Al2O3 crystal boules. This may be attributed to the speed factor of the pull rate of the crystal that then caused changes in the heat flow in the furnace and then causes the homogeneities is changed of species distribution of atoms along crystal.

Relaxation Oscillation with Picosecond Spikes in a Conjugated Polymer Laser.

Optically pumped conjugated polymer lasers are good competitors for dye lasers, often complementing and occasionally replacing them. This new type of laser material has broad bandwidths and high optical gains comparable to conventional laser dyes. Since the Stokes’ shift is unusually large, the conjugated polymer has a potential for high power laser action, facilitated by high concentration. This paper reports the results of a new conjugated polymer, the poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}](PFO-co-MEH-PPV) material, working in the green region. Also discussed are the spectral and temporal features of the amplified spontaneous emissions (ASE) from the conjugated polymer PFO-co-MEH-PPV in a few solvents. When pumped by the third harmonic of the Nd:YAG laser of 10 ns pulse width, the time-resolved spectra of the ASE show relaxation oscillations and spikes of 600 ps pulses. To the best of our knowledge, this is the first report on relaxation oscillations in conjugated-polymer lasers.

Hydrodynamic Instability in High-speed Direct Laser Deposition for Additive Manufacturing

High speed direct laser deposition, when product forms from metal powder, transferred by gas-powder jet, supplied coaxially or non-coaxially to focused laser beam, in one of most prospective additive technologies for production parts for aircraft engines. The limit of process productivity is connected with development of hydrodynamic instability of the melt pool in conditions of high power laser action and material supply by gas-powder jet. Theoretical analysis and experiments allowed clarified a physical nature of instability appearance, determine a stability conditions and invent a methods which allow avoid instability in deposition process. Nozzles for direct laser deposition, designed with consideration of stability conditions, allow get a level of process productivity more then 2 kg/h. The developed technology of deposition and technological equipment, based on high power fiber laser, has been used for manufacturing of parts for “high temperature” unit of aircraft engine.

Colour centre-free perovskite single crystals

Yb 3+:YAlO 3 (YAP) and Yb 3+:GdAlO 3 (GAP) are interesting 1 μm high-power laser media thanks to their very good thermo-mechanical properties. However, as-grown perovskite single crystals exhibit colour centres. Parasitic thermal load generated by these centres is deleterious for high-power laser action and can lead to crystal damages. Moreover these defects decrease Yb 3+ lifetime. They are related to trapped holes on the oxygen network. In the present work, several schemes to remove colour centres are presented. Attention is focused on cerium codoping, thermal annealing under reducing atmosphere and growth of non-stoechiometric compounds.

Thermal Effects in Amorphous YBaCuO Layers under High-Power Laser Action

We have studied the effect of pulsed UV laser radiation (KrF, ħω = 5.01 eV, τ = 25 ns) on the optical transmission and temperature distribution in amorphous YBaCuO layers. The interaction of laser radiation with such layers exhibits an adiabatic character, with an exponential decrease in the temperature in depth of the sample. The slope of the temperature profile is determined by the optical absorption coefficient for the radiation employed. The specific heat capacity of amorphous YBaCuO is c = 1.15 J/(g K).

Change in the optical constants of a semiconductor gap crystal under conditions of high-power laser action

Change in the optical constants of a semiconductor gap crystal under conditions of high-power laser action

High power pure rotational laser due to vibrational excitation

Vibrational-rotational-translational relaxation is suggested as an excitation source of high power laser action based on rotational transitions in the far-IR spectral range. The conditions entailed by the operation of such a device can be achieved through the free expansion of a previously heated mixture of hydrogen halide molecules and slowly relaxing molecules. Systems similar to the present H2-HF gas dynamic laser, with powerful CW lasing in the far-IR, may find applications in plasma diagnostics and isotope separation. 16 references.

High-efficiency infrared xenon laser excited by a UV preionized discharge

We report an efficient high-power laser action in Ar-Xe mixtures at 1.4 atm, without an e-beam, using a simple UV preionized discharge. A wall-plug efficiency of 1.5 percent is obtained with an output energy of 48 mJ, and 70 percent of this energy is delivered on the 1.73 μm line. We describe the experimental optimization of the laser efficiency by varying the partial and total pressures of the gas mixtures, the deposited energy density, and the intensity of the UV preionization. The best performances are obtained for a relatively low energy density (about 10 J/l). This result was expected, due to the very strong ionization rate constant of the xenon excited states. We have also achieved interesting results in Kr-Xe, He-Xe, He-Kr, and He-Ar mixtures.

1.2-J XeCI Laser Excited by Electric Discharge

High-power laser action on the 308-nm band of XeCl excimer excited by electric discharge is reported. A double pulse forming line formed by two parallel flat-plate water capacitors is terminated by a TE lasertube through a double surface gap. An output energy of 1.2 J (60 ns FWHM) per pulse is obtained fora mixture gas of HCl : Xe : He = 3 : 20 : 2600 Torr. The output energy increases by a factor of 1.67 compared with the traditional single pulse forming line.

High-power visible laser action in neutral atomic fluorine

Atomic fluorine is produced by dissociation of NF3 in a fast-pulsed electrical discharge in helium. High-power laser action is observed, with 70 kW on five lines near 7100 Å, all of which are assigned to electronic transitions in neutral atomic fluorine. Two of the laser lines are reported here for the first time. Some scalability appears possible for this laser, which already has proven to be an excellent pump source for infrared laser dyes.

HIGH POWER XENON LASER ACTION IN HIGH CURRENT PINCHED DISCHARGES

Recent experiments using high current capacitor discharges have produced high power laser action in multiply ionized xenon. Strongest oscillation was found on five simultaneous transitions in the green. These lines had a total peak power of 1.4 kW. In addition, streak camera pictures have shown that the onset of laser action begins and is sustained during the interval of time when the plasma is being compressed (``pinched'') by its self-electromagnetic forces.