Laser Emission Characteristics Research Articles

Enhanced fundamental and self-frequency-doubling laser emission efficiency in F43/2 directly pumped Nd-activated nonlinear crystals: The case of GdCa4O(BO3)3

The possibilities of improvement of laser emission characteristics and reduction of heat generation by direct pumping at 887 nm into the emitting level F43/2 of Nd3+ in the self-frequency-doubling crystal Nd–GdCOB [GdCa4O(BO3)3] are discussed. Enhanced laser emission performances at fundamental 1060 nm, and especially at the self-frequency-doubled 530 nm wavelengths as compared to the traditional 811 nm pumping into the F45/2 level, are demonstrated.

Quasi-three-level 946 nm CW laser emission of Nd:YAG under direct pumping at 885 nm into the emitting level

The possibility to enhance the laser emission characteristics and to reduce the heat generation for the 946 nm Nd:YAG laser by direct pumping into the emitting level is discussed. Improved laser characteristics are demonstrated with a 1 at.% Nd:YAG component under 885 nm pumping into the thermally activated transitions Z 2→R 1 and Z 3→R 2 of the 4 I 9/2→ 4 F 3/2 absorption.

Efficient laser emission in concentrated Nd laser materials under pumping into the emitting level

The possibility of using concentrated Nd laser materials for efficient laser emission and for scaling to high powers is discussed. It is shown that the increased optical absorption in these materials makes direct pumping into the emitting level feasible, with a reduction of the quantum defect between the pump and emission wavelengths, which in turn can enhance the laser emission characteristics and reduce heat generation under pumping. The investigation of the effect of Nd concentration on emission decay of Nd:YAG indicates that up to quite high concentrations, the reduction of the emission quantum efficiency by self-quenching can be compensated by an increase in the pump absorption. Efficient continuous-wave laser emission is demonstrated under direct pumping into the /sup 4/F/sub 3/2/ emitting level of Nd:YAG crystals with up to 3.5-at.% Nd, Nd:YAG ceramics with up to 6.8-at.% Nd, and Nd:YVO/sub 4/ crystals with up to 3-at.% Nd. Superior performance as compared to traditional pumping into the /sup 4/F/sub 5/2/ state were obtained. It is inferred that direct pumping into the emitting level of concentrated Nd materials can improve the efficiency of solid-state lasers in the free-generation or low-storage regimes and opens the possibility of scaling these lasers to high powers.

Comparative investigation of spectroscopic and laser emission characteristics under direct 885-nm pump of concentrated Nd:YAG ceramics and crystals

A high-resolution spectroscopic and emission-decay investigation of highly concentrated Nd:YAG single crystals and ceramics shows that the state of the Nd3+ ions and their interaction in these materials are similar and can be used for construction of efficient solid-state lasers directly pumped in the emitting level. This possibility is demonstrated by continuous-wave emission of concentrated Nd:YAG crystals with up to 3.5 at. % Nd and ceramics with up to 6.8 at. % Nd under resonant 885-nm end pump.

Oligo(phenyl-ethynylene)s for electroluminescence and distributed feedback laser action

We investigated the electroluminescence (EL) and optically pumped laser emission characteristics of oligo(phenyl-ethynylene)s end-capped with naphtyl groups and bearing dodecyloxy side-chains. Oligomers (oNPE x) made of 3- or 5-aryl groups are dispersed in poly(vinylcarbazole) (PVK) as a hole-transporting matrix to study EL properties. The emission spectrum of the trimer oNPE3 is centered at 460 nm, slightly blue shifted with respect to the pure phenyl derivative. The typical diode structure is composed of an indium tin oxide (ITO) anode ITO/oNPE x/PVK/and aluminium cathode. The EL spectrum matches photoluminescence (PL). Emission color changes with the concentration from violet to blue for oNPE3 and blue to blue-green for oNPE5 and oNPE5 b. Thin film of oNPE x/PVK also show laser emission around 447 nm in a distributed feedback laser (DFBL) optical pumping scheme. PVK acts in this case as an amorphous laser host matrix and oNPE x shows laser emission tunable by varying the incidence angle of the pump beam onto the film.

Photophysical and lasing properties of a new ester derivative of rhodamine 6G

Absorption and fluorescence spectra, fluorescence decay curves and laser emission characteristics of a newly synthesized dye belonging to the rhodamine family, dissolved in several aliphatic monoalcohols and in water/ethanol mixtures, have been obtained. The new dye incorporates the chromophoric group of rhodamine 6G, but with the ethyl substituent in the ester group of this molecule replaced by the p-ethoxycarbonylbenzyl group, and can be considered as a molecular model for a previously described rhodamine dye with a polymerizable double bond that has demonstrated to lase efficiently with good photostability in solid polymeric matrices. The results obtained indicate that the modifications in the dye molecule scarcely affect the photophysics of the rhodamine chromophore. The new rhodamine dye has lasing properties that correlate well with its photophysical characteristics. Laser emission in water solution with efficiencies as high as 10.5% has been obtained.

Frequency measurements on far-infrared emissions from12C16O2-pumped methyl chloride and from12C18O2-pumped difluoromethane

The frequencies of 42 far-infrared laser lines have been measured by mixing with high-order harmonics of microwave frequencies in a Josephson junction. A total of 5 emissions between 334 and 1887 μm have been measured from12C16O2-pumped methyl chloride (CH3Cl) and 37 emissions between 116 and 1092 μm in12C18O2-pumped difluoromethane (CH2F2). Additional data is given on the laser emission characteristics.

Surface and volume scattering, surface-damage, and optical homogeneity studies of ruby crystals and their connection with laser-emission characteristics

Results of our investigation of the optical homogeneity of ruby crystals and its relation to the main laser-emission characteristics (i.e., beam divergence, far-field intensity distribution, energy output, and spectra of modes) are described. Good correlation has been found between the laser characteristics and the optical properties of the investigated ruby samples. On the basis of the experimental data, the different sources of the optical inhomogeneity of the ruby crystals grown by the Verneuil method and their influence on the laser characteristics are analyzed. It is shown, in particular, that internal mechanical strains have the most injurious effect on the beam divergence, the intensity distribution, and the mode-selection conditions. It is found that a volume light scattering contribution in laser energy losses is, to a large extent, due to the Rayleigh component of scattering. Laser-produced surface-damage experiments with ruby and sapphire crystals are also described. A variable pulse duration between <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-400 \mu</tex> s under normal laser operation and 30-ns Q-switched pulsed laser operation have been employed in these experiments. Optical and structural surface properties and their effect on a surface-damage threshold have been studied and the mechanism of laser-produced surface damage is discussed.

Optical homogeneity of ruby crystals and its connection with laser emission characteristics

Optical homogeneity of ruby crystals and its connection with laser emission characteristics