110 W ceramic Nd<Superscript>3+</Superscript> : Y<Subscript>3</Subscript>Al<Subscript>5</Subscript>O<Subscript>12</Subscript> laser

A high-power, continuous-wave 0.6% Nd³⁺-doped ceramic Y₃Al₅O₁₂ (Nd:YAG) laser has been developed. 110 W laser output at 1064 nm was obtained, with a slope efficiency of about 41%. The M² factor was found to be around 6. The laser performance of the ceramic laser material was found to compare favorably with that obtained with single crystal Nd:YAG. PACS 42.55.-f; 42.55.Xi; 42.70.Hj     

Comparative laser performances of pyrromethene 567 and rhodamine 6G dyes in copper vapour laser pumped dye lasers

Narrowband laser performances and photochemical stability of alcoholic solutions of pyrromethene 567 and rhodamine 6G dyes, under high-repetition rate copper vapour laser (at 510 nm), as well as, high-peak intensity Nd:YAG laser (at 532 nm) excitation have been investigated. We have observed that pyrromethene 567 dye solutions offer higher efficiency, wider tuning range, but lower photochemical stability and higher lasing threshold than that of rhodamine 6G dye solutions. An addition of about 100 mM DABCO, as a singlet oxygen quencher, in pyrromethene 567 dye solutions improved its photochemical stability close to that of rhodamine 6G. The observation of higher slope efficiency, in spite of higher threshold pump energy for pyrromethene 567 dye than that of rhodamine 6G dye solutions, was explained by a predictive model on gain characteristics of both dye solutions as a function of pump energy. PACS 42.55.Mv; 42.55.Rz; 42.70.Hj; 42.70.Jk     

Environment effects on the lasing photostability of Rhodamine 6G incorporated into organic-inorganic hybrid materials

The effect on the lasing photostability of Rhodamine 6G (Rh6G), and the rigidity of a hybrid inorganic-organic matrix by controlled addition of di-, tri- and tetrafunctionalized alkoxides has been evaluated. The dye was incorporated into hybrid matrices of (2-hydroxyethyl methacrylate) (HEMA) or vol/vol copolymers of methyl methacrylate (MMA) and HEMA with different weight proportions of polycondensated dimethyldiethoxysilane (DEOS), methyltriethoxysilane (TRIEOS), and tetraethoxysilane (TEOS). The laser samples were transversaly pumped at 534 nm at 5.5 mJ/pulse and up to a 10 Hz repetition rate. The dependence of the laser photostability on organic-inorganic composition, pH of the medium, and thermal treatment of the samples was studied. Good stability, with a drop of the initial laser output of only 13% after 10000 pump pulses at 10 Hz in a thermally postcured (HEMA-15 wt%TRIEOS) matrix was obtained. Careful control of the synthesis process is required to reach the necessary photostability for a solid-state dye laser based on hybrid matrices to become competitive with liquid dye lasers. PACS 81.05.Lg; 81.05.Zx; 81.20.Fw; 42.55.Mv; 42.55.Rz; 42.60.Lh; 42.62.b; 42.70a; 42.70-Hj; 42.70.Jk     

Efficient laser action of Yb:LSO and Yb:YSO oxyorthosilicates crystals under high-power diode-pumping

We report here on the efficient laser action of a new Yb-doped crystal Yb³⁺:Lu₂SiO₅ (Yb:LSO) under high power diode-pumping (15 W). Its performances were compared to another Yb-doped crystal belonging to the oxyorthosilicate family: the Yb:YSO. For both crystals, more than 7 W of laser radiation around 1 m was obtained under 14.4 W of incident pump power at 978 nm, leading to high optical conversions of more than 50%. Finally, both crystals demonstrate little sensitivity to pump wavelength drift and exhibit broad tunability at a multiwatt level (more than 4 W over 50 nm and 60 nm, respectively for Yb:LSO and Yb:YSO). PACS 42.55.Xi; 42.60.Pk; 42.70.Hj     

Polarization characteristics of a light-emitting polymer microring laser

Microring cavities were fabricated by depositing poly(2-methoxy-5-(2’-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) on glass fibers by a dip-coating method. Laser emissions in whispering gallery modes were observed by pumping with a frequency-doubled Nd:YAG laser. The threshold energy of the MEH-PPV microring laser was as low as 10 nJ per pulse (1.5 μJ/mm²). The polarization characteristics of the microring lasers were studied and a polarization model was developed to explain the observed phenomena. PACS 42.55.Sa; 42.70.Jk     

CW and tunable laser operation of Yb<Superscript>3+</Superscript> doped CaF<Subscript>2</Subscript>

We present the spectroscopic properties and room temperature of a cw tunable laser operation with Yb³⁺ doped CaF₂ single crystals grown in our laboratory. A laser slope efficiency of 50% with respect to the absorbed 920 nm pump power was obtained, and the laser wavelength could be tuned between 1000 and 1060 nm. PACS 42.55R; 42.70An erratum to this article can be found at     

Comparative spectroscopic and laser properties of Yb<Superscript>3+</Superscript>-doped CaF<Subscript>2</Subscript>, SrF<Subscript>2</Subscript> and BaF<Subscript>2</Subscript> single crystals

We present the spectroscopic properties and room-temperature cw tunable laser operation of Yb³⁺-doped CaF₂, SrF₂ and BaF₂ single crystals grown and studied in the same conditions. Emission cross sections, lifetimes, laser thresholds, laser slope efficiencies and laser wavelength tuning ranges are compared. It appears that Yb³⁺-doped BaF₂ might be more promising for diode-pumped high power laser operation. PACS 42.55.Rz; 42.70.Hj     

Influence of various coumarin dyes on the laser performance of laser dyes co-doped into ORMOSILs

Several kinds of coumarin dyes (C440, C460, C500, C503 and C540A) were co-doped with perylene red (p-red) or pyrromethene 567 (p567) into VTES- and MTES-derived organically modified silicates (ORMOSILs) respectively, by the sol-gel process. The effects of coumarin dyes and their concentration on the laser properties and photostabilities of p-redand p567 were studied and the mechanisms involved were discussed. At optimized coumarin dye concentration, the slope efficiency of co-doped p-redincreased by a factor of 2 while only minor increases in the laser efficiency of p567 were observed. A broader tunable range with increased conversion efficiency and at least a 3-fold improvement in the photostabilities of p-redand p567 in the presence of coumarin family dyes have also been achieved. The mechanism responsible for the improvement in the laser performances and photostabilities of p-redand p567 resulted from the energy transfer between p-red/567 and coumarin dyes. PACS PACS 42.55.Mv; 42.55.Rz; 42.70.Hj     

Continuous wave and tunable laser operation of Yb3+ in disordered NaLa(MoO4)2

Continuous-wave Yb³⁺ laser operation is studied in single crystals of disordered NaLa(MoO₄)₂ at room temperature. The sample used was grown by the Czochralski technique and incorporates an Yb ion density of 3.1×10²⁰ cm^-3. The effect of the Yb concentration on some of the crystal properties is described as well as the spectroscopic Yb³⁺ properties at 5 K. Maximum slope efficiencies of about 40% for π and 38% for σ polarization were obtained under Ti:sapphire laser pumping near 976 nm, respectively. The maximum output power for the π polarization was 400 mW at 1039.5 nm, the threshold in this case amounted to 240 mW (absorbed pump power). The laser emission was tunable between 1016 and 1064 nm with a Lyot filter. Lasing was also realized by pumping with a fiber-coupled diode laser module. Maximum output power of 900 mW at 1035 nm was achieved in this case for the π polarization and the threshold was 280 mW. The results, in terms of output power and tunability, are superior in comparison to all previous reports on Yb-doped disordered double tungstate or molybdate crystals and represent a significant improvement in comparison to earlier experiments with low-doped Yb:NaLa(MoO₄)₂.PACS 42.55.Rz; 42.55.Xi; 42.70.Hj     

Photo-physical properties and amplified spontaneous emission of a new derivative of fluorescein

The synthesis of new high-performance dyes and the implementation of new ways of incorporating the organic molecules into the solid host matrices have produced a great deal of activity in the field of solid-state dye lasers. In this article, the new laser dye, 2-(6-allyl-3-oxo-3H-xanthen-9-yl)-benzoic acid ethyl ester [AXBE] has been synthesized, and its chemical structure was confirmed by ¹H NMR, ¹³C NMR, IR and elemental analysis. This new dye was covalently bonded with methyl methacrylate (MMA) and 2-hydroxy ethyl methacrylate (HEMA) copolymer backbone and evaluated as the active medium of the solid-state laser dye. Its optical properties were experimentally investigated. Amplified spontaneous emission (ASE) and photostability were studied by pumping the dye sample with 355 nm (8 ns) pulsed Nd-YAG laser.     

Co2+:LMA crystal as saturable absorber for a diode-pumped passively Q-switched Nd:YVO4 laser at 1342 nm

We have demonstrated an efficient diode-pumped passively Q-switched Nd:YVO₄ laser at 1342 nm by using an uncoated Co²⁺:LaMgAl₁₁O₁₉ (Co²⁺:LMA) crystal as the saturable absorber. With the absorbed pump power of 11.7 W, the pulse width could be as low as 42 ns, with a corresponding average output power of 580 mW. At around 40 kHz repetition rate, the energy of a single Q-switched pulse was estimated to be about 14.5 μJ and the peak power was 346 W. The passive Q switching operation for the Co²⁺:LMA in different polarization states was also investigated. PACS 42.55.-f; 42.55.Xi; 42.60.Gd; 42.70.Mp     

Optimization of the laser performance in Nd3+:YAG ceramic microchip lasers

Based on the four-level system, a theoretical model of diode-laser end-pumped fundamental continuous-wave Nd³⁺:YAG ceramic microchip lasers is proposed. The fluorescence concentration quenching effect and the absorption efficiency of the host have been taken into account in the model. The theoretical results of the numerical calculations are in good agreement with those of experiments. The effects of the concentration of the Nd³⁺:YAG ceramic, the thickness of the Nd³⁺:YAG ceramic, and the transmission of the output coupler on the laser performance (threshold and output power) are addressed. The optimization of the concentration and the thickness for the Nd³⁺:YAG ceramic microchip laser is presented. This modeling is not only applicable to the Nd³⁺:YAG ceramic microchip laser but also to other four-level microchip lasers. PACS 42.55.-f; 42.55.Xi; 42.70.Hj; 02.60.Cb     

High-power picoseconds 355 nm laser by third harmonic generation based on CsB3O5 crystal

We report on the high average power third harmonic generation (THG) of a mode-locked picosecond laser in a CsB₃O₅ (CBO) crystal. The picosecond laser beam at 1064 nm is produced by a home-made 30 W master oscillator power-amplifier (MOPA) Nd:YVO₄ laser system. The maximum THG output at 355 nm is up to 5.4 W. We also investigate the phase matching angle at different temperatures. During high power operation, the temperature of the CBO crystal is set at a high temperature of more than 100 °C. The THG system has shown a fine long-term stability for more than two months of operation. PACS 42.55.Px; 42.55.Rz; 42.70.Mp; 42.70.Nq; 42.65.Ky     

Spectroscopy and laser properties of Tm<Superscript>3+</Superscript>:KY(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> crystal

The polarized absorption spectra of Tm³⁺-doped potassium yttrium tungstate (Tm:KY(WO₄)₂) crystal at room temperature were measured. The emission spectrum and lifetime of the ³ F ₄ excited state were determined. Using standard and modified Judd–Ofelt theories, the intensity parameters and the radiative lifetimes were calculated and good agreement with the experimental results was obtained for both theories. Continuous-wave laser operation in Tm:KYW crystal under laser diode pumping at 802 nm and 1750 nm was demonstrated with slope efficiency of 53% and 28% and output power of about 555 mW and 86 mW, respectively. PACS 42.55.Xi; 42.60.Pk; 42.70.Hj     

Effect of ytterbium concentration on cw Yb:YAG microchip laser performance at ambient temperature – Part I: Experiments

The microchip laser performance of Yb:YAG crystals doped with different ytterbium concentrations (C_Yb=10, 15, and 20 at. %) has been investigated at ambient temperature without active cooling of the gain media. Efficient laser oscillation for a 1-mm-thick YAG doped with 10 at. % Yb³⁺ ions was achieved at 1030 and 1049 nm with slope efficiencies of 85% and 81%, correspondingly. The laser performance of heavy-doped Yb:YAG crystals was limited by the thermal population at terminated lasing level and thermal lens effect at room temperature without sufficient cooling of the samples. The laser emitting spectra of Yb:YAG microchip lasers with different Yb concentrations and output couplings are addressed with the local temperature rise, due to the absorption of the pump power inside the gain media under different pump levels. PACS 42.55.Xi; 42.70.Hj; 42.55.Rz     

Continuous-wave laser action of Yb3+-doped lanthanum scandium borate

Lanthanum scandium borate (LSB) has been proved to be an interesting laser matrix when doped with Nd³⁺ and Er³⁺ ions. In this paper, we demonstrate that it is also a very efficient laser material when doped with Yb³⁺ ions. The main spectroscopic characteristics of the system are presented, showing very broad absorption and emission bands, comparable to those found in Yb-doped GdCOB and YCOB crystals. From spectroscopic measurements the relevant laser parameters have been obtained, and a tunability of about 50 nm could be deduced. Room-temperature, continuous-wave laser action of Yb-doped LSB is demonstrated at a wavelength of 1045 nm with a slope efficiency as high as 64%. PACS 42.55.Rz; 42.70.Hj; 78.55.-m     

<Emphasis Type="Italic">Z</Emphasis>-scan measurement of optical nonlinearity in solid-state dye doped media

Nonlinear refraction in various polymethyl methacrylate (PMMA) solid hosts when doped with fluorescent organic dyes, commonly used as a laser active medium, has been studied. The observed thermal lensing effect arising from optical nonlinearity, results from non-radiative energy transfer from the dye molecules to the solid matrix and is, therefore, strongly dependent on the thermal properties and material parameters of the polymeric host. The non-linear index of refraction, n₂, for each sample of dye doped polymeric host, has been measured employing the standard Z-scan technique. These measured values of n₂, have been used to determine the extent of variation in the index of refraction with varying temperature, dn/dT, for the various host materials. Estimation of dn/dT is critical in determining the extent of thermal lensing in the dye doped solid-state medium, that in turn determines the spatial quality and divergence of the generated laser beam delivered by a dye doped solid-state laser system. PACS 42.55.Mv; 42.65.Jx; 42.70.Jk     

Diode-pumped chirped pulse amplification to the joule level

The POLARIS project aims at the development of an all-diode-pumped, high-peak-power femtosecond laser system reaching the petawatt level. The laser amplifiers are based on pumping Yb³⁺-doped fluoride phosphate glass at 940 nm. Recently, stable operation of the first three amplifiers was achieved. Pulses with a bandwidth of 12 nm, which supports 135 fs pulses with energies up to 1.25 J, were generated in the third amplifier with a 12-pass configuration. The amplifier was pumped by 150 collimated high-power laser diodes. Successive polarization maintenance is used for a compact, stable, and convenient adjustable setup. Thermally induced abberations of lowest order were compensated by adaptive mirrors. PACS 42.55.Xi; 42.60.By; 42.70.Hj     

Spectroscopic properties and diode-pumped 1594 nm laser performance of Er:Yb:Li6Y(BO3)3 crystal

An Er³⁺/Yb³⁺-codoped Li₆Y(BO₃)₃ crystal was grown by the Czochralski method. The polarized absorption spectra and the fluorescence decay curve were recorded. The efficiency of energy transfer from Yb³⁺ to Er³⁺ ions was estimated. Quasi-continuous-wave output power of 325 mW at 1594 nm was realized under the absorbed pump power of 10.4 W in a hemispherical cavity. The absorbed pump threshold and slope efficiency of the laser are 6.0 W and 7.2%, respectively. PACS 42.55.Xi; 42.70.Hj     

5.3 W deep-blue light generation by intra-cavity frequency doubling of Nd:GdVO4

We report the efficient compacted deep-blue laser at 456 nm generation by intra-cavity frequency doubling of a continuous-wave (cw) laser operation of a diode-pumped Nd:GdVO₄ laser on the ⁴ F _3/2→⁴ I _9/2 transition at 912 nm. The different long LiB₃O₅ (LBO) crystals, cut for critical type I phase matching at room temperature, are used for second harmonic generation (shg) of the laser. At an incident pump power of 30 W, up to 5.3 W of cw output power at 456 nm is achieved with 15-mm-long LBO (3.8 W with 10 mm-long LBO). The conversion efficiency is 17.7% from pump diode input to second harmonic wave output.PACS 42.70.Hj; 42.55.Xi; 42.65.Ky