Laser performance of high optical quality 4 at.% Pr3+: Sr0.7La0.3Mg0.3Al11.7O19 (Pr:ASL) single crystals.

In this work, we present the visible laser performance of improved optical quality Czochralski-grown 4 at.% Pr3+-doped Sr0.7La0.3Mg0.3Al11.7O19 (Pr:ASL) single crystals in the deep red (726 nm), the red (645 nm) and the orange (620 nm) range using two different pumping sources. Using a high beam quality frequency doubled Ti:sapphire laser with 1 W output power as pump source, deep red laser emission was reached at a wavelength of 726 nm with 40 mW of output power and a laser threshold of 86 mW. The corresponding slope efficiency was 9%. At 645 nm in the red, up to 41 mW of laser output power were obtained with 15% slope efficiency. Moreover, orange laser emission at 620 nm was demonstrated with 5 mW output power and 4.4% slope efficiency. Using a 10 W multi-diode module as pumping source allowed to obtain the highest output power of a red and deep-red diode-pumped Pr:ASL laser to date. The respective output powers at 726 and 645 nm reached 206 mW and 90 mW.

High peak-power near-MW laser pulses by third harmonic generation at 355†nm in Ca5(BO3)3F nonlinear single crystals.

In this work, the performance of Ca5(BO3)3F (CBF) single crystals was investigated for the third harmonic generation at 355 nm. A high energy conversion efficiency of 16.9% at 355 nm was reached using a two-conversion-stage setup. First, using a high peak power, passively Q-switched Nd3+:YAG/Cr4+:YAG microlaser based gain aperture in micro-MOPA, the second harmonic at 532 nm was achieved with lithium triborate (LBO) crystal, reaching 1.35 MW peak power. On a second step, laser pulses at 355 nm were generated using a 5 mm-long CBF crystal growth by TSSG method with energy, pulse duration and peak power of 479 µJ, 568 ps and 0.843 MW, respectively. These results are currently the highest reported for CBF material.

Temperature stable operation of YCOB crystal for giant-pulse green microlaser.

In this work the performance of two yttrium calcium oxyborate (YCOB) crystals made by Czochralski and Bridgman growth process was measured. By using high peak power, passively Q-switched Nd3+:YAG/Cr4+:YAG microlaser, high conversion second harmonic generation efficiency were obtained. Laser pulses at 532 nm with 1.14 mJ energy and 223 ps duration were obtained with a 15-mm long YCOB crystal that was grown by Bridgman method. The conversion efficiency was 70.2%, comparable with the conversion efficiency of 72.8% that was achieved with 10-mm long lithium triborate (LBO) nonlinear crystal. Also, for the first time, experimental data on temperature tuning in type I YCOB crystal was measured with linear slope in 200°C temperature range equal to -0.057%/°C and -0.064%/°C for the Czochralski and Bridgman grown crystals, respectively. Such YCOB nonlinear crystal can become a serious option for developing laser sources with high-peak power at high repetition rate that can operate in harsh environment.

Dielectric frame, Sellmeier equations, and phase-matching properties of the monoclinic acentric crystal GdCa4O(BO3)3.

We directly measured the phase-matching properties of the biaxial GdCa4O(BO3)3 (GdCOB) crystal using the sphere method. We studied second-harmonic generation and difference frequency generation in two principal planes of the crystal. All these data allowed us to refine the Sellmeier equations of the three principal refractive indices. These equations are valid over the entire transparency range of GdCOB and then could be used to calculate the tuning curves of infrared optical parametric generation.

Prognostic Factors of Postoperative Morbidity and Mortality of Adult Strangulated Groin Hernia.

The aim of this work is provide the results of the surgical treatment of strangulated groin hernias and determine morbidity and mortality risk factors. It is a retrospective study related to the 288 records of patients aged 15 years and more, who underwent emergency surgery for strangulated groin hernia from January 2007 to December 2012. Postoperative evolution was assessed on the morbidity, mortality, and length of hospital stay. Mortality and morbidity risk factors were studied. The statistical analysis was conducted with the chi-square test and Fischer's exact test with a significance level of 5 %. Strangulated groin hernias account for 42.2 % of the overall groin hernia operations conducted during the study period (288/697). Necroses were present in 59 (20.5 %) patients. The mortality rate was 6.2 % (n = 18). Admission time superior or equal to 48 h (p = 0.002), American Society of Anesthesiologists (ASA) class superior or equal to III (p = 0.002), presence of preoperative strangulated groin hernia complication (peritonitis, occlusion, hernia abscesses) (p = 0.001), bowel necrosis (p = 0.000), and bowel resection (p = 0.000) were statistically related to a high risk of death. Forty-two (n = 42) postoperative complications were recorded in 34 (11.8 %) patients. These complications were outnumbered by postoperative parietal suppuration (n = 26) which led to three cases of evisceration. Bowel necrosis was related to a high risk of postoperative complications (p = 0.002). Reoperation was necessary for 13 patients. The length of stay in hospital was 4 days (range between 1 and 28 days). The average follow-up period was 7 months. No recurrence was noticed during this period. Delay in consultation, high ASA class, and moreover, bowel necrosis requiring bowel resection are the factors of unfavorable postoperative results. Groin hernias are an avoidable death cause provided that early treatment of strangulated hernias and the elective treatment of non-complicated hernias are conducted.

Rise in power of Yb:YCOB for green light generation by self-frequency doubling.

Spectroscopic properties and self-frequency-doubling laser performance are presented for Yb:YCa4O(BO3)3 (Yb:YCOB) crystals oriented for type I second-harmonic generation in the ZX plane. In a plane-concave cavity 10 cm long, up to 330 mW of green light (544.5 nm) is obtained for 14.7 W of laser diode incident pump power. Broad emission bands and weak anisotropy in the 1060-1100 nm range between the two eigenstates of polarization may explain the instability of the self-frequency-doubled output power.

240 kW peak power at 266 nm in nonlinear YAl3(BO3)4 single crystal.

We report the fourth harmonic generation at 266 nm using a type I YAl3(BO3)4 (YAB) single crystal from a Q-switch microchip laser Nd:YAG/Cr4⁺:YAG frequency doubled with a LiB3O5 (LBO) crystal. 240 kW peak power at 266 nm corresponding to a mean conversion efficiency of 12.2% from 532 to 266 nm has been obtained with a 2.94 mm thick YAB crystal. The influences of optical homogeneity and absorption on the conversion efficiency are discussed.

Spectral properties and laser performance of Ho:Sc2SiO5 crystal at room temperature.

Holmium doped scandium silicate (Ho:SSO) bulk crystal grown by Czochralski technique is reported. The absorption cross section of 4.8 × 10(-21) cm2 at pumping wavelength 1940 nm and emission cross section of 5.56 × 10(-21) cm2 at lasing wavelength 2112 nm were calculated, respectively. Lifetime was measured to be 1.51 ms at 300 K and 0.92 ms at 77 K. Continuous-wave laser was operated by using a diode-pumped Tm:YAP laser as pump source with central wavelength of 1940 nm. Output power of 385 mW at 2112 nm was primarily obtained.

Singular topology of optical absorption in biaxial crystals.

We show for the first time that biaxial crystals exhibit continua of directions of propagation where the absorption coefficient is the same for the two associated polarization modes. This statement is supported by both calculations and experimental data obtained in Nd:YCOB.

Nonlinear optical properties of Ca5(BO3)3F crystal.

A high quality Ca(5)(BO(3))(3)F (CBF) crystal, grown by flux method, was investigated for its non linear optical properties. This material is non hygroscopic and possesses a moderate birefringence suitable for UV light generation. On the basis of its refractive index dispersion curves, it is inferred that CBF has great potential applications as non linear optical material, notably for UV light generation at 355 and 266 nm. In order to characterize its non linear optical properties, CBF samples were first cut and oriented in phase matching conditions for second harmonic generation of 1064 nm. Experimental results demonstrate that CBF has the moderate NLO coefficients. The optical conversion efficiency from 1064 nm to 532 nm was investigated for the first time: up to 54% were achieved. Non linear d(eff) coefficients were also estimated as well as the external angular acceptance bandwidth of SHG at 1064 nm.

Absorption and fluorescence anisotropies of monoclinic crystals: the case of Nd:YCOB.

We report for the first time measurements and modelization of the angular distributions of absorption and fluorescence in a monoclinic crystal. Studies on Nd:YCOB revealed specific topologies with ombilics. These new data upgrade the knowledge on low symmetry crystal optics.

Diode-pumped Nd:YAG laser emitting at 899 nm and below.

We present what is, to the best of our knowledge, the first diode-pumped Nd:YAG laser emitting at 899 nm and below, based on the (4)F(3/2) - (4)I(9/2) transition, generally used for a 946 nm emission. A power of 630 mW at 899 nm has been achieved in cw operation and 16 mW at 884 nm with a fiber-coupled laser diode emitting 9 W at 808 nm. Intracavity second-harmonic generation in cw mode has also been demonstrated with a power of 100 mW at 450 nm by using a LiB(3)O(5) nonlinear crystal.

First measurement of the nonlinear coefficient for Gd(1-X)Lu(X)Ca(4)O(BO(3))(3) and Gd(1-X)Sc(X)Ca(4)O(BO(3))(3) crystals.

The effective nonlinear coefficient and temperature acceptance bandwidth of three Lu and Sc co-doped GdCa(4)O(BO(3))(3) type nonlinear crystals were measured. NCPM for SHG in to the blue-UV spectral region can be obtained by controlling the co-dopant concentration. Measurements were based on intra-cavity SHG of a CW Ti:Sapphire laser, and the effective nonlinear coefficients were found to be in the range of 0.5 to 0.6 pm/V for the three crystals used. The FWHM temperature acceptance bandwidth was measured to be more than 35 degrees C using a 6 mm long Gd(0.871)Lu(0.129)Ca(4)O(BO(3))(3) crystal. A maximum of 115 mW at 407.3 nm in a single direction was measured using a 6.5 mm long Gd0.96Sc0.04Ca(4)O(BO(3))(3) crystal.

Highly efficient, 0.84 slope efficiency, 901 nm, quasi-two-level laser emission of Nd in strontium lanthanum aluminate.

The possibility of using direct pumping into the emitting level of the Nd3+ ion in magnesium-compensated strontium lanthanum aluminate (Sr(1-x)La(x-y)Nd(y)Mg(x)Al(12-x)O19) to improve 900 nm 4F(3/2) --> 4I(9/2) laser emission is discussed. Selection of the composition parameters x and y for optimization of laser emission and reduction of heat generation is based on the spectroscopic and crystal growth characteristics. Pumping in the 865.5 nm absorption band 4I(9/2)(Z1) --> 4F(3/2)(R1) transforms the laser process into a quasi-two-level scheme of very low (below 4%) quantum defects. A very high slope efficiency (over 84%) for 901 nm continuous-wave laser emission is demonstrated with Ti:sapphire laser pumping in this band for a crystal with x = 0.4 and y = 0.05.

Optical planar and channel waveguides in the new nonlinear crystal Ca4YO(BO3)3 (YCOB) fabricated by He+ implantation.

We report the first study of optical planar and channel waveguides fabricated in the new nonlinear crystal Ca4YO(BO3) by use of MeV He+-implantations. The nx, ny, and nz refractive index modifications are studied. Losses in nonannealed YCOB waveguides measured with a CCD camera are found to be less than 2 dB cm(-1). This work is the first step toward the investigation of frequency conversion within the obtained guiding structures.

Channel waveguides in Ca4GdO(BO3)3 fabricated by He+ implantation for blue-light generation.

Blue light at 405 nm is generated by frequency doubling of a Ti:sapphire tunable laser in He(+)-implanted channel waveguides in gadolinium calcium oxoborate crystal. A conversion efficiency of approximately 2% W(-1) cm(-2) is achieved between TM00 fundamental and TE01 harmonic modes.