Izilda Marcia Ranieri

Crystal growth of Ce-doped and undoped LiCaAlF6 by the Czochralski technique under CF4 atmosphere

Ce-doped and undoped LiCaAlF6 (LiCAF) single crystals 50 mm in diameter were grown by the Czochralski technique. The formation of inclusions and cracks accompanying the crystal growth was investigated. The dependence of lattice parameters on the temperature was measured for LiCAFand LiSrAlF 6 single crystals. Linear thermal expansion coefficients for both these crystals were evaluated. Higher transmission properties for LiCAFsingle crystals were achieved in the UV and VUV wavelength regions. # 2001 Elsevier Science B.V. All rights reserved.

Diode pumping Nd-laser efficiency limitations due to up-conversion processes in Nd:YLF and Nd:GLF

Abstract The visible up-conversion fluorescences mainly from the 4G7/2 level in Nd-doped LiYF4 and GdLiF4 crystals have been studied at 300 K under c.w. diode laser pumping at 797 nm. These emissions originate from either two-step excitations, involving an excited-state absorption (ESA) from the 4F3/2 metastable level or from energy transfer up-conversion (ETU) processes. A model to estimate the probability rates of the ETU processes based on the Forster–Dexter method was proposed. By solving the rate equations for these systems under continuous diode pumping, it was possible to calculate the pumping efficiencies in order to attain the threshold conditions for the 1.047 μm laser action, which showed a non-linear behavior. The theoretical calculations clearly indicate that the maximum possible inverted population (at the 4F3/2 level) is around one-tenth of the total Nd concentration, for both crystals. The maximum gain is thus limited by the decrease of pumping efficiencies due to the up-conversion processes at the laser threshold.

Efficient and compact diode-side-pumped Nd:YLF laser operating at 1053?nm with high beam quality

A very efficient, diode-side-pumped Nd:YLF laser is demonstrated using a compact cavity design based on total internal reflection inside the gain medium. With one pass through the crystal using a single bounce at the pumped face, efficiency in excess of 40% in multimode operation was measured, giving 6.6 W of output power for 16.2 W of pump power. Using two bounces inside the crystal, the beam quality was improved to fundamental mode with 4.2 W of output power for 16.2 W of pump power.

Compact, diode-side-pumped Nd3+:YLiF4 laser at 1053 nm with 45% efficiency and diffraction- limited quality by mode controlling.

We demonstrate what we believe to be the highest efficiency obtained to date in a transversely diode-pumped Nd3+:YLiF4 slab laser operating at 1053 nm. The compact 11-cm-long laser cavity configuration is based on total internal reflection of the intracavity beam at the pump facet of the gain crystal to improve the overlap with the pump radiation. Multimode operation with 9.5 W of output power and an efficiency of 45% is obtained for 21 W of pump power in a single-pass configuration. Using a second pass through the crystal and a new mode-controlling technique, the beam quality is improved to the diffraction limit with 6.9 W of output power and 33% of optical-to-optical efficiency.

Crystal growth of Ce : LiLuF4 for optical applications

Abstract High-quality Cexa0:xa0LiLuF 4 (Cexa0:xa0LLF) crystals were grown by the Czochralski technique using CF 4 as reactive atmosphere. The segregation coefficient of Ce 3+ was determined to be 0.066 (3). No changes in the lattice parameters due to the presence of the Ce 3+ in the lattice were observed. Laser action in the ultraviolet region was obtained by pumping this active medium with a KrF excimer laser in 248xa0nm.

Growth and characterization of LiGd1−x−yYxNdyF4 single crystals

Abstract LiGdF 4 (GLF) crystals co-doped with yttrium concentrations up to 50xa0mol% and neodymium have been grown by the Czochralski method, under argon and CF 4 atmospheres. The best conditions for crystal growth were achieved using carbon-free chemicals and CF 4 atmosphere, and one good-quality crystal of LiGd 1− x − y Y x Nd y F 4 ( x =50xa0mol%, y =2.7xa0mol%) was obtained. The segregation coefficients measured for gadolinium and yttrium were close to 1 and for neodymium is 0.40, independent of the Gd/Y ratio. From the point of view of the application of these crystals as laser media there is the possibility to use two crystals with advantage over the Ndxa0:xa0YLF (Ndxa0:xa0YLF) the Ndxa0:xa0GLF and the Ndxa0:xa0GLF co-doped with 50xa0mol% Y. The characterization of these crystals is presented.

Influence of Excited-State-Energy Upconversion on Pulse Shape in Quasi-Continuous-Wave Diode-Pumped Er:LiYF

In this paper, we demonstrate the temporal dependency of an Er:LiYF4 laser on the upper laser level energy transfer upconversion. By spectroscopic measurements and numerical simulations, we calculate a value for this upconversion of 9 × 10-17 cm3/s. We also report a 60% higher average output power for short-pulse duration, which is complementary to some earlier findings.

_{4}

Abstract Crystals of LiY 1− x Lu x F 4 ( x =50, 75, 100 mol%) doped with neodymium were successfully grown by the Czochralski technique, under CF 4 atmosphere. The lattice parameters, calculated from X-ray diffraction data, showed a linear relationship with the molar composition, in accordance with the Vegard law for ideal solid solutions.

Lasers

This work presents a passively Q-switched and mode-controlled Nd:YLF laser that generates 150 kW of peak power at 1053 nm with 1kHz repetition rate. The new resonator design is capable of delivering 1.5 mJ and 10 ns pulses in a very compact, simple and lightweight set-up.

Growth of LiY1-xLuxF4 crystals under CF4 atmosphere

In this paper we demonstrate a tenfold pulse power enhancement by operating the Er:YLF laser at the strongly modulated relaxation oscillation region, at 3 μm wavelength. We obtained 1.2 W of average power for 250 μs pulse duration and up to 400 Hz of repetition rate for a 6.8 W, jitter free, single spike with nearly Gaussian temporal shape without any kind of intracavity Q‐switching device.