R. Gaumé

Diode-pumped Yb:Sr(3)Y(BO(3))(3) femtosecond laser.

We have developed a diode-pumped Yb(3+)Sr(3)Y(BO(3))(3) (Yb:BOYS) laser generating 69-fs pulses, at a central wavelength of 1062 nm. This laser is mode locked by use of a semiconductor saturable-absorber mirror and emits 80 mW of average power at 113 MHz. This is, to our knowledge, the first mode-locked Yb:BOYS laser and the shortest duration obtained from an ytterbium laser with a crystalline host. The central wavelength can be tuned from 1051 to 1070 nm, for sub-100-fs pulses. We have also achieved an average power as high as 300 mW with pulse duration of 86 fs at 1068 nm.

Apatite-structure crystal, Yb 3+ :SrY 4 (SiO 4 ) 3 O, for the development of diode-pumped femtosecond lasers

We report what is believed to be the first diode-pumped Yb(3+): SrY(4)(SiO(4)) (3)O laser. We investigate both the cw and the mode-locked regimes. In the cw regime an average output power of 1.05 W is demonstrated for 3.6 W of incident pump power. In the femtosecond regime a pulse duration of 94 fs for an average power of 110 mW is obtained at a central wavelength of 1068 nm. This is, to our knowledge, the first femtosecond mode-locked oscillator made with an Yb-doped apatitelike crystal. These properties are related to the unique spectroscopic properties of Yb(3+) ions in this atypical apatite-family crystal.

Spectroscopic properties of Yb-doped scandium based compounds Yb:CaSc2O4, Yb:SrSc2O4 and Yb:Sc2SiO5

Abstract Three Yb3+-doped scandium based materials are elaborated and their optical properties investigated. Scandium materials exhibit large energy levels splitting and favorable thermal properties. The energy level diagrams for Yb:CaSc2O4, Yb:SrSc2O4, and Yb:Sc2SiO5 are determined through optical spectroscopic analysis and semi-empirical crystal-field calculations using the simple overlap model. Laser parameters for Yb:Sc2SiO5 are compared to Yb:Y2SiO5 ones. Yb:Sc2SiO5 looks promising since it melts congruently and exhibits larger overall splitting of the 2F7/2Yb3+ ground state and broader absorption line width.

Optical and laser properties of Yb:Y2SiO5 single crystals and discussion of the figure of merit relevant to compare ytterbium-doped laser materials

Abstract In this paper, we explore two different directions in the investigation of Yb-doped solid-state laser crystals. At first, we describe the spectroscopic properties, site occupancies, energy-level diagrams and laser performances of Yb:Y2SiO5 (Yb:YSO), a new promising laser material. Then, in a more general point of view, we discuss the problem of evaluating the laser potential of the known Yb-based lasers. The approach proposed by De Loach et al. [IEEE J. Quantum Electron. 29 (1993) 1179] is shown to be incomplete to some extent. In a search for new figures of merit, it seems reasonable to include other parameters such as the thermal properties of the host.

Thermal lensing measurements in diode-pumped Yb-doped GdCOB, YCOB, YSO, YAG and KGW

A Shack–Hartmann wavefront sensor was used to measure thermal lensing in diode-end-pumped Yb-doped GdCOB, YCOB, YSO, YAG, and KGW crystals, under lasing or nonlasing conditions. Measured thermal lenses are aberration-free, and their focal lengths under lasing action range from 40 to 140 mm for 5 W of absorbed power. When laser action was inhibited the thermal lens dioptric power was increased significantly in most crystals, supplying evidence that nonradiative mechanisms exist. Reduction of thermal effects in a composite YCOB crystal is also investigated, as well as the dependence of thermal lensing on the emission wavelength in YSO. 2002 Elsevier Science B.V. All rights reserved.

Directly diode-pumped Yb3+:SrY4(SiO4)3O regenerative amplifier

We report a regenerative amplifier based on an Yb-doped apatite crystal: Yb3+:SrY4(SiO4)3O (Yb:SYS). We obtained 420-fs pulses at a central wavelength of 1066 nm with an energy of 100 microJ at 300 Hz after compression. To the best of our knowledge, this system is the first regenerative amplifier based on an Yb:SYS crystal and provides duration among the shortest ones generated by a directly diode-pumped regenerative amplifier.

Crystal field calculations of Yb3+-doped double borate crystals for laser applications

Crystal field effects are very important as far as laser performances of Yb-doped materials are concerned. In order to simplify the interpretation of low-temperature spectra, two tools derived from a careful examination of crystal field interaction are presented. Both approaches are applied in the case of new Yb-doped materials, namely Sr3Y(BO3)3 (BOYS) and Ba3Lu(BO3)3 (BLuB). The 2F7/2 splitting is particularly large in these materials and favorable to a quasi-3-level laser operating scheme. Calculations performed using the point charge electrostatic model (PCEM) for these compounds and using a consistent set of effective atomic charges confirm the experimental results. This should permit the use of this model in a predictive approach.

Diode-pumped continuous-wave and femtosecond laser operations of a heterocomposite crystal Yb 3+ :SrY 4 (SiO 4 ) 3 O?Y 2 Al 5 O 12

We report cw and femtosecond laser operations under diode pumping of a diffusion-bonding heterocomposite Yb-doped crystal: Yb3+:SrY4(SiO4)3O parallel Y2Al5O12(YAG paralell SYS:Yb). To show the advantages of this heterocomposite crystal over classical Yb:SYS crystal, we first investigate the high-power cw regime. A cw power of 4.3 W is demonstrated. The femtosecond regime is also investigated, and 1-W-average-power, 130-fs pulses at 1070 nm are produced, which represents, to our knowledge, the first demonstration of an Yb-doped heterocomposite mode-locked laser.

Mechanical, thermal and laser properties of Yb:(Sr1−xCax)3Y(BO3)3 (Yb:CaBOYS) for 1 μm laser applications

Abstract Yb:Sr3Y(BO3)3 also known as Yb:BOYS has recently demonstrated very attractive laser properties, but a drawback with this material is its brittleness. It could break into small pieces, even under weak thermal loading. This behavior is attributed to its very large thermal expansion anisotropy: αc/αa∼4. This ratio can be lowered to ∼1.7 by replacing 50% of Sr2+ by Ca2+ in the structure, which strengthen the crystal lattice and allows to reduce the brittleness. However, the thermal properties are affected by the Sr/Ca substitution as the thermal conductivity decreases by around 20 at.% for a 30 at.% calcium containing material. Laser characteristics under diode pumping with Yb3+:(Sr0.7Ca0.3)3Y(BO3)3 crystals (containing 15% Yb) remain comparable to those obtained with Yb:BOYS.

Crystal Chemistry Approach in Yb Doped Laser Materials

The emergence of new laser crystals has allowed progress in ultrashort-pulsed laser technology and high power lasers. Extensive researches on new Yb3+ doped crystals enable development of all-solid-state femtosecond lasers. Thermo-mechanical properties should be taken into account. The review of the state of the art on the Yb doped laser material for high power and ultrafast pulses generation is presented.