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The orthorhombic Tm

Cet article revient sur ce qui fait la specificite des ions de terres rares dans les solides et sur les fondamentaux qui permettent de comprendre leurs proprietes optiques de base : niveaux d’energie, transitions optiques radiatives et non radiatives, interactions entre les ions et transferts d’energie. Il montre comment ces proprietes peuvent etre differentes d’un materiau a l’autre si on tient compte des transitions optiques entre configurations electroniques fondamentale et excitee, et si on fait intervenir des transferts de charges avec des ions du materiau hote. Ces proprietes optiques et spectrales sont mises a profit dans de nombreuses applications.

We report the first laser operation at π-polarized 670.34-nm deep red laser in a 2-W InGaN-LD-pumped Pr 3+ :LiYF 4 (Pr:YLF) crystal with the aid of a 0.1-mm intracavity etalon, to the best of our knowledge. The maximum output power of this laser emission was up to 87.6 mW with slope efficiency of ~11.9$ % with respect to the absorbed pump power. The beam propagation factors in x-direction and y-direction were measured to be 1.49 and 1.05, respectively.

A promising alternative to the widespread Z-scan technique has been recently proposed. This technique, named Baryscan, is based upon the use of a Position Sensitive Detector (PSD) and is about 170 times more sensitive than the Z-scan technique while preserving its simple theoretical scheme and ease of implementation. In this paper, we demonstrate both numerically and experimentally that inserting a phase plate before the PSD and setting an opaque disk as close as possible to its active area results in a substantial sensitivity enhancement of the Baryscan technique.

CW laser wavelength tunability of 70 nm is demonstrated in the 900nm spectral range by pumping a Pr:LiYF4 single crystal with an OPSL laser and by using a V-shape resonator and a quartz birefringent plate.

High optical quality rare-earth-doped YLiF4 layers were grown by the liquid phase epitaxy technic. Optical characterization, CW and Q-switch laser operation obtained with these fluorides waveguides will be presented and discussed in this communication. Article not available.

We report an efficient diode pumped Yb:CaF2 regenerative amplifier delivering up to 100mJ at 10Hz repetition rate. Using this amplifier, we also report multi pulse operation in the femtosecond regime.

Several CaF2 single crystals doped with trivalent rare-earth ions have been grown in the recent years in the form of bulk crystals by using the Bridgman method and in the form of thin films by using the MBE and LPE techniques. The spectroscopic, gain and laser properties of these crystals doped with Pr3+, on the one hand, and with Yb3+, Tm3+ or Er3+ ions, on the other hand, have been studied and are reviewed here for their laser potentials in the red and in the infrared spectral domains, respectively.

Results of diode-pumped cw and fs laser operation of an Yb 3+ :CaF 2 single crystal are reported. With a 5-at.-% Yb 3+ -doped sample we obtained 5.8 W output power at 1053 nm, for 15 W of incident pump power at 980 nm. In passively mode-locked diode-pumped regime, using a Brewster-cut, 5-at.-% Yb 3+ -doped sample and prisms for dispersion compensation, the oscillator provided pulses as short as 150 fs, with 880 mW of average power and up to 1.4 W average output power, with pulse duration of 220 fs, centred at 1049 nm. The laser wavelength could be tuned from 1018 nm to 1072 nm in cw regime and from 1040 nm to 1053 nm in mode-locked regime. Using chirped mirrors for dispersion compensation, we obtained up to 1.74 W of average power, with pulse duration of 230 fs. For all these reasons, Yb:CaF 2 crystal is showing the great potential as active medium for high average power femtosecond oscillators and as amplifier medium for femtosecond pulses.

An experiment has been performed to analyse a nonlinear lensing effect in a flashlamp pumped Cr 3+ :LiSAF laser which has been found to be adiverging lensing effect. The latter is due to the refrctive index change which is assumed to be proportional to the excited ion population. The corresponding constant of proportionality has been measured from the time variation of the laser pulses far-field divergence.

We have studied the Yb3+ (reversible reaction) Tm3+ nonradiative energy transfer processes responsible for population of the 1G4 thulium level under Yb3+ or Tm3+ selective laser excitation of YLF:Tm3+,Yb3+ crystal. The microparameters and the rates of the energy transfer via cross-relaxation schemes are determined. It is concluded that the process of populating the 1G4 thulium level is greatly affected by up-conversion processes not only from the 3H4 but also from the 3F4 level, proceeding within the static decay model.

We report CW blue laser operation at 469.2, 471, and 473 nm by efficient intracavity second-harmonic generation and sum-frequency generation of the R2→Z5 (938.5 nm) and R1→Z5 (946 nm) F43/2→I49/2 intermultiplet transitions in Nd:YAG with an LiB3O5 nonlinear crystal. Single-wavelength laser operation at 469.2 nm and multiwavelength operation at 469.2, 471, and 473 nm are obtained with maximum output powers of 1.4 and 0.15 W, respectively, by using a glass etalon as frequency selector. The 469 nm blue laser is an efficient pumping source of Pr3+-doped materials.

This paper reports the main spectroscopic characterizations and laser experiments carried out on two new crystal hosts: the! yttrium orthosilicate Y2SiO5 and the silicate oxyapatite Sr2Y8(SiO4)6O2 (hereafter noted SYS), doped with Ytterbium and Erbium for a 1,55 μm laser emission and with Thulium for a 2 μm emission. Four new lasers have been demonstrated at 1,554 μm, 1,576 μm, 1,99 μm and 2,05 μm for respectively Yb,Er:SYS; Yb,Er:Y2SiO5; Tm:SYS and Tm:Y2SiO5. If for the Yb,Er codoped materials laser performances are still poor compared with the Yb,Er phosphate glass, the Tm doped materials exhibit laser performances similar to the Tm:YAG and look very promising.

International audience; We present a diode-pumped regenerative amplifier based on an Yb:CaF2 crystal optimized to produce short pulses for various repetition rates ranging from 100 Hz to 10 kHz. The shortest pulse duration generated is 178 fs, and the corresponding energy is 1:4 mJ before compression (620 μJ after), at a repetition rate of 500 Hz for 16 W of pump power. The bandwidth is 10 nm centered at 1040 nm. Higher repetition rate regimes have also been explored, allowing an optical-to-optical efficiency up to 10% at a high repetition rate.

Photoluminescence (PL) of Molecular Beam Epitaxy grown Er doped Ga 0.55Al0.45As has been studied under continuous and pulsed laser excitation . The observed PL lines are attributed to transitions from the first excited stated 4I13/2 to the ground state 4I15/2 . The life time of the 4I13/2 level is found to be 1 ms at 10K, which is comparable to the decay time observed in insulators.Using two-beam experiments we show that there are losses (Auger effect) that occur during the PL excitation.We propose the following model for the Er PL excitation process: excitons bound to Er are created and decay non radiatively by energy transfer to the rare earth (which is the cause of the Er related PL) or to free carriers by Auger effect (which is the cause of the observed losses).

We are presenting a 57 mJ multipass amplifier based on Yb:CaF2 operating at 20 Hz. Special attention has been given to the thermal measurement and management in order to push it to the 100 Hz regime.