Diode-pumped regenerative Yb:SrF2 amplifier

International audienceWe report what we believe to be the first Yb:SrF2 regenerative femtosecond amplifier. The regenerative amplifier produces 325-fs pulses at 100-Hz repetition rate with an energy before compression of 1.4 mJ. The interest of Yb:SrF2 in such regenerative amplifiers and its complementarity to its well-known isotype Yb:CaF2 is also discussed

Diode-pumped Yb:CaF 2 multipass amplifier producing 50 mJ with dynamic analysis for high repetition rate operation

International audienceThe dynamic thermal issues of the Yb:CaF 2 crystals within a multi-tens-mJ-energy multipass amplifier operating in the 20–100 Hz repetition rate range and pumped in quasi-cw regime have been studied at different timescales. Thermal response times of the system have been precisely investigated and analyzed, for the first time to our best knowledge in such amplifiers. This study includes a dual timescale analysis: in the long-timescale (second) with direct thermography mapping and in the millisecond range with thermal lensing in a pump-probe configuration. Very atypical positive lens behavior with fluorites will also be presented and discussed. This complete analysis is used to demonstrate the capability of Yb:CaF 2 multipass amplifier systems for operating the amplifier at 20 Hz with 57 mJ and 100 Hz with 32-mJ stable regime. Indeed, high repetition rate multipass amplifier has been realized for the first time with Yb:CaF 2 and for this energy. The results have been analyzed precisely to take into account the thermal issues and excellent beam quality, with a M 2 of 1.1. The pointing stability of 20 lrad has been measured documenting the reliability of the high repetition rate mJ amplifier

Ion-Exchanged Waveguide Amplifier in Erbium-Doped Glass for Broad-band Communications

We discuss the fabrication, characterisation and modelling of planar erbium-doped amplifiers realised as ion-exchanged waveguides in glass

Mode-locked operation of a diode-pumped femtosecond Yb : SrF2 laser

International audienceFemtosecond mode-locked operation is demonstrated for the first time, to our knowledge, with a Yb:SrF2 crystal. The shortest pulse duration is 143 fs for an average power of 450 mW. The highest average power is 620 mW for a pulse duration of 173 fs. Since Yb:SrF2 corresponds to the longest-lifetime Yb-doped crystal with which the mode-locking operation has been achieved, a detailed analysis is carried out to characterize the quality of the solitonlike regime

On Yb:CaF2 and Yb:SrF2 : Review of spectroscopic and thermal properties and their impact on femtosecond and high power laser performance

International audienceWe present an overview of laser results we obtained with Yb-doped calcium fluoride and its isotype strontium fluoride. In order to study the laser performance in femtosecond and high power regimes, spectral and thermal properties are first discussed including the potential of these crystals at room and cryogenic temperatures. Experimental demonstrations of high-power and ultrashort pulse oscillators and amplifiers are presented and analyzed

High-power diode-pumped cryogenically cooled Yb:CaF2 laser with extremely low quantum defect

International audienceHigh-power diode-pumped laser operation at 992-993nm under a pumping wavelength of 981 of 986nm is demonstrated with Yb:CaF2 operating at cryogenic temperature (77K), leading to extremely low quantum defects of 1.2% and 0.7%, respectively. An average output power of 33Whas been produced with an optical efficiency of 35%. This represents, to the best of our knowledge, the best laser performance ever obtained at such low quantum defects on intense laser lines

Thermal behaviour of ytterbium-doped fluorite crystals under high power pumping

International audienceWe report an in situ thermal study of Yb-doped fluorite crystals Yb:CaF2 and Yb:SrF2 under high power pumping, with or without laser operation. The experiment combines simultaneously thermography and measurement of the thermal aberrations. This setup allows us to measure temperature gradients, thermal lens, and absorption coefficients. From these measurements, we evaluate the thermal conductivity, fractional thermal load, and thermo-optic coefficient. Great differences are observed between the lasing and non lasing regimes. Our measured thermal lenses are greater than what are expected from the thermo-optic parameters found in previous work. Based on this thermal study, we design a laser cavity operating with large output power and TEM00, leading to better performances for Yb:CaF2 than Yb:SrF2

Diode-pumped 99 fs Yb : CaF2 oscillator

International audienceWe demonstrate the generation of 99 fs pulses by a mode-locked laser oscillator built around a Yb:CaF2 crystal. An average power of 380 mW for a 13 nm bandwidth spectrum centered at 1053 nm is obtained. The short-pulse operation is achieved thanks to a saturable absorber mirror and is stabilized by the Kerr lens effect. We investigated the limits of the stabilization process and observed a regime slowly oscillating between mode locking and Q switching

Anomalously high uniform upconversion in an erbium-doped waveguide amplifier

The performance of a planar Er3+-doped ion-exchanged waveguide is compared to a detailed model, including uniform upconversion estimated from spectral measurements. A discrepancy between experiment and theory requires a much higher level of uniform upconversion than predicted. We consider possible explanations for this anomaly

Spectroscopy of solid-solution transparent sesquioxide laser ceramic Tm:LuYO3

We report on a detailed spectroscopic study of a Tm3+-doped transparent sesquioxide ceramic based on a solid-solution (lutetia – yttria, LuYO3) composition. The ceramic was fabricated using commercial oxide powders by hot isostatic pressing at 1600°C for 3 h at 190 MPa argon pressure. The most intense Raman peak in Tm:LuYO3 at 385.4 cm−1 takes an intermediate position between those for the parent compounds and is notably broadened (linewidth: 12.8 cm−1). The transition intensities of Tm3+ ions were calculated using the Judd-Ofelt theory; the intensity parameters are W2 = 2.537, W4 = 1.156 and W6 = 0.939 [1020 cm2]. For the 3F4 → 3H6 transition, the stimulated-emission cross-section amounts to 0.27 × 10−20 cm2 at 2059nm and the reabsorption-free luminescence lifetime is 3.47 ms (the 3F4 radiative lifetime is 3.85 ± 0.1 ms). The Tm3+ ions in the ceramic exhibit long-wave multiphonon-assisted emission extending up to at least 2.35 µm; a phonon sideband at 2.23 µm is observed and explained by coupling between electronic transitions and the dominant Raman mode of the sesquioxides. Low temperature (12 K) spectroscopy reveals a significant inhomogeneous spectral broadening confirming formation of a substitutional solid-solution. The mixed ceramic is promising for ultrashort pulse generation at >2 µm