Jean-Louis Doualan

Sub-50 fs, Kerr-lens mode-locked Yb:CaF2 laser oscillator delivering up to 2.7 W

By means of a high-brightness optical pumping scheme with a fiber laser, we demonstrate Kerr-lens mode locking (KLM) with an Yb:CaF2 laser crystal. Stable 48 fs pulses are produced at an average power of 2.7 W.

InGaN-LD-Pumped Continuous-Wave Deep Red Laser at 670 nm in Pr 3+ :LiYF 4 Crystal

We report the first laser operation at π-polarized 670.34-nm deep red laser in a 2-W InGaN-LD-pumped Pr3+:LiYF4 (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

Kerr lens mode-locking of Yb:CaF2

% 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.

Femtosecond and dual-wavelength mode-locked operation in Nd,Lu:CaF2

Through high-brightness optical pumping with a fiber laser, we demonstrate a soft-aperture Kerr lens modelocked (KLM) operation in a Yb:CaF2 crystal. Stable 117 fs pulses are producing at an average power of 560 mW.

3.4 µm to 660 nm wavelength conversion using Er3+ doped materials

While CaF2:Nd3+,Lu3+ spectroscopic features are now well-known for its broadband laser operation near 1 µm and its good quantum efficiency, this material is appealing for a number of applications such as mode-locking operation. In this paper, we investigate this crystal for dual-wavelength picosecond and femtosecond operations by using a semiconductor saturable absorber mirror (SESAM). In dual-wavelength picosecond operation, synchronous mode-locking is demonstrated at 1054 and 1059 nm when pumping at 797nm and when using a high reflective mirror as an output coupler. Only one pulse train at 93,8MHz was formed and the intensity autocorrelation trace shown a period beat frequency of 1.34 THz. Pumping at 791 nm led to the formation of two asynchronous mode-locked pulses probably because the two emission lines at 1049 nm and 1061 nm were too far to be coupled. Hence by spectral filtering it is possible to make a single train mode locked laser at 1061 nm generating femtosecond pulses. The laser generated modelocked pulses with pulse duration of 435 fs, average power of 10 mW, and central wavelength of 1061 nm. More output power could be obtained by using a more transmissivity for the output coupler however degrading other performances. These results open the way for further investigation on CaF2:Nd3+,Lu3+ crystals, with the aim of their implementation as active components in high power femtosecond lasers.

Dy3+ doped CaF2 crystals spectroscopy for the development of Mid-infrared lasers around 3 µm

The 2-15 μm spectral range hosts many optical sensing applications from biology to environmental monitoring, and infrared spectroscopy is a simple and reliable way to provide fast and in-situ analysis method. Rare-earth ion emissions within chalcogenide glasses with low phonon energies proved to be efficient to address mid-IR luminescence based sensing applications. In particular, they give promising results for the development of all-optical gas sensors in the 3 to 5 μm spectral range based on IR conversion into visible light using rare earth excited state absorption mechanisms. In this article, we report the wavelength conversion of 3.4 μm radiation into 660 nm in Er3+:KPb2Cl5 bulk crystal, Er3+:Ga5Ge20Sb10S65 and Er3+:Ga5Ge20Sb5S70 glasses using an excited state absorption process. This wavelength conversion is the result of the excitation of Er3+ ions following the excited state absorption of IR photons and the Er3+ ions subsequent spontaneous emission in the visible domain. Using an 808 nm pumping, a 3.4 μm photon excited state absorption gives rise to a 660 nm emission. This wavelength conversion device can be further implemented for methane all-optical sensing at 3.4 μm, for the development of remote “all-optical” methane mid-IR sensors with only visible and near-IR input and output signals. This “all-optical concept” enables the use of silica fibers over large distances, thus considerably increasing the scope of possible applications.The 2-15 μm spectral range hosts many optical sensing applications from biology to environmental monitoring, and infrared spectroscopy is a simple and reliable way to provide fast and in-situ analysis method. Rare-earth ion emissions within chalcogenide glasses with low phonon energies proved to be efficient to address mid-IR luminescence based sensing applications. In particular, they give promising results for the development of all-optical gas sensors in the 3 to 5 μm spectral range based on IR conversion into visible light using rare earth excited state absorption mechanisms. In this article, we report the wavelength conversion of 3.4 μm radiation into 660 nm in Er3+:KPb2Cl5 bulk crystal, Er3+:Ga5Ge20Sb10S65 and Er3+:Ga5Ge20Sb5S70 glasses using an excited state absorption process. This wavelength conversion is the result of the excitation of Er3+ ions following the excited state absorption of IR photons and the Er3+ ions subsequent spontaneous emission in the visible domain. Using an 808 nm pumping, a 3.4 μm photon excited state absorption gives rise to a 660 nm emission. This wavelength conversion device can be further implemented for methane all-optical sensing at 3.4 μm, for the development of remote “all-optical” methane mid-IR sensors with only visible and near-IR input and output signals. This “all-optical concept” enables the use of silica fibers over large distances, thus considerably increasing the scope of possible applications.

MWIR emissions from 3.1 to 8 µm of Tb3+ doped seleno-telluride fibers (Conference Presentation)

In this communication, we present a spectroscopic study of Dy3+ -doped and Tm3+ -Dy3+ codoped CaF2 as promising candidates to develop solid-state laser sources around 3 μm. In view of the preliminary experimental results, we first demonstrate the advantage of Tm3+ ions as sensitizers to improve the excitation of Dy3+ ions in CaF2 and then is highlighted a singular behavior of Dy3+ doped CaF2 crystals that present a multisite character due to clustering of rare earth ions. The spectroscopic characteristics of each site is studied and discussed, as well as the potential of Tm3+ codoping for laser applications around 3μm.

Highly doped Tm:YLF LPE crystalline layers for 1.9µm lasers

Chalcogenide glasses appear as good candidates to build all optical gas sensors due to their wide infrared transparency and the possibility of incorporate rare earth active in MWIR spectral range. To detect and quantify gases, one way is to develop chalcogenide glasses presenting transparency compatible with the molecules absorption band frequency. Two domains of interest can be distinguished: MWIR and LWIR corresponding respectively to the 3–5 μm and 8–12 μm spectral ranges. Selenide and sulfide based chalcogenide glasses are known for their excellent infrared transmission properties in the 1-15 µm region with good thermo-mechanical properties. Doped with Dy3+or Pr3+, sulfide glass fibers have been used as MWIR source for gas sensor for CO2 detection. To probe the far infrared beyond 12 µm, telluride chalcogenide glasses appear as a very interesting material due to it low phonon energy and a broad transparency (up to 25 µm). While these attractive optical properties of telluride glasses, particularly for LWIR, there is few study about rare earth incorporation for luminescence explained a challenging synthesis process avoiding crystallization. To get more stability in the glass state it is essential to add selenium. Thus for each system, it is required to determine the best compromise between the transparency domain and the glass state stability by playing on the ratio between selenium and tellurium atoms. Regarding the energy level of Tb3+, we can expect to have a radiative emission from 3.1 µm up to 8 µm. For gas sensor application, it is a range of interest regarding the LWIR absorption band of some hazardous gases. Thus, Tb3+ doped chalcogenide glasses with nominal composition of Ga5Ge20Sb10Se(65-x)Tex (x = 0, 10, 20, 25, 30, 32.5, 35, 37.5) were synthetized. Their physico-chemical properties (chemical composition, density, thermal characteristics) and optical properties (transmission and ellipsometry spectroscopies) are clearly modified by tellurium substitution to selenium. Based on a detailed study of the Ga5Ge20Sb10Se(65-x)Tex bulk glass and fiber properties, the optimal composition of seleno-telluride glass fiber was found to be Ga5Ge20Sb10Se45Te20. The luminescence properties of Tb3+ (500, 1000 and 1500 ppm) doped Ga5Ge20Sb10Se65 and Ga5Ge20Sb10Se45Te20 were studied in glass bulk and fiber samples. Radiative transitions calculated from Judd-Ofelt (J-O) theory were compared to the experimental values. Although an expected lower phonon energy for telluride glasses, selenide glasses stay more suitable for MWIR emission with a strong emission at 4.8 and 3.1 µm. The emission at 8 µm was successfully observed with careful luminescence investigations.

Fluoride Planar Waveguide Lasers

Laser operation at 2 µm is reported using an epitaxial, highly Tm-doped, 240 µm thick LiYF4 layer grown by liquid phase epitaxy. Simulation of laser operation is compared to experiments.

Yb doped Fluorides for High Power and Short-Pulse Laser Applications

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.