We report a systematic investigation of the effect of lanthanum incorporation on the polarization-resolved spectroscopic and laser properties of Pr 3+ -doped Sr 1- x La x Mg x Al 12- x O 19 (ASL) hexaaluminate solid-solution crystals, with reference to the parent SrAl 12 O 19 (SRA) compound. The addition induces inhomogeneous broadening of absorption and emission bands, while only weakly affecting the phonon spectra and radiative transition probabilities. In the red spectral region (the 3 P J → 3 F 2 transition), Pr 3+ :SRA exhibits a stimulated-emission cross section σ SE as high as 16.4 × 10 −20 cm 2 at 643.6 nm, with an emission bandwidth of 1.0 nm. For the La 0.47 composition, σ SE decreases to 6.1 × 10 −20 cm 2 at 645.8 nm, while the bandwidth is broadened to 4.1 nm. The luminescence lifetime remains nearly unchanged across the compositions, in the range of 36–38 µs. Under 465 nm GaN diode pumping, the optimized Pr 3+ :ASL (La 0.26 ) crystal delivers 164 mW at 644 nm, with a slope efficiency of 13.2% and a laser threshold of 0.30 W. Laser action in the deep red is also demonstrated. These results highlight the potential of La-substituted, Pr 3+ -doped hexaaluminates as broadly emitting visible laser gain media.

We report a systematic investigation of the effect of lanthanum incorporation on the polarization-resolved spectroscopic and laser properties of Pr3+-doped Sr1-xLaxMgxAl12-xO19 (ASL) hexaaluminate solid-solution crystals, with reference to the parent SrAl12O19 (SRA) compound. The addition induces inhomogeneous broadening of absorption and emission bands, while only weakly affecting the phonon spectra and radiative transition probabilities. In the red spectral region (the 3PJ -> 3F2 transition), Pr3+:SRA exhibits a stimulated-emission cross section 0SE as high as 16.4 & times; 10-20 cm2 at 643.6 nm, with an emission bandwidth of 1.0 nm. For the La0.47 composition, 0SE decreases to 6.1 & times; 10-20 cm2 at 645.8 nm, while the bandwidth is broadened to 4.1 nm. The luminescence lifetime remains nearly unchanged across the compositions, in the range of 36-38 & micro;s. Under 465 nm GaN diode pumping, the optimized Pr3+:ASL (La0.26) crystal delivers 164 mW at 644 nm, with a slope efficiency of 13.2% and a laser threshold of 0.30 W. Laser action in the deep red is also demonstrated. These results highlight the potential of La-substituted, Pr3+-doped hexaaluminates as broadly emitting visible laser gain media.

New methods based on laser induced fluorescence in life sciences and on holography for surface inspection require high power compact efficient visible lasers.

In the past years, fluoride glass fibers (ZBLAN) doped with various rare-earth ions enabled a breakthrough in the development of coherent light sources directly emitting in the visible under blue diode pumping. Holmium ions $(\text{Ho}^{3+})$ offer intense absorption around 450 nm (as the corresponding transition is spin-allowed) and enable green emission at 550 nm (the ${ }^{5} \mathrm{S}_{2}+{ }^{5} \mathrm{F}_{4} \rightarrow{ }^{5} \mathrm{I}_{8}$ transition). Li et al. reported on a low-brightness GaN diode-pumped Ho:ZBLAN laser delivering 376 mW at 544 nm, however with a low optical efficiency of ~12% [1]. High-brightness core pumping enables the development of compact laser sources with high overall optical efficiency [2]. In the present work, we report on an efficient green Ho:ZBLAN fiber laser with high-brightness diode-pumping.

We report on a continuous-wave (CW) praseodymium fluoride fiber laser delivering 10-watt level output power in the red spectral range. It employs a double-clad 0.8 mol% PrF3-doped ZBLAN fiber as a gain medium and a high-power fiber-coupled 442-nm GaN laser diode module as a pump source. The CW Pr-laser delivers 9.1 W at 635 nm with a slope efficiency of 27.0% (versus launched pump power), a laser threshold of 1.32 W, and a single-mode output. In the quasi-continuous-wave regime, its output is further scaled to 10.32 W. The spectrum broadening in this laser is explained by four-wave mixing and is well described by the square root law. This result represents a new milestone in developing visible fluoride fiber lasers. The temperature-dependent spectroscopy of Pr3+ ions in the ZBLAN glass is studied, and the limits for further power scaling of red fluoride fiber lasers are discussed.

We present a fiber laser system that generates femtosecond pulses at 914 nm from a continuous-wave solid-state laser source and using Nd-doped fiber amplifiers. This femtosecond laser architecture without mode-locking is based on picosecond pulse shaping by an electro-optic modulator followed by a Mamyshev regenerator to shorten the pulses down to 8 ps. Additional spectral broadening by self-phase modulation results in an output pulse spectrum of 10 nm, allowing the generation of nearly transform-limited 230 fs pulses.

We report on the fabrication and characterization of Dy3+-doped phosphate glass fibers for applications in yellow lasers. The fibers (core/cladding diameters: 11/125 mu m) were fabricated in the system P2O5-Al2O3-Ba2O-K2O with their core doped with 0.12 at.% Dy3+. For bulk glass, the absorption cross-section sigma(abs) is 0.11x10(-20) cm(2) at 452.4 nm (absorption bandwidth: 8.4 nm), in the range well addressed by blue GaN laser diodes. The transition probabilities for Dy3+ ions are calculated using the Judd-Ofelt theory. The stimulated-emission cross-section in the yellow sigma(SE) is 0.36x10(-20) cm(2) at 574.1 nm, and the luminescence lifetime for the F-4(9/ 2) manifold is 818 mu s, indicating a luminescence quantum efficiency close to unity. mu-Raman and mu-luminescence mapping was performed over the fiber end-facet indicating a homogeneous core composition and a uniform distribution of Dy3+ ions.

We report on the first visible orange samarium laser directly pumped by a blue 465-nm GaN semiconductor laser diode. The diode-pumped continuous-wave Sm:LiYF4 laser delivers 23.9 mW at 605 nm (4G5/2 -> 6H7/2 transition) with a slope efficiency of 9.4%, a laser threshold of 385 mW and a linear polarization (pi). We investigate the impact of pump beam quality on laser performance and revisit the polarized spectroscopic properties of Sm3+ ions in the LiYF4 crystal. The stimulated-emission cross-section sigma SE amounts to 1.27 x 10-20 cm2 at 604.8 nm for pi-polarized light, and the luminescence lifetime of the 4G5/2 level is 4.02 ms diode-pumped orange and red samarium lasers.

Currently, Praseodymium (Pr3+) doped fluoride crystals (LiYF4) and glasses (ZBLAN) are recognized for the development of multi-colour laser sources directly emitting visible radiation under pumping by blue GaN-based laser diodes or semiconductor lasers [1], [2]. Monolithic cavities employing composite gain media (i.e., those consisting of an undoped and a rare-earth doped part) benefit from reduced intracavity losses and improved thermal management. Such monolithic micro-lasers emitting in the visible are relevant for applications in biology, e.g., super-resolution microscopy, or as seed sources for laser amplifiers. We report on an efficient and power scalable diode-pumped monolithic red laser employing a composite gain medium based on Pr3+-doped LiYF4 (Pr:YLF) crystal.

A Tm:YLF laser operating on the 3H4→3H5 transition is intracavity upconversion pumped at 1.05 μm by a diode-pumped Nd:ASL laser. The continuous-wave 2.3-μm Tm-laser delivers 1.59 W at 35 W of laser diode power.

A Tm:LiYF 4 laser operating on the 3 H 4 → 3 H 5 transition is embedded in a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 µm. This leads to a record-high output power at 2.3 µm for any bulk thulium laser pumped by an upconversion process. The continuous-wave Tm:LiYF 4 laser delivers 1.81 W at 2.3 µm for 32 W of laser-diode pump power, making this kind of pumping competitive with direct diode pumping. The intracavity pumping process allows for counteracting the low absorption inherent to upconversion pumping and to dispatch the thermal loads on two separate laser crystals. The proposed laser architecture also features a relatively weak heating of the Tm:LiYF 4 crystal and an increased tolerance to Tm 3+ absorption. This laser design opens a new paradigm that holds great promise for high-power 2.3-µm solid-state lasers based on thulium ions.

We overview recent advances in visible single- and double-clad fluoride fiber lasers pumped by blue GaN laser diodes. The spectroscopic properties of ZBLAN glasses doped with Pr3+, Ho3+ and Dy3+ ions are revised. Power scalable efficient continuous-wave visible fluoride fiber lasers emitting in the green, yellow, red and deep-red spectral ranges are presented. Pumped by a single-emitter 6-W 443-nm GaN laser diode, a continuous-wave red double-clad Pr:ZBLAN fiber laser delivered 1.51 W at 634.5 nm with a slope efficiency of 31.0%, a laser threshold of 0.63 W and a spatially single-mode output (M-2 similar to 1.02). Employing a high-power fiber-coupled laser module, power scalability up to 4.61W was achieved at the expense of a lower slope efficiency of 22.8% and an increased laser threshold of 1.74 W. Green Ho:ZBLAN (543 nm) and yellow Dy:ZBLAN (575 nm) fiber lasers with high-brightness core pumping at 450 nm are also reported delivering 100 mW-level output with slope efficiencies of 31.2% and 19.6%, respectively, operating on the fundamental mode. A numerical model to predict the visible laser performance is presented and guidelines for further engineering of visible fiber laser sources are given.

We report on a low-threshold efficient yellow Dy-fiber laser with good beam quality featuring high-brightness pumping. It employs a single-clad 0.2 mol% Dy:ZBLAN fiber pumped by two 450-nm blue GaN laser diodes. The continuous-wave Dy-fiber laser delivers a maximum output power of 109 mW at 575 nm with a laser threshold of 218 mW, a slope efficiency of 19.6%, and beam quality factors M2 x,y ∼ 1.5. The overall optical efficiency versus incident pump power is 13.9%, being record-high, to the best of our knowledge, for this type of laser. The laser performance is simulated based on the spectroscopic data, being in good agreement with the experiment.

A Tm:LiYF4 laser operating on the 3H4 → 3H5 transition is integrated into a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 μm. This architecture leads to a record-high output power at 2.3 μm ever extracted from any upconversion pumped Thulium laser. The continuous-wave Tm-laser yields 1.81 W at 2.3 μm at 32 W of laser-diode pump power at 0.8 μm, rivalling direct diode pumping. The intracavity pumping mitigates weak absorption inherent to the upconversion pumping scheme and disperses the deposited heat over two laser crystals. This laser design minimizes heating of the Tm-crystal and enhances the tolerance to Tm3+ excited-state absorption, being promising for high-power 2.3-μm solid-state lasers based on thulium ions.

Fluoride fiber lasers are promising candidates for high power visible laser generation. Recent breakthrough and means to overcome current limitations will be presented. Full-text article not available; see video presentation

We present an all-PM fiber laser system seeded by a single-frequency CW laser source generating 230fs pulses at 914nm with a tunable repetition rate between 5 and 20 MHz. Ultra-short pulse train was achieved using a Mach-Zehnder modulator for pulse carving, Nd-doped fiber amplifiers and a Mamyshev regenerator.

We report on polarized spectroscopy and orange laser operation under 2ω-OPSL and GaN-diode pumping of Sm:LiYF4 crystals. The Samarium laser delivers 12 mW at 605 nm with a threshold of 51 mW and a linear polarization.

A Tm:YLF laser operating at 2.3 µm is pumped at 1.05 µm with a diode-pumped Nd:ASL laser via intracavity upconversion pumping. The continuous-wave Tm-laser delivers 1.81 W for 41 W of laser diode power.