High-power 2.3†µm Tm:YLF laser with intracavity upconversion pumping by a Nd:ASL laser at 1051†nm.

A Tm:LiYF4 laser operating on the 3H4 → 3H5 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:LiYF4 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:LiYF4 crystal and an increased tolerance to Tm3+ 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.

Deep-red double-clad fiber laser at 717†nm.

We report on a double-clad fiber laser operating on the 3P0 → 3F4 Pr3+ transition (in the deep-red spectral range) pumped by a GaN diode laser at ∼442 nm. It employs a 0.8-mol% PrF3-doped ZBLAN double-clad fiber with a 7.5-µm core, a double D-shaped inner cladding, and a length of 3.0 m. The laser delivers a maximum output power of 0.71 W at 716.7 nm with a slope efficiency of 9.0% (versus the launched pump power) and a laser threshold of 0.90 W. The laser emission is partially polarized. The laser performance is simulated providing a guideline for watt-level deep-red fiber laser sources.

Narrow linewidth near-UV InGaN laser diode based on external cavity fiber Bragg grating.

We realize a fiber Bragg grating InGaN-based laser diode emitting at 400 nm and demonstrate its high coherency. Thanks to the fabrication of a narrowband fiber Bragg grating in the near-UV, we can reach single-mode and single-frequency regimes for the self-injection locked diode. The device exhibits 44 dB side-mode suppression ratio and mW output power. Detailed frequency noise analysis reveals sub-MHz integrated linewidth and 16 kHz intrinsic linewidth. Such a narrow linewidth laser diode in the near-UV domain with a compact and low-cost design could find applications whenever coherency and interferometric resolutions are needed.

Watt-level visible laser in double-clad Pr3+-doped fluoride fiber pumped by a GaN diode.

We report on a red praseodymium fiber laser delivering 1.07 W at 634.5 nm with a slope efficiency of 20.7% (versus the incident pump), a laser threshold of 0.55 W, and a single-mode output (Mx,y2<1.1) in the quasi-continuous-wave regime. It is based on a 0.6 mol.% Pr3+-doped ZBLAN double-clad fiber with a 5.5 µm core, a double D-shaped (diameters, 115/125 µm) inner cladding, and a length of 5.0 m. The fiber is pumped by a multimode 443 nm GaN diode. The laser design is optimized using a numerical model. The proposed concept is suitable for the development of diode-pumped high brightness watt-level visible praseodymium fiber lasers.

Watt-level diode-pumped thulium lasers around 2.3 µm.

We report on efficient diode-pumped mid-infrared lasers based on Tm:LiYF4, Tm:Y3Al5O12, and Tm:YAlO3 crystals. These lasers operate in the continuous-wave (CW) regime and deliver watt-level output power at the wavelengths of 2.2-2.3 µm (the 3H4→3H5Tm3+ transition). In particular, a 1.8 at. % Tm:YAlO3 laser pumped at 789 nm generates a maximum CW output power of 1.32 W at 2272-2277 nm with a slope efficiency of 33.1% (with respect to the absorbed pump power), a linear laser polarization (E∥b), and a fundamental transverse output mode (the measured Mx2=1.26, My2=1.68). In the quasi-CW regime, the output peak power is scaled up to 2.69 W. The pump quantum efficiency and the fractional heat loading are estimated and discussed.

Deep ultraviolet lasers for flow cytometry.

Modern flow cytometers require multiple laser wavelengths to excite the wide variety of fluorescent probes now available for high-dimensional analysis. Ultraviolet (UV) lasers (typically solid state 355 nm) have become a critical excitation source for the Brilliant Ultraviolet (BUV) series of polymer fluorochromes. The BUV dyes have pushed the number of fluorescent probes available for simultaneous analysis to nearly 30, allowing an unprecedented level of precision for immune cell analysis. However, immunologists are already seeking analyze more than 30 simultaneous parameters, requiring both new fluorochromes and corresponding laser wavelengths. A group of polymer dyes requiring deep ultraviolet (UV) excitation (~280-300 nm) is currently under development, allowing the expansion of high-dimensional cytometry beyond the current 30 color limit. In this study, we evaluated a newly available laser emitting at 280 nm as a possible laser source for exciting these dyes. Since deep UV polymer dyes are not yet available, we used quantum nanoparticles (Qdots) as a surrogate probe to assess the utility of this laser wavelength for flow cytometry. Deep UV laser light was found to excite Qdots as well as traditional UV sources. Deep UV 280 nm did not excite BUV dyes well, suggesting that BUV and deep UV polymers will be spectrally compatible with low crossbeam spillover issues. Deep UV excitation did excite considerable autofluorescence in the violet to blue range, a limitation that will need to guide deep UV fluorochrome development. A deep UV 280 nm laser may therefore be the next essential wavelength for high-dimensional flow cytometry. © 2018 International Society for Advancement of Cytometry.

1064 nm Nd:YVO4 laser intracavity pumped at 912 nm and sum-frequency mixing for an emission at 491 nm.

We present for the first time a Nd:YVO(4) laser emitting at 1064 nm intracavity pumped at 912 nm by a Nd:GdVO(4) laser. We carried out a model to design the system properly, and laser performance was experimentally investigated. Intracavity sum-frequency mixing at 912 and 1064 nm was then realized in a BiBO crystal to reach the blue range. We obtained a cw output power of 155 mW at 491 nm with a pump laser diode emitting 20 W at 808 nm.

Diode-pumped Nd:YVO(4)/Yb:S-FAP laser emitting at 985 and 492.5 nm.

For the first time, to the best of our knowledge, Yb:S-FAP crystals have been intracavity pumped by a Nd:YVO(4) laser at 914 nm. This original pumping scheme allows efficient laser action on the three-level transition at 985 nm with 1.4 W output power. Second-harmonic generation is also presented with a total output power of 120 mW at 492.5 nm.