Continuous-wave Tm:YAlO3 laser at ∼2.3 µm.

The orthorhombic Tm3+:YAlO3 crystal is promising for laser operation at the H43→F43 (1.5 µm) and H43→H53 (2.3 µm) transitions. Stimulated-emission cross-sections for these transitions are determined with polarized light. Peak values of 0.59×10-20 cm2 and 0.80×10-20 cm2 are found at 1438 nm and 2275 nm, respectively, both for E∥b. The cross-relaxation defining the upper-laser level lifetime is quantified. Continuous-wave lasing at the H43→H53 transition is achieved with an a-cut 1.5 at.% Tm:YAlO3 crystal. The laser generated 254 mW at 2273 nm with a slope efficiency of 17.8% and linear polarization (E∥b).

Thulium laser at ∼2.3 µm based on upconversion pumping.

We report on novel upconversion (UC) pumping schemes for 2.3 µm thulium (Tm) lasers (the H43→H53 transition) based on a photon avalanche mechanism populating the intermediate metastable level (F43) acting as an effective ground state. The proposed pump wavelengths are ∼1 and ∼1.5 µm, each one corresponding to a resonant excited-state absorption transition F43→F2,33 and F43→H43, respectively. UC pumping at 1040, 1055, and 1451 nm of 2.3 µm Tm:LiYF4 lasers is demonstrated. In the former case, the laser generates 102 mW at 2302 nm with a slope efficiency of 14.6% (versus the incident pump power). The laser dynamics is studied. UC pumping is promising for reaching high efficiencies in 2.3 µm Tm lasers.

Watt-level narrow-linewidth Nd:YAG laser operating on 4F3/2→4I15/2 transition at 1834 nm.

We report on a 808 nm diode-pumped Nd:YAG narrow linewidth laser at 1834.25 nm using a compact two-mirror linear cavity. In free-running mode, a maximum output power of 1.10 W is obtained with a slope efficiency of about 11.1% at a cooling temperature of the laser crystal of 18°C. Decreasing this temperature down to 8°C increases the output power linearly up to 1.31 W. Shortening the laser cavity reduces the output power down to about 0.70 W but on a single longitudinal mode. These laser results represent the best laser performance ever achieved with any Nd-doped bulk material in the 1.8 µm mid-infrared spectral range.

Broadband-tunable CW laser operation of Pr(3+):LiYF(4) around 900 nm.

We present here the first broadband-tunable CW laser operation of a Pr(3+)-doped LiYF(4) crystal in the 900-nm spectral range after pumping with an optically pumped semiconductor laser at 479 nm. It is confirmed that the entire emission band can be assigned to the same set of thermalized emitting levels (I(6)1,P3(0,1)). It is also demonstrated that laser performance could be improved up to laser slope efficiencies of about 33% with threshold absorbed pump powers not exceeding 100 mW.

Passively Q-switched Nd:YAlO3nanosecond laser using MoS2as saturable absorber.

We report on the first passively Q-switched Nd:YAlO3 laser at ~1079.5 nm using MoS2 as saturable absorber. The MoS2 saturable absorber is fabricated by transferring the liquid-phase-exfoliated MoS2 nanosheets onto a BK7 glass substrate. By inserting the glass MoS2 saturable absorber into a plano-concave Nd:YAlO3 laser cavity, we obtain a stable Q-switched laser operation with a maximum average output power of 0.26 W corresponding to a pulse repetition rate of 232.5 kHz, a pulse width of 227 ns and a pulse energy of about 1.11 µJ. The results experimentally confirm the promising application of the new kind of 2D material, few-layer MoS2, in solid state lasers.

Green, orange, and red Pr(3+)∶YLiF(4) epitaxial waveguide lasers.

Efficient guided laser oscillation in the visible spectral region is demonstrated with praseodymium-doped YLiF(4) layers grown by liquid phase epitaxy. By exciting Pr(3+) ions at 479.2 nm with an optically pumped semiconductor laser, maximum slope efficiencies of 40% at 639 nm and 32% at 604 nm are obtained in a cw regime. Green laser oscillation at 522.5 nm, in a quasi-cw regime, with an average output power of 66 mW, is demonstrated for the first time, to our knowledge, in a crystalline fluoride epitaxial waveguide. Furthermore, a record efficiency of 60% at 639 nm in the quasi-cw regime is reported.

2.8 W end-pumped Yb3+:LiYF4 waveguide laser.

Continuous wave, room temperature laser oscillation around 1 µm is reported for the first time (to our knowledge) from an Yb(3+)-doped fluoride crystalline waveguide fabricated by using the liquid phase epitaxy technique. Maximum slope efficiencies of 76% and 41% were obtained for laser emissions at 994 and 1020 nm, respectively. A maximum output power of 2.8 W was obtained at 1020 nm by pumping around 980 nm with a high-brightness fiber laser in an 87 mm long V-shaped cavity.

Red and orange Pr3+:LiYF4 planar waveguide laser.

In this Letter we report on room temperature continuous wave laser operation in the red (639 nm, (3)P(0)→(3)F(2)) and orange (604 nm, (3)P(0)→(3)H(6)) spectral regions of Pr(3+)-doped LiYF(4) planar waveguides fabricated by liquid phase epitaxy. Output powers of 25 and 12 mW and slope efficiencies of 5% and 6% were achieved at 639 and 604 nm, respectively, by pumping with an optically pumped semiconductor laser operating at 479.2 nm.

Tm:LiYF4 planar waveguide laser at 1.9 µm.

Continuous wave laser operation at 1.87 µm of liquid-phase epitaxially (LPE) grown Tm(3+)-doped YLiF(4) (Tm:YLF) layers is demonstrated. The waveguide laser delivers 560 mW by pumping with a Ti:Sapphire laser at 780 nm leading to an efficiency of 76% with respect to the absorbed pump power. This constitutes the first Tm(3+)-doped crystalline fluoride waveguide laser ever demonstrated as well as a record in efficiency and output power for an LPE grown waveguide laser operating in the 2 µm spectral range.

Baryscan: a sensitive and user-friendly alternative to Z scan for weak nonlinearities measurements.

A new and efficient technique for measuring weak optical nonlinearities is reported. Like Z scan, its implementation is basic, both experimentally and theoretically, but leads to an improved sensitivity of λ/5.104, which represents, to date, one of the highest observed enhancements. With this technique, which is based upon the use of a position sensitive detector, nonlinear properties are deduced by monitoring the barycentric position of a truncated pump-probe laser beam as the sample is moved along the optical axis. The technique is experimentally validated by measuring the pump-induced refractive index change and the underlying polarizability variation resulting from the excitation of the Cr(3+) ions in ruby.

Visible laser operation of Pr3+-doped fluoride crystals pumped by a 469 nm blue laser.

We report continuous-wave (CW) laser operation of Pr3+-doped LiLuY4, LiYF4 and KY3F10 single crystals in the Red, Orange and Green spectral regions by using a new pumping scheme. The pump source is an especially developed compact, slightly tunable and intracavity frequency-doubled diode-pumped Nd:YAG laser delivering a CW output power of 0.9W at 469.12 nm. At this pump wavelength, efficient room temperature laser emissions corresponding to the 3P0→3F2, 3P0→3H6 and 3P1→3H5 Pr3+ transitions are observed. While a maximum slope efficiency of 45% is obtained in the red with Pr:LiYF4, the demonstration is made for the first time of the orange laser operation of Pr:KY3F10 at about 610 nm.

Short-pulse and high-repetition-rate diode-pumped Yb:CaF2 regenerative amplifier.

We present a diode-pumped regenerative amplifier based on an Yb:CaF(2) 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 microJ 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.