A Kerr-lens mode-locked laser based on a Yb

Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10−20 cm2 for σ polarization and 5.32 × 10−20 cm2 for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10−20 cm2 at 980 nm for σ polarization and 2.28 × 10−20 cm2 at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at 2F5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y3+ in the crystal is partially replaced by Lu3+ and Gd3+, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals.

Nd3+-doped calcium niobium gallium garnet single crystal fibers (Nd:CNGG SCFs) with varying Nd3+ concentrations were successfully grown using the laser-heated pedestal growth (LHPG) method. The study thoroughly examines the fundamental physical structure, optical properties, and laser characteristics of the as-grown Nd:CNGG SCFs. Results indicate that the Nd:CNGG SCF exhibits broader absorption and emission full width at half maximum (FWHM) compared to bulk single crystals. Moreover, pumped by a commercial 808 nm laser diode, continuous-wave laser operation at 1061 nm with a half-height width of 1.86 nm was achieved. The laser output power reached 1.04 W at an absorbed power of 7.46 W, with a slope efficiency of 25.4% relative to the absorbed pump power. These findings suggest that Nd:CNGG SCF holds promise as a practical and potent candidate for laser gain medium, offering significant research potential in the field of lasers. (c) 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Ho,Pr:CaYAlO4 (Ho,Pr:CYA) crystal doped with 1 at.% Ho3+ and 0.1 at.% Pr3+ was successfully grown using the Czochralski method. Polarized absorption spectra, emission spectra, and fluorescence lifetime measurements were performed. The impact of Pr3+ co-doping on the similar to 3 mu m emission of Ho3+ ions was analyzed. The energy transfer efficiency from Ho3+:I-5(7) to Pr3+:F-3(2) energy level was calculated to be 60.66 %, indicating that Pr3+ effectively mitigated the self-termination effect in Ho,Pr:CYA crystals. The absorption cross-section at 645 nm was found to be 1.53 x 10(-20) cm(2) for sigma polarization and 2.62 x 10(-20) cm(2) for pi polarization. The emission cross-section at 2842 nm was calculated to be 0.86 x 10(-20) cm(2) for sigma polarization and 1.33 x 10(-20) cm(2) for pi polarization at 2908 nm, with a full width at half maximum (FWHM) of 139 nm and 88 nm, respectively. The fluorescence lifetimes of the I-5(6) and I-5(7) levels were measured to be 0.17 ms and 2.01 ms, respectively. These results collectively suggest that Ho,Pr:CYA crystals hold great potential as a candidate for 2.8 mu m laser applications.

A novel, to the best of our knowledge, Tm,Ho:GdScO3 crystal grown using the Czochralski method was investigated for its polarized spectroscopic properties and laser performance in both tunable continuous-wave (CW) and mode-locked regimes. The crystal's multisite structure (Gd3+/Sc3+ site) and Tm3+/Ho3+ dopants contributed to spectral broadening, enabling a tunable laser operation from 1914 to 2125 nm (with a broad range of 215 nm). Additionally, a pulse duration of 72 fs was achieved for E || b polarization. These results demonstrate the potential of the Tm,Ho:GdScO3 perovskite crystal as a promising gain material for ultrafast lasers operating around 2 µm.

Ho3+, Pr3+ co-doped CaGdAlO4 (Ho,Pr:CGA) crystal fibers were successfully grown by the micro-pulling-down (mu-PD) technique for the first time. Detailed investigations were conducted on the polarized absorption spectra, fluorescence spectra, and lifetime decay curves. The 2 at.% Ho, 0.4 at.% Pr:CGA crystal fiber exhibits a broad absorption band at 1147 nm with full width at half maximum (FWHM) of 25.5 nm and 64.5 nm for sigma and pi polarization, respectively. Increasing the concentration of Pr3+ led to a decrease in emission intensity at 2001 nm and an increase in emission intensity at 2861 nm. The FWHMs of the crystal fiber containing 2 at.% Ho and 0.4 at.% Pr:CGA at 2861 nm were 44.5 nm for sigma polarization and 24.3 nm for pi polarization. Additionally, the lifetime ratio (I-5(7)/I-5(6)) decreases from 25.18 to 2.85 in the crystal fibers containing 2 at.% Ho:CGA and 2 at.% Ho, 0.4 at.% Pr:CGA, respectively. These findings suggest that the presence of deactivated Pr3+ ions can significantly reduce the lifetime gap between the I-5(6) and I-5(7) energy levels, potentially mitigating the self-termination phenomenon on the similar to 3 mu m emission.

A Kerr-lens mode-locked laser based on a Yb3+-doped disordered gadolinium scandate (Yb:GdScO3) crystal is reported for the first time, to the best of our knowledge. The crystal with the perovskite structure was grown using the Czochralski method, and its room temperature (RT) and low temperature (LT) spectra were also investigated. Due to the crystal's multisite structure (Gd3+/Sc3+ site), Yb:GdScO3 offers broad and intense polarized emission spectra in the near-infrared range (975-1075 nm). The stimulated emission cross section σSE is 0.46 × 10-20 cm2 at 1000 nm with an emission band width of 75.7 nm for E // b polarization. The continuous wave (CW) laser was operated pumped by a 976 nm fiber-coupled LD laser, resulting in a maximum output power of 8.74 W with a slope efficiency of 76.1% was obtained. Additionally, a pulses as short as 74 fs are generated at ∼1061.7 nm via Kerr-lens mode-locking. The average output power amounts to 32 mW at a pulse repetition rate of 101.4 MHz. All results indicate Yb:GdScO3 a promising candidate for 1 µm ultrashort laser.

Yb:CaYAlO 4 (Yb:CALYO) shaped crystal fibers with different Yb 3+ doping concentration were successfully grown by the micro-pulling-down ( mu-PD) method. The effect of the Yb 3+ concentration on the structure, absorption, emission and lifetime was systematically studied. The strongest absorption peaks of Yb:CALYO crystal fibers are located at 977 nm for a and n polarization. The micro-photoluminescence indicate that Yb 3+ ions in CALYO single crystal fiber grown by the mu-PD method distributed evenly across a cross-section. The emission crosssection of 5 at.% Yb:CALYO crystal fiber was calculated to be 0.86 x 10 -20 and 1.08 x 10 -20 cm 2 at 983 nm for a and n polarizations. Benefited from the disordered structrure of CaYAlO 4 crystal, the full width at half maximum (FWHM) at 978 nm was 68.9 nm and 80.9 nm, respectively. The fluorescence lifetime of 2 F 5/2 energy level of Yb:CALYO crystal fibers with concentration of 0.5 at.%, 1 at.%, 2 at.% and 5 at.% was calculated to be 435 mu s, 484 mu s, 514 mu s and 453 mu s, respectively. The experimental results show that Yb:CALYO crystal fiber is a potential laser medium for ultrashort laser operation.

Nd3+-doped Sr0.7La0.3Mg0.3Al11.7O19 and LaMgAl12O19 shaped crystal fibers have been successfully grown by the micro-pulling-down (μ-PD) method for the first time. The polarized absorption spectra, fluorescence spectra and fluorescence lifetime decay curves were measured at room temperature. The most intense emission peak of 5 at.% Nd:Sr0.7La0.3Mg0.3Al11.7O19 crystal fiber appears at 1052 nm with the full width at half maximum (FWHM) of 6.8 nm for σ polarization and at 1052 nm with FWHM of 6.9 nm for π polarization, respectively. The decay lifetimes of 4F3/2 level state of Nd:ASL shaped crystal fibers with different neodymium concentration were calculated. All the results show that Nd:ASL crystal fiber has potential as a laser gain medium for ultrashort and tunable laser system.