Power scaling of the self-frequency-doubled quasi-two-level Yb:YCOB laser with a 30% slope efficiency.

The lab-on-chip integration of photonic devices has been attracting increasing attention recently. Multifunctional materials provide natural platforms for the desirable performance by the coupling of different functionalities. The insufficient coupling efficiency of the laser and nonlinear processes in self-frequency-doubled (SFD) lasers is the limiting factor for the output power and further practical applications. Here we demonstrate a SFD Yb3+-doped calcium yttrium oxoborate (Yb:YCOB) crystal laser with an unprecedented slope efficiency of 30% and output power of 6.2 W at 513 nm. The successful realization of this laser operating in a quasi-two-level configuration is based on enhanced coupling of the laser and frequency-doubling processes using a monolithic configuration, benefiting from an ultimately small laser quantum defect, the anisotropic gain cross sections, and the high effective nonlinearity of the monoclinic YCOB outside the principal planes. Solid-state lasers in the spectral range around 510 nm are scarce, and the results not only present a significant advancement in the field of SFD lasers, but also pave the way for future applications of such green lasers, especially in areas such as medical treatment, daily life, and scientific investigations.

Synthesis and Unprecedented Complexation Properties of ß-Cyclodextrin-Based Ligand for Lanthanide Ions.

Here, we report the synthesis and detailed studies on the coordination chemistry of a novel chemically modified polyaminocarboxylate (5) based on ß-cyclodextrin (CD) scaffold for lanthanides. The target ligand is prepared in a highly efficient manner (seven total steps) from ß-CD using the readily available iminodiacetic acid as a starting material. A propargyl group is attached to the iminodiacetate via N-alkylation, and the obtained derivative is efficiently conjugated to the ß-CD scaffold via the copper(I)-mediated 1,3-dipolar cycloaddition. The generated 1,2,3-triazolmethyl residues advantageously provide a competent chelating group while displacing the metal coordination center away from the primary rim of ß-CD, to afford the required conformational flexibility. The functional groups from each of the two adjacent glucopyranosyl units of ß-CD complete a uniquely created octavalent coordination sphere for lanthanides while still sparing one site for dynamic water coordination. To help study the coordination chemistry of CD ligand 5, we also design a relevant maltoside ligand 6, which faithfully represents one submetal-binding section of ligand 5. Thanks to HRMS and NMR studies, we successfully elucidate the coordination chemistries of synthesized ligands. The octavalent coordination sphere of ligand 5 shows strong binding affinity to lanthanides. By potentiometric titration experiments, ligand 5 is found to bind gadolinium(III), forming 1:1, 1:2, and 1:3 multinuclear complexes with lanthanides, thus possessing great capacity for catalyzing the dynamic water-exchange. Further NMR studies also reveal that the formed ligand 5/Gd(III) complexes show significantly better abilities to alter T1 relaxivities of coordinated water than DOTA-Gd(III) and also some of the synthetic CD probes reported in the literature.

High repetition rates optically active langasite electro-optically Q-switched laser at 1.34 µm.

An electro-optically Q-switched pulsed laser at 1.34 µm with a repetition rate of 100 kHz applying optically active langasite (La3Ga5SiO14) crystal has been reported. With Nd:YVO4 as laser crystal, the electro-optically Q-switched pulsed lasers were obtained with the maximum repetition rate of 100 kHz, maximum average output power of 2.42 W, and a minimum pulse width of 2.4 ns. Based on the theory of rate equations, the optimal pulse energy of the electro-optical Q-switching could be calculated. The experimental results have been found to be matched well with the theoretical calculations. To the best of our knowledge, this work presents the highest repetition rate and shortest pulse width which are achieved by an electric-optic LGS Q-switching at the wavelength of 1.34 µm, and it enriches the material categories for generating the high repetition rate pulsed laser.

Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal.

With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc.