Tm∶CaGdAlO4单晶光纤的生长及激光性能研究OA

In this study,a Tm3+-doped CaGdAlO4(Tm∶CALGO)disordered single-crystal fiber with a doping concentration of 4%(molar fraction)was grown by the micro-pulling-down method.The crystal structure,optical properties,continuous-wave laser performance,and passively Q-switched pulsed laser characteristics integrated with BiOX(X=Cl,Br,I)layered crystal saturable absorbers were systematically investigated.The crystal belongs to the tetragonal system with the space group I4/mmm.X-ray diffraction and Raman spectroscopy show that the as-grown crystal exhibits a pure CALGO phase with good crystallinity.The absorption spectrum reveals a main absorption peak at 793 nm with a full width at half maximum of 19.4 nm,which is attributed to the inhomogeneous broadening induced by the disordered structure.The highest phonon energy measured by Raman spectroscopy is 614 cm-1,which is lower than that of YAG crystal and beneficial for suppressing non-radiative relaxation.Fourier-transform infrared transmission spectroscopy shows that the crystal exhibits a transmittance exceeding 80%in the 2～6 µm mid-infrared region,with an infrared cut-off edge extending beyond 10 µm.In a straight cavity configuration,a maximum continuous-wave output power of 3.338 W is achieved from the Tm∶CALGO single-crystal fiber,with a slope efficiency of 27.3%and a central wavelength of 1 982.8 nm.When BiOX crystals were integrated into the laser cavity as saturable absorbers,stable passively Q-switched pulsed laser outputs were obtained under an output coupler transmittance of 5%.With BiOCl,BiOBr,and BiOI as saturable absorbers,the maximum single-pulse energies obtained are 18.564,20.335,and 17.599 µJ,the shortest pulse widths are 420,570,and 506 ns,and the highest peak powers are 44.199,35.675,and 34.781 W,respectively.This work demonstrates the excellent performance of Tm∶CALGO disordered single-crystal fibers as gain media for 2 µm lasers and provides a feasibility validation for the integration of single-crystal fibers with novel saturable absorbers.