摘要
The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.
基金
the support by the fund of the National Key Research and Development Program of China (Grant No. 2024YFA1208800)
National Natural Science Foundation of China (NSFC) (Grant No. U23A20358)
Natural Science Foundation of Shandong Province (Grant Nos. ZR2023ZD05 and 2022TSGC2120)
the Shenzhen Fundamental Research Program (Grant No. GJHZ20220913142605011)
Xiaomi Foundation/Xiaomi Young Talents Program
