Study On Luminescence And Valence State Conversion Of Rare-earth Ions Under Ultrafast Laser Field

Due to their unique 4f electronic structure,rare earth ions possess special physical and chemical properties,optical properties in particular.The luminescence of rare earth ions features pure chromaticity,stable physical and chemical properties,high energy conversion efficiency and low toxicity,and has been widely used in areas of laser sources,color display,medical imaging and bio-labeling.Compared to the intensively studied luminescence behavior,researches on their valence state conversion are relatively lagging behind.The valence state conversion in rare earth ion doped materials can find significant applications in high-density optical storage and new opo-electronic devices.This thesis focuses on the luminescence and valence state conversion of doping rare earth ions and the following studies have been carried out.First,we have studied the influences of the polarization state of the 800 nm femtosecond laser field on the luminescence and valence state conversion of the trivalent samarium ions doped in sodium aluminoborate glass.When the femtosecond laser polarization is changed from being linear to being circular,both the luminescence intensity of trivalent ions and their valence state conversion efficiency into divalent courterparts are observed to decrease by about 50%.Both experimental and theoretical results indicate that the laser polarization dependence of luminescence and valence state conversion behavior is directly correlated with the 4f intermediate state of the trivalent samarium ion.The mechanism underlying the valence state conversion is further explored by experimentally studying the femtosecond laser power dependence and the absorption spectra of the sample.Second,we have prepared the nanoparticles of Ba FCl:Sm³⁺via hydrothermal chemical reaction and studied the luminescence and valence state conversion of the doped trivalent samarium ions under 800 nm femtosecond laser field.Highly efficient state conversion of trivalent samarium ions to divalent ones are observed in the experiment.The femtosecond laser power dependence of the valence state conversion of trivalent ions to divalent ones has been studied.The“erasing”effect of oxidizing divalent ions back to trivalent ones under 532 nm cw laser illumination is also tentatively performed.