The Spectra Of Ternary CdSSe/ZnS Quantum Dots And Photoluminescent Transmission Of The Doped Fiber

The semiconductor nanocrystals have widely application potential in optoelectronic and nonlinear devices due to their unique optical and electrical properties from the effect of three-dimensional quantum confinement compared with the bulk materials.Different from rare earth ions,quantum dots(QDs)have the advantages of narrower emission-spectrum band,higher quantum efficiency and tunable emission wavelengths.The wavelength of absorption,photoluminescence(PL)and the full width half max(FWHM)of the spectrum can be desirably obtained by controlling the size of traditional QDs.Therefore,it is possible to achieve wavelength tunable laser if the doped QDs are appropriate in the fiber.In this dissertation,the ternary alloy QD dispersed in UV gel is studied.The new ternary alloy CdSSe QD can achieve corresponding PL wavelengths to coordinate with the absorption and emission characteristics by changing the composition ratio of chalcogen elements.The wavelength range of absorption and PL can cover the entire visible band by regulating their composition continuously,thereby,improving the performance of the optical device and bringing great applications in the future.The absorption coefficient,absorption and emission cross-sections of the ternary CdSxSe1-x/ZnS QDs by measuring absorption-emission spectra of the QDs with different composition ratio x are determined.CdSSe /ZnS QD doped fibers are prepared in a solid fiber core of UV gel in the doping concentration of 0.1~5 mg/mL and the fiber length of 1~20 cm.The absorption decay rate of 473-nm laser pumped into the QD doped fiber are measured for different doping concentrations.The PL-spectrum intensity of the doped fiber varies with the fiber length and doping concentration is measured by fiber optic spectrometer.The absorption cross-section of QDs shows an increase with theincrease of QD size,indicating a decrease with the x increase.In therange of 4.5~2.29-nm radius and x=0.4~0.9,the absorption cross-sectionis(2~1.02)×10-16 cm2.For the fibers doped with CdSSe/ZnS QDs in4.5-nm radius,the absorption-decay rate and the cross-section areweakly dependent on the doping concentration,and the PL-peakintensity of the doped fiber varies with the fiber length and the dopingconcentration.There is a saturating doping concentration and desiredfiber length corresponding to the maximum PL intensity.The intensity of PL-peak reaches largest when the doping concentration comes to 0.4 mg/ml and the fiber length is in 11 cm.The experimental results provide a support for development of CdSSe/ZnS-QD gain photo-electronic devices in the future.