Preparation And Research Of The PbSe Quautum Dot Doped PMMA Fiber Materials

Quantum dots (QDs) are quasi-zero-dimensional semiconductor nanocrystals. PbSe QD in the diameter of (4~7nm) has desirable absorption and emission in the near-infrared communication band (1.2~1.8mm). Compared with the conventional erbium-doped optical fiber amplifiers (EDFAs), QD doped optical fiber amplifiers (QDFAs) have a wider wave band, higher flatten gain and lower noise, which is favorable for broadband wavelength division multiplexing (WDM) communication.However, the surface energy of quantum dots is so high that it is easily to be agglomerated each other, resulting into moving absorption-emission wavelengths due to size dependence. In this dissertation, for avoiding the agglomeration of QDs, the PbSe QDs are doped into a polymethyl methacrylate, forming a PbSe/PMMA QD nanocomposite material, on the one hand, the PMMA macromolecule polymer chain can prevent the QD forming agglomeration, on the other hand, the PMMA is a desirable plastic material that can be used as a plastic optical fibers used in communicaiotn devices.We use three different methods to prepare PbSe/PMMA, i.e., the pulsed laser ablation method, the blending method and the in-situ polymerization method. The crystallization, size and distribution of the PbSe QDs in PMMA are observed by X-ray diffraction (XRD), transmission election microscopy (TEM) and scanning electron microscopy (SEM). The absorption and photoluminescence (PL) spectra of the PbSe/PMMA are also measured by an UV-visible-near-infrared spectrophotometer and a fluorescence spectrometer, respectively. The obtained results are described as follows:(1) In the pulsed laser ablation method, when the laser-pulsed energy density increased to 2.8 J/cm2, there are PbSe QD generated which size is about 13nm, the PbSe QD size decreases while the density increases with increase of the laser-pulsed energy density. When the laser-pulsed energy density increased to 4.3J/cm2, PbSe QD size is reduced to 6nm.(2)In the blending method, the PbSe QDs particle in the PbSe/PMMA nanocomposite have the average diameter of 5nm which has less agglomeration than PbSe QD in aqueous media. There is no agglomeration observed in the PbSe/PMMA nanocomposite even after 120 day. (3) In the in-situ polymerization method, PbSe QDs are distributed uniformly in the PMMA basement. The generated QD size increases as the reaction temperature of PbO and Se increases. Strong PL emission is observed in the experiment, FWHM (Full Width at Half Maximum) achieving 100~300nm, and peak wavelength locating in 1431~2365nm. Depending closely on the QD size, the Stokes shift of 15~72nm is observed between the absorption peak and PL peak. In addition, we develop the experimental method available, e.g, czochralski and template, to prepare the PbSe QD doped PMMA fiber in a laboratory. This study can be helpful to realize the QD doped fiber amplifier with high performance on the bandwidth, gain and noise in the future.