Controllable Synthesis And Photonic Properties Of Single Crystaline Rare-earth Silicate Nanowires

In recent years,micro-nano scale silicon photonics has attracted increasing attention and research efforts,which also plays a key role in the development of information technology due to their potential applications for the miniturized silicon photonic devices and low-cost integration using existing complementary metal-oxide-semiconductor(CMOS)technology.High-performance micro-nano scale Si-based or Si-compatible emitters,amplifiers,modulators and photodetectors that woked at communication bands are the fundamental unit of silicon photonics devices.Up to now,some important Si-based components such as high speed modulators and photodetectors have already been realized.However,the development of Si-based or Si-compatible optical emitters and amplifiers are still face a big challenge because Si is a indirect bandgap semiconductors with low emission efficiency.In order to overcome the difficulty,two main approaches that microstructuring the Si-based materials or introducing light-emitting impurities into Si based materials were used to improve the luminescence efficiency of Si.Erbium(Er)doped Si-compatible materials has been paid a lot of attention for that near-infrared emission of Er3+ matches wellwith the communication wavebands.In addition,Er silicate compounds contain a higher Er density about 2-3 times in contrast to Er doped Si-based materials and all of Er3+ are demonstrated to be optically active,which makes it become the most potential material to realize Si-based high gain devices.This paper studies different kinds of single crystalline Er or Er/Yb silicate nanowires prepared by conventional chemical vapor deposition(CVD)method.Including single crystalline(ErxYb1-x)3Cl(SiO4)2 nanowires with Er3+ concentration tunable,single crystalline Si-(Er/Yb)2Si2O7 core-shell structure nanowres with core diameters tunable and single crystalline Er2SiO5 nanowres.Firstly,we studied the morphology,elemental composition and micro structure properties of the as-grown samples.Er3+ concentration dependent up-conversion and near-infrared luminescence and lifetime were systematically investigated by micro photoluminescence measurement instruments.Sub-micrometer communication optical amplifier was constructed by using the single crystalline Si-(Er/Yb)2Si2O7 core-shell structure nanowres.Optical temperature sensing properties were studied based on individual single crystalline Er2SiO5 nanowres.The main achievements are summarized as follows:1.Single crystalline(ErxYb1-x)3CI(SiO4)2 nanowires are synthesized for the first time through a controllable chemical vapor deposition(CVD)route with Er3+concentration tunable by control the supplied mole ratio of Er and Yb atoms in the source boats.The XRD results demonstrate that the Er3+ concentration of the as-grown nanowire is tunable.Both of the up-conversion and near-infrared luminescence properties are studied.The results show that the as-grown sample at Er composition of x=0.73(1.2 × 1022 cm-3)have the strongest up-conversion luminescence while at x=0.3(0.48 × 1022 cm-3)exhibit the most efficient near-infrared emission,which indicating the existence of competition between the two emission bands.The lifetime of the nanowires with Er3+ density of 0.48 × 1022 cm-3is-2.8 ms,which provides a new material platform for achieving micro-nano scale high gain optical amplifiers.2.Single crystalline Si-(Er/Yb)2Si2O7 core-shell structure nanowires are successfully prepared through chemical vapor deposition(CVD)route with high refractive index silicon as the core,high gain silicate as the shell.The size of the core and the shell could be controlled by change the experiment parameters.The typical structure characterization indicates the nanowire have a highly smooth surface and high crystal quality for both the core and the shell region.The theoretical simulation results performed by COMSOL show that the optical confinement can be largly improved as the core diameter increasing for a core-shell nanowire with a total diameter of 600 nm.Two-dimensional modal analysis and three-dimensional light propagation analysis result all demonstrate that more than 95%of optical power at the wavelength of 1.5 ?m is confined in the nanowire with a core diameter of 300 nm.What's more interesting is that most of the optical power is located in the interface region between the core and the shell and propagate efficiently along the nanowire,which is benefit to achieveing high optical gain.Then we measured the loss and gain properties of the core-shell nanowire by evanescent coupling method.The loss of the nanowire is decreased with the increasing of the core diameter,which is consistant with the theoretical simulation result.Experimental results further demonstrate that an optimized core-shell nanowire can exhibit an excellent a net gain up to 20 dB mm-1,for the first time,we realized the sub-micrometer high gain optical amplifiers worked at communication bands,which mark an important step towards efficient on-chip photonic integration.3.Single crystalline Er2SiO5 nanowire are synthesized by chemical vapor deposition(CVD)route for the first time.These kinds of nanowire show excellent up-conversion luminescence and optical waveguide properties under the excitation of 980 nm laser.For the first time,excellent temperature sensing properties based on green UC emissions were demonstrated on individual Er2SiO5 nanowire.These results show a maximum sensitivity about 9.05×10-3 K-1 in the experiment range we can afford,which is higher than that of the reported Er-doped silicon oxides and comparable to the sensitivity of Er-doped fluoride,which indicates strong practical potential of the Er2SiO5 nanowire for use in Si-compatible optoelectronics and optical temperature sensing.4.In the last part,we report the realization of low thresholds and high quality two-and three-photon pumped lasing based on single all-inorganic CsPbBr3 nanorods with triangular cross section at room temperature.The mechanisms of two-and three-photon lasing were investigated by time-resolved PL spectroscopy and excitation fluence dependent spectra.Moreover,multi-photon PL excitation spectra in the near-infrared region were measured to reveal the two-and three-photon absorption efficiency of the CsPbBr3 nanorods.Our results show excellent multi-photon absorption efficiency and lasing properties in a wide spectral range(700 nm-1400 nm)of the as-synthesized all-inorganic CsPbBr3 nanorods.The realization of two-and three-photon pumped lasing from all-inorganic CsPbBr3 nanorods would provide promising candidates for on chip integrated photonics.