The visualization of embryonic development is important for the study of basic physiological development. It is also indispensable for evaluating the effects of modification and editing of genetic engineering. Compared with traditional invasive methods of monitoring embryo development, optical coherence tomography (OCT) has its great advantages, such as high resolution, real time and non-invasive. These characteristics of OCT make it possible to observe a living embryo in its whole growth development. In this paper, we use OCT to monitor the embryonic development of locusts noninvasively and reconstruct the two-dimensional and three-dimensional image of the embryo at different development stages. The phenomena of anatrepsis, revolution and katatrepsis are observed. The in-vitro observations of the prior studies with invasive methods are confirmed by the in-vivo experimental results. We hope OCT is a useful tool for the understanding of the embryonic development of insects.
To understand the physical process of SRS lasing in SOI waveguides and to optimize the performance of continuouswave Raman silicon lasers, in this paper numerical simulation on the output characteristics of continuous-wave Raman silicon lasers with different parameters is performed. Based on power propagation equations in SOI waveguides and boundary conditions, the output powers as functions of the launched pump power, the gain length, the reflectivity of the output end, and the effective mode area of the SOI waveguide are presented. It is shown that two-photon absorption (TPA) and free-carrier absorption (FCA) lead to a significant reduction to the output power of continuous-wave Raman silicon lasers, which is in good agreement with the experimental reports. Numerical analysis predicts that in the absence of TPA and FCA there are optimum values for the silicon waveguide length, the effective mode area and the output reflectivity, respectively.
In this paper, we demonstrate the output characteristics of a kind of all-fiber optical source based on Er3+/Yb3+ co-doped double-clad fiber (EY-DCF) in a master oscillator-power amplifier (MOPA) configuration. The amplifier is composed of a 10m long EYDCF, two isolators at both input and output terminals, and a 976nm pump diode connecting with the EYDCF via a side-pump fiber coupler. A DFB diode laser operating at 1547.8nm serves as the master oscillator. A maximum output power of 1.16W is obtained. The gain of the fiber amplifiers is up to 30.7dB. The wavelength centered at 1547.8nm with a spectral width no more than 0.02nm shows longtime stability.
The Y2Si2O7:Tb3+ phosphor was synthesized by high temperature solid state method. The crystal structure and
luminescent properties of phosphors were studied by XRD pattern, excitation and emission spectra in this paper. XRD
pattern showed that the sample was single phase Y2Si2O7 crystal and the crystal lattice constants a=0.806nm, b=0.934
nm, and c=0.692 nm. The excitation spectrum is composed of a broad band centered 290nm and three narrow bands
corresponding to 4 - 4 transition of Tb3+ centered 378 nm, 400nm and 420nm, respectively. The emission peaks of
phosphor were located at 487nm, 546nm, 584nm and 623nm, which were corresponding to 5D4-7F6, 5D4-7F5, 5D4-7F4 and
5D4-7F3, respectively. The influences of Tb3+ concentration on the luminescent intensity of Y2Si2O7:Tb3+ phosphor was
studied. The results indicated that this phosphor could act as a candidate green phosphor for UV-excited white LED.
Eu3+ doped yttrium orthosilicate (Y2SiO5) phosphor was prepared by the sol-combustion method using citric acid as
complexing agent in this experiment. The X-ray diffraction (XRD) pattern, excitation and emission spectra were used to
investigate the crystal structure and luminescent properties of the phosphor. XRD pattern showed that pure Y2SiO5:Eu3+
phosphor was obtained. The excitation spectrum was composed of a broad band from 200-350 nm and a series of narrow
bands from 350-500 nm, in which the excitation peaks at 400 nm and 470 nm were stronger. The emission spectrum
showed the most intense emission peak was located at 613 nm, which corresponded to the 5D0→7F2 transition of Eu3+.
The results showed that this phosphor could be excited by UV or blue light and emit red light. The luminescent intensity
depends on the concentration of Eu3+ and it reached the maximum when the molar concentration of Eu3+ was 4 mol%. In
this study, we found that the emission intensity reached maximum when the ratio of citric acid and Y3+ was 1.5:1. The
results indicated that Y2SiO5:Eu3+ is a potential red-emitting candidate phosphor for white light-emitting diodes.
The red long afterglow phosphor CaTiO3 activated with Pr3+ was formed by wet-dry method in this study. The luminescent properties of this sample had been studied systematically. The X-ray diffraction (XRD) patterns of the powder reveal that CaTiO3:Pr phase was obtained by wet-dry process. The afterglow decay curves were measured and the afterglow time was over 40 minutes. The excitation spectra and emission spectra were measured. The emission peak was at 613nm, due to the transition of 1D2-3H4. With the function of weak crystal field the main emission divided into
612nm and 614nm. In spite of the main emission peak, phosphor had a shoulder emission peak at 620-628nm. Changes of Pr3+ molar ratio had little effect on the emission spectra, but with Pr3+ 0.2%, phosphor had an emission peak at 626nm. The excitation peak was at 342nm, with a shoulder peak at 400nm. Compared with SS, this less time and less energy was used and the same result is obtained.
The red phosphors of Y2O2S:Eu3+ were synthesized by combustion reactions from mixed metal nitrate reactants and a fuel CH4N2S with ignition temperatures of 450°C. Sulfur was produced by CH4N2S decomposed at high temperature.
Y2O3 decomposed by Y(NO3) 3 reacted in Sulfur atmosphere to synthesize Y2O2S host. From altering the ratio of CH4N2S and metal nitrate, the pure phase Y2O2S:Eu3+ red phosphor was obtained. The conclusion was proved by XRD patterns and emission spectrum.
Powder phosphors of yttrium aluminum garnet Y3Al5O12 (YAG), activated with trivalent cerium (Ce3+) was synthesized
by combustion from mixed metal nitrate reactants and urea with ignition temperature of 500C°~550C°. Sintering the
precursor can improve the crystallization of YAG: Ce3+ phosphors so to promote the luminescence intensity. The
influence of the concentration of Ce 3+ on the luminescence character was studied. The crystalline structure and
morphology are observed by x-ray powder diffraction picture and SEM picture respectively.
Eu2+, Nd3+ co-doped calcium aluminate (CaAl2O4) phosphor with high brightness and long afterglow were fabricated by urea-nitrate solution combustion synthesis at 600°C. The phosphor powder of combustion synthesis were generally more homogeneous and had fewer impurity than phosphor fabricated by conventional solid-state methods, the character could conduce to obtain more exact data. The excitation and emission spectrum indicated that there waxs only one luminescence center Eu2+, both of the characteristic spectrums of Eu3+ and Nd3+ weren't discovered. As a secondary activator, Nd3+ could make remarkable influence on the afterglow of phosphor. From altering the moral ratio of Eu2+ and Nd3+, the lasting time of afterglow and thermoluminescence were studied respectively, when Nd3+ wasn't appended, the intensity of initial brightness could compared with other materials which had different ratio of Eu2+ and Nd3+, however the brightness of afterglow decayed rapidly, the lasting time and brightness of afterglow were improved with reduce the radio of Eu2+ and Nd3+, while the ratio achieved some value, the lasting time of afterglow become shorten with the reduce of ratio of Eu2+ and Nd3+. Moreover the depth of trap was calculated from the parameter of thermoluminescence. However, the emission spectrum and XRD patterns didn't change obviously with the altering ratio of Eu2+ and Nd3+. It showed that the little amount of doped rear earth ions (Eu2+ and Nd3+) had almost no effect on the CaAl2O4 phase composition. Based on these conclusions, the model of the luminescence process of CaAl2O4:Eu2+, Nd3+ was built.