<正>YAG:Ce crystal with a diameter of 110 mm is successfully grown by the temperature gradient technique (TGT).The effects of annealing on the luminescence efficiency of YAG:Ce crystal are investigated,and the optimal annealing temperature and atmosphere are obtained.The mechanism of variation behavior of the luminescence efficiency of YAG:Ce under different annealing conditions is discussed and some details on the luminescence associated with color centers are analyzed. 相似文献
A non-close-packed three-dimensional photonic crystal of titania hollow spheres has been fabricated. The fabricated process
is based on the silica template technique, thermal sintering, and the sol–gel process. The band-structure calculations and
optical measurements both indicate that a quasi-full three-dimensional photonic bandgap located at the visible wavelength
has been presented between the eighth and ninth bands. This indicates that the non-close-packed structure of titania hollow
spheres was easier to open the complete photonic bandgaps than other face-centered cubic structures made by self-assembling
methods at the visible region. 相似文献
The Er3+-Yb3+ codoped Al2O3 nanoparticles with an average particle size of about 50 nm have been synthesized by an arc discharge synthesis method. The
green and red up-conversion emissions centered at about 526, 547 and 677 nm, corresponding respectively to the 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+, were detected by a 978-nm semiconductor laser diode excitation. The Annealing has evident effect on the up-conversion emissions
of the samples: The red up-conversion emission is noticeable before annealing; however, the green up-conversion emission becomes
predominant after annealing. The mixture of (Er,Yb)3Al5O12 and α-(Al,Er,Yb)2O3 phases is more favorable for green up-conversion emissions due to an enhancement of the ESA (I) of 4I11/2+a photon→4F7/2 and ET (III) of 2F5/2(Yb3+)+4I11/2(Er3+)→2F7/2(Yb3+)+4F7/2(Er3+) processes. The two-photon absorption up-conversion process is involved in the green and red up-conversion emissions. The
results have proved that arc discharge synthesis is a new promising preparation technology for optical materials.
Supported by National Natural Science Foundation of China (Grant No. 10804015), the Scientific Research Foundation for Doctor
of Liaoning Province (Grant No. 20071095), and the Educational Committee Foundation of Liaoning Province (Grant No. 2008123) 相似文献
With a type-I critical phase-matching LBO crystal, an intracavity frequency doubled solid-stated Yb:YAG green laser is reported. Using a plano-concave resonator, with pump power of 1.37 W, 24.5 mW TEM00 continuous wave laser at 525 nm was obtained. The optical conversion efficiency is 1.8%. By adjusting the placed angle of LBO, several lasers wavelength from 525.0 to 537.8 nm could be extracted. The maximum output power at 537.8 nm is 3.1 mW. 相似文献
We report the laboratory experiment on a segmented mirror testbed that shows the use of a dispersed Rayleigh interferometer to phase segmented mirrors.Segment alignment of tip-tilt is fulfilled by overlapping diffraction pattern centroids of the three individual segments on the focal plane.A spherical interferometer is introduced to evaluate the performance of piston, tip-tilt sensing, and control closed-loop, and finally a total residual root-mean-square (RMS) surface error of about 45 nm is achieved, in which a typical error of about 20 nm is contributed by piston.These results demonstrate that the dispersed Rayleigh interferometer can successfully sense the piston of segmented mirrors and be used in phasing segmented telescopes under extensive studies. 相似文献
Gaussian modulation is one of the key steps for the implementation of continuous-variable quantum key distribution (CVQKD) schemes. However, imperfection in the Gaussian modulation may introduce modulation noise that can deteriorate the performance of CVQKD systems. In this paper, we mainly investigate how to improve the performance of a CVQKD system from different aspects. First, we explore the several different origins, impacts and monitoring schemes for the modulation noise in detail. Then, we discuss the practical performance of a CVQKD system with an untrusted noise model and neutral party model, respectively. These analyses indicate that the neutral party model should be reasonably regarded as a general noise model, which will passively and greatly raise the performance of the system. Further, we propose a dynamic auto-bias control scheme to actively resist the modulation noise which comes from the drift of bias point of the amplitude modulator. Together these methods contribute to the improvement of the practical performance of CVQKD systems with imperfect Gaussian modulation.