All-inorganic copper based metal halides have aroused wide attention as emissive materials due to their excellent optoelectronic properties, such as high photoluminescence quantum yield (PLQY) and good environmental stability. We report a facile low temperature solution process to obtain high quality Cs3Cu2I5 film by using chlorobenzene (CB) as antisolvent. The light-emitting diodes based on the high quality Cs3Cu2I5 films as emissive layers achieved a luminance of 74 cd/m2 and an external quantum efficiency (EQE) of 0.013%.
This paper discusses the widely existing problems of increasing demand of professional engineer in electronic science major and the backward of the teaching mode at present. From one specialized course “Virtual Instrument technique and LABVIEW programming”, we explore the new group-teaching mode based on the Virtual Instrument technique, and then the Specific measures and implementation procedures and effect of this teaching mode summarized in the end.
The range of the accuracy of scalar diffraction theory and effective medium theory for binary rectangular groove phase grating is evaluated by the comparison of diffraction efficiencies predicted from scalar theory and effective medium theory, respectively, to exact vector results calculated by Fourier modal method. The effect of element parameters (depth, period, index of refraction, angle of incidence, and fill factor) on the accuracy of scalar treatment and effective medium theory is quantitatively determined. Generally, it is found that the scalar method is valid when the normalized period is more than fourfold wavelength of incident light at normal incidence. The error of transmittances between vector method and scalar method increases as the incident angle and refractive index increase. Furthermore, when the higher diffraction orders other than zero-th order are not to propagate, the effective medium theory is accurate to evaluate the transmittance of grating at normal incidence. The error of transmittances between effective medium method and rigorous vector theory increases as the incident angle and refractive index increase. Also, the error of diffraction efficiencies between the simple methods and the vector method on the polarization state of incident light is clearly demonstrated.
A dynamically configurable optical add/drop multiplexer (OADM) device was proposed based on volume holographic
gratings in doubly doped lithium niobate crystals and the principles of optical crystallography. The device consists of a
wavelength demultiplexer module and an array of 2×2 electro-optic switches based on the internal reflection on the
surface of the crystal. Two design schemes were presented: OADM based on discrete crystals with unifunctional
integration and OADM based on monolithic crystal with multifunctional integration. This device can dynamically
select signal channels that need to be added or dropped and simultaneously add/drop arbitrary signal channels. The
suggested OADM has superior properties of simple and compact construction, convenient manipulation, lowered
insertion losses and resistance to environmental perturbation.
In this paper the erasure characteristics with different readout conditions, especially off-Bragg readout, during nonvolatile holographic storage in doubly doped LiNbO3 crystals are investigated. The results show that off-Bragg readout by red beam can achieve modest diffraction efficiency while self-enhancement readout gets highest and self-depletion readout has lest diffraction efficiency. During erasing phase, the fast erasure case is that off-Bragg red beam and ultraviolet light are simultaneously used for illumination. It is indicated that the greatest effect on the erasure of the former recorded gratings during multiplexing holograms is the recording of the others gratings, and new recording schedule during multiplexing technique should be considered according to off-Bragg erasing. The experimental results are well verified by theoretical simulation basing on two-center material equations and two beam coupling equations.
We present calculations of the temporal evolution of beam fanning in doubly-doped photorefractive crystals that is initiated by scattering from noise based on jointly solving the two-center material equations and the coupled-wave equations. The optimal conditions for material prescriptions and oxidation-reduction processing et al are discussed in detail. The theoretical results can confirm and predict experimental results.
External electric field has great effect on grating formation via additional carrier drift during nonvolatile holographic recording. The photorefractive properties of doubly doped LiNbO3:Fe:Mn crystals are theoretically investigated by jointly solving the two-center material equations with nonzero external electric field and the coupled-wave equations. The external electric field dependence of the refractive-index changes n1, the diffraction efficiency η as well as the photorefractive sensitivity S are studied for oxidized LiNbO3:Fe:Mn crystals. Significant improvement of the photorefractive performance has been revealed by applying external electric fields to oxidized LiNbO3:Fe:Mn. The enhanced material performance under external electric field improves the applicability of doubly doped LN crystals.
Grating spacing has great influence on grating formation via electron transport in the conduction band during holographic recording. Grating spacing dependence of two center holographic recording is investigated by writing nonvolatile holograms in doubly doped LiNbO3 crystals. Several types of electron characteristic transport lengths are defined. The effects of electron characteristic transport lengths and oxidation-reduction state on the amplitude of nonvolatile holographic grating are numerically discussed within the range of grating spacing from 0.14μm to 10μm. It is found that the bulk photovoltaic effect is the dominant electron transport mechanism of doubly doped LiNbO3 crystals, while the diffusion effect does have appreciable effect on the grating formation when grating spacing is smaller than 1μm. Theoretical analysis and experimental results confirm that the logarithm of the amplitude of nonvolatile holographic grating Log (δn) increases with increasing grating spacing Λ within region of small grating spacing (Λsmaller than 1μm) and further increasing of grating spacing won’t influence the values of Log (δn) greatly.
The dependence of nonvolatile holographic recording on Ce and Cu dopant composition ratios in doubly doped LiNbO3 crystals is investigated experimentally. Three groups of congruent LiNbO3:Ce:Cu crystals have been grown by the Czochralski method with the compositions of 0.085 wt % Ce2O3 and 0.011 wt % CuO, 0.045 wt % Ce2O3 and 0.045 wt % CuO, 0.011 wt % Ce2O3 and 0.085 wt % CuO, respectively. The recording results and the transmission spectra show that the absorption characteristics of the crystals to ultraviolet light have great impact on the finally fixed diffraction efficiency, and the larger the absorption to ultraviolet light, the higher the fixed diffraction efficiency. At the same time, the dependence of the absorption characteristics to ultraviolet light of the medium on both dopant composition ratios and oxidization/reduction annealing conditions is analyzed. As a result, the weakly oxidized crystal with composition of 0.011 wt % Ce2O3 and 0.085 wt % CuO has the highest fixed diffraction efficiency.
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