A switchable dual-wavelength erbium-doped fiber laser(EDFL) with tunable wavelength is demonstrated. The ring cavity consists of two branches with a fiber Bragg grating(FBG) and a spherical-shape structure as fiber filters, respectively. By adjusting the variable optical attenuator(VOA), the laser can be switched between the single-wavelength mode and the dual-wavelength mode. The spherical-shape structure has good sensitivity to the temperature. When the temperature changes from 30 °C to 190 °C, the central wavelength of the EDFL generated by the branch of spherical-shape structure varies from 1 551.6 nm to 1 561.8 nm, which means that the wavelength interval is tunable.
We investigate the electron injection effect of inserting a thin aluminum(Al) layer into cesium carbonate(Cs2CO3)injection layer. Two groups of organic light-emitting devices(OLEDs) are fabricated. For the first group of devices based on Alq3, we insert a thin Al layer of different thickness into Cs2CO3 injection layer, and the device's maximum current efficiency of 6.5 cd/A is obtained when the thickness of the thin Al layer is 0.4 nm. However, when the thickness of Al layer is 0.8 nm, the capacity of electron injection is the strongest. To validate the universality of this approach, then we fabricate another group of devices based on another blue emitting material. The maximum current efficiency of the device without and with a thin Al layer is 4.51 cd/A and 4.84 cd/A, respectively. Inserting a thin Al layer of an appropriate thickness into Cs2CO3 layer can result in the reduction of electron injection barrier, enhancement of the electron injection, and improvement of the performance of OLEDs. This can be attributed to the mechanism that thermally evaporated Cs2CO3 decomposes into cesium oxides, the thin Al layer reacts with cesium oxides to form Al–O–Cs complex, and the amount of the Al–O–Cs complex can be controlled by adjusting the thickness of the thin Al layer.
We synthesize Tm3+/Tb3+/Eu3+triply-doped ZrF4–BaF2–LaF3–AlF3–NaF(ZBLAN) transparent glass by using a melt-quenching method. Under excitation of 365 nm, the white emission with Commission internationale deL'Eclairage(CIE) coordinates of(0.33, 0.33) is achieved at the Eu3+concentration of 1.1 mol%. The mechanisms for white emission and the energy transfer process of Tb3+→ Eu3+are discussed in terms of the photoluminescence, photoluminescence excitation spectra, and the light emission decay curves. The nature for the Tb3+→ Eu3+energy transfer is described with the aid of an energy level diagram.
The Nd^(3+) doped fluorochlorozirconate(FCZ) glass was prepared by melt-quenching method. The 3.9 μm emission from Nd^(3+) ions is attributed to the two-photon absorption process. The strong emission transition at 3.9 μm fluorescence peak intensity, corresponding to the ~4G_(11/2)→~2K_(13/2) transition, is directly proportional to the NaCl concentration. With the increase of the Cl-ions amount, the mid-infrared(MIR) luminescent intensity is significantly enhanced. Additionally, the Judd-Ofelt(J-O) parameter ?_2 is larger than that of the fluorozirconate(FZ) glass, which indicates the covalency of the bond between RE ions and ligand is stronger as Cl-ions substitution of F-ions in chloride FZ glass. The X-ray diffraction(XRD) patterns show that the amorphous glassy state keeps the FZ glass network structure. In brief, the advantageous spectroscopic characteristics make the Nd^(3+)-doped FCZ glass be a promising candidate for application of 3.9 μm emission.
制备了一种有机铅卤钙钛矿-有机本体异质结杂化串联太阳能电池。采用紫外可见吸收光谱、原子力显微镜对薄膜形貌进行了表征。结果表明:有机本体异质结层可以有效改善钙钛矿的表面形貌,增强了可见光的吸收。优化后的串联结构电池的短路电流可达19.14 m A/cm2,开路电压为0.76 V,光电转换效率达到了6.54%。钙钛矿电池和有机本体异质结电池串联结构可以同时提高短路电流及填充因子,二者具有较好的相容性和协同作用。
We report an effective method to improve the performance of p-type copper phthalocyanine(Cu Pc)based organic field-effect transistors(OFETs) by employing a thin para-quaterphenyl(p-4p) film and simultaneously applying V2O5 to the source/drain regions.The p-4p layer was inserted between the insulating layer and the active layer,and V2O5 layer was added between Cu Pc and Al in the source–drain(S/D) area.As a result,the fieldeffect saturation mobility and on/off current ratio of the optimized device were improved to 5102cm2/(V s)and 104,respectively.We believe that because p-4p could induce Cu Pc to form a highly oriented and continuous film,this resulted in the better injection and transport of the carriers.Moreover,by introducing the V2O5 electrode's modified layers,the height of the carrier injection barrier could be effectively tuned and the contact resistance could be reduced.
We report a new quantum dot superluminescent diode with a new device structure. In this device, a multimode-interferometer configuration and a J-bend structure were monolithically integrated. Owing to the multi-modeinterferometer structure, the superluminescent diode exhibits 60% increase in output power and 43% reduction in the differential resistance compared with the uniform waveguide width superluminescent diode fabricated from the same wafer. Our device produces an emission spectrum as wide as 103.7 nm with an output power of 2.5 m W at 600 m A continue-wave injection current. This broadband emission spectrum makes the axial resolution of the optical coherence tomography system employing the superluminescent diode to 6 m in theory, which is high enough for most tissue imaging.
