Y3MgAl3SiO12:Dy 3+,Eu 3+荧光粉的能量传递与暖白光实现

采用高温固相法合成了Dy ³⁺、Eu ³⁺共掺杂Y₃MgAl₃SiO₁₂石榴石型荧光粉。采用XRD、荧光光谱仪等仪器对样品的结构以及光谱特性进行表征,探究了Dy ³⁺/Eu ³⁺在Y₃MgAl₃SiO₁₂基质结构中的光谱特征以及离子间的能量传递机制。在367 nm近紫外光激发下,Y₃MgAl₃SiO₁₂:Dy ³⁺,Eu ³⁺的发射光谱包含Dy ³⁺的6F9/2到6H15/2和6H13/2的电子跃迁特征发射(487 nm蓝光和592 nm黄光)和Eu ³⁺的5D0 7F2 and 5D0 7F4特征发射峰(616 nm和710 nm红光)。在400~500 nm范围内Dy ³⁺发射谱与Eu ³⁺激发谱重叠,表明Dy ³⁺与Eu ³⁺之间存在着能量传递,能量传递的机理为电四极-电四极相互作用。该荧光粉通过调整Dy ³⁺和Eu ³⁺的掺杂浓度比封装近紫外LED芯片,可以实现单基质暖白光LED照明。     

Red, Green, and Blue Light Through Cooperative Up-Conversion in Sol-Gel Thin Films Made With Yb0.80La0.15Tb0.05F3 and Yb0.80La0.15Eu0.05F3 Nanoparticles

Silica and zirconium dioxide sol-gel thin films made with Yb_0.80La_0.15Tb_0.05F₃ or Yb _0.80La_0.15Eu_0.05F₃ nanoparticles are reported. Bright blue (413 and 435 nm), green (545 nm), and red (585 and 625 nm) emissions are produced from Tb³⁺ ions through cooperative up-conversion of 980 nm light. Similarly, red (591 and 612 nm) emission is generated from Eu³⁺ ions. These up-convertors may find use in white light sources. The cooperative up-conversion of Yb³⁺-Tb³⁺ ions is more efficient than of Yb³⁺-Eu³⁺ ions because the efficiency of energy transfer from excited Yb³⁺ ions to a Tb ³⁺ ion (0.37) is more than two-times higher than of excited Yb³⁺ ions to a Eu³⁺ ion (0.15), as estimated from the lifetime of excited Yb³⁺ ion. The estimated quantum yields of both Tb³⁺ ion and Eu³⁺ ion emissions are on the order of 40%, and hence are not the cause of the difference in efficiency. This approach does not work for Sm³⁺, Pr³⁺ , and Dy³⁺. Incorporation of the respective Ln³⁺ ions in nanoparticles is crucial, as controls, in which the various Ln³⁺ ions are incorporated directly into the sol-gel, that do not show cooperative up-conversion     

Transient gratings in rare-earth-doped phosphosilicate opticalfibres through periodic population inversion

Transient gratings with R>96% at 1526 nm have been observed in Er³⁺/Yb³⁺-doped phosphosilicate optical fibres holographically processed with 193 nm light. These arise primarily from the index change associated with population inversion of the Er³⁺ ions     

透明叠层结构Ag/MoO_3/Ag阳极对绿光OLED器件性能的影响

本文采用一种结构为Ag/MoO_3/Ag的金属/氧化物/金属(M_1/O/M_2)叠层替代ITO作为OLED器件的阳极,研究Ag/MoO_3/Ag叠层结构变化对于OLED器件电极透过率、亮度、光谱等性能的影响。实验采用真空蒸镀方法制备了一系列器件,器件结构为Ag/MoO_3/Ag/MoO_3(10nm)/NPB(40nm)/Alq_3(60nm)/LiF(1nm)/Al(150nm)。对比器件的电压-电流密度、电压-亮度、光谱特性等数据,表明Ag/MoO_3/Ag的结构为20/20/10(nm)时,器件性能较好。在驱动电压为11V时,其亮度达到18 421cd/m~2,电流效率为2.45cd/A;且因器件中存在微腔效应,其EL光谱蓝移,半高宽变窄。但考虑到530nm处其电极透过率仅为17%,所以经换算该器件实际发光亮度比ITO电极器件更高。该Ag/MoO_3/Ag叠层阳极制作相对简单,经优化后在顶发射和柔性OLED器件方面将具有一定的应用前景。     

氮化硅集成微腔光频梳器件关键制备技术(特邀)

微腔光频梳,又称微腔梳,是通过腔内四波混频过程产生的一种高相干宽谱的集成光源,有着优异的时频特性,可用于超精密分子光谱、相干通信、激光雷达、轻型化装备等测量应用,是基础科学、计量学及军事装备的重要工具,是一项颠覆性的技术。报道了一种集成氮化硅（Si₃N₄）微腔光频梳器件制备的关键技术,提出了一种方法平衡Si₃N₄的应力、厚度和化学计量之间的矛盾,以满足反常色散和减少双光子吸收的要求。利用这种改进的大马士革工艺微结构降低Si₃N₄厚膜的应力,减少应力缺陷对器件性能的影响,实现高品质Si₃N₄薄膜的可控制备。在微腔刻蚀工艺中,采用30 nm氧化铝牺牲层补偿掩模抗刻蚀能力,实现微环和波导侧壁粗糙度小于15 nm,满足了微腔高Q值的要求。经双光泵浦测量得到1 480~1 640 nm波段内的宽光谱高相干克尔光频梳。     

Spectroscopic properties and efficient diode-pumped laser operationof neodymium-doped lanthanum scandium borate

We report on the spectroscopic properties and laser performance of Czochralski-grown LaSc₃(BO₃)₄ (LSB) crystals with high neodymium concentrations up to 2.5·10²¹ cm^-3. The low-concentration quenching of the upper laser level of neodymium and the polarization dependence of the spectra indicate that LaSc₃(BO₃)₄ crystalizes in a huntite-type structure like Nd³⁺:YAl₃(BO₃)₄ (NYAB). With diode laser pumping at 808 nm, a multimode Nd³⁺:LaSc₃ (BO₃)₄ (NLSB) laser at 1063 nm is demonstrated. Optical slope efficiency was 64% with respect to absorbed pump power. The possibility of second-harmonic generation in the laser crystal is discussed     

Improved Ti:sapphire laser performance with new high figure ofmerit crystals

The continuous-wave (CW) laser performance of Ti:Al₂O ₃ crystals with high figure of merit is described. Using a 0.1% Ti:Al₂O₃ crystal (FOM=1000), output powers of 3.5 W at 800 nm are obtained, pumping with a 9.6 W argon ion laser operating multiline. Continuous tunability of the CW Ti:Al₂O ₃ laser extending from 665 to 1070 nm is also demonstrated for a 5 W pump power     

Broad-band amplification using a novel amplifier topology

A new broad-band amplifier topology that provides a continuous gain across 75 nm (1528-1603 nm) of optical bandwidth using Er³⁺ -doped SiO₂ fiber is demonstrated. The noise figure is low and does not present any discontinuity across the entire amplification bandwidth. The topology has a buried 1550/1585-nm splitter to reduce input signal loss and to provide amplified spontaneous emission suppression. The topology has been optimized using hybrid fiber; Er³⁺-doped SiO₂ for the first stage and Er ³⁺-doped TeO₂ for the second stage, achieving 82 nm (1526-1618 nm) of optical bandwidth     

Spectroscopic Properties and Laser Performance of Er3+ and Yb3+ Co-Doped GdAl3(BO3)4 Crystal

An Er:Yb:GdAl₃(BO₃)₄ crystal was grown and room-temperature polarized absorption, emission, and gain spectra were investigated. Fluorescence decay curves of Er³⁺ at 1530 nm and Yb³⁺ at 1040 nm in the crystal were measured. Efficient laser operation of Er:Yb:GdAl₃(BO₃)₄ crystal at 1.5-1.6 mum was realized. Quasi-continuous-wave output powers of 1.8 W with slope efficiency of 19% and 0.78 W with slope efficiency of 14% were achieved in diode-pumped c-cut and c-cut and a-cut crystals, respectively. The output spectrum and polarization of Er:Yb:GdAl₃(BO₃)₄ laser were also investigated.     

Reliable Low-Cost Fabrication of Low-Loss $hbox{Al}_{2}hbox{O} _{3}{:}hbox{Er}^{3+}$ Waveguides With 5.4-dB Optical Gain

A reliable and reproducible deposition process for the fabrication of Al₂O₃ waveguides with losses as low as 0.1 dB/cm has been developed. The thin films are grown at ~ 5 nm/min deposition rate and exhibit excellent thickness uniformity within 1% over 50times50 mm² area and no detectable OH^- incorporation. For applications of the Al₂O₃ films in compact, integrated optical devices, a high-quality channel waveguide fabrication process is utilized. Planar and channel propagation losses as low as 0.1 and 0.2 dB/cm, respectively, are demonstrated. For the development of active integrated optical functions, the implementation of rare-earth-ion doping is investigated by cosputtering of erbium during the Al₂O₃ layer growth. Dopant levels between 0.2-5times10²⁰ cm^-3 are studied. At Er³⁺ concentrations of interest for optical amplification, a lifetime of the ⁴I_13/2 level as long as 7 ms is measured. Gain measurements over 6.4-cm propagation length in a 700-nm-thick Al₂O₃:Er³⁺ channel waveguide result in net optical gain over a 41-nm-wide wavelength range between 1526-1567 nm with a maximum of 5.4 dB at 1533 nm.     

Small-signal gain measurement in a Ti:Al2O3amplifier

A small-signal single-pass power gain of e^5.2=180 has been measured for a signal in the π polarization at 790.7 nm in a longitudinally pumped Ti:Al₂O ₃ amplifier. A double-pass power gain of e^5.2 ≈10⁴ has been attained for the same polarization at 799.8 nm. The ratio of the gain cross sections at 632.8 and 790.7 nm is 1/25. The gain anisotropy at 632.8 nm is g_π/g _σ=2.3. The lifetime of the upper lasing level decreases with increased pumping, probably as the result of amplified spontaneous emission     

Plasma-Enhanced Atomic Layer Deposition of Amorphous Ga2O3 for Solar-Blind Photodetection

Wide-bandgap gallium oxide (Ga₂O₃) is one of the most promising semiconductor materials for solar-blind (200 nm to 280 nm) photodetection. In its amorphous form, amorphous gallium oxide (a-Ga₂O₃) maintains its intrinsic optoelectronic properties while can be prepared at a low growth temperature, thus it is compatible with Si integrated circuits (ICs) technology. Herein, the a-Ga₂O₃ film is directly deposited on pre-fabricated Au interdigital electrodes by plasma enhanced atomic layer deposition (PE-ALD) at a growth temperature of 250 °C. The stoichiometric a-Ga₂O₃ thin film with a low defect density is achieved owing to the mild PE-ALD condition. As a result, the fabricated Au/a-Ga₂O₃/Au photodetector shows a fast time response, high responsivity, and excellent wavelength selectivity for solar-blind photodetection. Furthermore, an ultra-thin MgO layer is deposited by PE-ALD to passivate the Au/a-Ga₂O₃/Au interface, resulting in the responsivity of 788 A/W (under 254 nm at 10 V), a 250-nm-to-400-nm rejection ratio of 9.2×103, and the rise time and the decay time of 32 ms and 6 ms, respectively. These results demonstrate that the a-Ga₂O₃ film grown by PE-ALD is a promising candidate for high-performance solar-blind photodetection and potentially can be integrated with Si ICs for commercial production.     

Crystal growth, frequency doubling, and infrared laser performanceof Yb3+:BaCaBO3F

Yb:BaCaBO₃F(Yb:BCBF) has been investigated as a new laser crystal with potential for self-frequency doubling, Yb³⁺ in BCBF exhibits a maximum absorption cross section at 912 nm of 1.1×10^-20 cm² with a bandwidth (FWHM) of 19 nm. The maximum emission cross section at 1034 nm is 1.3×10^-20 cm² with a transition bandwidth of 24 nm. The measured emission lifetime of Yb³⁺ is 1.17 ms. An Yb:BCBF laser has been demonstrated with a Ti:sapphire pump source, and a measured slope efficiency of 38% has been obtained for the fundamental laser output. Single crystal powders of BCBF have been compared with KD ⁺P for a relative measure of the second-harmonic generating potential, yielding d_eff(BCBF)~0.26 pm/V. The phasematching angle has been estimated from the refractive index data for type I second-harmonic generation of 0.517 μm light; the predicted angle is 37° from the c-axis. The growth, spectroscopy, laser performance, and linear and nonlinear optical properties of Yb:BCBF are reported     

Development of Nd-doped solid-state laser materials for 944 nmoperation

We have grown neodymium-doped mixed apatite crystals [(Sr_1-x Ba_x)₅(PO₄)₃F, Sr₅ (P_1-xV_xO₄)₃F, and Ba ₅(P_1-xV_xO₄)₃F] and spectroscopically studied them as potential gain media for a laser source for atmospheric water sensing operating at 944.11 nm. We conclude that an appropriate apatite host material for a 944.11 nm laser should be a mixture of Sr₅(PO₄)₃F. With a small fraction of Ba₅(PO₄)₃F. Precise wavelength tuning around 944.11 nm can be accomplished by varying the host composition, temperature, and threshold population inversion. In apatite crystals of mixed composition, the amplified spontaneous emission (ASE) loss at 1.06 μm is predicted to be significantly smaller than that in the end members     

Effect of substrate temperature on the properties of deep ultraviolet transparent conductive ITO/Ga2O3 films

正ITO/Ga_2O_3 bi-layer films were deposited on quartz glass substrates by magnetron sputtering.The effect of substrate temperature on the structure,surface morphology,optical and electrical properties of ITO/Ga_2O_3 films was investigated by an X-ray diffractometer,a scanning electron microscope,a double beam spectrophotometer and the Hall system,respectively.The structural characteristics showed a dependence on substrate temperature. The resistivity of the films varied from 6.71×10~(-3) to 1.91×10~3Ω·cm as the substrate temperature increased from 100 to 350℃.ITO(22 nm)/Ga_2O_3(50 nm) films deposited at 300℃exhibited a low sheet resistance of 373.3Ω/□and high deep ultraviolet transmittance of 78.97%at the wavelength of 300 nm.     

Low Weibull slope of breakdown distributions in high-k layers

The reliability of various Al₂O₃, ZrO₂ and Al₂O₃/ZrO₂ double layers with a physical oxide thickness from 3 nm to 15 nm and TiN gate electrodes was studied by measuring time-to-breakdown using gate injection and constant voltage stress. The extracted Weibull slope β of the breakdown distribution is found to be below 2 and shows no obvious thickness dependence. These findings deviate from previous results on intrinsic breakdown in SiO₂, where a strong thickness dependence was explained by the percolation model. Although promising performance on devices with high-k layers as dielectric can be obtained, it is argued that gate oxide reliability is likely limited by extrinsic factors     

利用CsN3n型掺杂电子传输层改善OLED器件性能的研究

为了能够有效地提高电子的注入和传输能力,改善有机电致发光器件的性能,本文利用CsN₃作为n型掺杂剂,对有机电子传输材料Bphen进行n型电学掺杂,制备了结构为ITO/MoO₃（2 nm）/NPB（50 nm）/Alq₃（30 nm）/Bphen（15 nm）/Bphen：CsN₃（15 nm,x%,x=10,15,20）/Al（100 nm）的器件。实验结果表明,CsN₃是一种有效的n型掺杂剂,以掺杂层Bphen：CsN₃ 作为电子传输层,可以有效地降低电子的注入势垒,改善器件的电子注入和传输能力,从而降低器件的开启电压,同时提高了器件的亮度和发光效率。在掺杂浓度为10%时器件的性能最优,开启电压仅为2.3 V,在7.2 V的驱动电压下,达到最大亮度29 060 cd/m²,是非掺杂器件的2.5倍以上。当驱动电压为6.6 V时,达到最大电流效率3.27 cd/A。而当掺杂浓度进一步提高时,由于Cs扩散严重,发光区形成淬灭中心,造成器件的效率下降。     

Design and Fabrication of AlGaN-Based Resonant-Cavity-Enhanced p-i-n UV PDs

AlGaN-based resonant-cavity-enhanced (RCE) p-i-n photodetectors (PDs) for operating at the wavelength of 330 nm were designed and fabricated. A 20.5-pair AlN/Al_0.3Ga_0.7N distributed Bragg reflector (DBR) was used as the back mirror and a 3-pair AlN/Al_0.3Ga_0.7N DBR as the front one. In the cavity is a p-GaN/i-GaN/n-Al_0.3Ga_0.7N structure. The optical absorption of the RCE PD structure is at most 59.8% deduced from reflectance measurement. Selectively enhanced by the cavity effect, a response peak of 0.128 A/W at 330 nm with a half-peak breadth of 5.5 nm was obtained under zero bias. The peak wavelength shifted 15 nm with the incident angle of light increasing from 0deg to 60deg.     

Theoretical and experimental investigations of a diode-pumpedquasi-three-level laser: the Yb3+-doped Ca4GdO(BO3)3 (Yb:GdCOB) laser

We present a theoretical and experimental analysis of a diode-pumped Yb³⁺-doped Ca₄GdO(BO₃)₃ (Yb:GdCOB) laser. A new model for a diode-pumped quasi-three-level laser is described. The effects of absorption saturation, temperature profile, and the beam quality M² factor of the pump diode have been taken into account, for the first time to our knowledge. We have obtained a good agreement between experimental measurements and theoretical calculations with two different pump wavelengths, 902 and 976 nm. Our model has given good predictions of the laser performances for different crystal temperatures and different M² factors of the pump beam. As much as 440 mW of output power (at 1082 nm) have been achieved for 640 mW of absorbed pump power at 976 nm, corresponding to one of the highest slope efficiencies (81%) ever obtained with Yb-doped lasers     

Nd:Y2O3透明陶瓷4F3/2-4I11/2跃迁光谱及高效激光输出

报道了采用真空烧结法结合热等静压技术制备的Nd:Y₂O₃透明陶瓷的荧光光谱特性及相关激光输出。通过与Nd:YAG透明陶瓷的荧光光谱对比,表明Nd:Y₂O₃透明陶瓷的4F_3/2-4I_11/2跃迁光谱存在着多个增益相当的谱线,这更有利于实现同时双波长段激光振荡;不同斯塔克子跃迁光谱的离散特性有利于通过腔镜镀膜控制不同波长损耗,获得丰富的1.0~1.1 μm波段激光。利用简单的平平两镜腔结构完成进一步的实验,通过选择的输出镜片镀膜获得了输出功率3.62 W、转换效率40.4%的1074.6 nm和1078.8 nm的双波长输出和输出功率1.7 W、转换效率19.4%的1130.3 nm波长输出。