Mid-Infrared Lasers With Low Threshold and Photodetectors

We report the growth, fabrication, and operation of 2.0μm InGaAsSb/AlGaAsSb laser diodes and 8.5μm GaInAs/AlInAs quantum cascade lasers with low threshold current and the latest improvements in the performance of InGaAsSb photodetectors by passivation treatment.     

A High Conversion Efficiency Q-Switched Intracavity Nd:YVO_4/KTA Optical Parametric Oscillator under Direct Diode Pumping at 880nm

We report a high conversion efficiency Q-switched Nd:YVO_4/KTiOAsO_4(KTA) intracavity optical parametric oscillator(IOPO) operating near 3.5 um based on direct 880 nm laser diode(LD) pumping. A maximum average idler output power of 2.6 W with a pulse width of about 7.9 ns is achieved under an absorbed LD power of 45.4 W at a pulse repetition rate(PRR) of 10 kHz. The maximum optical-optical conversion efficiency from LD power to OPO mid-infrared(MIR) output of 6.74% is achieved. To our knowledge, this is the highest conversion efficiency for a KTA-IOPO by exploiting a Q-switched laser as the parent fundamental pump source. The beam quality factors M~2 of the MIR beam at the full output power with a PRR of 10 kHz are within 2.12 in both the horizontal and vertical directions, indicating a near Gaussian mode.     

高能量高转换效率355 nm紫外激光器

为了得到一种三倍频效率高达60%的355 nm脉冲激光器,采用曲率半径分别为2 m的凹凸高斯镜和9 m的平凹全反镜组合作为谐振腔,加以电光调Q,得到1 064 nm高光束质量激光输出,再将其进行行波放大,获得重复频率10 Hz、脉宽7.3 ns、单脉冲能量1.01 J的1 064 nm基频光输出。利用Ⅰ类相位匹配LBO晶体进行二倍频、Ⅱ类相位匹配LBO晶体进行三倍频以得到波长为355 nm的紫外光输出。通过二倍频和三倍频输出特性和非线性晶体参数的分析和实验调试,最终获得了单脉冲能量为608 mJ、脉宽为5.7 ns、线宽为2 nm的紫外激光输出。通过优化二倍频的转换效率,可使1 064 nm基频光到三倍频得到的355 nm紫外光的转换效率达60%。     

氟氧化物玻璃陶瓷中高效低阈值的红色上转换发光现象

本文报道了一种Er3 + 和Tm3 + 共掺杂新的氟氧化物玻璃陶瓷材料中高效低阈值的红色上转换发光现象。材料组份为 6 5GeO2 2 5NaF 8 5BaF 0 5Tm2 O3 1Er2 O3 (mol% ) ,文中给出了样品的制备方法。在 978nmLD激发下 ,观察到了非常强的红色上转换发光。据我们所知 ,在如此低的Er3 + 和Tm3 + 掺杂浓度下实现了如此之强的红色上转换发光 ,文献中未见报道 ;更令人惊奇的是在 2 0 0mA工作电流 (此时功率为 3 5mW )LD激发下 ,激发的功率密度为 170mW·cm-2 ,其红色光仍裸眼可见。讨论了这种高效低阈值上转换发光的机理。研究了LD的工作电流与上转换发光强度的关系     

A High Power Conversion Efficiency L-Band Erbium Doped Fiber Amplifier

By using two sections of erbium doped fiber and a fiber optical reflector, a novel, highly efficient L bandamplifier is demonstrated with significantly power-conversion-efficiency enhancement and the gain increasing of as much as 13 dB.     

低温808nm高效率半导体激光器

为了提高低温工作环境下808 nm半导体激光器的输出特性,深入研究了电光转换效率的温度特性。结合载流子泄漏抑制和器件串联电阻的优化考虑,从理论上深入分析了有源区量子阱内的载流子限制现象,提出针对低温工作环境下的势垒高度及相应的量子阱结构设计方法,包括势垒层的材料组分、厚度等重要参数的优化,极大地改善了器件在低温工作环境下的性能。采用优化后的外延结构,制备了腔长2 mm的半导体激光巴条。在工作温度-50℃、注入电流为600 A时,巴条输出功率达到799 W,电光转换效率为71%,斜率效率为1.34 W/A;注入电流为400 A时,器件达到最高电光转换效率73.5%,此时的载流子限制效率约为99%,串联电阻为0.43 mΩ;在-60～60℃温度范围内,中心波长随温度的漂移系数为0.248 nm/℃。     

Design of a Novel Mid-Infrared Single-Polarization Single-Mode Photonic Crystal Fiber with Low Loss,High Nonlinearity,and Large Bandwidth

ABSTRACT

A novel mid-infrared Ge₂₀Sb₁₅Se₆₅ chalcogenide-based single-polarization single-mode (SPSM) photonic crystal fiber (PCF) with rectangular latticed circular air holes is proposed. The properties of SPSM bandwidth, confinement loss, and nonlinearity are analyzed in the 3 μm~8 μm mid-infrared region using the finite -difference time-domain (FDTD) method. The influences of different geometrical parameters on the properties of SPSM-PCF are analyzed. All numerical computational results reveal that for the optimized geometrical parameters, the proposed PCF can deliver a SPSM region of more than 2.3814 μm with high nonlinearity of 3,705 w^?1 km^?1. Therefore, such a SPSM-PCF will become an excellent candidate for mid-infrared photonic.     

高稳定高转换效率光参变放大器倍频抽运光源研究

为了实现光参变放大抽运光源高稳定输出的目的。通过对倍频过程的数值模拟分析,提出倍频中存在“稳定区”的概念,在基频光强一定的条件下(小于倍频晶体破坏阈值),通过非共线双程倍频的方式或串联倍频的方式可有效延长倍频晶体的有效作用长度,保证倍频工作区能够被控制在“稳定区”内,从而实现高稳定高转换效率的倍频输出。实验数据验证了这一结论,实验中,利用非共线双程倍频的方式使得倍频工作区在“稳定区”内,对波动±5.7%的1064 nm高斯脉冲基频光,倍频光波动小于±2%,脉冲形状为高阶高斯脉冲,转换效率大于70%,实验结果表明,倍频光的稳定性指标相对于基频光提高了近3倍。     

High and Stable Conversion Efficiency Obtaining in Single-Stage Multi-Crystal Optical Parametric Chirped Pulse Amplification System

An optical parametric chirped-pulse amplification system is demonstrated to provide 32.9% pump-to-signal conversion efficiency. Special techniques are used to make the signal and pump pulses match with each other in both spectral and temporal domains. The broadband 9.5-mJ pulses are produced at the repetition rate of 1 Hz with the gain of over 1.9×10^8. The output energy fluctuation of 7.8% is achieved for the saturated amplification process against the pump fluctuation of 10%.     

Transmission Reflection Integrated Programmable Metasurface for Real-Time Beam Control and High Efficiency Transmission Polarization Conversion

The functional versatility and flexibility of multifunctional metasurfaces are of great significance for the application of electromagnetic (EM) metasurfaces in military stealth, holographic imaging, base station antennas, and other fields. Nevertheless, the functions of active programmable coding multifunctional metasurfaces are mostly reflective or transmissive, and the research on active multifunctional metasurfaces with transmission and reflection integration is still in its infancy. Here, a transmission reflection integrated active programmable coding metasurface is proposed to manipulate the transmission and reflection of different polarized electromagnetic waves independently in real time. As a proof of concept, a metasurface that can implement diverse programmable functionalities is designed. Numerical and experimental results indicate that the strategy has excellent performance in beam control and polarization conversion, which provides tremendous potential for extending highly integrated multifunctional devices.     

阈上电离与高次谐波

通过数值求解一维含时薛定锷方程，研究阈上电离与高次谐波随激光强度的变化关系，结果表明，两者具有相同的特性，都具有平台区和截止位置，但两者又有差别，较低激光强度作用下，谐波谱有平台而光电了能谱为单调下降的，激光强度较高时，两者都平台，对应的平台区和截止位置相同。     

Velocity of Electric Wind and Efficiency of Electric Energy Conversion

The results of the theoretical and experimental studies of the electric wind velocity and efficiency are considered. The experiments are carried out in air at atmospheric pressure using the electrode system as a flat multispike electrode–two parallel tube.     

Vaporization and Plasma Shielding during High Power Nanosecond Laser Ablation of Silicon and Nickel

A thermal model to describe the high-power nanosecond pulsed laser ablation is presented. It involves the vaporization and the following plasma shielding effect on the whole ablation process. As an example of Si target, we obtainthe time evolution of the calculated surface temperature, ablation rate and ablation depth. It can be seen that plasma shielding plays a more important role in the ablation process with time. At the same time, the ablation depth with laser fluence based on different models is shown. Moreover, we simulate the pulsed laser irradiation Ni target. The evolution of the transmitted intensity and the variation of ablation depth per pulse with laser fluence are performed. Under the same experimental conditions, the numerical results calculated with our thermal model are more in agreement with the experimental data.     

等离子体密度标长对高次谐波转换效率的影响

通过等离子体粒子模拟研究了在强激光与等离子体相互作用产生高次谐波的过程中,等离子体密度标长对转换效率的影响,计算了在不同密度标长下p偏振非相对论强度激光与高密度等离子体相互作用产生高次谐波的转换效率,发现等离子体密度标长对转换效率有重要的影响,这种影响与谐波级次,等离子体密度,激光脉冲宽度有关。     

LD泵浦腔外倍频高转换效率Nd3+∶GdVO4固体激光器

通过合理设计精密调控各元件和温控电流，得到了平均功率为70 mW，脉冲宽度为22 ns，重复频率为14 kHz，峰值功率高达230 W的Nd3+∶GdVO4/Cr4+YAG红外脉冲激光器.先采用双凸透镜组合成的望远镜系统对1 063 nm的红外激光进行扩束，再对该光束聚焦，最后经双轴晶体LBO倍频后，得到了平均功率为40.6 mW，脉冲宽度为16 ns，重复频率为14 kHz，峰值功率高达181 W的绿光激光输出，1063 nm→532 nm的转换效率高达58%.测量了532 nm的光谱线宽曲线.解释了该聚焦方法比单一薄透镜效果明显好的原因，并指出了这种聚焦方法的使用对象.     

高功率激光器电光调Q技术研究

通过分析激光速率方程得出增加初始态粒子反转数与阈值态粒子反转数比值(Ni/Nt),可以提高激光峰值功率,减小激光脉冲建立时间.采用双Q开关技术有效地抑制自激振荡,提高了Ni/Nt比值.设计了触发管高压脉冲发生电路,产生下降沿很快的高压脉冲信号,提高了Q开关速度,从而使得激光输出峰值功率达50 MW,效率达1.37%,对提高固体激光器的峰值功率与效率具有参考价值.     

A Linearly-Polarized Cesium Vapor Laser with Fundamental Mode Output and Low Threshold

We report a cesium vapor laser with fundamental mode output and a wavelength of 894 nm. The laser is pumped by a laser diode array with an external cavity of a holographic grating by using Littrow＇s structure. A slope efbciency of 22.4% is obtained by using a pumping source with a linewidth of 0.26 nm and 80 kPa methane as the buffer gas. The threshold pumping power is 1.56 W.     

高亮度下具有较高效率的绿色和蓝绿色有机电致发光器件的制备和性能研究(英文)

以铱配合物Ir(tfmppy)2(tpip)(1,tfmppy=4-三氟甲基苯基吡啶,tpip=四苯基膦酰胺)和Ir(dfp-py)2(tpip)(2,dfppy=4,6-二氟苯基吡啶)为发光中心分别制备了绿色和蓝绿色有机电致发光器件ITO/TAPC(1,1-bis[4-[N,N-di(p-tolyl)amino]phenyl]cyclohexane,60 nm)/Ir(Ⅲ)complex(x%,质量分数)∶Sim-CP(3,5-bis(9-carbazolyl)tetraphenylsilane,40 nm)/TPBi(2,2’,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole,60 nm)/LiF(1 nm)/Al(100 nm)。配合物Ir(tfmppy)2(tpip)掺杂质量分数为6%时,以其为发光中心的绿色器件在5 930 cd/m2亮度下的最大电流效率为47.10 cd/A,CIE色坐标为(0.28,0.65),在16.4V驱动电压下的最大发光亮度为38 674 cd/m2。配合物Ir(dfppy)2(tpip)掺杂质量分数为10%时,以其为发光中心的蓝绿色器件在3 175 cd/m2亮度下的最大电流效率为14.80 cd/A,色坐标为(0.15,0.50),在11.8 V驱动电压下的最大发光亮度为25 985 cd/m2。     

大功率、高效率、高消光比铒光纤多波长超荧光光源

采用改进的反射式Mach-Zehnder干涉滤波器，对双程后向结构掺铒光纤超荧光光源(DPB SFS) 分别进行光谱分割和光谱预分割，构建了两种结构的多波长超荧光光纤光源（MW SFS），波长间隔为～0.8 nm时，在1550 nm附近（1542～1559 nm）20个波长的功率波动小于0.5 dB其中前者消光比高达27 dB；后者消光比～18 dB，在泵浦光功率为72.8 mW时，最大输出功率25.3 mW，光光转换效率高达34.8%改变Mach-Zehnder干涉仪的臂长差，采用光谱预分割技术，得到1550 nm附近波长间隔～0.4 nm、消光比～16 dB的50个波长输出