Optimal spectral phase control of femtosecond laser-induced up-conversion luminescence in Sm3+:NaYF4 glass

The spectral phase of the femtosecond laser field is an important parameter that affects the up-conversion(UC)luminescence efficiency of dopant lanthanide ions.In this work,we report an experi-mental study on controlling the UC lmiiinescence efficiency in Sm^3+:NaYF4 glass by 800-nm femtosec-ond laser pulse shaping using spectral phase modulation.The optimal phase control strategy efficiently enhances or suppresses the UC luminescence intensity.Based on the laser-power dependence of the UC luminescence intensity and its comparison with the luminescence spectrum under direct 266-nm fem-tosecond lciser irradiation,we propose herein an excitation model combining non-resonant two-photon absorption with resonance-media ted three-photon absorption to explain the experimental observations.     

Comparison of two cold atmospheric pressure plasma jet configurations in argon

The present study compares the operation of two cold atmospheric plasma jet (CAPJ) configurations: needle-to-cylinder electrode configuration (CAPJ I) and single high-voltage cylinder electrode around the quartz tube (CAPJ II). The CAPJs were operated in argon flowing through a quartz capillary with 0.5-mm inner diameter into the ambient air, and the plasma was generated by sinusoidal kHz frequency AC power supplies. The main emphasis of the study was on the mechanism of the initiation of ionization waves for these two configurations. For both CAPJs, there appeared several ionization waves during one half-period of the applied voltage waveform, and the number of ionization waves increased at higher voltage amplitudes. However, we discovered marked differences in the initiation of the ionization waves for two different CAPJ configuration. The applied voltage controlled the initiation of consecutive ionization waves, which propagated from the grounded electrode towards the tube orifice in CAPJ I. In the case of CAPJ II, certain time had to pass for the initiation of a new ionization wave, and subsequent ionization waves within the same half-period started at the tube orifice. In addition to the differences in the initiation of the ionization waves, we observed that the CAPJ I was ignited and sustained at lower voltages, while CAPJ II produced a longer plasma jet. The observed advantages and deficiencies of investigated CAPJ configurations point out their potential in different applications.     

膜厚监控系统的光谱宽度对窄带滤光片性能的影响

讨论了膜厚监控系统的光谱宽度对波分复用窄带滤光片特性的影响,分析了监控过程中所出现的信号异常现象,其主要原因是控制光光谱宽度以及控制波长与滤光片中心波长不一致,所以控制光光谱分辨率必须小于单个法布里-珀罗滤光片最后2层膜折转点波长宽度的一半,即对100GHz的滤光片,监控系统的光谱宽度必须小于0．2nm。一旦产生中心波长偏离,就必定产生厚度控制误差。讨论了高折射率膜和低折射率膜的信号变化规律,发现当中心波长比监控波长长时,虽然信号变化规律正确,但判读到极值时的膜厚变薄。中心波长偏离越长,厚度将越薄。而当中心波长比监控波长短时,信号将出现反转。中心波长越短,反转量越大。最后指出了监控误差对滤光片Tmax和半峰全宽的影响。     

Semi-gas kinetics model for performance modeling of flowing chemical oxygen-iodine lasers (COIL)

The gas pressure in a laser cavity of flowing chemical oxygen-iodine laser (COIL)is about 133.31333 Pa[1]. In this pressure range, effects of homogeneous and inhomo-geneous broadening competing with each other on the performances of a COIL are no-ticeable. Generally, a rate equation (RE) model is adopted to the performance modeling of a supersonic COIL, such as in refs. [1—4]. This model assumes the spectral line pro-file is homogeneously broadened. Homogeneous broadening assumption sim…     

Dispersion Characteristics of Waveguide Arrays in Optical Spectrum Analyzers

Formulas for calculating the spectral characteristics of waveguide arrays, which are incorporated into waveguide spectrum analyzers based on planar waveguides, channel waveguides, and fiber optical waveguides, are derived taking into account the contribution of both the waveguide dispersion and the material dispersion to the dispersion factor. These formulas are used to study the dependence of the dispersion factor on the waveguide-system parameters for specific models of waveguide arrays. It is shown that consideration of contributions of the waveguide dispersion and material dispersion can affect profoundly the spectral characteristics of waveguide arrays.     

Polarization and phase control of two-photon absorption in an isotropic molecular system

<正>We theoretically and experimentally study the polarization and phase control of two-photon absorption in an isotropic molecular system.We theoretically show that the two-photon transition probability decreases when the laser polarization changes from linear through elliptical to circular,and the laser polarization does not affect the control efficiency of two-photon transition probability by shaping the spectral phase.These theoretical results are experimentally confirmed in coumarin 480.Furthermore,we propose that the combination of the laser polarization with the spectral phase modulation can further increase the control efficiency of the two-photon absorption.     

Design and Performances of a Carbon Monoxide Sensor Using Mid-Infrared Absorption Spectroscopy Technique at 4.6 µm

Based on infrared absorption spectroscopy technique, a carbon monoxide sensor was developed using the fundamental absorption band of carbon monoxide molecule at the wavelength around 4.6 µm. The developed sensor consists of pulse-modulated wideband incandescence, open ellipsoid light-collector gas-cell, dual-channel detector, and control and signal-processing module. With the prepared standard carbon monoxide gas sample, sensing characteristics on carbon monoxide were investigated using the sensor. Experimental results reveal that the limit of detection is about 10 ppm, the relative error at the limit of detection point is less than 14%, and that is less than 7.8% within the low concentration range of 20～180 ppm. The maximum absolute errors of 50 min long-term measurement on the 0 and 14 ppm CO gas samples are about 3 and 3.17 ppm, respectively, and the standard deviations are as small as 0.18 and 1.25 ppm, respectively. Compared with the reported carbon monoxide detection systems utilizing quantum cascaded lasers and distributed feedback lasers, the proposed sensor shows potential applications in carbon monoxide detection under the circumstances of coal-mine and environmental protection, by virtue of high performance, low cost, simple optical structure, and so on.     

啁啾参数对光束远场分布的影响

啁啾脉冲光束的远场特性对其具体应用具有重要意义。利用夫琅禾费衍射积分公式导出了啁啾脉冲高斯光束远场光强分布的解析式,并通过数值计算分析了啁啾参数对远场分布的影响。结果表明,脉冲光束的远场中心光强随着脉宽的减小而增大,其远场轴上功率谱随着脉宽的增大而减小,与普通脉冲高斯光束相比,脉宽的变化对于啁啾脉冲光束的影响更大。脉冲光束的中心光强也随着谱宽的增大而增大,但啁啾参数的变化不会对其产生影响。     

一种新型芴类衍生物的光谱性质研究

合成了具有大π共轭性的对称型芴类衍生物9,9-二(2-乙基已基)-2,7-二(2-(4-甲氧基)苯-2,1-乙烯基)芴(简写为MO-Flu-MO)。通过元素分析、质谱、紫外-可见光谱和红外光谱对其进行了表征。测试了该染料在乙腈、二氯甲烷、四氢呋喃和正己烷4种不同极性溶剂中的线性吸收光谱和单光子荧光谱。结果发现溶剂效应对吸收光谱和荧光光谱表现出不同程度的影响,对产生这些光谱行为的主要原因进行了讨论。     

铟封前后透射式GaAs光电阴极光谱响应特性的测试与分析

利用自行研制的光谱响应测试仪工程化样机,对透射式GaAs光电阴极在高温激活结束、低温激活结束以及铟封成管后的光谱响应特性进行了测试。结果显示,铟封后阴极整个响应波段的光谱响应下降,长波响应受到最显著的影响,表现为800~815 nm之间长波响应大幅度衰减,截止波长和峰值波长向短波移动,峰值响应和积分灵敏度减小,最终的光谱响应曲线变得平坦。阴极参量的计算结果反映铟封后阴极的表面逸出几率降低,说明铟封引起阴极表面激活层发生变化,使得能量较低的长波段光生电子不容易逸出,阴极长波响应和灵敏度随之降低。进一步分析了铟封过程中影响阴极表面激活层的因素。