基于二阶导数谱与特征吸收窗的红外光谱定量检测方法

红外光谱分析技术已被液体、固体和气体混合物各组分的定量检测广泛应用。针对红外光谱定量检测过程中存在的计算过程复杂、受背景及噪声干扰、多组分谱线混叠的问题,一方面,通过获取谱线二阶导数去除背景及噪声干扰,并一定程度上区分混叠谱峰。在获取二阶导数谱线过程中运用Savitzky-Golay滤波器进行平滑滤波处理,并根据谱线频率特征选取Savitzky-Golay滤波器最佳滤波参数,解决了滤波参数缺乏标准化选取方法的问题。另一方面,根据被测组分的吸收分布情况生成特征吸收窗分别对待测原始吸收谱线以及二阶导数谱线加以处理,提取出在浓度计算过程中占据重要性更大的特征吸收的区域,从而排除非吸收区域中背景、噪声及其他组分对计算结果的干扰。以一组丙烷、丙烯和甲苯混合气体为例,运用二阶导数方法以及特征吸收窗方法进行定量检测,并与直接利用原始谱线的检测结果进行比较分析。实验结果表明采用二阶导数谱与特征吸收窗的定量检测方法精度更高,相对误差基本在5%以内。     

低频波长调制光谱的理论与实验研究

通过调制半导体激光外腔压电陶瓷的电压实现低频波长调制 ,并慢扫描激光器的波长 ,测量了CS 原子D2线 [6S1 2 (F =4)→ 6P3 2 ]的吸收光谱 ,利用锁相放大器处理了二次、四次、六次谐波信号 ,实验结果与理论分析相吻合 ,在实验过程中还发现高次谐波探测可以有效地提高探测信号的信噪比     

Sweep optical frequency synthesizer with a distributed-Bragg-reflector laser injection locked by a single component of an optical frequency comb

A sweep optical frequency synthesizer is demonstrated by using a frequency-stabilized optical frequency comb and injection-locked distributed-Bragg-reflector (DBR) laser diode. The injection-locked DBR laser acts as a single-frequency filter and, simultaneously, a high-gain amplifier of the optical frequency comb. The frequency instability of the heterodyne beat signal between two independently injection-locked DBR lasers is measured to be 2.3 x 10(-16) at 1 s averaging time. The output frequency of the sweep optical frequency synthesizer can be precisely tuned over 1 GHz, and a saturated absorption spectrum of the Cs D2 line at 852 nm is recorded by the injected DBR laser.     

A relation between Holstein's photon escape transmission factor and the equivalent width

It is shown that the photon escape transmission factor for a spectrum line in a homogeneous gas, defined by Holstein in his study of the imprisonment of resonance radiation, is a useful derivative of the equivalent width or total absorption of the line.     

A simple scanning semiconductor diode laser source and its application in wavelength modulation spectroscopy around 825 nm

A very simple and inexpensive tunable semiconductor diode laser controller is designed for stable operation of the diode laser. The diode laser controller is stable within +/−8 μA and +/−10 mK, respectively. The noise spectrum of the current controller is studied by FFT analysis. We have used our home-made diode laser system in a tunable diode laser absorption spectrometer (TDLAS) to probe weak overtone transitions of water vapour molecule. The diode laser wavelength is coarsely tuned by changing the operating temperature to probe (2, 1, 1)←(0, 0, 0) band overtone transitions of water vapour within 818–835 nm. To demonstrate line shape study, seven transitions are scanned by ramping the drive current of the diode laser (at constant operating temperature) under different perturber (laboratory air) pressures within the sample cell. A balanced detector and a lock-in amplifier are used for phase sensitive detection purpose. Small current modulation amplitude, balanced detection and proper adjustment of the lock-in amplifier help to obtain a S/N ratio ranging from 100 to 7 using a small sample path length of 1.5 m. Experimentally obtained derivative spectrum is numerically integrated to reveal the original line shape and fitted with a nonlinear least squares fitting program to extract air broadening coefficients and line strength parameters. The spectroscopic line parameters are compared with the results from HITRAN database.     

C60三阶微商吸收光谱分析

利用三阶微商吸收光谱观测到了紫外一可见区Ｃ６０更为丰富捐收跃迁结构，基于 伦兹线型假设，实验上拟合确定了相应迁能量和寿命加宽参数，并对跃迁结构进行了初步指认，给出了部分振动模的频率。与常规吸收光谱比较，表明了三阶微商光谱是分析Ｃ６０等团簇光物理特性的有效手段。     

异丙甲草胺农药残留吸收光谱检测方法研究

除草剂可以快速、有效地进行除草，已被广泛应用，但是在除草剂使用同时也会对周围环境和农作物带来一定程度的污染，例如农业生产过程中经常发现由于除草剂使用不当而使果树中毒的现象。异丙甲草胺是一种酰胺类选择性除草剂，被广泛应用于旱地作物、蔬菜和果园、苗圃。根据相关文献报道，基于气相色谱法、气相色谱-质谱联用法和固相萃取等方法可以实现异丙甲草胺残留检测，而基于吸收光谱法对异丙甲草胺的分析未见相关文献报道，提出直接利用吸收光谱及其导数光谱分析法实现异丙甲草胺农药及其在苹果汁中的农药残留检测。首先利用分光光度计对不同浓度异丙甲草胺药液进行吸收光谱实验研究，发现在266 nm处有明显吸收光谱特征峰。对农药吸收光谱进行拟合分析，得到异丙甲草胺药液浓度和吸光度之间预测模型函数方程，函数方程为y=2.147 09x+0.031 98，相关系数为0.998 5。然后利用分光光度计对苹果汁-异丙甲草胺混合溶液进行吸收光谱实验研究，相对于纯苹果汁吸收光谱，在混合溶液吸收光谱中发现266 nm处为异丙甲草胺所对应的特征峰。对苹果汁中药物浓度和吸光度进行建模，模型函数为：y=0.704 9+0.826 8x，其相关系数为0.991 1。可以看出，当苹果汁中异丙甲草胺残留量很低时，其农药吸收光谱特征峰并不明显。为进一步提高检测效果，对混合溶液吸收光谱进行一阶导数处理，得到其一阶导数吸收光谱。与苹果汁吸收导数光谱相比较，苹果汁-农药混合溶液导数光谱有两个明显特征光谱峰，分别位于269和276 nm处。进一步分析苹果汁-异丙甲草胺混合溶液的导数吸收光谱峰值与农药含量之间的关系，对异丙甲草胺含量与导数光谱吸光度进行函数拟合。其中269 nm对应预测模型函数关系式：y=0.005 3-0.090 6x，相关系数r=0.992 5；276 nm对应预测模型函数关系式为y=-0.000 769-0.302 8x，相关系数r=0.990 6。为验证由吸收光谱和其一阶导数光谱所得苹果汁中农药残留预测模型的准确性，另外配置五种浓度苹果汁-异丙甲草胺混合溶液。然后在同等条件下对其进行吸收光谱实验，将266，269和276 nm处的吸光度分别代入对应模型函数可求得浓度预测值，结合已知浓度值可计算其平均回收率，其中吸收光谱266 nm对应平均回收率为104.68%，导数光谱269 nm对应平均回收率为104.59%，276 nm对应平均回收率为105.18%。对苹果汁中异丙甲草胺检测模型进行分析，计算得到检出限(LOD)和定量限(LOQ)参数值，其中原始吸收光谱对应LOD和LOQ分别为0.014 8和0.049 2 mg·mL-1，一阶导数光谱对应LOD和LOQ最小值分别为0.001 5和0.004 9 mg·mL-1。研究结果表明，采用吸收光谱方法对苹果汁中异丙甲草胺进行直接检测与分析是快速和可行有效的，而且对吸收光谱进行导数运算处理后，检测效果更优。     

双重傅里叶变换滤波二阶比光谱导数分光光度法同时测定苯酚、邻苯二酚及对苯二酚

本文针对三组分混合体系分析提出了双重傅里叶变换滤波二阶比光谱导数分光光度法。对所测的吸收光谱用较大滤波窗口先后进行两次滤波 ;利用两次对混合体系光谱和单组分光谱比光谱求导使某两个组分对混合体系比光谱导数的贡献为零 ,而剩余组分的比光谱导数与其浓度成正比。对双重傅里叶变换滤波效果、实验参数的优化作了研究。用此方法对苯酚、邻苯二酚及对苯二酚含量为 0 0 1 0 0 9～ 0 0 5 3 2 5mg·mL- 1 的混合溶液进行测定 ,所得结果的相对误差为 0 0 7%～ 5 4%。     

基于KMnF_3∶Yb~(3+),Er~(3+)纳米晶的红光聚合物平面光波导放大器

制作了基于KMnF_3∶Yb~(3+),Er~(3+)纳米晶材料的工作波长655 nm的聚合物平面光波导放大器。材料的吸收光谱表明,KMnF_3∶Yb~(3+),Er~(3+)纳米晶在980 nm附近有很强的吸收。在980 nm激光的激发下,由于Er~(3+)和Mn2+能级之间的能量传递,KMnF_3∶Yb~(3+),Er~(3+)纳米晶产生了很强的红色上转换发光。根据KMnF_3∶Yb~(3+),Er~(3+)纳米粒子的发光特性,制备了KMnF_3∶Yb~(3+),Er~(3+)NCs-PMMA复合材料,用其作为芯层设计了掩埋形结构光波导放大器,利用传统的半导体工艺完成器件制备。器件测试结果表明,当655 nm信号光功率为0.1 m W、980 nm泵浦功率为260 m W时,器件获得了2.7 d B的相对增益。     

双光子吸收光谱

本文报道以皮秒脉冲激光抽运的光参量放大器为宽带可调谐激发光源，直接测量非线性光学材料的双光子吸收谱的方法。光参量放大器不但可调谐谱带很宽，而且可用一对尼科尔棱镜很容易地实现全波段功率足够强和相等，使此方法的测量结果准确可靠。用此方法研究了一个新有机化合物的双光子吸收谱。实验结果表明所测的新有机化合物在很宽的波长范围内呈现出很大的双光子吸收截面。     

Absorption line profile recovery based on TDLS and MEMS micro-mirror for photoacoustic gas sensing

A novel and efficient absorption line recovery technique is presented. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used to generate laser intensity modulation through the mirror reflection. Tunable diode laser spectroscopy (TDLS) and photoacoustic spectroscopy (PAS) are used to recover the target absorption line profile which is compared with the theoretical Voigt profile. The target gas is 0.01% acetylene (C2H2) in a nitrogen host gas. The laser diode wavelength is swept across the P17 absorption line of acetylene at 1535.4 nm by a current ramp, and an erbium-doped fibre amplifier (EDFA) is used to enhance the optical intensity and increase the signal-to-noise ratio (SNR). A SNR of about 35 is obtained with 100 mW laser power from the EDFA. Good agreement is achieved between the experimental results and the theoretical simulation for the P17 absorption line profile.     

变栅距光栅实现啁啾脉冲光谱整形

为了充分利用放大介质的增益带宽,获得脉宽更短,功率更高的输出脉冲,需要将输入到主放大链的种子脉冲进行光谱整形来补偿放大过程中的增益窄化效应。提出了利用变栅距反射光栅实现中心波长1053nm,谱宽6nm啁啾脉冲的光谱整形。运用严格的光栅衍射耦合波理论分析光栅的衍射特性,发现该方案不会引入相位畸变。分别计算和分析了刻槽深度、入射角大小、光栅周期以及入射光波长的变化对衍射效率的影响,通过选取适当的光栅参量可获得0.5%~84%的光谱调制深度。     

Wideband chaotic oscillation in a self-oscillatory system with a nonlinear transmission line on magnetostatic waves

Wideband chaotic microwave oscillation in a ring self-oscillatory system is studied. The system includes a solid-state power amplifier and a wideband nonlinear transmission line with a ferromagnetic film in which magnetostatic waves of different types are excited. It is found that the eigenmodes of the self-oscillatory system excited in the passband of the transmission line on magnetostatic waves become noisy because of spin wave parametric excitation due to the magnetostatic wave and nonlinearity of the power amplifier. A continuous spectrum of modes observed in the wideband chaotic signal is associated with the presence of a descending portion in the dynamic characteristic of the nonlinear transmission line, which arises when a magnetostatic surface wave is excited.     

基于石英音叉增强型光谱技术(QEPAS)的实时探测系统研究

利用石英音叉增强型光谱技术(QEPAS)结合基于Lab-VIEW设计的数字 频率锁定技术建立了一套气体实时探测系统, 该方案使用3f信号作为误差反馈信号, 将激光器锁定在待测气体吸收峰的中心位置, 保证了长时间测量的准确度并且提高了探测效率. 实验中采用中心波长位于1.396 μm的DFB半导体激光器作为光源, 选择常压下空气中的水汽作为研究对象, 对系统性能进行了测试, 并对影响影响系统探测灵敏度的主要因素进行了分析. 实验结果表明, 该系统可以将激光器稳定在± 0.001 cm^-1范围内, 对激光器长时间工作时的波长漂移起到了很好的抑制作用, 系统的检测限约为1 ppm, 该方案可以直接应用于工业气监测、痕量污染物实时测量等领域.     

基于激光驱动等离子体光源的近红外傅里叶变换光谱系统

近红外傅里叶变换光谱仪作为一种常用的科研级近红外光谱检测仪器,广泛应用于各个科研领域。目前的近红外光谱仪着重于光谱分辨率方面的提升,在光谱信噪比提升方面关注较少。光谱信噪比直接影响光谱线指数测量精度的优劣,光谱信噪比越高,光谱线指数测量精度越高,越有利于对微量物质进行精细光谱比对。因此,提升光谱仪的光谱信噪比是十分必要的。对比常用的钨灯光源,激光驱动等离子体光源(LDLS)不仅在近红外区域具有高光照强度的优点,而且其独特的高频调制输出信号在经锁相放大器调制解调后能够很好的抑制背景信号对干涉光谱所带来的影响。高亮度与辐射调制的结合使得以LDLS作为光源的近红外傅里叶变换光谱系统在光谱信噪比方面获得显著提升。基于上述原因,提出利用新型激光驱动等离子体光源作为光谱信号输出源的近红外傅里叶变换光谱系统,并与含有调制能力的钨灯光源搭建的近红外傅里叶变换光谱系统进行了信噪比的比较实验。首先利用钨灯光源由斩波器高频调制再经过锁相放大器解调的方式,对锁相放大器积分时间进行优化并通过计算干涉光谱信噪比进行评估,分别对比了积分时间为0.5,1,5,10和20 ms的干涉光谱信噪比与对称度,确定后续系统中的锁相放大器最佳积分时间为5 ms,该状态下钨灯光源所实现的干涉光谱信噪比经计算约为90∶1;其次利用激光驱动等离子体光源代替钨灯光源和斩波器,在最佳积分时间下进行干涉光谱信噪比对比评估,结果表明激光驱动等离子体光源的干涉光谱信噪比与传统钨灯光源相比提升111倍;最后,利用近红外标准片对系统进行光谱测量准确性评估,结果表明利用该光源的近红外傅里叶变换光谱系统的近红外吸收峰值误差<0.5 nm,具有高光谱准确性与分辨能力。     

On the Similarity of the Statistical Characteristics of Spontaneous Radiation of a Quantum Amplifier at Different Gain Factors

The transformation laws governing the statistical properties of the quantum noise of an optical amplifier when its gain factor and spectral line profile are varied are considered. The correlation functions of quantum noise both at the amplifier output and after nonlinear transformation normalized to the correlation time of quantum noise at the amplifier output were found to be independent of the amplifier gain provided that it exceeds 10 for the Gaussian spectral line profile and 10³ for the Lorentzian profile. The spectral density of quantum noise transformed in a nonlinear system was shown to possess the same similarity property. It was found that the statistical characteristics possess a similarity property even in the case of variation of the spectral line profile from Gaussian to Lorentzian. It was concluded that such a characteristic of quantum noise of an optical amplifier as the correlation time bears virtually all information on the above-mentioned statistical properties at a reasonably large amplifier gain. The similarity property revealed has an important application. It allows finding the matching condition between the optical signal spectrum and the gain profile of the optical quantum amplifier to achieve the highest sensitivity of signal detection by the amplifier.     

导数光度法测定食品中的微量铁

本文在邻二氮菲光度法的基础上，引入导数光谱峰面积技术，对微量铁进行定量测定，该方法避免了有关离子的干扰，提高了准确度，用之于面粉、奶粉和肝等食品样品分析，所获结果令人满意。     

Frequency locking to the center of a 532 nm iodine absorption line by using stimulated brillouin scattering from a single-mode fiber

A simple method for frequency locking a frequency-doubled Nd:YAG laser to the center of line 1109 of the iodine absorption spectrum is described. The 31.6 GHz frequency shift provided by stimulated-Brillouin scattering from a single-mode silica fiber provides a probe signal that lies on the edge of line 1105 of the iodine spectrum. We adjust the frequency of the laser to maintain the transmission of a 5 cm iodine absorption cell at a value that places the unshifted laser line in the center of line 1109.     

An inhomogeneous theoretical model for analysis of PbSe quantum-dot-doped fiber amplifier

Optical fiber doped with lead salts quantum dots (QDs) of different radii, has previously been proposed as a wide-band amplifier in the optical communication range. The emission and absorption spectra of QDs are size-dependent. Optical fiber amplifier doped with QDs of different sizes is an inhomogeneous gain medium. This inhomogeneity is the principle of operation of wide-band quantum-dot-doped fiber amplifiers (QDFAs). To study the effects of inhomogeneity such as spectral hole burning on the amplifier behavior, a fiber amplifier with an arbitrary size distribution of QDs is taken into consideration. The light propagation equations and rate equations for the inhomogeneous medium are presented. To investigate the gain spectrum, the amplifier bandwidth and the spectral hole burning effect on the amplifier behavior, the system of governing equations for the steady-state regime of operation are solved and numerical results are presented.     

High repetition rate Tm：Ho：LuLiF master-oscillator and Tm-doped fiber power-amplifier system

A high repetition rate Tm:Ho:LuLiF master-oscillator and polarization-maintaining (PM) Tm-doped fiber power-amplifier system is presented.A 11.3-kHz,0.4-nm line width,0.89-W Tm:Ho:LuLiF seed laser is developed.Using a two-stage PM Tm-doped fiber power amplifier system,32.4-W output power is obtained with 0.4-nm line width at a central wavelength of 2058.5 nm,corresponding to 0.66-W seed laser.The laser spectrum and pulse profile are measured.