人鼻咽癌细胞株SUNE-1和CNE-1的光声光谱研究

为了解人鼻咽癌细胞的光生物学特性，采用单光束光声光谱技术对2株人鼻咽癌细胞SUNE-1、CNE-1进行了研究，获得了它们的归一化光声光谱。结果发现，在波长420nm附近，它们的光声光谱都存在吸收峰；在波长380～700nm内，SUNE-1的光谱吸收强度大于CNE-1。研究结果表明SUNE-1和CNE-1的光生物学特性存在显著差异，为鼻咽癌的研究提供了一种新途径。     

导数光声光谱技术

本文报道了一种新的光声光谱技术即导数光声光谱技术，它利用一台单色仪和一个波长分束器，同时获得两束光强相同但波长有微小差别的两束光，这两束光分别入射到两个光声传感器，光声传感器的输出信号输送到锁相放大器并实现差分输出，输出信号输送室X-Y记录仪进行记录，最后扫描单色仪的波长从而获微得导数光声光谱，这种光谱技术既具有光声光谱技术灵敏度高的优点，又具有导数光谱技术分辨率高的优点。     

用光声光谱技术测量光电探测器的光谱响应

根据光声效应原理,用驻极体电容微音器作为传感器,用吸收系数接近1的碳黑作为吸收物质,制作了高灵敏度的光声传感器。用该传感器作为光源功率监测器,用归一化的光声光谱技术测量了光电探测器的相对光谱响应曲线,从而消除了光电探测器量子效率对光源滤长的依赖性,获得了光电探测器比较准确的相对光谱响应特性曲线。     

用染色技术提高细胞的光声光谱检测灵敏度

为了提高细胞的光声光谱检测灵敏度和光谱吸收特性的区分度，对胎盼蓝染色的两种人鼻咽癌细胞株进行光声光谱检测，并与对应无染色细胞株的光声光谱进行比较。结果：(1)无染色组和胎盼蓝染色组的人鼻咽癌细胞(CNE-2、CNE-1)的光声光谱吸收系数大小规律是一样的：CNE-2、CNE-1；(2)染色的人鼻咽癌细胞的光声光谱吸收强度比无染色的明显增大，提高了光声光谱检测灵敏度，同时又提高了它们的光谱吸收特性的区分度。结论：用染色剂方法可以有效提高细胞样品的光声光谱检测灵敏度和光谱吸收特性的区分度。     

光声光谱技术在现代生物医学领域的应用

光声光谱技术是一种研究物质吸收光谱的新技术,已经成为分子光谱学的一个重要分支。作为现代生物医学领域研究的一种有力的分析工具,光声光谱技术克服了组织散射特性对测量结果的影响,为生物组织样品的研究提供了一种灵敏度高、样品可不经预处理的无损有效检测方法。简述了光声光谱技术的基本原理、实验装置,重点介绍了光声光谱技术在现代生物医学领域研究中的最新应用情况。     

缓冲气体对光声光谱法气体检测的影响

为了研究气压及缓冲气体种类对光声信号及共振频率的影响，采用光声光谱技术，设计了一套基于光声光谱技术原理的痕量气体检测系统。实验中以NH₃标准气作为待测气体，采用向光声池内充入缓冲气体的方法来改变光声池内气压，在气压作为单一变量的条件下得出0.03MPa~0.1MPa气压范围内光声信号及共振频率的变化；采用分别向光声池内充入不同种类缓冲气体的方法，得出不同缓冲气体条件下0.03MPa~0.1MPa气压范围内光声信号及共振频率的变化。结果表明，随着气压的升高，光声信号幅值增大，并且越重的缓冲气体使光声信号增幅越大；气压的升高使得共振频率偏移，共振频率的偏移量与光声池内混合气体分子的摩尔质量成反比。该研究为解决在现场进行气体检测时，气压及背景气体变化的复杂环境对检测结果的影响提供了参考。     

基于可调谐CO2激光器的SF6差分光声检测研究

为了对电力场所SF₆气体浓度进行有效监测,采用光声光谱气体检测技术,基于波长可调谐CO₂激光器,设计了一套大气环境下的SF₆痕量气体检测系统,并提出一种差分光声光谱技术以提升光声系统的检测灵敏度。结果表明,所设计的SF₆气体检测光声系统的共振中心频率为1066Hz,品质因数为32.04,光声池常数为89.74Pa·m·W-1;利用单谱线光声法,在激光谱线10P12处检测SF₆气体的灵敏度为0.06×10-6（体积分数）;采用差分光声光谱气体技术后,在激光谱线10P12和10P16处3W强度调制光的照射下,光声系统的灵敏度提升到0.02×10-6（体积分数）。差分光声光谱技术能有效降低噪声影响,提升光声检测系统的灵敏度,具有一定的实用价值。     

激光共振光声法检测香港空气中的乙烯污染

介绍利用亥姆霍兹共振光声池的激光光声光谱技术定量检测香港地区典型地点空气中的乙烯污染万分。     

光声喇曼光谱中线光声信号的影响

本文探讨了光声喇曼光谱中线性光声信号对灵敏度，探测极限和频移影响，导出了连续和脉冲光声喇曼光谱中线性光声信号的普适表达式，进而导出了光声喇曼光谱的信噪比和探测及限，理论值与实验值基本一致。     

小型化光声光谱气体传感器研究进展

光声光谱技术用于探测痕量气体的浓度,小型化集成的光声光谱气体传感器利于实现便携式在线检测。光声探测作为光声光谱的关键技术决定了系统的灵敏度和体积,小型化的光声探测系统的核心是微型吸收单元和声光谐振器。总结了近年来光声光谱气体传感器在小型化与集成方面的进展,分析并比较三种光源、微型吸收单元以及小型化声光谐振器的研制进展以及各自利弊。介绍了北京航天控制仪器研究所近年的研究成果,采用共振管增强的石英音叉作为紧凑型封装的声光测量器件,通过铥钬共掺的光纤放大器实现波长为2 mm,功率为200 m W的激光输出,提高了测量精度,实现对氨气和二氧化碳的同时测量。     

Practical upper limits to cutoff wavelength for different single-mode fiber designs

A practical upper limit to cutoff wavelength in single-mode fiber is investigated. Based on the relationship between the attenuation of the LP11mode and the length dependence of cutoff wavelength, a formula is developed to predict this limit for four fiber designs commonly seen in commercially available fibers. It is found that, depending on fiber design, the upper limit of factory-measured fiber cutoff wavelength is anywhere from 20 to 60 nm above the system operating wavelength, even for a worst case "straight fiber" layout. Under actual field layout conditions, however, the limits converge to approximately 65 nm above the system wavelength for all four fiber designs. The practical upper limit predicted here is confirmed through an experimental evaluation of modal noise effects in a 1.2-Gbit/s single-mode fiber system.     

Large-Scale Waves in the Thermosphere Observed by the AE-C Satellite

Atmosphere Explorer C (AE-C) data are analyzed to study wavelike perturbations in the thermosphere at an altitude of about 260 km. The data were measured during one orbit on January 20, 1975. The examples shown are typical of many other orbits of both satellites AE-C and AE-E. Four geophysical parameters are analyzed: nitrogen and oxygen densities, electron density, and ion temperature, as measured by three different instruments. The data are processed by normalizing them to their average values and extracting their trends. Their fluctuations are obtained by passing the normalized detrended data through a high-pass filter. Strong periodicities are apparent that persist throughout the records, regardless of filter cutoff frequency. Fluctuations are compared by computing cross correlation functions. Spectra are obtained using the MEM and FFT procedures. It is demonstrated, for the first time, that relationships between ion variations and neutral variations are coherent over a wide range of scale sizes over global distances. It is also inferred from plane wave modeling studies and from the persistent periodicities over global distances that a quasi-stationary wave structure is present in the thermosphere that may slowly dissipate and be regenerated by auroral region sources. Large-scale structures are found in all four parameters with horizontal scale sizes ranging from about 400 to about 4000 km. The spectra for all parameters contain peaks at wavelength that are confirmed by the periods of the fluctuations, and decrease with decreasing wavelength with a power law type of variation.     

Diode laser wavelength tracking using an integrated dual slabwaveguide interferometer

The problem of tracking small changes in the output wavelength of laser diodes is addressed using a dual slab waveguide interferometer fabricated from silicon oxynitride. Waveguide mode dispersion differences between the waveguide modes provide a mechanism for identifying input wavelength shifts that are measured as shifts in the output far-field diffraction image. At visible wavelengths the device can transduce input wavelength changes into phase responses with a sensitivity of +0.9 rad/nm. The lower threshold limit of detection for laser output frequency shifts, is 2.2 GHz or 6 pm at a center wavelength of 635 nm. The TE and TM sensitivities to wavelength are approximately equivalent in the device described     

Compression Limit by Third-Order Dispersion in the Normal Dispersion Regime

Broadband continua at gigahertz rates generated in high-nonlinear dispersion-flattened fibers in the normal dispersion regime near the zero-dispersion wavelength can be used for a subsequent efficient pulse compression, leading to stable high-repetition-rate trains of femtosecond pulses. We show experimentally and theoretically that third-order dispersion defines a critical power, where beyond further compression is inhibited. This fundamental limit is caused by a pulse-breakup     

Input impedance of a monopole antenna at the center of a finite ground plane

A technique for computing the input impedance of a monopole on a finite ground plane is provided. The case of an infinite ground plane is first examined, and then the concept of using a magnetic edge current as an equivalent source of diffraction on the limited size ground plane is introduced. The technique used is serf-consistent in that the circular ground plane considered is the limit of a polygonal ground plane as the number of sides tends to infinity. Good agreement has been demonstrated when the nearest edge of the ground plane is at least 0.3 wavelength from the base of the monopole.     

增益钳制半导体光放大器波长转换的研究

数值模拟了增益钳制SOA(GC-SOA)的波长转换过程,分析了GC-SOA实现波长转换的原理.首次发现了GC-SOA波长转换中类似接通延迟的现象,这种现象将限制GC-SOA在高速波长转换中的应用.     

Switching between the mode-locking and Q-switching modes in two-section QW lasers upon a change in the absorber properties due to the Stark effect

The passive Q-switching and mode-locking modes are implemented in two-section lasers with three quantum wells. It is demonstrated that raising the reverse bias on the absorbing section changes its spectral and dynamic properties and, accordingly, leads to a change from the Q-switching mode to mode-locking. The pulse-repetition frequency in the mode-locking mode is 75 GHz, with the product of the pulse duration by the spectrum bandwidth being 0.49, which is close to the theoretical limit. It is shown that, in structures with three quantum wells, strong absorption at the lasing wavelength gives rise to a photocurrent across a section of the saturable absorber, which is sufficient for compensation of the applied bias.     

Parameter optimization in graded-index dispersion-shifted single-mode fibers

The characteristics of graded-index single-mode nonsegmented-core fibers with a single cladding region, in which the wavelength of zero dispersion is shifted to 1.55 μm, are studied analytically. It is found that for a given relative index difference above a certain value, there are two core sizes at which this zero dispersion shifting is realized. The larger core has certain advantages and has been invariably used in practice. For fibers in which the core is Ge-doped and the index of refraction has a triangular or a parabolic profile, we calculate the rate of change of dispersion with wavelength, the sensitivity of the zero dispersion wavelength to small changes in the core radius and in the refractive index difference, and the outer radius of the cladding needed to limit microbending losses in the cabled fiber. There is a doping level at which the wavelength of zero dispersion is not sensitive to the exact level of doping. The factors involved in choosing a doping level are expounded.     

多碱光电阴极光电发射过程研究

论述了多碱阴极及光致荧光的特点,测量了多碱阴极在514.5 nm和785 nm波长激光激发条件下的荧光谱。结果表明,多碱阴极在514.5 nm波长激光激发条件下,荧光峰值强度比785 nm波长激光激发条件下荧光峰值强度强40倍,说明514.5nm波长的电子跃迁几率低于785nm波长的电子跃迁几率,同时514.5 nm波长激光激发的荧光峰值波长为860 nm,而785 nm波长激光激发的荧光峰值波长为870 nm,514.5 nm波长激光激发的荧光峰值波长与激发光波长的偏移为345 nm,而785 nm波长激光激发的荧光峰值波长与激发光波长的偏移仅为85 nm,说明514.5 nm波长激发的跃迁电子的能量损失远大于785nm波长激发的跃迁电子的能量损失。原因是短波光子的能量较高,所激发的跃迁电子来源于较深能级,因此能量损失较大。多碱阴极的量子效率在2.11 eV达到最大,当光子的能量大于2.11 eV以后,由于跃迁电子的能量损失随光子能量的增加而增加,因此多碱阴极的量子效率随光子能量的增加而减小。多碱阴极的量子效率与电子跃迁几率成正比,但实测的量子效率曲线与电子跃迁几率曲线的峰值波长不一致,原因是随着光子能量的增加,跃迁电子的能级也增加,当电子跃迁的几率达到最大并下降时,尽管跃迁电子的几率减小,但因电子跃迁的能级还在提高,因此量子效率仍在增加。只有当跃迁几率的因素超过能级的因素以后,量子效率才随光子能量的增加而减小,因此造成量子效率曲线的峰值波长与跃迁几率的峰值波长不一致。通过多碱阴极光致荧光谱的分析,揭示了多碱阴极电子跃迁过程中的客观规律,解释了多碱阴极量子效率在达到最大值之后,量子效率随光子能量增加而减小以及多碱阴极量子效率存在短波限的原因。     

Dependence of cross-phase modulation on channel number in fiber WDMsystems

The phase term appearing in the expression for cross-phase modulation due to the optical Kerr effect depends on the sum of the powers carried by each wavelength channel. For this reason, one might expect that the amount of cross-phase modulation would increase with increasing channel number, causing increased interference among channels and hence limiting the total number of channels that a WDM system can support. However, computer simulations of multichannel systems have shown no change in signal distortion as the number of wavelength channels is increased from four to eight. In a simulated three-channel system, the signal distortion of the central channel approaches that of a single-channel system as the wavelength separation is increased to approximately 2 nm. Thus, even a moderate amount of dispersion tends to cancel out the influence of cross-phase modulation, so that beyond a certain wavelength spacing, additional channels do not interfere with the channel under consideration. From these observations, we conclude that cross-phase modulation does not limit the number of wavelength channels that a single optical fiber can support. However, self- and cross-phase modulation are not the only nonlinear effects influencing fiber lightwave systems. Stimulated Raman scattering tends to transfer optical power from short-wavelength channels to channels operating at longer wavelength, degrading their signal-to-noise ratio. The efficiency of this process increases with increasing wavelength spacing. Clearly, a compromise needs to be reached between the conflicting requirements imposed by the optical Kerr effect and by stimulated Raman scattering