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1.
秦伟平 《物理学进展》2011,20(2):93-167
反斯托克斯荧光制冷 (Anti StokesFluorescentCooling)也被称为激光制冷 (LaserCooling)。自 1 995年以来 ,该项研究取得了飞速的发展。目前 ,人们利用激光制冷的方法已经得到了比家用冰箱冷冻室还低的温度 ,并能够利用半导体量子阱材料得到低于液氮温区的降温。由于这项技术具有全光性 ,它的制冷器具有体积小、重量轻、无电磁辐射、无振动、无噪声等特点 ,因此也就具有了非常诱人的应用前景和符合军事、空间、集成光学、微电子、医学等领域的特殊要求 ,而被国外研究者所重视。做为一项基本技术 ,激光制冷研究的突破必然会导致许多对温度有特殊要求的高技术实用化 ,推动那些领域向前发展。本文详细地介绍了反斯托克斯荧光制冷研究的历史和最新进展 ,详细地介绍了该项研究中的方法和理论。着重介绍了激光制冷的热力学限制、发光过程的热力学理论 ,探讨激光制冷产生的机制和制冷理论。最后 ,对激光制冷器的发展前景和设计依据进行了讨论 ,尝试性地探讨了线圈型制冷器、用于芯片的制冷器和单分子 光子泵型制冷器的应用考虑。  相似文献   

2.
让相干原子束更像激光   总被引:2,自引:1,他引:1  
戴闻 《物理》1999,28(11):703-703
激光具有极佳的准直性以及随之而产生的无与伦比的聚焦性能.激光的应用遍及当今世界从高技术武器到摇滚音乐会场的各个领域.1995年,碱金属原子的玻色-爱因斯坦凝聚(BEC)实验获得成功.之后不久,理论物理学家就作出了预言,从超冷的BEC中可以发射像激光一样的相干原子束.1997年,麻省理工学院的Ketterle小组令相干原子流从捕获的BEC中“滴出”,获得了物质波激射的雏形.随后,德国马普量子光学所(慕尼黑)的TheodoreH¨ansch小组和美国耶鲁大学的BPAnderson等也分别做出了有…  相似文献   

3.
超导电性制冷唯象理论   总被引:3,自引:0,他引:3  
本文以超导热力学唯象为基础,讨论了有退磁效应和远退磁效应的两种I类超导体样品在外场从0增加到临界场HC(T)过程中所产生的制冷效应,我们发现:对于有退磁效应的样品,其制冷效应发生在中间态区;而从Meissner态到中间态和从中间态到正常态的相变过程是二级相为,所以无制冷效应,这可能是超导体制冷实验研究的核心问题。  相似文献   

4.
氦氖激光对链霉菌原生质体种间融合频率的影响   总被引:3,自引:0,他引:3  
采用双亲灭活原生质体融合技术对金霉素链霉菌(Streptomycesaureofaciens)和龟裂链霉菌(Streptomycesrimous)种间原生质体融合进行了研究,分别利用聚乙二醇(PEG)、HeNe激光以及PEG与HeNe激光混合诱导融合,结果表明:PEG及激光的双重诱导作用,使链霉菌原生质体种间融合频率得到显著提高.通过同工酶谱分析对融合子进行了初步鉴定.  相似文献   

5.
双温制冷装置的节能循环研究刘咸定(西安建筑科技大学环工系西安710055)林燧,王振义,曾昭曙(ConcordiaUniversity,Canada)关键词冷冻冷藏箱,节能,替代制冷剂1引言R12是应用最广泛的制冷工质,由于对臭氧层有破坏作用,即将淘...  相似文献   

6.
利用脉冲激光束与分子的相互作用,对CsI分子进行了光离解。同时,用另一束可调谐激光对CsI分子离解后产生的中性铯原子进行共振激发,然后把处在激发态的铯原子进行光电离。对Cs+的飞行时间质谱进行了分析,并对光离解及光电离过程中可能存在的多光子电离(MPI)进行了讨论。  相似文献   

7.
利用飞行时间质谱仪研究了CH3I分子在430~490nm激光作用下的多光子电离(MPI)离解过程和机制。得到了分子的飞行时间质谱,从整个实验波段430~490nm的MPI离子谱发现,短波的MPI离子谱峰相对较高,长波的MPI离子谱峰相对较宽而弥散,对MPI离子谱中的一些共振峰标识为分子的(5pπ,8s)(5pπ,6p)以及(5pπ,7s)里德堡态共振吸收峰。还标识了(5pπ,7s)里德堡态的系列振  相似文献   

8.
用Z扫描方法测量掺C60有机改良介质的非线性折射率   总被引:1,自引:0,他引:1  
用Z扫描方法和波长1.064μm、脉宽150ps的锁模激光测定了C60/NH2-(CH2)3-Si(OC2H5)3(简称C60/KH550)溶胶和凝胶的三阶光学非线性系数。理论拟合曲线计算得出,溶胶复合材料的非线性折射率n2=5.6×10-12esu,经两天凝结之后的凝胶复合材料的n2=6.2×10-12esu。在相同的激光强度下溶胶和凝胶的不同透过率归因于溶胶液体对激光的非线性散射。  相似文献   

9.
Na-Cs混合蒸汽中的碰撞能量合并已在[2]中研究过。当在池中充入缓冲气体后,碰撞过程出现新的特点,缓冲气体增大了Na(3P)和Cs(6S)间的能量转移,这可从测量由Na(3P)/Cs(6P)和Cs(6P)/Cs(5D)碰撞而被布居的高能级所发射的荧光得到证实。得到三体碰撞速率系数k3=5.9×10-27cm6s-1。  相似文献   

10.
郭文跃  方黎 《光学学报》1998,18(5):19-526
用多光子电离飞行时间质谱法三光子与丙酮分子3d形态和4s态共振的激光波长区域获得了丙酮分子的共振多光子电离分质量多光子电离(MPI)光谱和飞行时间质谱,实验观察到的主要产物是CH3CO^+和CH^+3,还观察到了少量的C^+,CH^+,CH^+2和CHO^+,在实验的激光波长范围内未见到母体离子,分质量多光子电离光谱具有相似的光谱结构,几个主要谐峰分别对应着(n0,3d)和(n0,4s)里德堡跃迁  相似文献   

11.
Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.  相似文献   

12.
A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.  相似文献   

13.
Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·104 Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.  相似文献   

14.
A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.  相似文献   

15.
The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.  相似文献   

16.
17.
We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.  相似文献   

18.
Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.  相似文献   

19.
A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.  相似文献   

20.
Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.  相似文献   

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