Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Design and calibration of hot-electron spectrometer array for angle-resolved measurement
No full textChinese Academy of Sciences [CXJJ-15S114]A hot-electron spectrometer array with two-dimensional distribution has been designed with a wide-angle range and high-energy resolution to measure the spatially resolved electron spectra for high-power-laser plasma interaction experiments. It consisted of 19 identical electron spectrometers set in three directions with an interval of 10 degrees. Each electron spectrometer was designed with a uniform magnetic field to detect electrons in the range from 20 to 500 keV. The spectrometers were calibrated using electrons from an accelerator. In an experiment, the spatially resolved electron energy spectra, which approximately had a Maxwell distribution, were obtained from an aluminum foil target irradiated by a 0.53-mu m m laser pulse. Published by AIP Publishing
Spectrally and angularly resolved measurements of three-halves harmonic emission from laser-produced plasmas
No full textNational Science and Technology Innovation Foundation of Chinese Academy of Sciences [CXJJ-15S114, CXJJ-16S042]Spectra of three-halves harmonic emissions (3 omega(0)/2) from laser-produced plasmas were measured at different angles, including both forward and backward sides, from the direction of incident laser beams. The 3 omega(0)/2 emitted from carbon-hydrogen (CH) targets was observed to be larger than that from aluminum (Al) targets with the same incident laser intensity, which supports the argument that the two-plasmon decay (TPD) instability could be inhibited by using medium-Z ablator instead of CH ablator in direct-drive inertial confinement fusion. Besides, the measured 3 omega(0)/2-incident intensity curves for both materials suggest relatively lower threshold of TPD than the calculated values. In experiments with thin Al targets, the angular distribution of the blue-and red-shifted peaks of 3 omega(0)/2 spectra were obtained, which shows that the most intense blue-and red-shifted peaks may not be produced in paired plasmons, but the spectra produced by their 'twin' plasmons were not observed. Because 3 omega(0)/2 may have been influenced by other physical processes during their propagation from their birth places to the detectors, the mismatches on emission angle, wavelength shift, and threshold may be qualitatively explained through the assumption that small-scale light filaments widely existed in the corona of laser-produced plasmas
1 J, 1 Hz lamp-pumped high-gain Nd: phosphate glass laser amplifier
No full textWe present a lamp-pumped Nd: phosphate glass laser amplifier delivering up to 1 J of pulse energy at 1053 nm with a repetition rate of 1 Hz and an injected pulse energy of 2.5 mJ. The amplifier system employs a beam-shaping module and a four-pass, lamp-pumped amplifier. The thermally induced wavefront distortion is mitigated and a uniform gain distribution is obtained by a four-lamp-pumped laser head in the amplifier. Thus, an excellent beam quality is obtained
Analysis of the thermal effects in diode-pumped Tm:YAG ceramic slab lasers
No full textNational Natural Science Foundation of China [61378069]; State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, DongHua University [LK1113]; Shanghai Municipal Education Commission [ZZGCD15082]Tm:YAG ceramics with a quasi-three-level system are sensitive to temperature. The optical and thermodynamic properties of Tm: YAG ceramics can change with changing temperature, and this affects the output power stability and beam quality of lasers. Thus temperature control is a key and difficult problem for Tm: YAG lasers, especially for high power laser output. In combination with slab structure and grad-doping techniques for composite ceramics, the temperature distributions of Tm: YAG ceramics are analyzed. It is found that the temperature difference of a rationally designed grad-doping Tm: YAG ceramic can be reduced significantly with the same absorption pump power, which results in higher output power and beam quality
Interference pattern period measurement at picometer level
No full textTo produce large scale gratings by Scanning Beam Interference Lithography (SBIL), a light spot containing grating pattern is generated by two beams interfering, and a scanning stage is used to drive the substrate moving under the light spot. In order to locate the stage at the proper exposure positions, the period of the Interference pattern must be measured accurately. We developed a set of process to obtain the period value of two interfering beams at picometer level. The process includes data acquisition and data analysis. The data is received from a photodiode and a laser interferometer with sub-nanometer resolution. Data analysis differs from conventional analyzing methods like counting wave peaks or using Fourier transform to get the signal period, after a preprocess of filtering and envelope removing, the mean square error is calculated between the received signal and ideal sinusoid waves to find the best-fit frequency, thus an accuracy period value is acquired, this method has a low sensitivity to amplitude noise and a high resolution of frequency. With 405nm laser beams interfering, a pattern period value around 562nm is acquired by employing this process, fitting diagram of the result shows the accuracy of the period value reaches picometer level, which is much higher than the results of conventional methods
Cyphertext-only attack on the double random-phase encryption: experimental demonstration
No full textWe demonstrate experimentally that the traditional double random phase encoding (DPRE) technique is vulnerable to the cyphertext-only attack (COA). With the statistical ergodic property of the speckle, we show that the plaintext image can be recovered from the cyphertext alone owing to the fact that their energy spectral density functions are identical. Our result reveals the most serious security issue with the DRPE as it suggests that even the one-time-pad does not guarantee its security. This will open up new inside understanding of current optical security techniques. (C) 2017 Optical Society of Americ
Polarization phase-shifting lateral shearing interferometer with two polarization beam splitter plates
No full textInternational Science & Technology Cooperation Program of China [2016YFE0110600]; International Science & Technology Cooperation Program of Shanghai [16520710500]; Youth Innovation Promotion Association CASWe proposed a compact and simple polarization phase-shifting lateral shearing interferometer using two polarization beam splitter plates (PBSP). This interferometer is composed of two PBSP, a quarter-wave plate, an analyzer and a CCD camera. With the two PBSP positioned in appropriate spatial positions, optical path difference compensation is achieved, which allows for the implement of aplanatic and common-path shearing interferometer. Therefore, the system possesses significant advantages of simple structure, compact and strong anti-interference ability. The effectiveness of the interferometer is demonstrated by simulations and experiments
Shearing interferometric electron beam imaging based on ptychographic iterative engine method
No full text提出了基于Mollenstedt电子双棱镜的电压扫描剪切干涉全场ptychographic iterative engine (PIE)显微成像技术.从低到高逐步改变电子双棱镜的电压,并同时记录所形成的剪切干涉条纹,待测样品透射电子束的强度和相位分布就可以用PIE算法得以快速重建,而且双棱镜的方向、位置和实际电场强度分布等诸多实验中不可避免地偏差都可以在迭代过程中自动得以更正.所提技术能够克服现阶段用电子束进行PIE成像的诸多技术困扰,从而有望推动PIE技术在电子显微成像领域的发展和应用.National Natural Science Foundation of China [11647144]; Natural Science Foundation of Jiangsu Province, China [BK2012548]Ptychographic iterative engine (PIE) method can provide high-resolution amplitude and phase distributions in short-wavelength imaging, such as electron beam and X-ray imaging. Traditional PIE relies on the sub field of view (sub-FoV) scanning, and the coincidence between these adjacent sub-FoVs is required in order to ensure the high accuracy in sample information retrieval. However, in the applications of electron beam imaging, attachments or contaminants on the sample surface will be dragged with the probe light during the sub-FoV scanning due to the adsorption of charges, and the inevitable attachment and contaminant shifting will change the probe light, therefore generating inconsistent probe light, and reducing the imaging resolution and accuracy, since the deteriorated probe light destroys the PIE scanning demands. In order to maintain the high resolution and accuracy in the electron beam imaging, the attachment and contaminant shifting during the sub-FoV scanning should be avoided. Here, a shearing interference based PIE using Mollenstedt biprism is proposed in this paper. Mollenstedt biprism is widely used in the electron beam imaging, and by applying the voltage to the wire, the generated electrical field can control the deflection of the electron beam, working similarly to a biprism modulating the wavefront passing through it. In the proposed approach, setting the Mollenstedt biprism after the sample, and changing the voltage on the Mollenstedt biprism, the beam deflection angle proportional to the added voltage can generate a series of interferograms with different fringe densities. Because the traditional sub-FoV scanning is replaced by wide-field scanning by changing the voltage on the Mollenstedt biprism, the proposed method can maintain the stable probe light, avoiding the inevitable attachment and contaminant shifting, and both the amplitude and phase can be retrieved from these interferograms by using a modified PIE algorithm. In order to verify the proposed PIE method, besides the theoretical analysis, numerical calculations are provided. The biprism phase distribution is adopted to simulate the electron beam deflection caused by the Mollenstedt biprism. Additionally, by changing the voltage on the wire, different biprism phase distributions are generated to produce various interferograms. By the modified PIE method, accurate amplitude and phase distribution within error less than 0.2% can be obtained through using less than 50 iterations, indicating a rapid convergence rate. Moreover, the errors in the imaging system, such as phase deviation, position shifting, and rotation are also quantitatively analyzed. Numerical computation proves that the direction of the biprism can be precisely determined according to the frequency distribution of the fringe, and the accurate sample information can still be retrieved even with a deviation of 30% in phase deviation and 30 mu m in position shifting, proving the deviations of the direction and position of the Mollenstedt biprism, as well as the phase distribution can be corrected automatically in the iterative process. Finally, the modified PIE relying on the lensfree configuration can reach the resolution of the diffraction limit in imaging similar to those PIE approaches. The proposed technique can overcome difficulties of current PIE in using electron beam, thus promoting the development and application of PIE in electron microscopy
Preparation of dibenzo-based two-photon materials and their basic research as biological probes
No full text本文以芴酮、二苯并噻吩和二苯并呋喃为中心共轭桥制备了10种未见报道的吡啶阳离子衍生物，研究了新化合物在N，N-二甲基甲酰胺(DMF)中的单光子光学性质，包括线性吸收光谱、荧光光谱和荧光量子产率。采用脉宽为120 fs、波长为800 nm和重复频率为1 kHz(Ti：蓝宝石激光器)的脉冲激光研究了新化合物的双光子光学性质，采用参比法计算了不同波长下新化合物在DMF溶液中的双光子吸收截面；研究了目标化合物和小牛胸腺DNA在Tris-HCl缓冲溶液中相互作用前后的吸收光谱、单光子荧光光谱和双光子荧光光谱变化。讨论了化学结构对新材料单、双光子光学性质和光开关效应的影响。 以新材料作为生物荧光探针染色小鼠成肌细胞3T3，利用德国Carl Zeiss LSM710激光共聚焦荧光显微镜对染色样品进行了单、双光子荧光成像研究。通过新材料与商用细胞核染色剂Hochest 33342的共染色成像实验，研究了新材料作为荧光探针的核定位能力；通过新材料与商用线粒体染色剂MTR的双染实验，研究了新材料在细胞多色标记方面的膜渗透性和复染相容性；研究了不同渗透深度下新材料与商用核定位剂DAPI在3T3细胞中的三维成像能力。在波长分别为800 nm和740 nm的双光子共聚焦激光的持续辐照下，研究了新材料和DAPI在3T3细胞中的双光子荧光强度随时间的变化趋势；比较和分析了从荧光发射到熄灭过程中新材料和DAPI的荧光持续时间、荧光衰减速率和荧光衰减幅度，讨论了化学结构对新材料光稳定性的影响。In this paper, a series of novel pyridine cationic deriatives containing fluorenone, dibenzothiophene and dibenzofuran as the central π-conjuated bridges were reported. The one-photon optical properties of new compounds in N,N-dimethylfomamide solution were studied, including linear absorption spectra, fluorescence spectra and fluorescence quantum yields. The two-photon optical properties of new compounds were studied by pulse laser (Ti: sapphire) with a pulse width of 120 fs, a wavelength of 800 nm and a repetition rate of 1 kHz. The two-photon absorption cross-sections of new compounds in DMF solution at different wavelengths were calculated by using the reference method; The absorption spectra, one-photon fluorescence spectra and two-photon fluorescence spectra of the target compounds and calf thymus DNA before and after the interaction in Tris-HCl buffer solution were studied. The influence of chemical structure on the one and two-photon optical properties and fluorescence “off-on” effects of new materials were discussed. The new materials were used as biological fluorescent probes to stain the 3T3-Swiss albino cells, and the one and two-photon fluorescence imaging experiments were performed with the Zeiss LSM710 Carl laser confocal fluorescence microscope. The nuclear localization ability of the new materials were studied by the co-staining experiment between the new material and the commercial nuclear staining reagent Hochest 33342; The membrane permeability and the counterstain compatibility of the new materials in multicolor cell labeling application were studied by means of the double-staining experiments between the new materials and the commercial mitochondrial dye MTR; Three dimensional imaging capabilities of new materials and commercial nuclear staining agent DAPI in 3T3 cells under different penetration depths were studied. Under continuous irradiation at wavelengths of 800 nm and 740 nm, respectively, the change trends of the time-dependent two-photon fluorescence intensity of new materials and DAPI in 3T3 cells were studied; the fluorescence duration, fluorescence decay rate and fluorescence decay amplitude of new materials and DAPI were compared and analyzed, and the influences of chemical structure on the photostability of new materials were also discussed
Emission properties of 1.8 and 2.3 mu m in Tm3+-doped fluoride glass
No full textChinese National Natural Science Foundation [61605192, 51372235, 51401197]; Zhejiang provincial Natural Science Foundation of China [LR14E020003]; International S&T Cooperation Program of China [2013DFE63070]In this work a Tm3+-doped fluoride glass with good thermal stability is prepared. Intensive 1.8 and 2.3 mu m emissions are obtained when pumped by an 800 nm laser diode. And the 1.48 mu m emission is limited because of the much strong radiation around 1.8 mu m. On the basis of absorption spectrum, radiative properties are investigated and discussed according to Judd-Ofelt parameters (Omega(2), Omega(4), Omega(6)) calculated by Judd-Ofelt theory. Besides, absorption and emission cross-sections of (3) F (4) -> (3) H (6) transition are figured out and analyzed by using McCumber and Beer-Lambert theories. The high gain around 1.8 mu m was predicted by the large sigma(emi)tau(rad) product (29.8 x 10(-21) cm(2) ms). The results obtained indicate that the Tm3+-doped fluoride glass can be a promising 2.0 mu m laser glass material