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  • Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences  (1,646)
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  • Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences  (1,646)
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  • 1
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2009
    In:  Acta Physica Sinica Vol. 58, No. 3 ( 2009), p. 1793-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 58, No. 3 ( 2009), p. 1793-
    Abstract: The characteristics of co-doping Al3+ in ytterbium-doped silica-based fiber used for high-power cladding pumped laser were analyzed based on experimental analysis. The results show that the optimum mole percent of Al3+ to Yb3+ is 9—11 for high concentration of ytterbium-doped silica-based fiber at which low concentration quenching probability, high absorption coefficient and proper numerical aperture can be obtained. Meanwhile, ytterbium-doped silica-based fiber preforms were fabricated by MCVD and special solution doping technique. By soot layer temperature experiment and test of the related parameters of the drawn fiber, the results show that the optimum temperature for making soot layer can be accurately controlled and the absorption coefficient at 976 nm was as high as 620 dB/m with good repeatability. This conclusion makes a useful reference for fabrication of ytterbium-doped Al3+ co-doped fiber.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2009
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  • 2
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 53, No. 2 ( 2004), p. 406-
    Abstract: Preliminary results for the generation and application of the high power ion beam(HPIB) on the FLASH Ⅱ accelerator are reported. The structure and principle of the pinch reflex ion beam diode are introduced. The equation of parapotential flow is corrected for the reduction of diode A-K gap due to the motion of cathode and anode plasma. The HPIB peak current of ~160kA is obtained with a peak energy of ~500keV. Experimental investigations of generating 6—7MeV quasi-monoenergetic pulsed γ-rays with high power ion(proton) beams striking 19F target are presented. In addition, the results of the thermal-mechanical effects on the material irradiated with HPIB, which are applied to the simulation of 1keV black body radiation x-rays, are also discussed.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2004
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  • 3
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2018
    In:  Acta Physica Sinica Vol. 67, No. 8 ( 2018), p. 084102-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 8 ( 2018), p. 084102-
    Abstract: China Academy of Engineering Physics terahertz free electron laser (CAEP THz FEL,CTFEL) is the first THz FEL oscillator in China,which is jointly built by CAEP,Peking University and Tsinghua University.It is designed as a high-repetition-rate and high-duty-cycle linac-based FEL facility. This THz FEL mainly consists of a gallium arsenide (GaAs) photocathode high-voltage direct current (DC) gun,a superconducting radio frequency (RF) linac,a planar undulator,and a quasi-concentric optical resonator. The DC gun provides a high-brightness electron beam with the bunch charge of about 100 pC and the repetition rate of 54.167~MHz.The normalized emittance of the electron beam is less than 10m,and the energy spread is less than 0.75%.A 24-cell superconducting RF accelerator provides an effective field gradient of about 10 MV/m and energizes the electron beam to 6-8~MeV.The beam then goes through the undulator and generates the spontaneous radiation,which is reflected back and forth in the optical resonator and then stimulated by the electron beam. The first stimulated saturation of CTFEL in the macro-pulse mode was obtained in August,2017.In this paper,the THz spectrum is measured by a Fourier spectrometer (Bruker VERTEX 80 V).The macro-pulse energy is measured by an absolute energy meter from Thomas Keating Instruments.The longitudinal beam length is preliminarily calculated by the auto-correlation curve from the time-domain signal of the spectrometer.The macro-pulse duration is captured by a GeGa cryogenic detector from QMC Instrument.The measurement results indicate that the terahertz laser frequency is continuously adjustable from 2 THz to 3 THz.The macro-pulse average power is more than 10 W and the micro-pulse power is more than 0.3 MW.The single-pass gain is larger than 2.5%. This facility is now working in macro-pulse mode in the first step,also called step one.The minimum macro-pulse duration is about 50s and the maximum is about 2 ms.The macro-pulse repetition is 1 Hz or 5 Hz.The typical pulse duration and repetition rate are 1 ms and 1 Hz,respectively.In the middle of 2018,the duty cycle will upgrade to more than 10% as step two.And the continuous wave (CW) operation will be obtained in step three by the end of 2018.The spectrum adjustment range will also be expanded to cover from 1 THz to 4 THz by then. Some application experiments have been carried out on the platform of CTFEL.This facility will greatly promote the development of THz science and its applications in material science,chemistry science,biomedicine science and many other cutting-edge areas in general.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2018
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  • 4
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2005
    In:  Acta Physica Sinica Vol. 54, No. 9 ( 2005), p. 4072-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 54, No. 9 ( 2005), p. 4072-
    Abstract: The preliminary experimental results obtained for the energy spectra of high-power ion beam(HPIB) with a pile of thin films on FLASH Ⅱ accelerator are reported. Code was developed to calculate the theoretical energy-loss of proton and C ion beams transmited through the Mylar films with different thickness. T he apertures of Faraday Cups are covered with Mylar films of different thicknes s, and then the signal attenuations can be recorded with oscilloscope. The energ y spectra of HPIB and the diode voltage are obtained according to the signal al lenuations. The diode voltage measured with a pile of thin films agrees with the voltage measured with a differential ring. And the ion number versus time curv e was given. In addition, the ion energy of HPIB is also measured with Thomson spectrometer and time of flight method and the results agree with those measured with a pile of thin films.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2005
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  • 5
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 71, No. 10 ( 2022), p. 104206-
    Abstract: The rapid growth of the demand for optical communication capacity promotes optical fiber communication technology. As a method to break through the capacity limitation of conventional single-mode fiber, multi-core fiber based on space division multiplexing technology has attracted extensive attention. In order to respond to the capacity of traditional single-mode fiber positively, we design a scheme of single-mode multi-core fiber combining the arrangement of heterogeneous fiber cores with secondary structure of low refractive index trench. The scheme consists of nineteen fiber cores arranged in a hexagonal closed-packed structure. Heterogeneous trench-assisted multi-core fiber (Hetero-TA-MCF) has low inter-core crosstalk and excellent anti-bending performance. Compared with conventional single-mode fiber, the Hetero-TA-MCF has the large transmission capacity and average effective area of each core of about 80 μm〈sup〉2〈/sup〉. The transmission capacity of 19 cores is equivalent to the sum of the transmission capacities of 19 single-core single-mode fibers. We use COMSOL Multiphysics to simulate the fiber structure, finding the parameters that affect the properties of the fiber, selecting parameters and structures for optimal performance. Then we calculate the transmission characteristics by the finite element method,and the results of substantive simulating compute are as follows. The Hetero-TA-MCF achieves a low inter-core crosstalk (XT) of about –39 dB/100 km so that each core can be transmitted as a separate channe. It meets the standard of multi-core fiber long distance transmission. The XT of the heterogeneous 19-core single-mode fiber is suitable for multi-core fiber long distance transmission standards. The bending loss of the outermost fiber core is –7.7×10〈sup〉–5〈/sup〉 dB/m when the bending radius is 10 cm, which reflects the low loss characteristics of the structure. The nonlinear coefficients of three kinds of core are 1.28 W〈sup〉–1〈/sup〉·km〈sup〉–1〈/sup〉, 1.31 W〈sup〉–1〈/sup〉·km〈sup〉–1〈/sup〉, and 1.30 W〈sup〉–1〈/sup〉·km〈sup〉–1〈/sup〉 respectively, reducing the nonlinear effect of optical fiber effectively; the dispersions of three kinds of cores are less than 24 ps/(nm·km). In addition, the steady single-mode transmission is achieved in 〈i〉C〈/i〉+〈i〉L〈/i〉 band. Compared with traditional single-mode fiber and single-trench homogeneous fiber, the proposed fiber in this work has low crosstalk, good bending resistance and large mode field area, which is suitable for long distance and large capacity transmission in space division multiplexing system.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2022
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  • 6
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 71, No. 4 ( 2022), p. 044206-
    Abstract: A broadband mode-division multiplexer based on asymmetric three-core photonic crystal fiber is proposed in this paper. The device is mainly composed of a central core, which can provide the transmission of fundamental mode and higher-order mode, and two side cores providing fundamental mode transmission. According to the theory of optical coupling, the LP〈sub〉01〈/sub〉 mode light is input to the three fiber cores at the initial port separately, and in the transmission process the LP〈sub〉01〈/sub〉 mode on the left side core will be coupled and converted into the LP〈sub〉21〈/sub〉 mode light in the central core gradually. Similarly, the LP〈sub〉01〈/sub〉 mode of the right side core is transformed into the LP〈sub〉31〈/sub〉 mode of the center core. By optimizing the structural design and selecting the length of optical fiber, the best conversion from side core into central core can be completed at the output end simultaneously, thereby realizing the multiplexing of LP〈sub〉01〈/sub〉, LP〈sub〉21〈/sub〉 and LP〈sub〉31〈/sub〉 modes in the central core. In the opposite direction, if the output end of the device is used as the initial port, the demultiplexing of three modes of light from the central core to the three cores can be realized. In thiswork, the finite element method and beam propagation method are used to optimize the simulation, and the optical coupling theory and supermode theory are combined to conduct analysis and calculation. The results show that at wavelength band from 1.49 μm to 1.63 μm, the maximum insertion loss of the device is 0.72 dB, and the lowest insertion loss is 0.543 dB at 1.55 μm, which is far lower than the general evaluation standard of 1 dB insertion loss. The low insertion loss also makes it possible to design cascaded multi-core photonic-crystal-fiber mode-division multiplexer. Compared with the existing mode-division multiplexing scheme, the device is more integrated and less affected by the external environment. When it is used with multi-core space division multiplexing fiber, it can better improve the mode-conversion efficiency and mode purity, reduce the coupling complexity and expand the communication capacity.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2022
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  • 7
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 10 ( 2016), p. 108501-
    Abstract: In recent decades, infrared (IR) detection technology has been widely used in many fields such as weather monitoring, environmental protection, medical diagnostics, security protection, etc. With the progress and mature of the technologies, more attention has been paid to the imaging detections of weak IR signals. So the higher efficiency of the device is required. Moreover the next-generation IR photodetection technology focuses on large-scale, high-speed and low-dark-current imaging. The mechanical bonding between infrared detector chip and silicon readout circuit inevitably causes a thermal mismatch problem. Up-conversion IR photodetectors can solve the problem about the performance deterioration of photodetector and the thermal mismatch with silicon-based readout circuit, hence they have great advantages in realizing large-format focal plane array detection.However, the poor light extraction efficiency due to total reflection severely restricts the overall efficiency of the up-conversion device, which has become one of the bottlenecks to improve the device efficiency. In this paper, surface microstructures with micro-pillar morphology are designed and fabricated on quantum-cascade up-conversion IR photodetectors. The effect on the up-conversion efficiency is investigated by enhancing the light extraction efficiency.Firstly, by the optical ray retracing method, the influence of surface microstructure on light extraction efficiency is studied when considering different morphology parameters, and optimized surface microstructure is designed to possess a pillar base length of 150 nm, height of 105 nm and side wall angle of 75.Then based on the results of simulation, up-conversion IR photodetectors with surface microstructures are fabricated using polystyrene nanospheres as mask. The self-assembled monolayer nanospheres are first etched to a proper size by using O2 plasma, then the patterns are transferred to SiNx film, which acts as an ICP dry etching mask of the micro-pillars. Finally, the up-conversion device and a silicon detector are together loaded on a cold finger of a cryogenic dewar. The characteristics of the up-converter and up-conversion system are evaluated using a blackbody source.The experimental results show that the devices with and without surface microstructure exhibit similar IR responses and dark currents, while the emission of device with microstructure is obviously increased. Taking into consideration other factors related to external quantum efficiency, the light extraction efficiency of the device with micro-pillar structure on surface can be increased by up to 130%. Therefore it can be concluded that this method is an efficient way to improve the efficiency of up-conversion IR photodetector. The finding in this paper can also be applied to other semiconductor device with light extraction efficiency.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2016
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  • 8
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2009
    In:  Acta Physica Sinica Vol. 58, No. 10 ( 2009), p. 6703-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 58, No. 10 ( 2009), p. 6703-
    Abstract: We used random matrix theory (RMT) to remove the noises in lung cancer gene expression data and used the modules approach and the hierarchical clustering approach to construct the gene networks. Comparing the results given by the two methods, we found that RMT-hierarchical clustering method gives true modules as well as the correlations between the modules. The results indicate that RMT-hierarchical clustering method is an effective new method for identifying gene networks.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2009
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  • 9
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 63, No. 15 ( 2014), p. 154210-
    Abstract: We demonstrate an approach for triangular-shaped pulse train generation experimentally based on harmonic fitting. The operation principle is that a Mach-Zehnder modulator is firstly employed to suppress modulation of the optical carrier. Thus a periodically variable lightwave can be obtained at the output. Then the signal is coupled into a section of dispersive fiber. Due to the dispersion-induced power fading, the undesired 4th order harmonics in the optical intensity can be fully removed. By adjusting modulation index to an optimum value (m=2.305), the generated harmonics of the optical intensity can be made corresponding to the Fourier components of typical periodic triangular pulses. Finally, the triangular-shaped pulse train at a repetition rate two times of the driving frequency can be obtained. In the experiments, 19.724 Gb/s and 15.356 Gb/s triangular-shaped pulse trains are generated by using 9.862 GHz and 7.678 GHz driving signals respectively. Besides, the repetition rate can be switched to another value by using a different fiber dispersion ( 2L). It is found that the experimental data agree well with theoretical results.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2014
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  • 10
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 73, No. 3 ( 2024), p. 037803-
    Abstract: Up-conversion nanoparticle (UCNP) can collect near-infrared (NIR) light and convert it into visible light. Therefore, UCNP has potential applications in fields such as biomedicine, anti-counterfeiting, and solar cells. However, the efficiency of traditional UCNP in the above-mentioned fields is relatively low, greatly limiting its use in related fields. Therefore, enhancing the up-conversion luminescence intensity of up-conversion nanoparticles is particularly important and urgently needed. In this work, anodic alumina templates are used to enhance the luminescence intensity of up-conversion nanocrystals. NaYF 〈 sub 〉 4 〈 /sub 〉 :Yb 〈 sup 〉 3+ 〈 /sup 〉 , Er 〈 sup 〉 3+ 〈 /sup 〉 with a diameter of 35 nm is prepared by using co-precipitation method. Single pass AAO templates with pore size and pore spacing of 88 nm and 100 nm are prepared by using two-step anodization method. Finally, NaYF 〈 sub 〉 4 〈 /sub 〉 :Yb 〈 sup 〉 3+ 〈 /sup 〉 , Er 〈 sup 〉 3+ 〈 /sup 〉 /AAO composite structures are formed by using spin coating method. The red green light emission intensity of NaYF 〈 sub 〉 4 〈 /sub 〉 :Yb 〈 sup 〉 3+ 〈 /sup 〉 , Er 〈 sup 〉 3+ 〈 /sup 〉 /AAO sample can increase 4.4 and 9.0 times that of NaYF 〈 sub 〉 4 〈 /sub 〉 :Yb 〈 sup 〉 3+ 〈 /sup 〉 , Er 〈 sup 〉 3+ 〈 /sup 〉 /Al reference sample, respectively. The enhancement mechanism is explored by using the finite difference time domain method, and the results show that the primary source of enhancement is the localized surface plasmon resonance effect of the pores in the anodic alumina template. At the same time, the relationship between the up-conversion luminescence intensity of NaYF 〈 sub 〉 4 〈 /sub 〉 :Yb 〈 sup 〉 3+ 〈 /sup 〉 , Er 〈 sup 〉 3+ 〈 /sup 〉 /AAO sample and the incident angle is investigated. The experimental results show that as the incident angle increases, the luminescence intensity of the red and green light of NaYF 〈 sub 〉 4 〈 /sub 〉 :Yb 〈 sup 〉 3+ 〈 /sup 〉 , Er 〈 sup 〉 3+ 〈 /sup 〉 /AAO samples first decrease and then increase. Due to the coupling of the local surface plasmon resonance with the excitation wavelength and emission wavelength, the up-conversion luminescence intensity of the sample can be affected. The relationship of AAO channel enhancement factor with incident angle at excitation wavelength and emission wavelength is studied by using the finite difference time domain method. The results indicate that as the incident angle increases, the enhancement factor at the excitation wavelength decreases, while the enhancement factor at the emission wavelength increases after being illuminated at an incident angle of 15°. Therefore, when the incident angle is less than 20°, the electric field intensity at 980 nm dominates, but when it is greater than 20°, the electric field intensity at 540 nm and 650 nm takes precedence. The above results provide a reference for putting them into practical applications in the fields of anti-counterfeiting and solar cells.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2024
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