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  • 1
    Online Resource
    Online Resource
    Education Mode Promoted 〈i〉via〈/i〉 Non-Standard-Answer Examination:Taking General Chemistry as an Example
    Acta Physico-Chimica Sinica & University Chemistry Editorial Office, Peking University ; 2018
    In:  University Chemistry Vol. 33, No. 11 ( 2018), p. 53-61
    Details
    In: University Chemistry, Acta Physico-Chimica Sinica & University Chemistry Editorial Office, Peking University, Vol. 33, No. 11 ( 2018), p. 53-61
    Type of Medium: Online Resource
    ISSN: 1000-8438
    URL: Article
    DOI: 10.3866/PKU.DXHX201802009
    Language: English
    Publisher: Acta Physico-Chimica Sinica & University Chemistry Editorial Office, Peking University
    Publication Date: 2018
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  • 2
    Online Resource
    Online Resource
    Scaling fractal-lattice franctance approximation circuits of arbitrary order and irregular lattice type scaling equation
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2018
    In:  Acta Physica Sinica Vol. 67, No. 7 ( 2018), p. 070202-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 7 ( 2018), p. 070202-
    Abstract: Although Carlson fractal-lattice fractance approximation circuit belongs to the ideal approximation, it can only have operational performance of fractional operator of negative half-order. When series of this circuit increases, the approximation benefit decreases. Even though the fractance approximation circuit of -1/2n (n is an integer greater than or equal to 2) order can be obtained by using nested structures, the structure of this kind of circuit is complicated and fractional operation of arbitrary order cannot be achieved by this circuit. The Liu-Kaplan fractal-chain fractance class, which can be regarded as scaling extension circuits of the Oldham fractal-chain fractance class, has high approximation benefit and can realize operational performance of arbitrary fractional order. Based on analogy, arbitrary order scaling fractal-lattice franctance approximation circuits of high approximation benefit and corresponding lattice type scaling equation can be achieved through respectively making scaling extension to the Carlson fractal-lattice franctance approximation circuit and its normalized iterating equation. There exists the possibility to verify the validity of this scaling extension and scaling fractal-lattice fractance approximation circuits with operational performance of arbitrary order in different ways, including the transmission parameter matrix algorithm, the iterating matrix algorithm and the coefficient vector iterating algorithm. Arbitrary order scaling fractal-lattice franctance approximation circuits can be realized by adjusting both the resistance progressive-ratio and the capacitance progressive-ratio parameters. The approximation benefit of scaling fractal-lattice franctance approximation circuit of arbitrary order is determined by both the scaling factor and the circuit series. The introduced extension benefit function is to be used in performance analyses. Besides, performance comparisons have been made between the Carlson fractal-lattice franctance approximation circuit of five series and the scaling fractal-lattice franctance approximation circuit of negative half-order. With the increasing of the value of the scaling factor, approximation efficiency of the scaling fractal-lattice franctance approximation circuits gradually increases, which are higher than those of the Carlson fractal-lattice franctance approximation circuits. The Carlson fractal-lattice franctance approximation circuit and the scaling fractal-lattice franctance approximation circuit of five series are designed to be used in the active differential operational circuit of half-order to construct experimental testing systems. The approximation performances of both circuits are investigated from the aspects of order-frequency characteristic and F-frequency characteristic. The approximation performance of the scaling fractal-lattice franctance approximation circuit outperforms that of the Carlson fractal-lattice franctance approximation circuit. As the successful application case, the active differential operational circuit designed by the scaling fractal-lattice franctance approximation circuit is used to do the half-order calculus of triangular and square wave signals. This paper is merely an incipient work on scaling fractal-lattice franctance approximation circuits of arbitrary order and irregular lattice type scaling equations.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.67.20171671
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2018
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  • 3
    Online Resource
    Online Resource
    Scanning broadband optical parametric chirped pulse amplification based on optical beam deflection
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2019
    In:  Acta Physica Sinica Vol. 68, No. 2 ( 2019), p. 024205-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 68, No. 2 ( 2019), p. 024205-
    Abstract: One of the goals pursued in laser pulse is to achieve a laser with a shorter duration and higher intensity. In the past two decades, the laser pulse duration has been shortened by more than 7 orders of magnitude due to the development of Q-switched, Mode-locked and pulse compression technology. The peak power of laser pulse has been increased to PW, even EW and ZW from initial MW with the development of pulse amplification technology, whose focused intensity can reach to 10〈sup〉23〈/sup〉 W/cm〈sup〉2〈/sup〉. Thus, it provides unprecedented extreme conditions, and speeds up the laser applications in ultrafast nonlinear optics, strong field physics, fast ignition of laser nuclear fusion, optic communication, etc. The optical parametric chirped pulse amplification (OPCPA) is one of the important technologies in ultra-short laser pulse field. It is of great significance to increase the gain bandwidth for improving the conversion efficiency of OPCPA and achieving broadband optical parametric amplification. Combining the optical beam deflection and non-collinear OPCPA, a novel scanning broadband OPCPA model is proposed based on the optical beam deflection. The basic principle of increasing the gain bandwidth for the scanning broadband OPCPA is analyzed theoretically, which ensures the phase matching of each frequency component of signal by optical beam deflecting to change the non-collinear angle constantly. Namely, the non-collinear angles of incident frequency components of signal are different from each other, which, however, makes the whole phase matching of signal, i.e. momentum conservation in optics. The optical parametric amplification of signal pulse with 800 nm central wavelength and almost 100 nm bandwidth is simulated numerically by the proposed scanning broadband OPCPA. The results show that the bandwidth after being amplified is almost the same as before and there is no spectral narrowing, and the scanning broadband OPCPA increases the gain bandwidth and conversion efficiency greatly compared with the amplification with a constant given non-collinear angle, which leads to broadband optical parametric amplification. Finally, it is necessary to make sure that the on-load voltage to the KTN crystal matches with the frequency of signal pulse in time and reduces the unfavorable voltage deviation and time-delay for the maximizing gain bandwidth and conversion efficiency and ensuring the phase matching of each signal frequency component. The results of this paper not only provide an approach to increasing the gain bandwidth of OPCPA, but also supply some theoretical references and the basis for the experimental work of OPCPA in ultra-short laser pulse system.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.68.20181538
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2019
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  • 4
    Online Resource
    Online Resource
    Ultrafast azimuthal beam smoothing scheme based on vortex beam
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2019
    In:  Acta Physica Sinica Vol. 68, No. 2 ( 2019), p. 024207-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 68, No. 2 ( 2019), p. 024207-
    Abstract: The illumination uniformity of laser beams in inertial confinement fusion (ICF) facility is a key factor, which plays a crucial role in suppressing the laser plasma instabilities. However, the prevailing beam smoothing techniques cannot meet all the requirements for improving the irradiance uniformity of laser beams and mitigating the laser plasma instabilities, which are determined by the high-frequency spatial modulations and the fine-scale speckles of the focal spots. An ultrafast azimuthal beam smoothing scheme based on vortex beams is proposed in this paper. In this scheme, two of the four beams in a laser quad are transformed from super-Gaussian (SG) beams into vortex beams by inserting two spiral phase plates with opposite topological charges into the beam path, whereas the other two SG beams remain unchanged. By controlling the polarization and the center wavelength of each beam, the SG beam and the transformed vortex beam in the quad are coherently superposed on the target plane, so are the remaining two beams. Owing to the difference in central wavelength and the existence of the topological charges, two focal spots rotating in a period of a few picoseconds are generated in the target plane, which can redistribute the speckles quickly in temporal domain and thus improve the irradiance uniformity of the laser quad. By establishing the physical model of the azimuthal smoothing scheme, the smoothing characteristics including the rotation period, the illumination uniformity and the fractional-power-above-intensity of the focal spots are analyzed in detail. In order to improve the smoothing characteristics significantly, the novel smoothing scheme is further combined with another ultrafast smoothing scheme, i.e. radial smoothing scheme. The influence of the key parameters of the combined smoothing scheme on the illumination uniformity and on the smoothing velocity are discussed. Results indicate that the azimuthal smoothing scheme can achieve the ultrafast smooth of the laser quad in the azimuthal direction and the best illumination uniformity within a few picoseconds as well. Though the degree of improvement in the irradiance uniformity of the azimuthal smoothing scheme is lower than that of the radial smoothing, the combination of these two schemes can improve the uniformity effectively and rapidly. The novel smoothing scheme provides a potential smoothing approach for the high-power laser facilities.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.68.20181361
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2019
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  • 5
    Online Resource
    Online Resource
    A single-element interferometer for measuring parallelism and uniformity of transparent plate
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2017
    In:  Acta Physica Sinica Vol. 66, No. 6 ( 2017), p. 069501-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 66, No. 6 ( 2017), p. 069501-
    Abstract: The transparent plates (such as organic glass, plastic plate) are widely used in the construction industry, high-tech products and scientific research applications, and its parallelism and uniformity measurement in the manufacture and quality control become more and more inevitable. Interferometer is a label-free, high-precision, and high-efficient device that can be used in many fields. According to a single-element interferometer, we demonstrate a measurement for the parallelism and uniformity of transparent medium. Beam-splitter cube is a key component. Half of plane wave laser source passes through the measured medium and the remaining half directly passes through the air, then these two halves with different optical paths meet in the beam-splitter cube. The parallelism or uniformity is determined by calculating interference fringe shift number during rotating the measured sample. The coherent beam is divided into two parts by a beam-splitter, one passes through the lens and then arrives at a photoelectric counter, and the other arrives at the observation plane of the charge-coupled device. The photoelectric counter is used to count the integer part of fringe shift number during rotating the sample; and the decimal part can be detected by calculating the phase difference of the two interferograms captured before and after rotation. The measurement principle of the proposed device is analyzed in detail, and the numerical simulations of the fringe shift number and the gray level changing with the sample rotation angle, the thickness and the refractive index of the sample are carried out. The simulation results show that the bigger the rotation angle, thickness and refractive index of the sample, the greater the fringe shift number will be. Therefore, the measurement accuracy can be improved by increasing the rotation angle and the thickness of the sample. In addition, we also simulate the measurement processes of two kinds of samples, which are unparallel and inhomogeneous transparent plates. The simulation results prove the feasibility and high accuracy of the proposed method. Finally, the optical experiment is conducted to demonstrate the practicability of the present device. The parallelism of a cuvette used for more than one year, is tested by our device. The results show that the difference in thickness between the cuvettes is on a micron scale, the peak-valley (PV) value is 9.92 m, and the root mean square (RMS) value is 2.2 m. And the difference between the contrast test results and the results from the proposed method is very small, the PV value is 0.569 m, and the RMS value is 0.131 m. The stability and repeatability of the proposed setup are tested in the experimental condition. The mean value and standard deviation of the fringe shift number during 30 min are 0.0012 and 0.0008, respectively. These results further testify the high accuracy and stability of our method. In conclusion, the performance of our measurement method is demonstrated with numerical simulation and optical experiment.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.66.069501
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2017
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  • 6
    Online Resource
    Online Resource
    Fiber modal content analysis based on spatial and spectral Fourier transform
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2016
    In:  Acta Physica Sinica Vol. 65, No. 15 ( 2016), p. 154202-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 15 ( 2016), p. 154202-
    Abstract: As is well known, a typical measure of the quality of an optical beam is the M2 parameter, but characterizing the beam quality only by M2 is insufficient. A low value of M2 is generally considered to be equivalent to the single-mode operation with a stable beam. However, even when a large amount of power is contained in high-order modes, the existence of a low value of M2is still possible. Hence, a low value of M2 does not guarantee the single-mode operation. Therefore, a new measurement technique, which aims at measuring modal content of high power fiber laser, is proposed and demonstrated in this paper. This method is named spatial and spectral Fourier transform, or F2 transform in short, and it is based on measuring Fourier transform of both spatial domain and spectral domain of output laser. The experimental set is simple in structure and high in robustness. Another advantage of the method is that it requires no prior detailed knowledge of the fiber properties. In this paper, the patterns of the high-order modes between and after Fourier transform are simulated. From the graph it is evident that the energy of spot diffuses outward and is convenient to measure. We also simulate and compare the group delay difference curve of F2 with existing S2, which are well matched with each other. Experimentally, the high-order modes are stimulated by extruding the fiber periodically, which ensures that we can measure it. Firstly, by scanning two-dimensional (2D) pattern of beam after spatial domain Fourier transform and recording the experimental data, and then through the Fourier transform of data in spectral domain, the group delay differences between the high-order modes and the fundamental mode can be obtained. Finally, different modes in spatial domain are reconstructed and the relative power of every mode is calculated. Additionally, we set up an automatic measuring device to verify the effectiveness of the method. The reconstructed modal patterns are presented in the final section of this paper. We can clearly identify the fundamental mode and the high-order modes, such as LP01, LP02, LP03, LP21, LP11, LP12, LP13 and LP14. It reconfirms that this method is feasible. Compared with the S2 method, this method reduces the requirement for precision of mobile platform greatly and thus it is suited to measure the modal content of high power fiber laser output beam. This technique can be effectively applied to a wide variety of measurements, such as dispersion compensator of large-mode-area fiber, bend loss measurement of the high-order modes, refractive index profiles measurement of fiber and mode convertor fiber.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.65.154202
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2016
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  • 7
    Online Resource
    Online Resource
    Graphene-based broadband all-optical spatial modulator
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2018
    In:  Acta Physica Sinica Vol. 67, No. 21 ( 2018), p. 214201-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 21 ( 2018), p. 214201-
    Abstract: In this paper, the all-optical spatial modulation of monolayer graphene-coated microfiber is proposed. Graphene is used as a saturable absorber wrapped on the microfiber produced by heating the carbon dioxide laser. When the signal light travels along the microfiber, part of the light will pass along the surface of the microfiber in the form of an evanescent field, and it will be absorbed by the graphene. Simultaneously we shoot the 808 nm pump light into the micro-nanofiber wrapped by the graphene vertically from the space. According to graphene characteristic of preferential absorption, the absorption of the signal light is controlled by the pump light, thus the broadband all-optical space modulation is realized. In a conventional graphene microfiber all-optical modulator, signal light and pump light are generally input into a microfiber via a coupler. However, the mode of operation of pump light and graphene in all-optical spatial modulation are different from those of the traditional modulation, the pump light works on the graphene outside the microfiber, which realizes the separation of the pump light and the signal light. The output signal does not need to be optically filtered for the pump light to obtain the modulated signal. The output signal light of the spatial all-optical modulator has the characteristics of “clean”. We also verify this in experiment. In addition, the pump light is vertically incident from space, the effect of the graphene length on the modulation is not considered and the modulation time is only related to the relaxation time of graphene, which is helpful in improving the response time. Modulation experiments include static spectral modulation and dynamic frequency modulation. In the static spectral modulation, the broad spectrum signal has a maximum modulation depth of 6 dB at 1095 nm when the pump power is 569 mW. The relationship among pump power, wavelength and modulation depth is also analyzed. The higher the pump power, the higher the modulation depth will be; with the same pump power, the modulation depth of long wave length is higher than that of short wave. In the dynamic modulation experiment with the modulation bandwidth~50 nm and the modulation rate~1.5 kHz, the influence of pump light and signal light on output dynamic signal are studied, the feasibility of all-optical space modulation based on graphene is verified experimentally. The composite waveguide of all-optical spatial modulator opens the door to micro-nano ultrafast signal, processing in a more flexible and efficient way.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.67.20180307
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2018
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  • 8
    Online Resource
    Online Resource
    Analysis of wavelength dependence of mode in high power fiber laser
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2017
    In:  Acta Physica Sinica Vol. 66, No. 19 ( 2017), p. 194202-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 66, No. 19 ( 2017), p. 194202-
    Abstract: High power fiber lasers and amplifiers are widely used in the scientific and industrial field. In order to meet the requirements for high output powers the effective area of fibers becomes larger and larger to reduce optical nonlinearities. With the increase of effective area, the number of high-order modes will increase. In the case of high output power, the spectral shift and broadening of the optical fiber will also affect the modal number and content. The number and content of fiber modes affect the pointing stablity and quality of the laser beam. The M2-parameter is commonly used to define the quality of the laser beam, but a small M2 number is not guaranteed for single mode operation. Therefore, the relationship between wavelength and transmission mode in fiber transmission is studied in this paper. We use the spatial and spectral Fourier transform (F2) method to establish a theoretical-experimental method of describing the relationship between wavelength and mode. This method can directly give out the modal content of optical fibers without any priori parameter such as the properties of fiber and requirement for setup accuracy. On the one hand, the theoretical modeling of wavelength affects modal content. In the simulation, the sources with the same wavelength bandwidth and different central wavelengths are used to test the fiber. The results show that the modal content and number of the fiber change with the wavelength bandwidth and center wavelength. The mode components of the corresponding optical fiber will change after changing the central wavelength. As the spectral width of the light source increases, the number of high-order modes increases. On the other hand, in order to further verify the relationship between wavelength and mode of fiber, the F2 method is used to measure the optical fiber modal content with different wavelengths. The final experimental results are in agreement with the theoretical results. The experimental and simulation results show that the mode field distribution of each mode varies with wavelength:the longer the wavelength, the larger the mode field is. The beam quality has little change with the wavelength except for those positions with frequency near the cutoff frequency, and the power ratio of each mode relates to the wavelength.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.66.194202
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2017
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  • 9
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    Online Resource
    A new scheme of spectral dispersion smoothing based on hybrid grating
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2016
    In:  Acta Physica Sinica Vol. 65, No. 20 ( 2016), p. 204201-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 20 ( 2016), p. 204201-
    Abstract: The irradiance uniformity on target plane is a key issue in laser-driven inertial confinement facilities. In the typical schemes of one-dimensional smoothing by spectral dispersion (1D-SSD) and the “star” grating, the stripe pattern inside the focal spot appears inevitably, besides, the fabrication of the “star” grating is relatively difficult. Thus, a new spectral dispersion smoothing scheme based on a hybrid grating is proposed, which not only achieves the better smoothing effect, but also exhibits some specific advantages in the fabrication and the dispersion way. According to the different direction of the spectral dispersion, the hybrid grating is divided into inner and outer dispersion areas. That is, the dispersion direction of the inter dispersion area is in the horizontal or vertical direction, and the dispersion direction of the outer dispersion area is in the azimuthal direction. When the laser beam with the temporal phase modulation propagates through the hybrid grating, the dispersion directions of the laser beam in the inner and the outer dispersion areas are different, leading to the redistribution of the speckles inside the focal spot in the resultant direction of the translation and rotation on the target plane. Consequently, the focal spot on the target plane achieves the beam smoothing in radial and horizontal or vertical direction. In the present paper, the theoretical model of the hybrid grating scheme based on the spectral dispersion smoothing is built up. Using the theoretical model, the smoothing effect of the hybrid grating scheme is analyzed, and compared with those of the typical schemes of 1D-SSD and the “star” grating. The contrast and the fractional power above the intensity (FOPAI) are used to evaluate the smoothing characteristic of the focal spot. In addition, the influences of the area ratio and groove density in the different dispersion areas of the hybrid grating on beam-smoothing effect are also discussed. Results indicate that when the inner dispersion area accounts for the 0.3-0.5 of the total dispersion area, the hybrid grating scheme can effectively suppress the stripe intensity modulation both in the radial direction and the vertical direction. With increasing the groove densities of the inner and the outer dispersion area in a certain range, the irradiance uniformity of the focal spot is further improved. However, considering the actual processing of the hybrid grating, the appropriate groove density should be selected. Compared with the typical scheme of the 1D-SSD, the scheme of the hybrid grating can achieve the better smoothing effect with the multi-direction spectral dispersion smoothing. Furthermore, the fabrication of the hybrid grating is relatively simple and the irradiation uniformity on the target plane is also good compared with those of the “star” grating scheme.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.65.204201
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2016
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  • 10
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    Online Resource
    Analysis of characteristics of combined beam in spectral beam combining system based on multilayer dielectric grating
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2016
    In:  Acta Physica Sinica Vol. 65, No. 5 ( 2016), p. 054205-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 5 ( 2016), p. 054205-
    Abstract: Aiming at the application of multilayer dielectric gratings (MDGs) in spectral beam combining (SBC) systems, a theoretical model of rectangular MDGs is built up and a beam propagation model of SBC systems based on the rectangular MDGs is further developed. The phase modulation introduced by the rectangular MDG is composed of the optical path difference on the top surface of reliefs and that of the relief structure itself, and is affected by the MDG parameters such as the grating groove depth, the grating duty cycle, the incidence angle of the central beam, etc. By the diffraction integral method and the principle of incoherent superposition, the intensity distribution of the combined beam of the SBC system based on the rectangular MDGs is numerically calculated and analyzed. Additionally, the beam quality of the combined beam is also obtained by the intensity second-order moments method, and the effects of the MDG parameters such as the groove depth, the duty cycle, the incidence angle of the central beam, and the fabrication errors of the MDG on the characteristics of the combined beam of the SBC systems are simulated and discussed in detail. The simulation results show that the beam quality of the combined beam after passing through the SBC systems is significantly better than that of the laser array. Since the quality of the combined beam is almost the same as that of an individual laser beam, for a SBC system without fabrication error, changing the groove depth, the duty cycle of the rectangular MDG or the incidence angle of the central beam does not affect the beam quality while it has obvious influence on the energy of the combined beam. This is mainly because the diffraction efficiency of the rectangular MDG depends on both the parameters of the MDG and the incidence angle of the central beam. However, fabrication error of MDG is unavoidable, and the fabrication error has a significant effect on both the beam quality and the energy of the combined beam. Compared with the effect generated by the groove depth error on beam quality, the influence introduced by the duty cycle error is more obvious. It is worth mentioning that the theoretical model of the SBC system based on the rectangular MDG can be applied to some other high-power laser systems due to its advantages such as low absorption and high damage threshold.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.65.054205
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2016
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