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Optimizing the generation of second harmonic optical vortices from nonlinear photonic crystals
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作者 LIU Shiqiang ZHANG Xinyu +4 位作者 CHEN Yan LI Shifeng ZHAO Gang ZHU Shining HU Xiaopeng 《物理学进展》 北大核心 2025年第4期161-168,共8页
The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex... The generation of optical vortices from nonlinear photonic crystals(NPCs)with spatially modulated second-order nonlinearity offers a promising approach to extend the working wavelength and topological charge of vortex beams for various applications.In this work,the second harmonic(SH)optical vortex beams generated from nonlinear fork gratings under Gaussian beam illumination are numerically investigated.The far-field intensity and phase distributions,as well as the orbital angular momentum(OAM)spectra of the SH beams,are analyzed for different structural topological charges and diffraction orders.Results reveal that higher-order diffraction and larger structural topological charges lead to angular interference patterns and non-uniform intensity distributions,deviating from the standard vortex profile.To optimize the SH vortex quality,the effects of the fundamental wave beam waist,crystal thickness,and grating duty cycle are explored.It is shown that increasing the beam waist can effectively suppress diffraction order interference and improve the beam’s quality.This study provides theoretical guidance for enhancing the performance of nonlinear optical devices based on NPCs. 展开更多
关键词 optical vortex nonlinear photonic crystal second harmonic generation orbital angular momentum
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Arbitrary azimuthal optical field manipulation by dual-spiral arrays
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作者 MA Li WANG Ying +2 位作者 LI Min ZHANG Ying ZHAO Bo 《中国光学(中英文)》 北大核心 2025年第4期921-930,共10页
Optical field manipulation,an emerging frontier in photonics,demonstrates significant potential in biomedical microscopy,quantum state engineering,and micro-nano fabrication.To address the critical limitations of curr... Optical field manipulation,an emerging frontier in photonics,demonstrates significant potential in biomedical microscopy,quantum state engineering,and micro-nano fabrication.To address the critical limitations of current optical modulation technologies in achieving full-parameter precision control,we proposed a novel approach for dynamic azimuthal optical field modulation based on dual-spiral arrays.By designing spatially interleaved spiral structures with different initial radii while maintaining identical periodic parameters,we achieved continuous optical modulation spanning the full 0-2πrange in azimuthal field distribution.Through rigorous numerical simulations,we systematically established a quantitative correlation between the structural parameters and azimuthal optical field patterns,revealing,for the first time,a quasi-linear relationship between the radius difference and the resultant optical distribution.This theoretical framework advances our fundamental understanding of structured optical field manipulation as well as provides a new paradigm for programmable photonic device design,with distinct technical advantages in super-resolution imaging and optical tweezer systems. 展开更多
关键词 optical manipulation topological charge spiral array
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Yb:Sc_(2)O_(3) Transparent Ceramics Fabricated from Co-precipitated Nano-powders:Microstructure and Optical Property
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作者 YE Junhao ZHOU Zhenzhen +8 位作者 HU Chen WANG Yanbin JING Yanqiu LI Tingsong CHENG Ziqiu WU Junlin IVANOV Maxim HRENIAK Dariusz LI Jiang 《无机材料学报》 北大核心 2025年第2期215-224,共10页
Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2... Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment. 展开更多
关键词 NANO-POWDER Yb:Sc_(2)O_(3) transparent ceramic hot isostatic pressing optical property
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Optical memory behavior of MoS_(2) nanoflakes doped liquid crystals hybrid
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作者 GONG Xiaohui ZHANG Hao +1 位作者 YANG Dongfang LIU Yang 《液晶与显示》 北大核心 2025年第5期665-673,共9页
The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variet... The memory behavior in liquid crystals(LCs)that is characterized by low cost,large area,high speed,and high-density memory has evolved from a mere scientific curiosity to a technology that is being applied in a variety of commodities.In this study,we utilized molybdenum disulfide(MoS_(2))nanoflakes as the guest in a homotropic LCs host to modulate the overall memory effect of the hybrid.It was found that the MoS₂nanoflakes within the LCs host formed agglomerates,which in turn resulted in an accelerated response of the hybrids to the external electric field.However,this process also resulted in a slight decrease in the threshold voltage.Additionally,it was observed that MoS₂nanoflakes in a LCs host tend to align homeotropically under an external electric field,thereby accelerating the refreshment of the memory behavior.The incorporation of a mass fraction of 0.1%2μm MoS₂nanoflakes into the LCs host was found to significantly reduce the refreshing memory behavior in the hybrid to 94.0 s under an external voltage of 5 V.These findings illustrate the efficacy of regulating the rate of memory behavior for a variety of potential applications. 展开更多
关键词 optical memory behavior MoS_(2)nanoflake liquid crystal
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First‑principles study on electronic structure,optical and magnetic properties of rare earth elements X(X=Sc,Y,La,Ce,Eu)doped with two‑dimensional GaSe 被引量:3
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作者 QIU Shenhao XIAO Qingquan +1 位作者 TANG Huazhu XIE Quan 《无机化学学报》 SCIE CAS CSCD 北大核心 2024年第11期2250-2258,共9页
The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity funct... The electronic structure,magnetic,and optical properties of two-dimensional(2D)GaSe doped with rare earth elements X(X=Sc,Y,La,Ce,Eu)were calculated using the first-principles plane wave method based on den-sity functional theory.The results show that intrinsic 2D GaSe is a p-type nonmagnetic semiconductor with an indi-rect bandgap of 2.6611 eV.The spin-up and spin-down channels of Sc-,Y-,and La-doped 2D GaSe are symmetric,they are non-magnetic semiconductors.The magnetic moments of Ce-and Eu-doped 2D GaSe are 0.908μ_(B)and 7.163μ_(B),which are magnetic semiconductors.Impurity energy levels appear in both spin-up and spin-down chan-nels of Eu-doped 2D GaSe,which enhances the probability of electron transition.Compared with intrinsic 2D GaSe,the static dielectric constant of the doped 2D GaSe increases,and the polarization ability is strengthened.The ab-sorption spectrum of the doped 2D GaSe shifts in the low-energy direction,and the red-shift phenomenon occurs,which extends the absorption spectral range.The optical reflection coefficient of the doped 2D GaSe is improved in the low energy region,and the improvement of Eu-doped 2D GaSe is the most obvious. 展开更多
关键词 first principle two-dimensional GaSe electronic structure magnetic property optical property
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Optical facet coatings for high-performance LWIR quantum cascade lasers atλ∼8.5μm 被引量:1
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作者 MA Yuan LIN Yu-Zhe +5 位作者 WAN Chen-Yang WANG Zi-Xian ZHOU Xu-Yan ZHANG Jin-Chuan LIU Feng-Qi ZHENG Wan-Hua 《红外与毫米波学报》 SCIE EI CAS CSCD 北大核心 2024年第4期497-502,共6页
We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)A... We report on the performance improvement of long-wave infrared quantum cascade lasers(LWIR QCLs)by studying and optimizing the anti-reflection(AR)optical facet coating.Compared to the Al2O3 AR coat⁃ing,the Y_(2)O_(3)AR coating exhibits higher catastrophic optical mirror damage(COMD)level,and the optical facet coatings of both material systems have no beam steering effect.A 3-mm-long,9.5-μm-wide buried-heterostruc⁃ture(BH)LWIR QCL ofλ~8.5μm with Y_(2)O_(3)metallic high-reflection(HR)and AR of~0.2%reflectivity coating demonstrates a maximum pulsed peak power of 2.19 W at 298 K,which is 149%higher than that of the uncoated device.For continuous-wave(CW)operation,by optimizing the reflectivity of the Y_(2)O_(3)AR coating,the maximum output power reaches 0.73 W,which is 91%higher than that of the uncoated device. 展开更多
关键词 quantum cascade lasers long-wave infrared optical facet coatings catastrophic optical mirror damage
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Optical Properties of GaAs/AlGaAs Nanowires Grown on Pre-etched Si Substrates
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作者 ZHANG Zhihong MENG Bingheng +2 位作者 WANG Shuangpeng KANG Yubin WEI Zhipeng 《发光学报》 EI CAS CSCD 北大核心 2024年第10期1639-1646,共8页
GaAs-based nanomaterials are essential for near-infrared nano-photoelectronic devices due to their exceptional optoelectronic properties.However,as the dimensions of GaAs materials decrease,the development of GaAs nan... GaAs-based nanomaterials are essential for near-infrared nano-photoelectronic devices due to their exceptional optoelectronic properties.However,as the dimensions of GaAs materials decrease,the development of GaAs nanowires(NWs)is hindered by type-Ⅱquantum well structures arising from the mixture of zinc blende(ZB)and wurtzite(WZ)phases and surface defects due to the large surface-to-volume ratio.Achieving GaAs-based NWs with high emission efficiency has become a key research focus.In this study,pre-etched silicon substrates were combined with GaAs/AlGaAs core-shell heterostructure to achieve GaAs-based NWs with good perpendicularity,excellent crystal structures,and high emission efficiency by leveraging the shadowing effect and surface passivation.The primary evidence for this includes the prominent free-exciton emission in the variable-temperature spectra and the low thermal activation energy indicated by the variable-power spectra.The findings of this study suggest that the growth method described herein can be employed to enhance the crystal structure and optical properties of otherⅢ-Ⅴlow-dimensional materials,potentially paving the way for future NW devices. 展开更多
关键词 GaAs nanowires GaAs/AlGaAs core-shell structure crystal phase optical property
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Structural Color Dynamic Graphics Display Based on Microlens Array 被引量:1
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作者 LI Xue-han LIU Ling-zhi +1 位作者 HUANG Min LI Xiu 《印刷与数字媒体技术研究》 北大核心 2025年第2期162-168,共7页
It is of great scientific significance to construct a 3D dynamic structural color with a special color effect based on the microlens array.However,the problems of imperfect mechanisms and poor color quality need to be... It is of great scientific significance to construct a 3D dynamic structural color with a special color effect based on the microlens array.However,the problems of imperfect mechanisms and poor color quality need to be solved.A method of 3D structural color turning on periodic metasurfaces fabricated by the microlens array and self-assembly technology was proposed in this study.In the experiment,Polydimethylsiloxane(PDMS)flexible film was used as a substrate,and SiO2 microspheres were scraped into grooves of the PDMS film to form 3D photonic crystal structures.By adjusting the number of blade-coated times and microsphere concentrations,high-saturation structural color micropatterns were obtained.These films were then matched with microlens arrays to produce dynamic graphics with iridescent effects.The results showed that by blade-coated two times and SiO2 microsphere concentrations of 50%are the best conditions.This method demonstrates the potential for being widely applied in the anticounterfeiting printing and ultra-high-resolution display. 展开更多
关键词 Structural color Microlens array Dynamic graphics display Moirémagnification optical anti-counterfeiting
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Design of high-speed MUTC-PD with electric field regulation layer
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作者 XU Jian-bo LIU Kai +4 位作者 DONG Xiao-wen DUAN Xiao-feng HUANG Yong-qing WANG Qi REN Xiao-min 《中国光学(中英文)》 北大核心 2025年第2期393-400,共8页
This paper proposes a novel modified uni-traveling-carrier photodiode(MUTC-PD)featuring an electric field regulation layer:a p-type doped thin layer inserted behind the PD’s n-doped cliff layer.This electric field re... This paper proposes a novel modified uni-traveling-carrier photodiode(MUTC-PD)featuring an electric field regulation layer:a p-type doped thin layer inserted behind the PD’s n-doped cliff layer.This electric field regulation layer enhances the PD’s performance by not only reducing and smoothing the electric field intensity in the collector layer,allowing photo-generated electrons to transit at peak drift velocity,but also improving the electric field intensity in the depleted absorber layer and optimizing the photo-generated carriers’saturated transit performance.Additionally,the transport characteristics of the peak drift velocity of photogenerated electrons in the device’s collection layer can be used to optimize its parasitic characteristics.The electron’s peak drift velocity compensates for the lost transit time.Thus improving the 3 dB bandwidth of the PD’s photo response.Finally obtains a MUTC-PD with a 3 dB bandwidth of 68 GHz at a responsivity of 0.502 A/W,making it suitable for 100 Gbit/s optical receivers. 展开更多
关键词 peak electron drift velocity transit performance MUTC-PD optical fiber communication optical interconnect
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First-principles study on the structure-property relationship of AlX and InX(X=N,P,As,Sb)
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作者 HE Zhihao DING Jiafu +1 位作者 WANG Yunjie SU Xin 《无机化学学报》 北大核心 2025年第5期1007-1019,共13页
This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materi... This paper delves into the theoretical mechanisms of the electronic structure and optical properties of aluminum-based semiconductors(AlX,X=N,P,As,Sb)and indium-based semiconductors(InX,X=N,P,As,Sb)as potential materials for optical devices.Band structure calculations reveal that,except for InSb,all other compounds are direct bandgap semiconductors,with AlN exhibiting a bandgap of 3.245 eV.The valence band maximum of these eight compounds primarily stems from the p-orbitals of Al/In and X.In contrast,the conduction band minimum is influenced by all orbitals,with a predominant contribution from the p-orbitals.The static dielectric constant increased with the expansion of the unit cell volume.Compared to AlX and InX with larger X atoms,AlN and InN showed broader absorption spectra in the near-ultraviolet region and higher photoelectric conductance.Regarding mechanical properties,AlN and InN displayed greater shear and bulk modulus than the other compounds.Moreover,among these eight crystal types,a higher modulus was associated with a lower light loss function value,indicating that AlN and InN have superior transmission efficiency and a wider spectral range in optoelectronic material applications. 展开更多
关键词 aluminium‑based semiconductor indium‑based semiconductor first principle electronic structure optical property
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Analysis of multi-factor influences of tilt-to-length coupling noise in a test mass interferometer
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作者 ZHAO Meng-yuan SHEN Jia +5 位作者 PENG Xiao-dong MA Xiao-shan YANG Zhen LIU He-shan MENG Xin ZHANG Jia-feng 《中国光学(中英文)》 北大核心 2025年第3期704-714,共11页
For space-borne gravitational wave detection missions based on the heterodyne interferometry principle,tilt-to-length(TTL)coupling noise is an important optical noise source,significantly influencing the accuracy of t... For space-borne gravitational wave detection missions based on the heterodyne interferometry principle,tilt-to-length(TTL)coupling noise is an important optical noise source,significantly influencing the accuracy of the measurement system.We present a method for analyzing TTL coupling noise under the joint influence of multiple factors.An equivalent simulated optical bench for the test mass interferometer was designed,and Gaussian beam tracing was adopted to simulate beam propagation.By simulating the interference signal,it can analyze the impact of various factors on the TTL coupling noise,including positional,beam parameters,detector parameters,and signal definition factors.On this basis,a random parameter space composed of multiple influential factors was constructed within a range satisfying the analysis requirement,and the corresponding simulation results from random sampling were evaluated via variance-based global sensitivity analysis.The calculated results of the main and total effect indexes show that the test mass rotation angle and the piston effect(lateral)significantly influence the TTL coupling noise in the test mass interferometer.The analysis provides a qualitative reference for designing and optimizing space-borne laser interferometry systems. 展开更多
关键词 space interferometry optical simulation tilt-to-length coupling noise
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Cloning scheme for multipartite entangled pure states via photonic quantum walk
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作者 WANG Guocui LIN Zhi +2 位作者 LI Xikun YANG Qing YANG Ming 《量子电子学报》 北大核心 2025年第2期206-216,共11页
The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes ... The no-cloning theorem has sparked considerable interest in achieving high-fidelity approximate quantum cloning.Most of the previous studies mainly focused on the cloning of single particle states,and cloning schemes used there are incapable of cloning quantum entangled states in multipartite systems.Few schemes were proposed for cloning multiparticle states,which consume more entanglement resources with loss of qubits,and the fidelity of the cloned state is relatively low.In this paper,cloning schemes for bipartite and tripartite entangled states based on photonic quantum walk and entanglement swapping are proposed.The results show that according to the proposed schemes,two high-fidelity(up to 0.75)cloned states can be obtained with less quantum resource consumption.Because of the simple cloning steps,few quantum resources and high fidelity,these schemes are both efficient and feasible.Moreover,this cloning machine eliminates the need for tracing out cloning machine,thereby minimizing resource waste. 展开更多
关键词 quantum optics entanglement cloning photonic quantum walk multipartite entanglement
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Application of gurney and flight of fragment calculations for water jet velocities in explosive applications
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作者 Rachel L.Bauer Tate B.Friedrich Catherine E.Johnson 《Defence Technology(防务技术)》 2025年第7期68-78,共11页
This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the ... This study investigates the application of Gurney and flight of fragment equations,typically used to predict metal fragment velocities,in modeling the water jet behavior.Three shotgun cartridge sizes were used as the energy source:2.59 g,5.83 g,and 7.13 g.Two configurations were tested:standard(full-barrel water load)and"negative 8"(partial water load).High-speed footage captured water column velocities,and Gurney models,including infinitely tamped and open-faced configurations,combined with the flight of fragment model were used to assess prediction accuracy.Results showed charge strength significantly affects water column velocity,with higher strengths yielding greater stability and velocity retention over distance.The infinitely tamped Gurney model closely predicted experimental velocities,deviating by as little as 1.4%for standard charges and 2.8% for negative 8 charges.Additionally,interesting dynamics such as a 1-2°rise in jet height and the rear overtaking the front was observed.These findings have significant implications for optimizing PAN disruptors and enhancing performance in high-velocity fluid applications and explosive breaching systems. 展开更多
关键词 Gurney calculations Water driven projectile Flight of fragment Incompressible fluid dynamics optical velocity measurement
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Design and optimization of the RGB beam combiner in micro display using entropy weight-TOPSIS method
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作者 ZHENG Yu ZHAO Yan-bing +4 位作者 ZOU Xin-jie WANG Ji-rong JIANG Xiang LIU Jian-zhe DUAN Ji-an 《Journal of Central South University》 2025年第2期483-494,共12页
Red-green-blue(RGB)beam combiners are widely used in scenarios such as augmented reality/virtual reality(AR/VR),laser projection,biochemical detection,and other fields.Optical waveguide combiners have attracted extens... Red-green-blue(RGB)beam combiners are widely used in scenarios such as augmented reality/virtual reality(AR/VR),laser projection,biochemical detection,and other fields.Optical waveguide combiners have attracted extensive attention due to their advantages of small size,high multiplexing efficiency,convenient mass production,and low cost.An RGB beam combiner based on directional couplers is designed,with a core-cladding relative refractive index difference of 0.75%.The RGB beam combiner is optimized from the perspective of parameter optimization.Using the beam propagation method(BPM),the relationship between the performance of the RGB beam combiner and individual parameters is studied,achieving preliminary optimization of the device’s performance.The key parameters of the RGB beam combiner are optimized using the entropy weight-technique for order preference by similarity to an ideal solution TOPSIS method,establishing the optimal parameter scheme and further improving the device’s performance indicators.The results show that after optimization,the multiplexing efficiencies for red,green,and blue lights,as well as the average multiplexing efficiency,reached 99.17%,99.76%,96.63%and 98.52%,respectively.The size of the RGB beam combiner is 4.768 mm×0.062 mm. 展开更多
关键词 optical waveguide combiners red-green-blue beam combiner beam propagation method entropy weight TOPSIS method multiplexing efficiency
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Temperature error compensation method for fiber optic gyroscope based on a composite model of k-means,support vector regression and particle swarm optimization
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作者 CAO Yin LI Lijing LIANG Sheng 《Journal of Systems Engineering and Electronics》 2025年第2期510-522,共13页
As the core component of inertial navigation systems, fiber optic gyroscope (FOG), with technical advantages such as low power consumption, long lifespan, fast startup speed, and flexible structural design, are widely... As the core component of inertial navigation systems, fiber optic gyroscope (FOG), with technical advantages such as low power consumption, long lifespan, fast startup speed, and flexible structural design, are widely used in aerospace, unmanned driving, and other fields. However, due to the temper-ature sensitivity of optical devices, the influence of environmen-tal temperature causes errors in FOG, thereby greatly limiting their output accuracy. This work researches on machine-learn-ing based temperature error compensation techniques for FOG. Specifically, it focuses on compensating for the bias errors gen-erated in the fiber ring due to the Shupe effect. This work pro-poses a composite model based on k-means clustering, sup-port vector regression, and particle swarm optimization algo-rithms. And it significantly reduced redundancy within the sam-ples by adopting the interval sequence sample. Moreover, met-rics such as root mean square error (RMSE), mean absolute error (MAE), bias stability, and Allan variance, are selected to evaluate the model’s performance and compensation effective-ness. This work effectively enhances the consistency between data and models across different temperature ranges and tem-perature gradients, improving the bias stability of the FOG from 0.022 °/h to 0.006 °/h. Compared to the existing methods utiliz-ing a single machine learning model, the proposed method increases the bias stability of the compensated FOG from 57.11% to 71.98%, and enhances the suppression of rate ramp noise coefficient from 2.29% to 14.83%. This work improves the accuracy of FOG after compensation, providing theoretical guid-ance and technical references for sensors error compensation work in other fields. 展开更多
关键词 fiber optic gyroscope(FOG) temperature error com-pensation composite model machine learning CLUSTERING regression.
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Vibration-induced bias error reduction using loop gain compensation for high-precision fiber optic gyroscopes
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作者 CHEN Heyu QIN Xuexin +2 位作者 XIE Huan KONG Linghai ZHENG Yue 《Journal of Systems Engineering and Electronics》 2025年第1期224-232,共9页
Vibration-induced bias deviation,which is generated by intensity fluctuations and additional phase differences,is one of the vital errors for fiber optic gyroscopes(FOGs)operating in vibration environment and has seve... Vibration-induced bias deviation,which is generated by intensity fluctuations and additional phase differences,is one of the vital errors for fiber optic gyroscopes(FOGs)operating in vibration environment and has severely restricted the applications of high-precision FOGs.The conventional methods for suppressing vibration-induced errors mostly concentrate on reinforcing the mechanical structure and optical path as well as the compensation under some specific operation parameters,which have very limited effects for high-precision FOGs maintaining performances under vibration.In this work,a technique of suppressing the vibration-induced bias deviation through removing the part related to the varying gain from the rotation-rate output is put forward.Particularly,the loop gain is extracted out by adding a gain-monitoring wave.By demodulating the loop gain and the rotation rate simultaneously under distinct frequencies and investigating their quantitative relationship,the vibrationinduced bias error is compensated without limiting the operating parameters or environments,like the applied modulation depth.The experimental results show that the proposed method has achieved the reduction of bias error from about 0.149°/h to0.014°/h during the random vibration with frequencies from20 Hz to 2000 Hz.This technique provides a feasible route for enhancing the performances of high-precision FOGs heading towards high environmental adaptability. 展开更多
关键词 vibration-induced error fiber optic gyroscope(FOG) loop gain
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Review of Infrared signature suppression systems using optical blocking method 被引量:13
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作者 Nidhi Baranwal Shripad P. Mahulikar 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2019年第3期432-439,共8页
With rapid advancements in Infra-Red (IR) detection techniques, the range from where the IR-guided missiles are able to lock the target aircraft has increased. To avoid the detection and tracking by modern IR-guided m... With rapid advancements in Infra-Red (IR) detection techniques, the range from where the IR-guided missiles are able to lock the target aircraft has increased. To avoid the detection and tracking by modern IR-guided missiles, the aircraft and helicopters also demand progress in its stealth techniques. Hence, study of Infra-Red Signature Suppression (IRSS) systems in aircraft and helicopters has become vital even in design stage. Optical blocking (masking) is one of the effective IRSS techniques used to block the Line- Of-Sight (LOS) of the hot engine parts of the exhaust geometry. This paper reviews the various patents on IR signature suppression systems based on the optical blocking method or a combination of IRSS techniques. The performance penalties generated due to installation of various IRSS methods in aircraft and helicopters are also discussed. 展开更多
关键词 IR SIGNATURE SUPPRESSION optical BLOCKING Performance PENALTY IR SIGNATURE level Engine back-pressure
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Surface roughness prediction model in ultrasonic vibration assisted grinding of BK7 optical glass 被引量:9
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作者 ZHAO Pei-yi ZHOU Ming +1 位作者 ZHANG Yuan-jing QIAO Guo-chao 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第2期277-286,共10页
Pre-knowledge of machined surface roughness is the key to improve whole machining efficiency and meanwhile reduce the expenditure in machining optical glass components.In order to predict the surface roughness in ultr... Pre-knowledge of machined surface roughness is the key to improve whole machining efficiency and meanwhile reduce the expenditure in machining optical glass components.In order to predict the surface roughness in ultrasonic vibration assisted grinding of brittle materials,the surface morphologies of grinding wheel were obtained firstly in the present work,the grinding wheel model was developed and the abrasive trajectories in ultrasonic vibration assisted grinding were also investigated,the theoretical model for surface roughness was developed based on the above analysis.The prediction model was developed by using Gaussian processing regression(GPR)due to the influence of brittle fracture on machined surface roughness.In order to validate both the proposed theoretical and GPR models,32sets of experiments of ultrasonic vibration assisted grinding of BK7optical glass were carried out.Experimental results show that the average relative errors of the theoretical model and GPR prediction model are13.11%and8.12%,respectively.The GPR prediction results can match well with the experimental results. 展开更多
关键词 surface roughness prediction model ultrasonic vibration optical glass GPR regression
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Optical investigations on lean combustion improvement of natural gas engines via turbulence enhancement 被引量:7
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作者 LI Jin-guang ZHANG Ren +3 位作者 YANG Peng-hui PAN Jia-ying WEI Hai-qiao CHEN Lin 《Journal of Central South University》 SCIE EI CAS CSCD 2022年第7期2225-2238,共14页
In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion insta... In the global background of“Carbon Peak”and“Carbon Neutral”,natural gas engines show great advantages in energy-saving and pollution reduction.However,natural gas engines suffer from the issues of combustion instabilities when operating under lean burning conditions.In this paper,the role of turbulence enhancement in improving the lean combustion of natural gas was investigated in an optical SI engine with high compression ratios.Variable swirl control valves(SCV)were designed and intake tumble and swirl were combined to regulate turbulent motion and turbulent intensity.Particle image velocimetry was employed to measure in-cylinder turbulence,and transient pressure acquisition and high-speed photography were synchronously performed to quantify combustion evolutions.The results show that incylinder turbulent intensity is enhanced significantly through reducing SCV closing angles.Such that flame propagation speed and thermal efficiency are significantly improved with an increment of turbulent intensity,which indicated that mean effective pressures are not sensitive to spark timing.The analysis of flame images shows that the combined turbulence increases in the radial orientation from the spark plug to the cylinder wall,leading to an earlier flame kernel formation and a faster burning rate.Therefore,the combined turbulence has the potential in reducing the cyclic variations of lean combustion in natural gas engines. 展开更多
关键词 optical engines lean combustion combined turbulence early flame kernel cyclic variations
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Optical design of freeform Fresnel TIR lens for LED uniform illumination 被引量:7
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作者 Hu Tiantian Zeng Chunmei +2 位作者 Rui Congshan Hong Yang Ma Suodong 《红外与激光工程》 EI CSCD 北大核心 2021年第2期165-172,共8页
A new design of total internal reflection(TIR)lens was presented which had a freeform Fresnel surface in the central part of the front to improve the heat dissipation capability.Snell’s law and the reflection law wer... A new design of total internal reflection(TIR)lens was presented which had a freeform Fresnel surface in the central part of the front to improve the heat dissipation capability.Snell’s law and the reflection law were applied to construct the freeform refractive surface and the freeform reflective surface for the TIR lens.The freeform refractive surface was transformed into the freeform Fresnel surface with universal design method of Fresnel lens.The simulation result for the freeform Fresnel TIR lens obtained by Monte Carlo ray tracing shows that the far field illumination uniformity of 82.0%and the luminous efficiency of 96.6%are achieved for the light source size of 2 mm×2 mm,in the meanwhile the lens weight is only 21.94 g.The freeform Fresnel TIR lens has nearly 20%reduction in lens weight and volume,only a 2%reduction in luminous efficiency,and no reduction in illumination uniformity compared to the TIR lens without the Fresnel surface.The result indicates that the Fresnelization for freeform surface of TIR lens can significantly reduce the volume and weight of TIR lens and shorten the optical path length,thus effectively improve its heat dissipation efficiency and service life while maintaining a high performance. 展开更多
关键词 optical design Fresnel TIR lens Snell’s law heat dissipation
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