Optics and Laser Technology最新文献

{"title":"Alamouti coding enabled polarization insensitive simplified self-homodyne coherent system for short-reach optical interconnects","authors":"Wei Wang ,&nbsp;Dongdong Zou ,&nbsp;Zhenpeng Wu ,&nbsp;Qi Sui ,&nbsp;Dongmei Huang ,&nbsp;Chao Lu ,&nbsp;Fan Li","doi":"10.1016/j.optlastec.2024.112164","DOIUrl":"10.1016/j.optlastec.2024.112164","url":null,"abstract":"<div><div>Coherent technology inherent with more available degrees of freedom is deemed as a competitive solution for next-generation ultra-high-speed short-reach optical interconnects. However, the high system cost, elevated power consumption, and large footprint size pose formidable barriers to the application of conventional coherent systems in short-reach scenarios. Self-homodyne coherent detection exhibits its potential for short-reach applications due to the sharing of the signal carrier and the local oscillator (LO), which not only reduces the system cost but also eliminates the frequency offset. Nevertheless, the self-homodyne coherent technique suffers from the polarization fading issue due to the random polarization states of the remote LO. In this paper, an Alamouti coding enabled simplified self-homodyne coherent detection technique is proposed to solve the polarization fading issue, resulting in a polarization-insensitive receiver. Besides, to further reduce the computational complexity of the system, the digital subcarrier multiplexing (DSCM) technique is discussed to alleviate the complexity of chromatic dispersion compensation (CDC), which is another dominant power consumption module of the receiver-side digital signal processing. The performance of the proposed scheme is demonstrated with a 50Gbaud 4-subcarrier 16/32QAM DSCM signal. The results show that polarization-insensitive self-homodyne detection is achieved by the transmitter-side Alamouti coding technique, circumventing the sophisticated automatic polarization controller for the polarization state tracking of the remote LO. In addition, by applying the joint dispersion compensation and equalization (JDCE) method for the DSCM signal, the CD-induced penalty can be fully addressed by increasing 4 taps in the equalizer for an 80 km single-mode fiber transmission without an individual CDC module, reducing the computational complexity of the system significantly.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112164"},"PeriodicalIF":4.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical analysis of All-Optical universal NAND and NOR photonic crystal logic gates by creating holes in silicon material","authors":"Fariborz Parandin,&nbsp;Pouya Karami","doi":"10.1016/j.optlastec.2024.112197","DOIUrl":"10.1016/j.optlastec.2024.112197","url":null,"abstract":"<div><div>All-optical NAND and NOR logical gates based on two-dimensional photonic crystals have been designed and analyzed in this research. A hole in the silicon substrate was created to design the desired gates, and the light emission analysis was performed using the FDTD numerical method. Most of the circuits that have been designed so far based on photonic crystals have included dielectric rods in the airfield. This research uses a hole in the silicon substrate, which is more suitable for fabrication. The proposed structure is created symmetrically using a small photonic crystal. The simulation results show that this small structure can be used as two NAND and NOR gates, which have a suitable power difference in the upper and lower logic states. Therefore, the proposed structure is suitable for precise logic circuits and high transmission speed. Due to the simplicity of structure and small size, the output stable time for NAND and NOR gates are 0.9 ps and 0.67 ps, respectively, indicating the gates’ low delay time. Also, the value of the contrast ratio for NAND and NOR gates is 7.26 dB and 6.35 dB, respectively, which indicates the appropriate power difference in the upper and lower logic states.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112197"},"PeriodicalIF":4.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-power pulsed Raman fiber laser with wavelength over 2.4 μm","authors":"Meng Wang ,&nbsp;Deqin Ouyang ,&nbsp;Yewang Chen ,&nbsp;Minqiu Liu ,&nbsp;Junqing Zhao ,&nbsp;Zhijian Zheng ,&nbsp;Chunbo Li ,&nbsp;Shuangchen Ruan","doi":"10.1016/j.optlastec.2024.112170","DOIUrl":"10.1016/j.optlastec.2024.112170","url":null,"abstract":"<div><div>In this paper, the compact high-power pulsed Raman fiber lasers based on single-pass stimulated Raman scattering have been experimentally presented. Home-built noise-like pulse laser centered at ∼1994.7 nm with an envelope width of ∼20.8 ns was utilized as the pump laser, which can provide a maximal output power of ∼19.1 W without a notable spectral broadening. The 1st-order Raman laser operated at ∼2190.8 nm with a maximal output power of ∼4.11 W and a spectral purity of ∼93 % was achieved. Furthermore, by finely optimizing the length of Raman-gain fiber, the 2nd-order Raman laser centered at ∼2408.5 nm with a maximal power of ∼2.36 W was achieved, which represents the maximal value of Raman laser at 2.4 μm in silica-core fiber, to the best of our knowledge. The high-power pulsed Raman fiber lasers may have the potential applications in polymer material processing and spectroscopy.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112170"},"PeriodicalIF":4.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence and mechanism of ultrafast laser-textured Cu substrate on wetting behavior of SAC305 solder","authors":"Tao Ma ,&nbsp;Zhihang Zhang ,&nbsp;Shiqiang Zhang ,&nbsp;Yue Zhao ,&nbsp;Wei Shao ,&nbsp;Jihua Huang ,&nbsp;Shuhai Chen ,&nbsp;Zheng Ye ,&nbsp;Wanli Wang ,&nbsp;Jian Yang","doi":"10.1016/j.optlastec.2024.112190","DOIUrl":"10.1016/j.optlastec.2024.112190","url":null,"abstract":"<div><div>Periodic arrays of grids, micro-cones, and grooves were successfully fabricated on Cu substrate using ultrafast laser technology. The wetting behavior of SAC305 solder on micro-nano structured Cu substrates was investigated, and the influence mechanism of superficial micro-nano structure was discussed using classical wetting model and molecular dynamics (MD) simulation. The results indicate that compared to polished surface, all the superficial micro-nano structures on Cu substrate improve the wettability and wetting kinetics of SAC305 solder. Especially, grid structure shows the most significant improvement, and the effect is further enhanced with the increase of processing depth. When the processing depth of grid structure is 25 μm, the smallest wetting angle of 15.1° and wetting equilibrium time of 29 s were achieved. The wetting process of SAC305 solder on Cu substrate is composed of rapid reaction stage, stable diffusion state, and equilibrium stage. <em>R</em>ⁿ ∼ <em>t</em> relationship curve reveals that the influence of micro-nano structure on wetting kinetics mainly occurs in the rapid reaction stage. The enhancement of wettability and wetting kinetics from superficial micro-nano structure can be attributed to the introduced extra capillary force and the improved atomic diffusion rate on the wetting interface.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112190"},"PeriodicalIF":4.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vibration monitoring of rotating shafts using DIC and compressed sensing","authors":"Yuchen Wei ,&nbsp;Yongsheng Huang ,&nbsp;Haipan Wu ,&nbsp;Penglong Wang ,&nbsp;Bing Chen ,&nbsp;Zeren Gao ,&nbsp;Yu Fu","doi":"10.1016/j.optlastec.2024.112189","DOIUrl":"10.1016/j.optlastec.2024.112189","url":null,"abstract":"<div><div>Monitoring vibrations in rotating shafts is essential for diagnosing and detecting mechanical faults. Digital image correlation (DIC), an optical full-field measurement technique, is increasingly employed in experimental mechanics. This study introduces a novel measurement approach that combines DIC with compressed sensing to monitor high-speed rotating shafts accurately. Traditionally, analyzing rotating shafts requires high-speed sampling devices, which increases experimental costs and reduces spatial resolution. To overcome these limitations, a random exposure sampling method was developed to capture speckle images on the shaft surface with a low frame-rate camera. By leveraging compressed sensing and DIC, the method reconstructs high-speed vibration signals from captured images. Step motion experiments demonstrated that the DIC system achieves a measurement accuracy of 10 µm. Experimental validation was conducted using various setups, including low-speed motors, high-speed rotating shafts, and milling machines, demonstrating the effectiveness of the approach. The measurement results of rotating shafts at 1200 rpm and 6000 rpm, compared with those obtained from laser Doppler vibrometry, demonstrated the effectiveness of the method in vibration measurement. Additionally, experiments on a milling machine showed that vibrations reconstructed using compressed sensing closely matched those measured with a high-speed camera. This measurement system shows significant potential for accurately assessing vibrations in high-speed rotating shafts, offering valuable insights for machinery monitoring and fault diagnosis.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112189"},"PeriodicalIF":4.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fabrication and quality improvement of film cooling holes via picosecond laser drilling assisted by waterjet and post-electrochemical machining","authors":"Hao Zhu ,&nbsp;Wenbo Xie ,&nbsp;Wenwu Du ,&nbsp;Qinglin Zhang ,&nbsp;Hao Yuan ,&nbsp;Kun Xu ,&nbsp;Yang Liu ,&nbsp;Jingtao Wang ,&nbsp;Viboon Saetang ,&nbsp;Zhaoyang Zhang","doi":"10.1016/j.optlastec.2024.112162","DOIUrl":"10.1016/j.optlastec.2024.112162","url":null,"abstract":"<div><div>Film cooling holes (FCHs) are of superior importance for blade protection and performance improvement in aircraft engine, while their fabrication requires high efficiency, high precision and extremely good surface quality, making it a challenging task. In this study, the ultrashort picosecond (ps) laser is employed to drill the FCHs on the DD6 single crystal superalloy, based on which the assisted waterjet is further introduced to reduce thermal damage, and the electrochemical machining (ECM) is also added as a post-processing manner for further quality improvement. It has been found through orthogonal tests that the pulse repetition frequency possessing most significant influence on hole taper during direct ps-laser drilling. The introduced low-pressure waterjet effectively eliminates the thermal damage such as slag attachment and recast layer, and the waterjet angle affects the hole profile obviously. After conducting post-ECM, the hole taper decreases continuously with an increase in processing time and applied voltage. In addition, the laser-induced periodic surface structure (LIPSS) has been observed on the sidewall, while an obvious decrease in LIPSS wavelength has been confirmed after post processing. Moreover, simulation study of temperature evolution is carried out by developing a two-temperature model, demonstrating that the lattice temperature surpasses the boiling point within 0.182 <!--> <!-->ps, and the ablation can be precisely localized within laser irradiation zone. The simulation of flow field on DD6 surface has also been conducted, and the distributions of flow velocity, pressure and thickness are obtained, which helps understand the effect of waterjet on the drilling process.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112162"},"PeriodicalIF":4.6,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of combined treatment of laser shock peening and shot peening on fatigue performance of laser-powder-bed-fusioned GH4169 nickel-based alloy","authors":"Peixuan Ouyang ,&nbsp;Zhichao Dong ,&nbsp;Xuekun Luo ,&nbsp;Shuting Zhang ,&nbsp;Lu Liu ,&nbsp;Bin Sun ,&nbsp;Lijie Zhou","doi":"10.1016/j.optlastec.2024.112141","DOIUrl":"10.1016/j.optlastec.2024.112141","url":null,"abstract":"<div><div>The laser-powder-bed-fusioned (LPBFed) GH4169 nickel-based alloys were respectively surface-strengthened by laser shock peening (LSP), shot peening (SP), and a combination of LSP and SP (LSP + SP). The surface roughness, microhardness, residual stress, and microstructures of the un-peened, (LSP + SP)ed, LSPed, and SPed sample were comparatively studied. The fatigue gain mechanism of the LSP + SP combined treatment on the LPBFed alloy was finally revealed. The vibration fatigue life of the (LSP + SP)ed sample under 680 MPa is at least 37.76 times, 1.58 times, and 0.79 times longer compared with the un-peened LSPed and SPed samples. The LSP + SP treatment decreased the stress concentration coefficient <em>K</em>_t compared with LSP treatment. The maximum compressive residual stress (CRS) of the (LSP + SP)ed sample is 68 % larger than that of the LSPed sample, and the CRS layer thickness is 1.12 times thicker compared with the SPed sample. The average grain size for the (LSP + SP)ed sample is the smallest, and the LAGBs fraction increases by 96 % and 50.9 % compared with the LSPed and SPed samples. The fatigue gain mechanism of the LSP + SP combined treatment on the LPBFed alloy is concluded that the largest maximum CRS, a thick CRS layer, the refined grains, and the decreased <em>K</em>_t extend the crack initiation life, and the smallest grain size, the highest density of dislocation substructures, as well as the highest fraction of LAGBs extend the crack propagation life. The results demonstrated that the LSP + SP combined treatment is an efficient surface strengthening method that can improve fatigue life of LPBFed nickel-based alloys.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112141"},"PeriodicalIF":4.6,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of crystal orientation and incident plane on n-type 4H-SiC wafer slicing by using picosecond laser","authors":"Yongping Yao ,&nbsp;Qiu Chen ,&nbsp;Bixue Li ,&nbsp;Jianfei Zhang ,&nbsp;Rongkun Wang ,&nbsp;Meng Bai ,&nbsp;Runze Liang ,&nbsp;Longnan Ma ,&nbsp;Tiejun Ma ,&nbsp;Jiayu Zhang ,&nbsp;Jinbao Xia ,&nbsp;Hongkun Nie ,&nbsp;Baitao Zhang","doi":"10.1016/j.optlastec.2024.112174","DOIUrl":"10.1016/j.optlastec.2024.112174","url":null,"abstract":"<div><div>Laser slicing has been considered as the most efficient technique for slicing SiC wafers with the advantages of small kerf width (loss) and crack, low roughness on cleaved surface, high quality and efficiency, etc. Here, laser slicing of n-type 4H-SiC was demonstrated by using a homemade 1064 nm picosecond laser combined with mechanical stretch stripping. The influence of laser processing along [11 <span><math><mrow><mover><mrow><mtext>2</mtext></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> 0] and [1 <span><math><mrow><mover><mrow><mtext>1</mtext></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> 00] crystal orientations on Si-face and C-face of n-type 4H-SiC, specifically on the internal laser ablation lines and cracks, the peeling tensile strength, and the surface roughness of the peeled surfaces was investigated. The semi-insulating 4H-SiC wafer laser slicing was conducted for comparison. Under the same laser conditions, laser slicing of semi-insulating 4H-SiC was easier than that of n-type. The laser modification quality along [1 <span><math><mrow><mover><mrow><mtext>1</mtext></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> 00] orientation was better than that along [11 <span><math><mrow><mover><mrow><mtext>2</mtext></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> 0] orientation for both the semi-insulating and n-type 4H-SiC and the reasons were explained. The results indicated that the optimal laser slicing scheme detailed laser scanning along [1 <span><math><mrow><mover><mrow><mtext>1</mtext></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> 00] orientation and incidence from the C-face. Finally, a 6-inch, 420.36 µm-thick n-type 4H-SiC wafer was successfully sliced.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112174"},"PeriodicalIF":4.6,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Demonstration of a three-active-section DFB laser with photon-photon resonance and detuned loading effects to obtain enhanced bandwidth and maintained high output power","authors":"Xiang Ma ,&nbsp;Hefei Qi ,&nbsp;Yuedi Ding ,&nbsp;Boyuan Liu ,&nbsp;Wenqi Yu ,&nbsp;Shaobo Li ,&nbsp;Weihua Guo","doi":"10.1016/j.optlastec.2024.112127","DOIUrl":"10.1016/j.optlastec.2024.112127","url":null,"abstract":"<div><div>Enhancement of the modulation bandwidth of the directly modulated semiconductor laser has attracted tremendous attention for applications in optical fiber communication and optical interconnects. However, modulation bandwidth is enhanced by some special technology such as integrating the active region or passive region regularly, which lead to low power and complex fabrication. Here we design and demonstrate a monolithic integrated three-active-section distributed feedback (TAS-DFB) laser with enhanced bandwidth theoretically and experimentally. The laser includes three sections: the DFB section, feedback section and active phase section. The three sections share the same multiple quantum-well structure. To enhance the modulation bandwidth beyond the intrinsic modulation bandwidth, both photon-photon resonance (PPR) and detuned loading (DL) effects are utilized to achieve over 55 GHz. The active phase section shows promise in achieving high bandwidth with PPR and relatively high output power of ∼ 10 mW at 25 °C under continuous-wave (CW) operation simultaneously. The fabrication process of the TAS-DFB laser is simplified due to the conventional and identical active layer structure.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112127"},"PeriodicalIF":4.6,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optical algorithm for derivative of real-valued functions","authors":"Murilo H. Magiotto,&nbsp;Guilherme L. Zanin,&nbsp;Wesley B. Cardoso,&nbsp;Ardiley T. Avelar,&nbsp;Rafael M. Gomes","doi":"10.1016/j.optlastec.2024.112137","DOIUrl":"10.1016/j.optlastec.2024.112137","url":null,"abstract":"<div><div>The derivation of a function is a fundamental tool for solving problems in calculus. Consequently, the motivations for investigating physical systems capable of performing this task are numerous. Furthermore, the potential to develop an optical computer to replace conventional computers has led us to create an optical algorithm and propose an experimental setup for implementing the derivative of one-dimensional real-valued functions using a paraxial and monochromatic laser beam. To complement the differentiation algorithm, we have experimentally implemented a novel optical algorithm that can transfer a two-dimensional phase-encoded function to the intensity profile of a light beam. Additionally, we demonstrate how to extend the optical algorithm to implement high-order derivatives of two-dimensional real-valued functions encoded in the phase of the transverse profile of photons.</div></div>","PeriodicalId":19511,"journal":{"name":"Optics and Laser Technology","volume":"182 ","pages":"Article 112137"},"PeriodicalIF":4.6,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142701355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}