A simple fiber sensor to measure angular displacement with high resolution, which is based on whispering gallery mode （WGM） resonance in bent optical fibers,is proposed. The sensor is composed of a single loop forme...A simple fiber sensor to measure angular displacement with high resolution, which is based on whispering gallery mode （WGM） resonance in bent optical fibers,is proposed. The sensor is composed of a single loop formed by loosely tying a knot using single mode fiber. To measure the transmission spectra, a tunable laser and an optic power meter are connected to the two ends of fi- ber loop, respectively. Significant WGM resonances occur over the investigated wavelength range for all the sensors with different bend radius. The angular-displacement sensitivity is studied in the range from -0. 1°to 0. 1°. The detection limit of 1.49 × 10 ^-7 rad can be achieved for the detecting system with the resolution of lpm. The simple loop-structure fiber sensor has potential application prospect in the field of architecture or bridge building with low detection limit and low cost.展开更多
During the last decades the whispering gallery mode based sensors have become a prominent solution for label-free sensing of various physical and chemical parameters.At the same time,the widespread utilization of the ...During the last decades the whispering gallery mode based sensors have become a prominent solution for label-free sensing of various physical and chemical parameters.At the same time,the widespread utilization of the approach is hindered by the restricted applicability of the known configurations for ambient variations quantification outside the laboratory conditions and their low affordability,where necessity on the spectrally-resolved data collection is among the main limiting factors.In this paper we demonstrate the first realization of an affordable whispering gallery mode sensor powered by deep learning and multi-resonator imaging at a fixed frequency.It has been shown that the approach enables refractive index unit(RIU)prediction with an absolute error at 3×10^(-6) level for dynamic range of the RIU variations from 0 to 2×10^(-3) with temporal resolution of several milliseconds and instrument-driven detection limit of 3×10−5.High sensing accuracy together with instrumental affordability and production simplicity places the reported detector among the most cost-effective realizations of the whispering gallery mode approach.The proposed solution is expected to have a great impact on the shift of the whole sensing paradigm away from the model-based and to the flexible self-learning solutions.展开更多
A linear and nonlinear analysis of crossed-field gyrotron operating on whispering-gallery mode TE<sub>m11</sub> is presented. The detailed discussions are given for the starting oscillationcondition, the e...A linear and nonlinear analysis of crossed-field gyrotron operating on whispering-gallery mode TE<sub>m11</sub> is presented. The detailed discussions are given for the starting oscillationcondition, the effect of the internal conductor in coaxial cavity on the cut-off frequency of modeand the spacing between adjacent modes as well as the effect of the applied voltage on thecyclotron frequency of electron, the starting oscillation beam power and the electron efficiency.It is shown that the efficiency of 41% can be attained for m=2. A comparison of these resultswith those in cylindrical cavity is made. The analyses are helpful for the engineering design.展开更多
The dynamics of the optomechanical entanglement between optical cavity field modes and a macroscopic me- chanical breathing mode in a whispering-gallery cavity as well as the continuous variable entanglement between t...The dynamics of the optomechanical entanglement between optical cavity field modes and a macroscopic me- chanical breathing mode in a whispering-gallery cavity as well as the continuous variable entanglement between the phase-quadrature amplitudes of the two whispering-gallery modes have been analysed. Simulated results indicate that under state-of-the^art experimental conditions, optomechanical entanglement is obvious and can occur even at temper- atures of above 40 K. Compared with the entanglement of the mechanical oscillator at the ground state temperature, optomechanical entanglement is more intense by several orders of magnitude.展开更多
We show that electric field on the plane surface of truncated sphere or cylinders(so called Janus particles)have sharp resonances versus the depth of removed segment of a sphere or cylinder.These resonances are relate...We show that electric field on the plane surface of truncated sphere or cylinders(so called Janus particles)have sharp resonances versus the depth of removed segment of a sphere or cylinder.These resonances are related to the excited whispering gallery waves caused by truncation.It is a new mechanism of the field localization.Optimization of this effect for cylinders permits to reach a super resolution in the line thickness,which can be used for contact optical lithography.展开更多
本文提出利用级联声光效应器和耦合回音壁模式微球腔的方案来实现非对称传输效果,并进行理论和实验验证.实验中利用加热拉锥的方式制备了两段式光纤,可同时实现声光效应的激发和回音壁模式的耦合.利用光纤中声光效应将纤芯基模中的矢量...本文提出利用级联声光效应器和耦合回音壁模式微球腔的方案来实现非对称传输效果,并进行理论和实验验证.实验中利用加热拉锥的方式制备了两段式光纤,可同时实现声光效应的激发和回音壁模式的耦合.利用光纤中声光效应将纤芯基模中的矢量模式转换到包层高阶模式,由于基模中不同矢量模式转换包层模式的矢量模式也不同,从而产生类似双折射效果,使输出的包层模式产生偏振变化.而后通过耦合回音壁模式微腔将包层模式转换回纤芯基模.由于回音壁模式的偏振选择效果,使得相反方向入射光能量具有不同的透射特性,其传输隔离度可达17 d B.此外,对两个方向传输的透射率随偏振角度变化进行测试,测得声光效应带来的偏振变化约为80°.本文的非对称传输方案继承了声光器件响应迅速、调谐性良好的优势,同时具有全光纤结构和无工作阈值的特点,在光开关、光隔离器等场景具有重要的应用潜力.展开更多
Whispering gallery modes (WGMs) were first discovered for sound waves in the whispering gallery of St Paul’s Cathedral and explained by Rayleigh [1] in 1878. In 1961, Garrett et al.[2] applied the concept of WGMs to ...Whispering gallery modes (WGMs) were first discovered for sound waves in the whispering gallery of St Paul’s Cathedral and explained by Rayleigh [1] in 1878. In 1961, Garrett et al.[2] applied the concept of WGMs to optical systems and realized stimulated emissions in Sm2+-doped CaF2 spheres.Since then, WGMs have been widely and intensively studied in a range of micro-sized systems, including microdroplets,microspheres, microtoroids, microdisks, and microtubes.展开更多
Conventionally, metallic nanostructures are used for surface-enhanced Raman spectroscopy(SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to ...Conventionally, metallic nanostructures are used for surface-enhanced Raman spectroscopy(SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to their improved stability and biocompatibility compared with metallic substrates. Here, we report the observation of enhanced Raman scattering from rhodamine 6 G molecules coated on silica microspheres. We excite the whispering gallery modes(WGMs) supported in the microspheres with a tapered fiber coupler for efficient WGM excitation, and the Raman enhancement can be attributed to the WGM mechanism. Strong resonance enhancement in pump laser intensity and modified Raman emission from the Purcell effect in the microsphere resonator are observed from the experiment and compared with theoretical results. A total Raman enhancement factor of 1.4 × 10~4 is observed, with contribution mostly from the enhancement in pump laser intensity. Our results show that, with an efficient pumping scheme, dielectric microspheres are a viable alternative to metallic SERS substrates.展开更多
In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using c...In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using conventional microfabrication techniques.The quality factor of the PPLN microdisk resonators with a 40-μm radius and a 700-nm thickness is 6.7×10~5. Second harmonic generation(SHG) with an efficiency of 2.2×10^(-6) mW(-1) is demonstrated in the fabricated PPLN microdisks. The nonlinear conversion efficiency could be considerably enhanced by optimizing the period and pattern of the poled structure and by improving the cavity quality factors.展开更多
Collaborative enhancements from surface plasmons （SPs） and whispering-gallery modes （WGMs） can induce intense near-field effects with high spatial localization around the surface of a semiconducting material. One ...Collaborative enhancements from surface plasmons （SPs） and whispering-gallery modes （WGMs） can induce intense near-field effects with high spatial localization around the surface of a semiconducting material. One can construct a highly efficient hybrid microcavity using semiconducting materials through resonant coupling between SPs and WGMs. Hexagonal ZnO micro-/nanostructures, which have been employed as natural WGM microcavities for ultraviolet （UV） lasing, can be used as ideal platforms to construct such hybrid microcavities. Here, we comprehensively review the recent efforts for improving lasing performance by resonant coupling between SPs and WGMs. Traditional SPs originating from various metals as well as novel SPs originating from atomic layers such as graphene are considered. Moreover, we discuss the mechanism of light-matter interactions beyond the improvements in lasing performance.展开更多
We present a study of single nanoparticle detection using parity-time(PT) symmetric whispering-gallery mode(WGM) resonators. Our theoretical model and numerical simulations show that, with balanced gain and loss, the ...We present a study of single nanoparticle detection using parity-time(PT) symmetric whispering-gallery mode(WGM) resonators. Our theoretical model and numerical simulations show that, with balanced gain and loss, the PT-symmetric WGM nanoparticle sensor, tailored to operate at PT phase transition points(also called exceptional points), exhibits significant enhancement in frequency splitting when compared with a single WGM nanoparticle sensor subject to the same perturbation. The presence of gain in the PT-symmetric system leads to narrower linewidth, which helps to resolve smaller changes in frequency splitting and improve the detection limit of nanoparticle sensing. Furthermore, we also provide a general method for detecting multiple nanoparticles entering the mode volume of a PT-symmetric WGM sensor one by one. Our study shows the feasibility of PT-symmetric WGM resonators for ultrasensitive single nanoparticle and biomolecule sensing.展开更多
The polarization properties of an evanescent-wave pumped Whispering Gallery Mode(WGM) fibre laser have been investigated. It is found that there are two kinds of polarization lasing beam emitting from the evanescent-w...The polarization properties of an evanescent-wave pumped Whispering Gallery Mode(WGM) fibre laser have been investigated. It is found that there are two kinds of polarization lasing beam emitting from the evanescent-wave pumped WGM fibre laser under two different pump conditions.When the pump beam is strictly along the axial direction of an optical fibre,the lasing emission is transverse electric wave and the electrical vectors at emitting points are along the radial direction of the fibre,which forms a special radial polarization radiation.However,when the pump beam deviates from the axial direction of the fibre,both transverse electric and transverse magnetic waves exist in the lasing emission,which forms a mixed polarization radiation with radial and axial polarized elements.Based on lasing radiation mechanism of evanescent-wave pumped WGM fibre laser,the observed polarization properties are well explained.展开更多
基金Supported by the National Basic Research Program of China （ ＂973＂ Program） （ 2011 CB013000 ） the National Natural Sci- ence Foundation of China （NSFC） （ 90923039 51105038）
文摘A simple fiber sensor to measure angular displacement with high resolution, which is based on whispering gallery mode （WGM） resonance in bent optical fibers,is proposed. The sensor is composed of a single loop formed by loosely tying a knot using single mode fiber. To measure the transmission spectra, a tunable laser and an optic power meter are connected to the two ends of fi- ber loop, respectively. Significant WGM resonances occur over the investigated wavelength range for all the sensors with different bend radius. The angular-displacement sensitivity is studied in the range from -0. 1°to 0. 1°. The detection limit of 1.49 × 10 ^-7 rad can be achieved for the detecting system with the resolution of lpm. The simple loop-structure fiber sensor has potential application prospect in the field of architecture or bridge building with low detection limit and low cost.
文摘During the last decades the whispering gallery mode based sensors have become a prominent solution for label-free sensing of various physical and chemical parameters.At the same time,the widespread utilization of the approach is hindered by the restricted applicability of the known configurations for ambient variations quantification outside the laboratory conditions and their low affordability,where necessity on the spectrally-resolved data collection is among the main limiting factors.In this paper we demonstrate the first realization of an affordable whispering gallery mode sensor powered by deep learning and multi-resonator imaging at a fixed frequency.It has been shown that the approach enables refractive index unit(RIU)prediction with an absolute error at 3×10^(-6) level for dynamic range of the RIU variations from 0 to 2×10^(-3) with temporal resolution of several milliseconds and instrument-driven detection limit of 3×10−5.High sensing accuracy together with instrumental affordability and production simplicity places the reported detector among the most cost-effective realizations of the whispering gallery mode approach.The proposed solution is expected to have a great impact on the shift of the whole sensing paradigm away from the model-based and to the flexible self-learning solutions.
文摘A linear and nonlinear analysis of crossed-field gyrotron operating on whispering-gallery mode TE<sub>m11</sub> is presented. The detailed discussions are given for the starting oscillationcondition, the effect of the internal conductor in coaxial cavity on the cut-off frequency of modeand the spacing between adjacent modes as well as the effect of the applied voltage on thecyclotron frequency of electron, the starting oscillation beam power and the electron efficiency.It is shown that the efficiency of 41% can be attained for m=2. A comparison of these resultswith those in cylindrical cavity is made. The analyses are helpful for the engineering design.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10647132 and 11104113)Hunan Provincial Natural Science Foundation, China (Grant Nos. 09JJ6011 and 11JJ6007)the Scientific Research Fund of Hunan Provincial Education,China (Grant No.10A100)
文摘The dynamics of the optomechanical entanglement between optical cavity field modes and a macroscopic me- chanical breathing mode in a whispering-gallery cavity as well as the continuous variable entanglement between the phase-quadrature amplitudes of the two whispering-gallery modes have been analysed. Simulated results indicate that under state-of-the^art experimental conditions, optomechanical entanglement is obvious and can occur even at temper- atures of above 40 K. Compared with the entanglement of the mechanical oscillator at the ground state temperature, optomechanical entanglement is more intense by several orders of magnitude.
基金This work was also supported by the Ministry of Science and Higher Education of the Russian Federation(project no.14.W03.31.0008)in part by the Russian Science Foundation(project no.20-12-00389)+1 种基金in part by the Russian Foundation for Basic Research(projects no.20-02-00715,no.21-58-10005,no.21-57-10001).Z.B.Wang acknowledges European ERDF grants(CPE 81400 and SPARCII c81133)through WEFO,and Royal society grants(IEC\NSFC\181378 and IEC\R2\202178).
文摘We show that electric field on the plane surface of truncated sphere or cylinders(so called Janus particles)have sharp resonances versus the depth of removed segment of a sphere or cylinder.These resonances are related to the excited whispering gallery waves caused by truncation.It is a new mechanism of the field localization.Optimization of this effect for cylinders permits to reach a super resolution in the line thickness,which can be used for contact optical lithography.
文摘本文提出利用级联声光效应器和耦合回音壁模式微球腔的方案来实现非对称传输效果,并进行理论和实验验证.实验中利用加热拉锥的方式制备了两段式光纤,可同时实现声光效应的激发和回音壁模式的耦合.利用光纤中声光效应将纤芯基模中的矢量模式转换到包层高阶模式,由于基模中不同矢量模式转换包层模式的矢量模式也不同,从而产生类似双折射效果,使输出的包层模式产生偏振变化.而后通过耦合回音壁模式微腔将包层模式转换回纤芯基模.由于回音壁模式的偏振选择效果,使得相反方向入射光能量具有不同的透射特性,其传输隔离度可达17 d B.此外,对两个方向传输的透射率随偏振角度变化进行测试,测得声光效应带来的偏振变化约为80°.本文的非对称传输方案继承了声光器件响应迅速、调谐性良好的优势,同时具有全光纤结构和无工作阈值的特点,在光开关、光隔离器等场景具有重要的应用潜力.
基金supported by the Shenzhen Fundamental Research Projects(Grant No.JCYJ20160427183259083)the National Natural Science Foundation of China(Grant No.91850204)the Shenzhen Engineering Laboratory on Organic-Inorganic Perovskite Devices
文摘Whispering gallery modes (WGMs) were first discovered for sound waves in the whispering gallery of St Paul’s Cathedral and explained by Rayleigh [1] in 1878. In 1961, Garrett et al.[2] applied the concept of WGMs to optical systems and realized stimulated emissions in Sm2+-doped CaF2 spheres.Since then, WGMs have been widely and intensively studied in a range of micro-sized systems, including microdroplets,microspheres, microtoroids, microdisks, and microtubes.
基金National Science Foundation(NSF)(CBET1264750,CBET 1264997)Army Research Office(ARO)(W911NF-16-1-0339)
文摘Conventionally, metallic nanostructures are used for surface-enhanced Raman spectroscopy(SERS), but recently there has been increasing interest in the enhancement of Raman scattering from dielectric substrates due to their improved stability and biocompatibility compared with metallic substrates. Here, we report the observation of enhanced Raman scattering from rhodamine 6 G molecules coated on silica microspheres. We excite the whispering gallery modes(WGMs) supported in the microspheres with a tapered fiber coupler for efficient WGM excitation, and the Raman enhancement can be attributed to the WGM mechanism. Strong resonance enhancement in pump laser intensity and modified Raman emission from the Purcell effect in the microsphere resonator are observed from the experiment and compared with theoretical results. A total Raman enhancement factor of 1.4 × 10~4 is observed, with contribution mostly from the enhancement in pump laser intensity. Our results show that, with an efficient pumping scheme, dielectric microspheres are a viable alternative to metallic SERS substrates.
基金supported by the National Natural Science Foundation of China(Grant Nos.11734009,11674181,11774182,and 11674184)the 111 Project(Grant No.B07013)+1 种基金PCSIRT(Grant No.IRT 13R29)CAS Interdisciplinary Innovation Team
文摘In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using conventional microfabrication techniques.The quality factor of the PPLN microdisk resonators with a 40-μm radius and a 700-nm thickness is 6.7×10~5. Second harmonic generation(SHG) with an efficiency of 2.2×10^(-6) mW(-1) is demonstrated in the fabricated PPLN microdisks. The nonlinear conversion efficiency could be considerably enhanced by optimizing the period and pattern of the poled structure and by improving the cavity quality factors.
文摘Collaborative enhancements from surface plasmons （SPs） and whispering-gallery modes （WGMs） can induce intense near-field effects with high spatial localization around the surface of a semiconducting material. One can construct a highly efficient hybrid microcavity using semiconducting materials through resonant coupling between SPs and WGMs. Hexagonal ZnO micro-/nanostructures, which have been employed as natural WGM microcavities for ultraviolet （UV） lasing, can be used as ideal platforms to construct such hybrid microcavities. Here, we comprehensively review the recent efforts for improving lasing performance by resonant coupling between SPs and WGMs. Traditional SPs originating from various metals as well as novel SPs originating from atomic layers such as graphene are considered. Moreover, we discuss the mechanism of light-matter interactions beyond the improvements in lasing performance.
基金Army Research Office(ARO)(W911NF-12-1-0026,W911NF1710189)National Natural Science Foundation of China(NSFC)(11674194,61134008,61622306)+4 种基金National Basic Research Program of China(973 Program)(2014CB921401)Tsinghua University Initiative Scientific Research ProgramTsinghua National Laboratory for Information Science and Technology(TNList)Cross-discipline FoundationNational Science Foundation(NSF)(ECCS-1303499)Directorate for Engineering(ENG)(EFMA1641109)
文摘We present a study of single nanoparticle detection using parity-time(PT) symmetric whispering-gallery mode(WGM) resonators. Our theoretical model and numerical simulations show that, with balanced gain and loss, the PT-symmetric WGM nanoparticle sensor, tailored to operate at PT phase transition points(also called exceptional points), exhibits significant enhancement in frequency splitting when compared with a single WGM nanoparticle sensor subject to the same perturbation. The presence of gain in the PT-symmetric system leads to narrower linewidth, which helps to resolve smaller changes in frequency splitting and improve the detection limit of nanoparticle sensing. Furthermore, we also provide a general method for detecting multiple nanoparticles entering the mode volume of a PT-symmetric WGM sensor one by one. Our study shows the feasibility of PT-symmetric WGM resonators for ultrasensitive single nanoparticle and biomolecule sensing.
基金supported by the National Natural Science Foundation of China(Grant Nos.60877037 and 10564005)
文摘The polarization properties of an evanescent-wave pumped Whispering Gallery Mode(WGM) fibre laser have been investigated. It is found that there are two kinds of polarization lasing beam emitting from the evanescent-wave pumped WGM fibre laser under two different pump conditions.When the pump beam is strictly along the axial direction of an optical fibre,the lasing emission is transverse electric wave and the electrical vectors at emitting points are along the radial direction of the fibre,which forms a special radial polarization radiation.However,when the pump beam deviates from the axial direction of the fibre,both transverse electric and transverse magnetic waves exist in the lasing emission,which forms a mixed polarization radiation with radial and axial polarized elements.Based on lasing radiation mechanism of evanescent-wave pumped WGM fibre laser,the observed polarization properties are well explained.
