Optical whispering-gallery microresonators have attracted considerable interest for ultrasensitive ultrasound detection and photoacoustic imaging because of the combination of high quality factors and small cavity siz...Optical whispering-gallery microresonators have attracted considerable interest for ultrasensitive ultrasound detection and photoacoustic imaging because of the combination of high quality factors and small cavity sizes.In the last decade,ultrasonic sensors with on-chip microcavities have been extensively developed;however,they are unsuitable for the near-field photoacoustic microscopy of micro/nanoscale objects in complex biological environments and endoscopic imaging.In this work,we developed ultrasonic sensors using two types of encapsulated microsphere resonators with different cavity materials.A noise equivalent pressure of as low as 160 Pa at 20 MHz was achieved with the acoustic response up to 70 MHz at-6 d B.Furthermore,the microsensor was used for photoacoustic microscopy in which we successfully performed 3 D imaging of hairs and leaf veins.The microsphere ultrasonic sensor has considerable potential as a probe-type ultrasonic detector for near-field photoacoustic microscopy of micro/nanoscale objects such as subcellular structures and high-resolution endoscopic photoacoustic imaging with its high sensitivity and wide bandwidth.展开更多
Nonlinear high-harmonic generation in micro-resonators is a common technique used to extend the operating range of applications such as self-referencing systems and coherent communications in the visible region.Howeve...Nonlinear high-harmonic generation in micro-resonators is a common technique used to extend the operating range of applications such as self-referencing systems and coherent communications in the visible region.However,the generated high-harmonic emissions are subject to a resonance shift with a change in temperature.We present a comprehensive study of the thermal behavior induced phase mismatch that shows this resonance shift can be compensated by a combination of the linear and nonlinear thermo-optics effects.Using this model,we predict and experimentally demonstrate visible third harmonic modes having temperature dependent wavelength shifts between−2.84 pm/ºC and 2.35 pm/ºC when pumped at the L-band.Besides providing a new way to achieve athermal operation,this also allows one to measure the thermal coefficients and Q-factor of the visible modes.Through steady state analysis,we have also identified the existence of stable athermal third harmonic generation and experimentally demonstrated orthogonally pumped visible third harmonic modes with a temperature dependent wavelength shift of 0.05 pm/ºC over a temperature range of 12ºC.Our findings promise a configurable and active temperature dependent wavelength shift compensation scheme for highly efficient and precise visible emission generation for potential 2f–3f self-referencing in metrology,biological and chemical sensing applications.展开更多
This paper deals with the surface analysis of spherical polymeric optical micro-resonators in order to correlate surface defects with optical characteristics. Atomic force microscopy was used on structures to determin...This paper deals with the surface analysis of spherical polymeric optical micro-resonators in order to correlate surface defects with optical characteristics. Atomic force microscopy was used on structures to determine surface quality, which is the main origin of optical scattering losses. Surface morphologies were numerically treated to enable a relevant investigation on surface parameters such as root mean square (RMS) roughness (30.1 +/- 3.0 nm) or correlation length (few microns) necessary to express optical quality factors. A statistical analysis was conducted for calibration of these parameters as a function of cavities’ diameter. Results are in perfect agreement with spectral analyses performed in parallel on others structures. This comparison highlights the main role of scattering losses on quality factor origin.展开更多
Whispering gallery mode(WGM)resonators made from dielectrics like glass or polymers have outstanding optical properties like huge cavity quality(Q)factors which can be achieved on scales compatible with on-chip integr...Whispering gallery mode(WGM)resonators made from dielectrics like glass or polymers have outstanding optical properties like huge cavity quality(Q)factors which can be achieved on scales compatible with on-chip integration.However,tunability of these resonances is typically difficult to achieve or not suitable for robust device applications.We report here on the fabrication of polymeric micro-goblet WGM resonators with an optically controlled and stable reversible tunability over a large spectral range.This tunability is achieved by integration of photo-responsive liquid crystalline elastomers(LCEs)into micro-goblet cavities.The optical response of the elastomer allows reshaping the goblet by employing low pump power,leading to a fully reversible tuning of the modes.The structure can be realistically implemented in on-chip devices,combining the ultra-high Q factors,typical of WGM resonators,with reliable,optical tunability.This result serves as an example of how light can control light,by invoking a physical reshaping of the structure.This way of optical tuning creates interesting possibilities for all-optical control in circuits,enabling interaction between signal and control beams and the realization of self-tuning cavities.展开更多
Our aim is to evidence new 3D composite diffractive structures whose effective permittivity tensor can exhibit very large positive or negative real eigenvalues.We use a reiterated homogenization procedure in which the...Our aim is to evidence new 3D composite diffractive structures whose effective permittivity tensor can exhibit very large positive or negative real eigenvalues.We use a reiterated homogenization procedure in which the first step consists in considering a bounded obstacle made of periodically disposed parallel high conducting metallic fibers of finite length and very thin cross section.As shown in[2],the resulting constitutive law is non-local.Then by reproducing periodically the same kind of obstacle at small scale,we obtain a local effective law described by a permittivity tensor that we make explicit as a function of the frequency.Due to internal resonances,the eigenvalues of this tensor have real part that change of sign and are possibly very large within some range of frequencies.Numerical simulations are shown.展开更多
In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimu...In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimum design parameters of the system, maximizing the sensitivity of the sensor, are determined. It is found that, when optimally designed, the sensor can detect relative refractive index changes of the order of △n/n≈3×10^-4, assuming that the experimental setup can detect relative wavelength shifts of the order of △λ/λ≈3×10^-5. The behavior of the system as bio-sensor has also been examined. It is found that, when optimally designed, the system can detect refractive index changes of the order of △n≈ 10^-3 for a layer thickness of t=- 10 nm, and changes in the layer thickness of the order of △t≈0.24 nm, for a refractive index change of △n=0.05.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2017YFE0104200)National Natural Science Foundation of China(Grant Nos.81421004,62105006)supported by the China Postdoctoral Science Foundation(Grant Nos.2020M680187,2021T140023)。
文摘Optical whispering-gallery microresonators have attracted considerable interest for ultrasensitive ultrasound detection and photoacoustic imaging because of the combination of high quality factors and small cavity sizes.In the last decade,ultrasonic sensors with on-chip microcavities have been extensively developed;however,they are unsuitable for the near-field photoacoustic microscopy of micro/nanoscale objects in complex biological environments and endoscopic imaging.In this work,we developed ultrasonic sensors using two types of encapsulated microsphere resonators with different cavity materials.A noise equivalent pressure of as low as 160 Pa at 20 MHz was achieved with the acoustic response up to 70 MHz at-6 d B.Furthermore,the microsensor was used for photoacoustic microscopy in which we successfully performed 3 D imaging of hairs and leaf veins.The microsphere ultrasonic sensor has considerable potential as a probe-type ultrasonic detector for near-field photoacoustic microscopy of micro/nanoscale objects such as subcellular structures and high-resolution endoscopic photoacoustic imaging with its high sensitivity and wide bandwidth.
基金We are grateful for financial supports from the Natural Science Foundation of Fujian Province(Grant No.2017J01756)National Natural Science Foundation of China(Grant No.R-IND12101,No.61675231)Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB24030300).
文摘Nonlinear high-harmonic generation in micro-resonators is a common technique used to extend the operating range of applications such as self-referencing systems and coherent communications in the visible region.However,the generated high-harmonic emissions are subject to a resonance shift with a change in temperature.We present a comprehensive study of the thermal behavior induced phase mismatch that shows this resonance shift can be compensated by a combination of the linear and nonlinear thermo-optics effects.Using this model,we predict and experimentally demonstrate visible third harmonic modes having temperature dependent wavelength shifts between−2.84 pm/ºC and 2.35 pm/ºC when pumped at the L-band.Besides providing a new way to achieve athermal operation,this also allows one to measure the thermal coefficients and Q-factor of the visible modes.Through steady state analysis,we have also identified the existence of stable athermal third harmonic generation and experimentally demonstrated orthogonally pumped visible third harmonic modes with a temperature dependent wavelength shift of 0.05 pm/ºC over a temperature range of 12ºC.Our findings promise a configurable and active temperature dependent wavelength shift compensation scheme for highly efficient and precise visible emission generation for potential 2f–3f self-referencing in metrology,biological and chemical sensing applications.
文摘This paper deals with the surface analysis of spherical polymeric optical micro-resonators in order to correlate surface defects with optical characteristics. Atomic force microscopy was used on structures to determine surface quality, which is the main origin of optical scattering losses. Surface morphologies were numerically treated to enable a relevant investigation on surface parameters such as root mean square (RMS) roughness (30.1 +/- 3.0 nm) or correlation length (few microns) necessary to express optical quality factors. A statistical analysis was conducted for calibration of these parameters as a function of cavities’ diameter. Results are in perfect agreement with spectral analyses performed in parallel on others structures. This comparison highlights the main role of scattering losses on quality factor origin.
基金This work has been supported by the joint Erasmus Mundus Doctorate program“Europhotonics”frame work agreement(European contract no.2010-0001-001/001)the Karlsruhe School of Optics and Photonics(KSOP)and also European Research Council under the European Union’s Seventh Framework Program(FP7/2007-2013)/ERC grant agreement no.291349 on photonic micro roboticsWe acknowledge support by Deutsche Forschungsgemeinschaft(DFG)and Open Access Publishing Fund of Karlsruhe Institute of Technology。
文摘Whispering gallery mode(WGM)resonators made from dielectrics like glass or polymers have outstanding optical properties like huge cavity quality(Q)factors which can be achieved on scales compatible with on-chip integration.However,tunability of these resonances is typically difficult to achieve or not suitable for robust device applications.We report here on the fabrication of polymeric micro-goblet WGM resonators with an optically controlled and stable reversible tunability over a large spectral range.This tunability is achieved by integration of photo-responsive liquid crystalline elastomers(LCEs)into micro-goblet cavities.The optical response of the elastomer allows reshaping the goblet by employing low pump power,leading to a fully reversible tuning of the modes.The structure can be realistically implemented in on-chip devices,combining the ultra-high Q factors,typical of WGM resonators,with reliable,optical tunability.This result serves as an example of how light can control light,by invoking a physical reshaping of the structure.This way of optical tuning creates interesting possibilities for all-optical control in circuits,enabling interaction between signal and control beams and the realization of self-tuning cavities.
基金support of ANR projects POEM(PNANO 06-0030)OPTRANS(2010 BLAN 012403).
文摘Our aim is to evidence new 3D composite diffractive structures whose effective permittivity tensor can exhibit very large positive or negative real eigenvalues.We use a reiterated homogenization procedure in which the first step consists in considering a bounded obstacle made of periodically disposed parallel high conducting metallic fibers of finite length and very thin cross section.As shown in[2],the resulting constitutive law is non-local.Then by reproducing periodically the same kind of obstacle at small scale,we obtain a local effective law described by a permittivity tensor that we make explicit as a function of the frequency.Due to internal resonances,the eigenvalues of this tensor have real part that change of sign and are possibly very large within some range of frequencies.Numerical simulations are shown.
文摘In this work, the behavior of refractive index sensors based on optical micro-ring resonators is studied in detail. Using a result of waveguide perturbation theory in combination with numerical simulations, the optimum design parameters of the system, maximizing the sensitivity of the sensor, are determined. It is found that, when optimally designed, the sensor can detect relative refractive index changes of the order of △n/n≈3×10^-4, assuming that the experimental setup can detect relative wavelength shifts of the order of △λ/λ≈3×10^-5. The behavior of the system as bio-sensor has also been examined. It is found that, when optimally designed, the system can detect refractive index changes of the order of △n≈ 10^-3 for a layer thickness of t=- 10 nm, and changes in the layer thickness of the order of △t≈0.24 nm, for a refractive index change of △n=0.05.
