Silicon carbide(SiC)has great potential for optomechanical applications due to its outstanding optical and mechanical properties.However,challenges associated with SiC nanofabrication have constrained its adoption in ...Silicon carbide(SiC)has great potential for optomechanical applications due to its outstanding optical and mechanical properties.However,challenges associated with SiC nanofabrication have constrained its adoption in optomechanical devices,as embodied by the considerable optical loss or lack of integrated optical access in existing mechanical resonators.In this work,we overcome such challenges and demonstrate a low-loss,ultracompact optomechanical resonator in an integrated 4H-SiC-on-insulator(4H-SiCOI)photonic platform for the first time,to our knowledge.Based on a suspended 4.3-μm-radius microdisk,the SiC optomechanical resonator features low optical loss(<1 dB∕cm),a high mechanical frequency f m of 0.95×10^(9)Hz,a mechanical quality factor Q_(m)of 1.92×10^(4),and a footprint of<1×10^(−5)mm^(2).The corresponding f_(m)·Q_(m)product is estimated to be 1.82×10^(13)Hz,which is among the highest reported values of optomechanical cavities tested in ambient environment at room temperature.In addition,the strong optomechanical coupling in the SiC microdisk enables coherent regenerative optomechanical oscillations at a threshold optical dropped power of 14μW,which also supports efficient harmonic generation at increased power levels.With such competitive performance,we envision a range of chip-scale optomechanical applications to be enabled by the low-loss 4H-SiCOI platform.展开更多
Atomic layers of hexagonal boron nitride(h-BN)crystal are excellent candidates for structural materials as enabling ultrathin,two-dimensional(2D)nanoelectromechanical systems(NEMS)due to the outstanding mechanical pro...Atomic layers of hexagonal boron nitride(h-BN)crystal are excellent candidates for structural materials as enabling ultrathin,two-dimensional(2D)nanoelectromechanical systems(NEMS)due to the outstanding mechanical properties and very wide bandgap(5.9 eV)of h-BN.In this work,we report the experimental demonstration of h-BN 2D nanomechanical resonators vibrating at high and very high frequencies(from~5 to~70 MHz),and investigations of the elastic properties of h-BN by measuring the multimode resonant behavior of these devices.First,we demonstrate a dry-transferred doubly clamped h-BN membrane with~6.7 nm thickness,the thinnest h-BN resonator known to date.In addition,we fabricate circular drumhead h-BN resonators with thicknesses ranging from~9 to 292 nm,from which we measure up to eight resonance modes in the range of~18 to 35 MHz.Combining measurements and modeling of the rich multimode resonances,we resolve h-BN’s elastic behavior,including the transition from membrane to disk regime,with built-in tension ranging from 0.02 to 2 N m−1.The Young’s modulus of h-BN is determined to be EY≈392 GPa from the measured resonances.The ultrasensitive measurements further reveal subtle structural characteristics and mechanical properties of the suspended h-BN diaphragms,including anisotropic built-in tension and bulging,thus suggesting guidelines on how these effects can be exploited for engineering multimode resonant functions in 2D NEMS transducers.展开更多
Nanoelectromechanical systems(NEMS)incorporating atomic or molecular layer van der Waals materials can support multimode resonances and exotic nonlinear dynamics.Here we investigate nonlinear coupling of closely space...Nanoelectromechanical systems(NEMS)incorporating atomic or molecular layer van der Waals materials can support multimode resonances and exotic nonlinear dynamics.Here we investigate nonlinear coupling of closely spaced modes in a bilayer(2L)molybdenum disulfide(MoS_(2))nanoelectromechanical resonator.We model the response from a drumhead resonator using equations of two resonant modes with a dispersive coupling term to describe the vibration induced frequency shifts that result from the induced change in tension.We employ method of averaging to solve the equations of coupled modes and extract an expression for the nonlinear coupling coefficient(λ)in closed form.Undriven thermomechanical noise spectral measurements are used to calibrate the vibration amplitude of mode 2(a_(2))in the displacement domain.We drive mode 2 near its natural frequency and measure the shifted resonance frequency of mode 1(f_(1s))resulting from the dispersive coupling.Our model yieldsλ=0.027±0.005 pm^(-2)·μs^(-2) from thermomechanical noise measurement of mode 1.Our model also captures an anomalous frequency shift of the undriven mode 1 due to nonlinear coupling to the driven mode 2 mediated by large dynamic tension.This study provides a direct means to quantifyingλby measuring the thermomechanical noise in NEMS and will be valuable for understanding nonlinear mode coupling in emerging resonant systems.展开更多
Miniaturized ultrasonic transducer arrays with multiple frequencies are key components in endoscopic photoacoustic imaging(PAI)systems to achieve high spatial resolution and large imaging depth for biomedical applicat...Miniaturized ultrasonic transducer arrays with multiple frequencies are key components in endoscopic photoacoustic imaging(PAI)systems to achieve high spatial resolution and large imaging depth for biomedical applications.In this article,we report on the development of ceramic thin-film PZT-based dual-and multi-frequency piezoelectric micromachined ultrasonic transducer(pMUT)arrays and the demonstration of their PAI applications.With chips sized 3.5mm in length or 10mm in diameter,square and ring-shaped pMUT arrays incorporating as many as 2520 pMUT elements and multiple frequencies ranging from 1 MHz to 8 MHz were developed for endoscopic PAI applications.Thin ceramic PZT with a thickness of 9μm was obtained by wafer bonding and chemical mechanical polishing(CMP)techniques and employed as the piezoelectric layer of the pMUT arrays,whose piezoelectric constant d_(31)was measured to be as high as 140 pm/V.Benefiting from this high piezoelectric constant,the fabricated pMUT arrays exhibited high electromechanical coupling coefficients and large vibration displacements.In addition to electrical,mechanical,and acoustic characterization,PAI experiments with pencil leads embedded into an agar phantom were conducted with the fabricated dual-and multi-frequency pMUT arrays.Photoacoustic signals were successfully detected by pMUT elements with different frequencies and used to reconstruct single and fused photoacoustic images,which clearly demonstrated the advantages of using dual-and multi-frequency pMUT arrays to provide comprehensive photoacoustic images with high spatial resolution and large signal-to-noise ratio simultaneously.展开更多
文摘Silicon carbide(SiC)has great potential for optomechanical applications due to its outstanding optical and mechanical properties.However,challenges associated with SiC nanofabrication have constrained its adoption in optomechanical devices,as embodied by the considerable optical loss or lack of integrated optical access in existing mechanical resonators.In this work,we overcome such challenges and demonstrate a low-loss,ultracompact optomechanical resonator in an integrated 4H-SiC-on-insulator(4H-SiCOI)photonic platform for the first time,to our knowledge.Based on a suspended 4.3-μm-radius microdisk,the SiC optomechanical resonator features low optical loss(<1 dB∕cm),a high mechanical frequency f m of 0.95×10^(9)Hz,a mechanical quality factor Q_(m)of 1.92×10^(4),and a footprint of<1×10^(−5)mm^(2).The corresponding f_(m)·Q_(m)product is estimated to be 1.82×10^(13)Hz,which is among the highest reported values of optomechanical cavities tested in ambient environment at room temperature.In addition,the strong optomechanical coupling in the SiC microdisk enables coherent regenerative optomechanical oscillations at a threshold optical dropped power of 14μW,which also supports efficient harmonic generation at increased power levels.With such competitive performance,we envision a range of chip-scale optomechanical applications to be enabled by the low-loss 4H-SiCOI platform.
基金We are grateful for support from the National Academy of Engineering(NAE)Grainger Foundation Frontier of Engineering(FOE)Award(FOE2013-005)the National Science Foundation CAREER Award(Grant ECCS-1454570)partial support from the Department of Energy(DOE)EERE Award(Grant DE-EE0006719),a ThinkEnergy Fellowship(X.-Q.Zheng),and the Case School of Engineering.A portion of the device fabrication was performed at the Cornell NanoScale Science and Technology Facility(CNF),a member of the National Nanotechnology Infrastructure Network(NNIN)supported by the National Science Foundation(Grant ECCS-0335765).
文摘Atomic layers of hexagonal boron nitride(h-BN)crystal are excellent candidates for structural materials as enabling ultrathin,two-dimensional(2D)nanoelectromechanical systems(NEMS)due to the outstanding mechanical properties and very wide bandgap(5.9 eV)of h-BN.In this work,we report the experimental demonstration of h-BN 2D nanomechanical resonators vibrating at high and very high frequencies(from~5 to~70 MHz),and investigations of the elastic properties of h-BN by measuring the multimode resonant behavior of these devices.First,we demonstrate a dry-transferred doubly clamped h-BN membrane with~6.7 nm thickness,the thinnest h-BN resonator known to date.In addition,we fabricate circular drumhead h-BN resonators with thicknesses ranging from~9 to 292 nm,from which we measure up to eight resonance modes in the range of~18 to 35 MHz.Combining measurements and modeling of the rich multimode resonances,we resolve h-BN’s elastic behavior,including the transition from membrane to disk regime,with built-in tension ranging from 0.02 to 2 N m−1.The Young’s modulus of h-BN is determined to be EY≈392 GPa from the measured resonances.The ultrasensitive measurements further reveal subtle structural characteristics and mechanical properties of the suspended h-BN diaphragms,including anisotropic built-in tension and bulging,thus suggesting guidelines on how these effects can be exploited for engineering multimode resonant functions in 2D NEMS transducers.
基金National Science Foundation(NSF)for funding through the IUSE program(Grant DUE-2142552)QuSeC-TAQS program(Grant OSI-2326528)supported in part by the Defense Advanced Research Projects Agency(DARPA)H6 program under cooperative agreement HR0011-23-2-0004.
文摘Nanoelectromechanical systems(NEMS)incorporating atomic or molecular layer van der Waals materials can support multimode resonances and exotic nonlinear dynamics.Here we investigate nonlinear coupling of closely spaced modes in a bilayer(2L)molybdenum disulfide(MoS_(2))nanoelectromechanical resonator.We model the response from a drumhead resonator using equations of two resonant modes with a dispersive coupling term to describe the vibration induced frequency shifts that result from the induced change in tension.We employ method of averaging to solve the equations of coupled modes and extract an expression for the nonlinear coupling coefficient(λ)in closed form.Undriven thermomechanical noise spectral measurements are used to calibrate the vibration amplitude of mode 2(a_(2))in the displacement domain.We drive mode 2 near its natural frequency and measure the shifted resonance frequency of mode 1(f_(1s))resulting from the dispersive coupling.Our model yieldsλ=0.027±0.005 pm^(-2)·μs^(-2) from thermomechanical noise measurement of mode 1.Our model also captures an anomalous frequency shift of the undriven mode 1 due to nonlinear coupling to the driven mode 2 mediated by large dynamic tension.This study provides a direct means to quantifyingλby measuring the thermomechanical noise in NEMS and will be valuable for understanding nonlinear mode coupling in emerging resonant systems.
基金the National Institutes of Health(NIH)under award#R01EB020601the National Key R&D Program of China under award#2018YFF01010904.
文摘Miniaturized ultrasonic transducer arrays with multiple frequencies are key components in endoscopic photoacoustic imaging(PAI)systems to achieve high spatial resolution and large imaging depth for biomedical applications.In this article,we report on the development of ceramic thin-film PZT-based dual-and multi-frequency piezoelectric micromachined ultrasonic transducer(pMUT)arrays and the demonstration of their PAI applications.With chips sized 3.5mm in length or 10mm in diameter,square and ring-shaped pMUT arrays incorporating as many as 2520 pMUT elements and multiple frequencies ranging from 1 MHz to 8 MHz were developed for endoscopic PAI applications.Thin ceramic PZT with a thickness of 9μm was obtained by wafer bonding and chemical mechanical polishing(CMP)techniques and employed as the piezoelectric layer of the pMUT arrays,whose piezoelectric constant d_(31)was measured to be as high as 140 pm/V.Benefiting from this high piezoelectric constant,the fabricated pMUT arrays exhibited high electromechanical coupling coefficients and large vibration displacements.In addition to electrical,mechanical,and acoustic characterization,PAI experiments with pencil leads embedded into an agar phantom were conducted with the fabricated dual-and multi-frequency pMUT arrays.Photoacoustic signals were successfully detected by pMUT elements with different frequencies and used to reconstruct single and fused photoacoustic images,which clearly demonstrated the advantages of using dual-and multi-frequency pMUT arrays to provide comprehensive photoacoustic images with high spatial resolution and large signal-to-noise ratio simultaneously.
