Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven a...Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.展开更多
The integration of multiple electrophysiological biomarkers is crucial for monitoring neonatal seizure dynamics.The present study aimed to characterize the temporal dynamics of neonatal seizures by analyzing intrinsic...The integration of multiple electrophysiological biomarkers is crucial for monitoring neonatal seizure dynamics.The present study aimed to characterize the temporal dynamics of neonatal seizures by analyzing intrinsic waveforms of epileptic electroencephalogram(EEG)signals.We proposed a complementary set of methods considering envelope power,focal sharpness changes,and nonlinear patterns of EEG signals of 79 neonates with seizures.Features derived from EEG signals were used as input to the machine learning classifier.All three characteristics were significantly elevated during seizure events,as agreed upon by all viewers(P<0.0001).Envelope power was elevated in the entire seizure period,and the degree of nonlinearity rose at the termination of a seizure event.Epileptic sharpness effectively characterizes an entire seizure event,complementing the role of envelope power in identifying its onset.However,the degree of nonlinearity showed superior discriminability for the termination of a seizure event.The proposed computational methods for intrinsic sharp or nonlinear EEG patterns evolving during neonatal seizure could share some features with envelope power.Current findings may be helpful in developing strategies to improve neonatal seizure monitoring.展开更多
基金Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDB 24030600)National Key Research and Development Program of China(2016YFF0200702)+1 种基金National Natural Science Foundation of China(NSFC)(61690222,61308037,61635013)CASSAFEA International Partnership Program for Creative Research Teams
文摘Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.
基金partially supported by the National Natural Science Foundation of China(Nos.62171028 and 62001026)the Beijing Natural Science Foundation(No.L232139)+2 种基金the Open Project of Key Laboratory of Medical Electronics and Digital Health of Zhejiang Province(Nos.MEDH202204 and MEDC202303)the High-Level Fellow Research Fund Program(No.3050012222022)the BIT Research and Innovation Promoting Project(No.2023YCXZ009).
文摘The integration of multiple electrophysiological biomarkers is crucial for monitoring neonatal seizure dynamics.The present study aimed to characterize the temporal dynamics of neonatal seizures by analyzing intrinsic waveforms of epileptic electroencephalogram(EEG)signals.We proposed a complementary set of methods considering envelope power,focal sharpness changes,and nonlinear patterns of EEG signals of 79 neonates with seizures.Features derived from EEG signals were used as input to the machine learning classifier.All three characteristics were significantly elevated during seizure events,as agreed upon by all viewers(P<0.0001).Envelope power was elevated in the entire seizure period,and the degree of nonlinearity rose at the termination of a seizure event.Epileptic sharpness effectively characterizes an entire seizure event,complementing the role of envelope power in identifying its onset.However,the degree of nonlinearity showed superior discriminability for the termination of a seizure event.The proposed computational methods for intrinsic sharp or nonlinear EEG patterns evolving during neonatal seizure could share some features with envelope power.Current findings may be helpful in developing strategies to improve neonatal seizure monitoring.
