Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 TH...Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 THz.A key breakthrough is developing a reliable single-shot detection method,essential for measuring the electric field of these broadband,low-repetition-rate pulses,which is vital for exploring the complex dynamics of THz emission and studying extreme nonlinear material responses in this range.Existing detection methods have been limited to lower frequencies.Here,we introduce the first potentially single-shot-capable THz detection technique for capturing ultra-broadband waveforms.Utilizing a 1-μm-thick SiN detection chip,we exploit THz field-induced second harmonic generation to achieve real-time monitoring of THz waveforms with frequency content up to 30 THz.By adjusting the angle between the THz and optical probe beams,we can fine-tune the detection window for enhanced flexibility.Our novel THz detector is ideally suited for high-energy,low-repetition-rate sources,unlocking new frontiers in THz research.展开更多
We propose a technique for chromatic dispersion monitoring based on optical time domain level monitoring. Experimental and simulation results show that the technique is effective for the monitoring of dispersion in 42...We propose a technique for chromatic dispersion monitoring based on optical time domain level monitoring. Experimental and simulation results show that the technique is effective for the monitoring of dispersion in 42.7-Gbps CS-RZ signals for dynamic dispersion compensation.展开更多
In this paper,we present a hybrid form of weighted compact nonlinear scheme(WCNS)for hyperbolic conservation laws by applying linear and nonlinear methods for smooth and discontinuous zones individually.To fulfill thi...In this paper,we present a hybrid form of weighted compact nonlinear scheme(WCNS)for hyperbolic conservation laws by applying linear and nonlinear methods for smooth and discontinuous zones individually.To fulfill this algorithm,it is inseparable from the recognition ability of the discontinuity detector adopted.In specific,a troubled-cell indicator is utilized to recognize unsmooth areas such as shock waves and contact discontinuities,while avoiding misjudgments of smooth structures.Some classical detectors are classified into three basic types:derivative combination,smoothness indicators and characteristic decomposition.Meanwhile,a new improved detector is proposed for comparison.Then they are analyzed through identifying a series of waveforms firstly.After that,hybrid schemes using such indicators,as well as different detection variables,are examined with Euler equations,so as to investigate their ability to distinguish practical discontinuities on various levels.Simulation results demonstrate that the proposed algorithm has similar performances to pure WCNS,while it generally saves 50 percent of CPU time for 1D cases and about 40 percent for 2D Euler equations.Current research is in the hope of providing some reference and establishing some standards for judging existing discontinuity detectors and developing novel ones.展开更多
The problem of sonar signal waveform design to detect a high-speed small target in an underwater environment is discussed. From theoretical analysis, time-frequency hop signal is regarded as the most suitable signal w...The problem of sonar signal waveform design to detect a high-speed small target in an underwater environment is discussed. From theoretical analysis, time-frequency hop signal is regarded as the most suitable signal waveform in this application. To get precise target parameter estimation ability, the signal should have high range-Doppler resolution performance. The results of signal analysis show that hop signal with frequency serial coding as Costas array has sharp ambiguity characteristic, so it can be used in an active sonar system to detect a high speed small target. A scheme of frequency coding is also presented.展开更多
基金supported by the Independent Research Fund Denmark(project THz-GRIP:2035-00365B).
文摘Recent advancements in high-energy terahertz(THz)sources,driven by powerful laser systems,now enable the generation of ultrashort THz pulses with energies up to several millijoules,spanning frequencies from 1 to 30 THz.A key breakthrough is developing a reliable single-shot detection method,essential for measuring the electric field of these broadband,low-repetition-rate pulses,which is vital for exploring the complex dynamics of THz emission and studying extreme nonlinear material responses in this range.Existing detection methods have been limited to lower frequencies.Here,we introduce the first potentially single-shot-capable THz detection technique for capturing ultra-broadband waveforms.Utilizing a 1-μm-thick SiN detection chip,we exploit THz field-induced second harmonic generation to achieve real-time monitoring of THz waveforms with frequency content up to 30 THz.By adjusting the angle between the THz and optical probe beams,we can fine-tune the detection window for enhanced flexibility.Our novel THz detector is ideally suited for high-energy,low-repetition-rate sources,unlocking new frontiers in THz research.
文摘We propose a technique for chromatic dispersion monitoring based on optical time domain level monitoring. Experimental and simulation results show that the technique is effective for the monitoring of dispersion in 42.7-Gbps CS-RZ signals for dynamic dispersion compensation.
基金supported by the National Natural Science Foundation of China(grant Nos.11972370,92252101,11927803).
文摘In this paper,we present a hybrid form of weighted compact nonlinear scheme(WCNS)for hyperbolic conservation laws by applying linear and nonlinear methods for smooth and discontinuous zones individually.To fulfill this algorithm,it is inseparable from the recognition ability of the discontinuity detector adopted.In specific,a troubled-cell indicator is utilized to recognize unsmooth areas such as shock waves and contact discontinuities,while avoiding misjudgments of smooth structures.Some classical detectors are classified into three basic types:derivative combination,smoothness indicators and characteristic decomposition.Meanwhile,a new improved detector is proposed for comparison.Then they are analyzed through identifying a series of waveforms firstly.After that,hybrid schemes using such indicators,as well as different detection variables,are examined with Euler equations,so as to investigate their ability to distinguish practical discontinuities on various levels.Simulation results demonstrate that the proposed algorithm has similar performances to pure WCNS,while it generally saves 50 percent of CPU time for 1D cases and about 40 percent for 2D Euler equations.Current research is in the hope of providing some reference and establishing some standards for judging existing discontinuity detectors and developing novel ones.
文摘The problem of sonar signal waveform design to detect a high-speed small target in an underwater environment is discussed. From theoretical analysis, time-frequency hop signal is regarded as the most suitable signal waveform in this application. To get precise target parameter estimation ability, the signal should have high range-Doppler resolution performance. The results of signal analysis show that hop signal with frequency serial coding as Costas array has sharp ambiguity characteristic, so it can be used in an active sonar system to detect a high speed small target. A scheme of frequency coding is also presented.
