A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is proposed.The Pearson correlation coefficient bet...A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is proposed.The Pearson correlation coefficient between the instantaneous frequency of the generated LFM signal and that of an ideal LFM signal is introduced to quantify the quality of the generated LFM signal.The closed-form solution of the correlation coefficient is given,which shows that the correlation coefficient is determined by the ratio of the LFM signal bandwidth to the square root of the total linewidth of the two LDs when the observation interval is fixed.Simulation results are also given,which proves the correctness of the theoretical results.展开更多
An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser syst...An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser systems.In this study,in-depth theoretical interpretation and experimental verification of the noncontinuous-state dynamics in laser system are presented,based on developed pulse-modulated frequency-shifted laser feedback interferometry(LFI).By introducing external pulse modulation,we investigate the nonlinear time-of-flight dynamics and related photon behaviors evolution of the pulsed LFI system by observing the changes in effective interference time sequences for interference realization and attainable minimum feedback photon number of the signal under various modulated noncontinuous states.Implementation of the pulse-modulated LFI scheme should exceed the pulse overlapping time window limit of 1.93μs to effectively extract and preserve the extracavity feedback photon information.Experiments reveal that the minimum feedback photon number of signals successfully measured by the pulsed LFI sensor is 0.067 feedback photons per Doppler cycle,exhibiting high sensitivity for extremely weak signal detection.Further,simultaneous measurement for velocity and distance of the moving object is performed to validate the feasibility and applicability of the pulsed LFI.The system can successfully achieve large-range simultaneous measurements within the velocity range of 73.5-612.6 mm∕s,over a distance of 25.5 km.This work opens the way to unexplored frontiers of pulsed LFI to fill the research gap in noncontinuous laser dynamics in this field,showcasing diverse and wide-ranging applications in the realm of integrated sensing,remote monitoring,and positioning and navigation.展开更多
The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing throug...The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing through spatial filters with different magnifications is analyzed by numerical simulation, according to the actual structure of the high power laser system. The results show that the spatial modulation period of low-frequency noise getting through the pinhole will be proportional to the magnification of the spatial filter. When the magnification is less than 1, the safe low-frequency noise will be extruded into the high-frequency region, which is the fast increasing part, and finally develops into the most dangerous part which can damage the optical devices. The conclusion of this research improves the relay imaging theory of a spatial filter and provides an important theoretical basis for a general design of high power laser systems.展开更多
基金supported by the National Key R&D Program of China(No.2017YFE0121500)the National Natural Science Foundation of China(Nos.61971193 and 61601297)+1 种基金the Open Fund of State Key Laboratory of Advanced Optical Communication Systems and Networks,Peking University,China(No.2020GZKF005)the Fundamental Research Funds for the Central Universities。
文摘A method to evaluate the influence of the laser linewidth on the linearly frequency-modulated(LFM)signals generated by heterodyning two free-running laser diodes(LDs)is proposed.The Pearson correlation coefficient between the instantaneous frequency of the generated LFM signal and that of an ideal LFM signal is introduced to quantify the quality of the generated LFM signal.The closed-form solution of the correlation coefficient is given,which shows that the correlation coefficient is determined by the ratio of the LFM signal bandwidth to the square root of the total linewidth of the two LDs when the observation interval is fixed.Simulation results are also given,which proves the correctness of the theoretical results.
基金National Natural Science Foundation of China(62275001,62105001)China Postdoctoral Science Foundation(GZC20242187)Zhejiang Province Postdoctoral Research Funding(ZJ2024097)。
文摘An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser systems.In this study,in-depth theoretical interpretation and experimental verification of the noncontinuous-state dynamics in laser system are presented,based on developed pulse-modulated frequency-shifted laser feedback interferometry(LFI).By introducing external pulse modulation,we investigate the nonlinear time-of-flight dynamics and related photon behaviors evolution of the pulsed LFI system by observing the changes in effective interference time sequences for interference realization and attainable minimum feedback photon number of the signal under various modulated noncontinuous states.Implementation of the pulse-modulated LFI scheme should exceed the pulse overlapping time window limit of 1.93μs to effectively extract and preserve the extracavity feedback photon information.Experiments reveal that the minimum feedback photon number of signals successfully measured by the pulsed LFI sensor is 0.067 feedback photons per Doppler cycle,exhibiting high sensitivity for extremely weak signal detection.Further,simultaneous measurement for velocity and distance of the moving object is performed to validate the feasibility and applicability of the pulsed LFI.The system can successfully achieve large-range simultaneous measurements within the velocity range of 73.5-612.6 mm∕s,over a distance of 25.5 km.This work opens the way to unexplored frontiers of pulsed LFI to fill the research gap in noncontinuous laser dynamics in this field,showcasing diverse and wide-ranging applications in the realm of integrated sensing,remote monitoring,and positioning and navigation.
文摘The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing through spatial filters with different magnifications is analyzed by numerical simulation, according to the actual structure of the high power laser system. The results show that the spatial modulation period of low-frequency noise getting through the pinhole will be proportional to the magnification of the spatial filter. When the magnification is less than 1, the safe low-frequency noise will be extruded into the high-frequency region, which is the fast increasing part, and finally develops into the most dangerous part which can damage the optical devices. The conclusion of this research improves the relay imaging theory of a spatial filter and provides an important theoretical basis for a general design of high power laser systems.
