Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM m...Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM multiplexing and achieve high-power laser output,providing substantial advantages for long-distance communication.Herein,we present an integrated CBC system for freespace optical links based on OAM multiplexing and demultiplexing technologies for the first time,to the best of our knowledge.A method to achieve flexible OAM multiplexing and efficient demultiplexing based on the CBC system is proposed and demonstrated both theoretically and experimentally.The experimental results exhibit a low bit error rate of 0.47%and a high recognition precision of 98.58%throughout the entire data transmission process.By employing such an ingenious strategy,this work holds promising prospects for enriching ultra-long-distance structured light communication in the future.展开更多
In this paper,we report a coherent beam combining(CBC)system that involves two thulium-doped all-polarization maintaining(PM)fiber chirped pulse amplifiers.Through phase-locking the two channels via a fiber stretcher ...In this paper,we report a coherent beam combining(CBC)system that involves two thulium-doped all-polarization maintaining(PM)fiber chirped pulse amplifiers.Through phase-locking the two channels via a fiber stretcher by using the stochastic parallel gradient descent(SPGD)algorithm,a maximum average power of 265 W is obtained,with a CBC efficiency of 81%and a residual phase error of λ/17.After de-chirping by a pair of diffraction gratings,the duration of the combined laser pulse is compressed to 690 fs.Taking into account the compression efficiency of 90%and the main peak energy proportion of 91%,the corresponding peak power is calculated to be 4 MW.The laser noise characteristics before and after CBC are examined,and the results indicate that the CBC would degrade the low frequency relative intensity noise(RIN),of which the integration is 1.74%in[100 Hz,2 MHz]at the maximum combined output power.In addition,the effects of the nonlinear spectrum broadening during chirped pulse amplification on the CBC efficiency are also investigated,showing that a higher extent of pulse stretching is effective in alleviating the spectrum broadening and realizing a higher output power with decent combining efficiency.展开更多
High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated.The active polarization control technology based on the root-mean-square propagation(RMS-p...High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated.The active polarization control technology based on the root-mean-square propagation(RMS-prop)algorithm is employed to guarantee a linearly polarized output from the system.A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio(PER)of>11.4 dB.In addition,the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser.The M2factor of the laser beam at the highest output power is measured to be less than 1.15,indicating a diffraction-limited beam quality.Finally,the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W.This is the first time,to the best of our knowledge,that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.展开更多
The high-power mode-programmable orbital angular momentum(OAM)beam has attracted significant attention in a wide range of applications,such as long-distance optical communication,nonlinear frequency conversion,and bea...The high-power mode-programmable orbital angular momentum(OAM)beam has attracted significant attention in a wide range of applications,such as long-distance optical communication,nonlinear frequency conversion,and beam shaping.Coherent beam combining(CBC)of an optical phased array(OPA)can offer a promising solution for both generating the high-power OAM beam and rapidly switching the OAM modes.However,achieving real-time phase noise locking and formation of desired phase structures in a high-power CBC system faces significant challenges.Here,an internal phase-sensing technique was utilized to generate the high-power OAM beam,which effectively mitigated thermal effects and eliminated the need for large optical devices.An OPA with six elements was employed for experimental demonstration.The first effective generation of over 1.5 kW mode-programmable OAM beam in a continuous-wave domain was presented.Moreover,the results demonstrated that the generated OAM beam could be modulated with multiple dimensions.The topological charge can be switched in real time from-1 to-2.Notably,this OAM beam emitter could function as an OAM beam copier by easily transforming a single OAM beam into an OAM beam array.More importantly,a comprehensive analysis was conducted on power scaling,mode switching speed,and expansion of OAM modes.Additionally,the system’s compact design enabled it to function as a packageable OAM beam emitter.Owing to the advantages of having high power and programmable modes with multiple dimension modulation in phase structures and intensity distribution,this work can pave the way for producing high-power structured light beams and advancing their applications.展开更多
Coherent beam combining of 107 beams has been demonstrated for the first time to the best of our knowledge.When the system was in closed loop,the pattern in far-field was stable and the fringe contrast was>96%.The ...Coherent beam combining of 107 beams has been demonstrated for the first time to the best of our knowledge.When the system was in closed loop,the pattern in far-field was stable and the fringe contrast was>96%.The impact of the dynamic tilt error,the piston error,and power inconsistency was theoretically analyzed.Meanwhile,the distribution law of dynamic tilt error was estimated and the correlation of the tilt dithering of different axis was analyzed statistically.The ratio of power in the central lobe was^22.5%.The phase residue error in the closed loop was~λ∕22,which was evaluated by the root-mean-square error of the signal generated from the photoelectric detector.展开更多
Coherent beam combining of 60 fiber lasers by using the stochastic parallel gradient descent algorithm has been demonstrated. The functions of pinhole(s) on the power distributions in the far-field have been systemati...Coherent beam combining of 60 fiber lasers by using the stochastic parallel gradient descent algorithm has been demonstrated. The functions of pinhole(s) on the power distributions in the far-field have been systematically simulated on both in-phase and out-of-phase modes. Only one photoelectric detector was used to detect the combined power in the far-field central lobe of the in-phase mode state. When the phase controller was in a closed loop, the contrast of the far-field intensity pattern was as high as ~97% with residual phase error of ~λ/30, and ~34.7% of the total power was contained in the central lobe.展开更多
We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locke...We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent(SPGD)algorithm,respectively.In this way,the phases of the whole array were locked,and the visibility of the interference pattern of the whole emitted laser array in the far field was∼93%.In addition,the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination(CBC)system due to its compact spatial structure.展开更多
Dynamic beam shaping is of importance for a wide range of applications, such as light field regulation, laser processing, and advanced manufacturing. In this paper, an internal phase-sensing tiled-aperture coherent be...Dynamic beam shaping is of importance for a wide range of applications, such as light field regulation, laser processing, and advanced manufacturing. In this paper, an internal phase-sensing tiled-aperture coherent beam-combining system with seven beam elements was constructed for dynamic beam shaping. This system could be performed as a digital laser,where each laser beamlet functioned as an individual laser pixel. The amplitude and phase of each laser pixel could be adjusted independently in real time. In our experiment, the laser array was operated in three different configurations:the triangular, pentagonal, and hexagonal laser arrays, while each laser pixel was modulated with a different piston phase of nπ(where n was an integer). We demonstrated various beam-shaping patterns based on this system with output powers scaling over 1 kW. Additionally, the energy distribution of the emitted laser could be flexibly varied and customized.These results highlighted that our dynamic beam-shaped laser exhibited excellent performance in both dynamic beam-shaping and power-scaling capabilities. This work holds great potential for numerous applications involving beam shaping.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.62305388)the Postgraduate Scientific Research Innovation Project of Hunan Province(Grant No.QL20230007).
文摘Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM multiplexing and achieve high-power laser output,providing substantial advantages for long-distance communication.Herein,we present an integrated CBC system for freespace optical links based on OAM multiplexing and demultiplexing technologies for the first time,to the best of our knowledge.A method to achieve flexible OAM multiplexing and efficient demultiplexing based on the CBC system is proposed and demonstrated both theoretically and experimentally.The experimental results exhibit a low bit error rate of 0.47%and a high recognition precision of 98.58%throughout the entire data transmission process.By employing such an ingenious strategy,this work holds promising prospects for enriching ultra-long-distance structured light communication in the future.
基金supported in part by the National Key Research and Development Program of China(No.2022YFB3606000)in part by State Key Laboratory of Pulsed Power Laser Technology(No.SKL2020ZR02).
文摘In this paper,we report a coherent beam combining(CBC)system that involves two thulium-doped all-polarization maintaining(PM)fiber chirped pulse amplifiers.Through phase-locking the two channels via a fiber stretcher by using the stochastic parallel gradient descent(SPGD)algorithm,a maximum average power of 265 W is obtained,with a CBC efficiency of 81%and a residual phase error of λ/17.After de-chirping by a pair of diffraction gratings,the duration of the combined laser pulse is compressed to 690 fs.Taking into account the compression efficiency of 90%and the main peak energy proportion of 91%,the corresponding peak power is calculated to be 4 MW.The laser noise characteristics before and after CBC are examined,and the results indicate that the CBC would degrade the low frequency relative intensity noise(RIN),of which the integration is 1.74%in[100 Hz,2 MHz]at the maximum combined output power.In addition,the effects of the nonlinear spectrum broadening during chirped pulse amplification on the CBC efficiency are also investigated,showing that a higher extent of pulse stretching is effective in alleviating the spectrum broadening and realizing a higher output power with decent combining efficiency.
基金supported by the Director Fund of State Key Laboratory of Pulsed Power Laser Technology(No.SKL2020ZR02)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.QL20220007)。
文摘High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated.The active polarization control technology based on the root-mean-square propagation(RMS-prop)algorithm is employed to guarantee a linearly polarized output from the system.A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio(PER)of>11.4 dB.In addition,the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser.The M2factor of the laser beam at the highest output power is measured to be less than 1.15,indicating a diffraction-limited beam quality.Finally,the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W.This is the first time,to the best of our knowledge,that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.
基金supported by the National Natural Science Foundation of China(Nos.62275272 and 62075242)Natural ScienceFoundationofHunanProvince,China(No.2019JJ10005)+1 种基金Training Program for Excellent Young Innovators of Changsha(No.kq2206003)Postgraduate Scientific Research Innovation Project of Hunan Province(No.QL20220013)。
文摘The high-power mode-programmable orbital angular momentum(OAM)beam has attracted significant attention in a wide range of applications,such as long-distance optical communication,nonlinear frequency conversion,and beam shaping.Coherent beam combining(CBC)of an optical phased array(OPA)can offer a promising solution for both generating the high-power OAM beam and rapidly switching the OAM modes.However,achieving real-time phase noise locking and formation of desired phase structures in a high-power CBC system faces significant challenges.Here,an internal phase-sensing technique was utilized to generate the high-power OAM beam,which effectively mitigated thermal effects and eliminated the need for large optical devices.An OPA with six elements was employed for experimental demonstration.The first effective generation of over 1.5 kW mode-programmable OAM beam in a continuous-wave domain was presented.Moreover,the results demonstrated that the generated OAM beam could be modulated with multiple dimensions.The topological charge can be switched in real time from-1 to-2.Notably,this OAM beam emitter could function as an OAM beam copier by easily transforming a single OAM beam into an OAM beam array.More importantly,a comprehensive analysis was conducted on power scaling,mode switching speed,and expansion of OAM modes.Additionally,the system’s compact design enabled it to function as a packageable OAM beam emitter.Owing to the advantages of having high power and programmable modes with multiple dimension modulation in phase structures and intensity distribution,this work can pave the way for producing high-power structured light beams and advancing their applications.
基金National Natural Science Foundation of China(61705265,61705264)Innovative Research Groups of Hunan Province(2019JJ10005)Training Program for Excellent Young Innovators of Changsha(KQ1905051).
文摘Coherent beam combining of 107 beams has been demonstrated for the first time to the best of our knowledge.When the system was in closed loop,the pattern in far-field was stable and the fringe contrast was>96%.The impact of the dynamic tilt error,the piston error,and power inconsistency was theoretically analyzed.Meanwhile,the distribution law of dynamic tilt error was estimated and the correlation of the tilt dithering of different axis was analyzed statistically.The ratio of power in the central lobe was^22.5%.The phase residue error in the closed loop was~λ∕22,which was evaluated by the root-mean-square error of the signal generated from the photoelectric detector.
基金supported by the National Natural Science Foundation of China (Nos. 61705265 and 61705264)the Innovative Research Groups of Hunan Province(No. 2019JJ10005)the Training Program for Excellent Young Innovators of Changsha (No. KQ1905051)
文摘Coherent beam combining of 60 fiber lasers by using the stochastic parallel gradient descent algorithm has been demonstrated. The functions of pinhole(s) on the power distributions in the far-field have been systematically simulated on both in-phase and out-of-phase modes. Only one photoelectric detector was used to detect the combined power in the far-field central lobe of the in-phase mode state. When the phase controller was in a closed loop, the contrast of the far-field intensity pattern was as high as ~97% with residual phase error of ~λ/30, and ~34.7% of the total power was contained in the central lobe.
基金supported by the National Natural Science Foundation of China(Nos.62275272 and 62075242)the Natural Science Foundation of Hunan Province,China(No.2019JJ10005)+1 种基金the Training Program for Excellent Young Innovators of Changsha(No.kq2206003)the Postgraduate Scientific Research Innovation Project of Hunan Province(No.QL20220013).
文摘We experimentally demonstrated a cascaded internal phase control technique.A laser array with 12 channels was divided into three sub-arrays and a stage array,and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent(SPGD)algorithm,respectively.In this way,the phases of the whole array were locked,and the visibility of the interference pattern of the whole emitted laser array in the far field was∼93%.In addition,the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination(CBC)system due to its compact spatial structure.
基金supported by the National Natural Science Foundation of China (No.62275272)the Training Program for Excellent Young Innovators of Changsha(No.kq2205025)。
文摘Dynamic beam shaping is of importance for a wide range of applications, such as light field regulation, laser processing, and advanced manufacturing. In this paper, an internal phase-sensing tiled-aperture coherent beam-combining system with seven beam elements was constructed for dynamic beam shaping. This system could be performed as a digital laser,where each laser beamlet functioned as an individual laser pixel. The amplitude and phase of each laser pixel could be adjusted independently in real time. In our experiment, the laser array was operated in three different configurations:the triangular, pentagonal, and hexagonal laser arrays, while each laser pixel was modulated with a different piston phase of nπ(where n was an integer). We demonstrated various beam-shaping patterns based on this system with output powers scaling over 1 kW. Additionally, the energy distribution of the emitted laser could be flexibly varied and customized.These results highlighted that our dynamic beam-shaped laser exhibited excellent performance in both dynamic beam-shaping and power-scaling capabilities. This work holds great potential for numerous applications involving beam shaping.
