A high power laser system was used to drive the ignition of inertial confinement fusion(ICF), of which the high energy,the uniform focal spot, the accurate laser waveform, and the synchronization between the laser bea...A high power laser system was used to drive the ignition of inertial confinement fusion(ICF), of which the high energy,the uniform focal spot, the accurate laser waveform, and the synchronization between the laser beams are key parameters.To accomplish this, global laser characteristics control should be assured, which was the main purpose of the injection laser system. In this paper, the key technological progress involved in the improvement of the performance of the injection laser of SG-II is reported, including frequency domain control, time domain control, near-field spatial shaping, preamplifier technology, and the optical parametric chirped pulse amplification pump source.展开更多
This study investigates a novel method to numerically generate orthogonal ultrawide band （UWB） shaping pulses based on compressed chirp signal. First, a pulse template with less than 1 ns duration time, which is use...This study investigates a novel method to numerically generate orthogonal ultrawide band （UWB） shaping pulses based on compressed chirp signal. First, a pulse template with less than 1 ns duration time, which is used to construct a Hermitian matrix, is produced with a compressed chirp pulse. Sub-nanosecond orthogonal pulses are then generated for UWB by using the Hermitian matrix eigenvectors. The simulation results show that the power spectral density distribution of the UWB shaping pulses met the constraint of Federal communications commissions （FCC） spectral mask. The shaping pulses not only have higher spectrum utilization ratio and very short time duration but also have excellent autocorrelation and cross-correlation properties, which is an advantage to reduce the interference between multiusers. Especially, a method to produce sub-nanosecond orthogonal UWB shaping pulses by using a relatively longer duration chirp signal is presented.展开更多
High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-...High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.展开更多
In the ultra-wideband （UWB） communication systems, a critical spectral mask is released to restrict the allowable interference to other wireless devices by the Federal Communications Commission （FCC）, and then som...In the ultra-wideband （UWB） communication systems, a critical spectral mask is released to restrict the allowable interference to other wireless devices by the Federal Communications Commission （FCC）, and then some pulse shaping methods have been presented to fulfil the mask. However, most pulse shaping methods do not consider the antenna distortion which cannot be neglected in the UWB communication systems compared with the conventional systems. To this end, an orthogonal wavelet based pulse shaping method is proposed in this paper to inte- grate compensation of antenna distortion into pulse shaping. Simulation results show that the novel pulse shaping method can be used to achieve compensation for antenna distortion, optimization of transmission power spectrum, and simplification of the algorithm, as well as simple implementation of the pulse generator.展开更多
Two new kinds of ultra-narrow trigger frequency alterable picosecond pulse generator are presented.One can produce positive pulses and the other can produce negative pulses.The two pulse generators are subdivided into...Two new kinds of ultra-narrow trigger frequency alterable picosecond pulse generator are presented.One can produce positive pulses and the other can produce negative pulses.The two pulse generators are subdivided into three parts:signal driving circuit,differentiator network and pulse shaping circuit.The pulse shaping circuit is made of step recovery diode(SRD) and short-circuit microstrip line.A positive pulse with width of 54 ps(50%-50%),rising time of 30 ps(10%-90%) and falling time of 32 ps(90%-10%),and a negative pulse with width of 54 ps(50%-50%),rising time of 30 ps(90%-10%) and falling time of 30 ps(10%-90%) are achieved in simulation.All of the components are ready-made and inexpensive.They can be applied in ultra-wideband(UWB) communication system,such as transmitters and receivers.展开更多
In this study we experimentally reveal that the phase change mechanism can be selectively triggered by shaping femtosecond pulse trains based on electron dynamics control （EDC）, including manipulation of excitations...In this study we experimentally reveal that the phase change mechanism can be selectively triggered by shaping femtosecond pulse trains based on electron dynamics control （EDC）, including manipulation of excitations, ionizations, densities, and temperatures of electrons. By designing the pulse energy distribution to adjust the absorptions, excitations, ionizations, and recombinations of electrons, the dominant phase change mechanism experiences transition from nonthermal to thermal process. This phenomenon is observed in quadruple, triple, and double pulses per train ablation of fused silica separately. This opens up possibilities for controlling phase change mechanisms by EDC, which is of great significance in laser processing of dielectrics and fabrication of integrated nano- and micro-optical devices.展开更多
Probabilistically shaped(PS) pulse amplitude modulation(PAM) is a promising technique for intra-data-center networks due to its superior performance, for which a low-complexity and cost-effective distributed matching ...Probabilistically shaped(PS) pulse amplitude modulation(PAM) is a promising technique for intra-data-center networks due to its superior performance, for which a low-complexity and cost-effective distributed matching method is critical. In this work, we propose an energy-level-assigned method to yield PS-PAM-4 signals with various bit rates based on variable probabilistic distributions. We experimentally demonstrate the proposed method in a 25 Gbaud PS-PAM-4 transmission over a bandwidth of approximately 10 GHz. Compared to a uniform PAM-4 system, the proposed multi-distributed PS-PAM-4 system approaches the hard decision threshold at a wide range of received optical power for different applications.展开更多
We experimentally investigate multigranularity optical subband switching functionality between two superchannels with slight error vector magnitude penalty. One is 4×39 Gb/s polarization-division-multiplexed（PDM...We experimentally investigate multigranularity optical subband switching functionality between two superchannels with slight error vector magnitude penalty. One is 4×39 Gb/s polarization-division-multiplexed（PDM） quadrature phase shift keying discrete Fourier transform spread orthogonal frequency division multiplexing（DFT-spread-OFDM） superchannel with 12.5 GHz band spacing. The other is 8×29 Gb/s PDM-16-quadrature amplitude modulation Nyquist pulse shaping superchannel with 6.25 GHz band spacing. To the best of our knowledge, this is the first time that optical switching functionality for individual band between different superchannels with multigranularity is realized.展开更多
Femtosecond coherent anti-Stokes Raman scattering （CARS） suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to real...Femtosecond coherent anti-Stokes Raman scattering （CARS） suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to realize the selective excitation and suppression of femtosecond CARS by manipulating both the probe and pump （or Stokes） spectra. These theoretical results indicate that the CARS signals between neighbouring Raman levels are differentiated from their indistinguishable femtosecond CARS spectra by tailoring the probe spectrum, and then their selective excitation and suppression can be realized by supplementally manipulating the pump （or Stokes） spectrum with the π spectral phase step.展开更多
文摘A high power laser system was used to drive the ignition of inertial confinement fusion(ICF), of which the high energy,the uniform focal spot, the accurate laser waveform, and the synchronization between the laser beams are key parameters.To accomplish this, global laser characteristics control should be assured, which was the main purpose of the injection laser system. In this paper, the key technological progress involved in the improvement of the performance of the injection laser of SG-II is reported, including frequency domain control, time domain control, near-field spatial shaping, preamplifier technology, and the optical parametric chirped pulse amplification pump source.
基金the National Natural Science Foundation of China （60331010） 0pen Fund of Key Laboratory of 0ptical Communication and Lightwave Technologies （BUPT）, Ministry of Education.
文摘This study investigates a novel method to numerically generate orthogonal ultrawide band （UWB） shaping pulses based on compressed chirp signal. First, a pulse template with less than 1 ns duration time, which is used to construct a Hermitian matrix, is produced with a compressed chirp pulse. Sub-nanosecond orthogonal pulses are then generated for UWB by using the Hermitian matrix eigenvectors. The simulation results show that the power spectral density distribution of the UWB shaping pulses met the constraint of Federal communications commissions （FCC） spectral mask. The shaping pulses not only have higher spectrum utilization ratio and very short time duration but also have excellent autocorrelation and cross-correlation properties, which is an advantage to reduce the interference between multiusers. Especially, a method to produce sub-nanosecond orthogonal UWB shaping pulses by using a relatively longer duration chirp signal is presented.
文摘High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.
基金the National Natural Science Foundation of China (Grant No. 60432040)the Program for New Century Excellent Talents in University (Grant No. NCET-04-0332)
文摘In the ultra-wideband （UWB） communication systems, a critical spectral mask is released to restrict the allowable interference to other wireless devices by the Federal Communications Commission （FCC）, and then some pulse shaping methods have been presented to fulfil the mask. However, most pulse shaping methods do not consider the antenna distortion which cannot be neglected in the UWB communication systems compared with the conventional systems. To this end, an orthogonal wavelet based pulse shaping method is proposed in this paper to inte- grate compensation of antenna distortion into pulse shaping. Simulation results show that the novel pulse shaping method can be used to achieve compensation for antenna distortion, optimization of transmission power spectrum, and simplification of the algorithm, as well as simple implementation of the pulse generator.
基金the National Natural Science Foundation of China (No.60970058)the Natural Science Foundation of Jiangsu Province (No.SBK200930425)+1 种基金the fund of the State Key Laboratory of Millimetre Waves of Southeast Universitythe Student Research Training Program (SRTP) of Southeast University
文摘Two new kinds of ultra-narrow trigger frequency alterable picosecond pulse generator are presented.One can produce positive pulses and the other can produce negative pulses.The two pulse generators are subdivided into three parts:signal driving circuit,differentiator network and pulse shaping circuit.The pulse shaping circuit is made of step recovery diode(SRD) and short-circuit microstrip line.A positive pulse with width of 54 ps(50%-50%),rising time of 30 ps(10%-90%) and falling time of 32 ps(90%-10%),and a negative pulse with width of 54 ps(50%-50%),rising time of 30 ps(90%-10%) and falling time of 30 ps(10%-90%) are achieved in simulation.All of the components are ready-made and inexpensive.They can be applied in ultra-wideband(UWB) communication system,such as transmitters and receivers.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CB013000)the National Natural Science Foundation of China (Grant Nos. 90923039 and 51025521)
文摘In this study we experimentally reveal that the phase change mechanism can be selectively triggered by shaping femtosecond pulse trains based on electron dynamics control （EDC）, including manipulation of excitations, ionizations, densities, and temperatures of electrons. By designing the pulse energy distribution to adjust the absorptions, excitations, ionizations, and recombinations of electrons, the dominant phase change mechanism experiences transition from nonthermal to thermal process. This phenomenon is observed in quadruple, triple, and double pulses per train ablation of fused silica separately. This opens up possibilities for controlling phase change mechanisms by EDC, which is of great significance in laser processing of dielectrics and fabrication of integrated nano- and micro-optical devices.
基金This work was supported by the National Natural Science Foundation of China(No.62075147).
文摘Probabilistically shaped(PS) pulse amplitude modulation(PAM) is a promising technique for intra-data-center networks due to its superior performance, for which a low-complexity and cost-effective distributed matching method is critical. In this work, we propose an energy-level-assigned method to yield PS-PAM-4 signals with various bit rates based on variable probabilistic distributions. We experimentally demonstrate the proposed method in a 25 Gbaud PS-PAM-4 transmission over a bandwidth of approximately 10 GHz. Compared to a uniform PAM-4 system, the proposed multi-distributed PS-PAM-4 system approaches the hard decision threshold at a wide range of received optical power for different applications.
基金supported by the National 973 Program of China(No.2010CB328201)the National 863 Program of China(No.2012AA011302)the National Natural Science Foundation of China(No.61077053)
文摘We experimentally investigate multigranularity optical subband switching functionality between two superchannels with slight error vector magnitude penalty. One is 4×39 Gb/s polarization-division-multiplexed（PDM） quadrature phase shift keying discrete Fourier transform spread orthogonal frequency division multiplexing（DFT-spread-OFDM） superchannel with 12.5 GHz band spacing. The other is 8×29 Gb/s PDM-16-quadrature amplitude modulation Nyquist pulse shaping superchannel with 6.25 GHz band spacing. To the best of our knowledge, this is the first time that optical switching functionality for individual band between different superchannels with multigranularity is realized.
基金Project supported by Programme for Changjiang Scholars and Innovative Research Team in University(PCSIRT)Shanghai Leading Academic Discipline Project(Grant No.B408)+3 种基金National Key Project for Basic Research of China(Grant Nos.2006CB806006 and 2006CB921105)Ministry of Education of China(Grant No.30800)Shanghai Municipal Natural Science Foundation(Grant No.09ZR1409300)Shanghai Municipal Science and Technology Commission(Grant No.07DZ22025)
文摘Femtosecond coherent anti-Stokes Raman scattering （CARS） suffers from poor selectivity between neighbouring Raman levels due to the large bandwidth of the femtosecond pulses. This paper provides a new method to realize the selective excitation and suppression of femtosecond CARS by manipulating both the probe and pump （or Stokes） spectra. These theoretical results indicate that the CARS signals between neighbouring Raman levels are differentiated from their indistinguishable femtosecond CARS spectra by tailoring the probe spectrum, and then their selective excitation and suppression can be realized by supplementally manipulating the pump （or Stokes） spectrum with the π spectral phase step.
