Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive ...Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated. Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation. The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.展开更多
In the terahertz（THz） band, the inherent shake of the human body may strongly impair the image quality of a beam scanning single frequency holography system for personnel screening. To realize accurate shake compens...In the terahertz（THz） band, the inherent shake of the human body may strongly impair the image quality of a beam scanning single frequency holography system for personnel screening. To realize accurate shake compensation in imaging processing, it is quite necessary to develop a high-precision measure system. However, in many cases, different parts of a human body may shake to different extents, resulting in greatly increasing the difficulty in conducting a reasonable measurement of body shake errors for image reconstruction. In this paper, a body shake error compensation algorithm based on the raw data is proposed. To analyze the effect of the body shake on the raw data, a model of echoed signal is rebuilt with considering both the beam scanning mode and the body shake. According to the rebuilt signal model, we derive the body shake error estimated method to compensate for the phase error. Simulation on the reconstruction of point targets with shake errors and proof-of-principle experiments on the human body in the 0.2-THz band are both performed to confirm the effectiveness of the body shake compensation algorithm proposed.展开更多
This paper presents the anisotropic optical feedback of a single frequency intra-cavity He-Ne laser. A novel phenomenon was discovered that the laser output an elliptical polarized frequency instead of the initial lin...This paper presents the anisotropic optical feedback of a single frequency intra-cavity He-Ne laser. A novel phenomenon was discovered that the laser output an elliptical polarized frequency instead of the initial linear polarized one. Two intensities with a phase difference were detected, both of which were modulated in the form of cosine wave and a fringe shift corresponds to a λ/2 movement of the feedback mirror. The phase difference can be continuously modulated by the wave plate in the external cavity. Frequency stabilization was used to stabilize the laser frequency so as to enlarge the measuring range and improve the measurement precision. This anisotropic optical feedback system offers a potential displacement measurement technology with the function of subdivision of λ/2 and in-time direction judgment. The three-mirror Fabry Perot cavity model is used to present the experimental results. Given the lack of need of lasing adjustment, this full intra-cavity laser can significantly improve the simplicity and stability of the optical feedback system.展开更多
Former frequency-domain blind devolution algorithms need to consider a large number of frequency bins and recover the sources in different orders and with different amplitudes in each frequency bin,so they suffer from...Former frequency-domain blind devolution algorithms need to consider a large number of frequency bins and recover the sources in different orders and with different amplitudes in each frequency bin,so they suffer from permutation and amplitude indeterminacy troubles. Based on sliding discrete Fourier transform,the presented deconvolution algorithm can directly recover time-domain sources from frequency-domain convolutive model using single frequency bin. It only needs to execute blind sepa-ration of instantaneous mixture once there are no permutation and amplitude indeterminacy troubles. Compared with former algorithms,the algorithm greatly reduces the computation cost as only one frequency bin is considered. Its good and robust per-formance is demonstrated by simulations when the signal-to-noise-ratio is high.展开更多
By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm i...By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.展开更多
Ways on energy enhancement for single frequency oscillator are reported in this paper.By quantitative analysis on gain and loss coefficients for each cavity mode with inserted etalons,a 37 mJ,100 Hz high energy single...Ways on energy enhancement for single frequency oscillator are reported in this paper.By quantitative analysis on gain and loss coefficients for each cavity mode with inserted etalons,a 37 mJ,100 Hz high energy single-frequency Nd:YAG oscillator is obtained.The pulse energy is promoted by enhancement of nearly 7 times for a single frequency oscillator reported.The result proves that this method does help for energy enhancement.It has attractive potential for high energy single frequency oscillator design,especially on condition of intensive side pumped or long cavity laser,where strong competitors exist and are hard to be suppressed.展开更多
In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic pro...In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.展开更多
Amplified spontaneous emission （ASE） in diode laser pumped double-clad fiber power amplifiers is studied experimentally, The dependences of ASE on fiber length and cross section of active core are discussed and the ...Amplified spontaneous emission （ASE） in diode laser pumped double-clad fiber power amplifiers is studied experimentally, The dependences of ASE on fiber length and cross section of active core are discussed and the variations of ASE power as the function of pumping and signal power are investigated. There are indications that long fibers with large mode area need stronger input signals to suppress ASE. It is shown that a 150 mW input signal can suppress the ASE by 40 dB in a 4 m large mode area fiber, while to efficiently suppress the ASE in a 10 m fiber, stronger input signal is needed. 12.5 W and 16.1 W single frequency CW output power are obtained from 4 m fiber and 10 m fiber respectively. No stimulated Brillouin scattering （SBS） was observed展开更多
A diode-pumped single frequcncy Tm,Ho：YLF laser operating at an eye-safe wavelength of 2 μm has been developed. Temperature of the laser crystal was controlled at room temperature with a thermoelectric cooler. The l...A diode-pumped single frequcncy Tm,Ho：YLF laser operating at an eye-safe wavelength of 2 μm has been developed. Temperature of the laser crystal was controlled at room temperature with a thermoelectric cooler. The line-width narrowing elements were two solid uncoated fused silica etalons whose thicknesses were 1 and 0.1 mm, respectively. Continuous wave single frequency power of 113 mW was obtained.展开更多
The single frequency network (SFN) can provide a multimedia broadcast multicast service over a large coverage area. However, the application of SFN is still restricted by a large amount of feedback. Therefore, we prop...The single frequency network (SFN) can provide a multimedia broadcast multicast service over a large coverage area. However, the application of SFN is still restricted by a large amount of feedback. Therefore, we propose a multicast resource allocation scheme based on limited feedback to maximize the total rate while guaranteeing the quality of service (QoS) requirement of real-time services. In this scheme, we design a user feedback control algorithm to effectively reduce feedback load. The algorithm determines to which base stations the users should report channel state information. We then formulate a joint subcarrier and power allocation issue and find that it has high complexity. Hence, we first distribute subcarriers under the assumption of equal power and develop a proportional allocation strategy to achieve a tradeoff between fairness and QoS. Next, an iterative water-filling power allocation is proposed to fully utilize the limited power. To further decrease complexity, a power iterative scheme is introduced. Simulation results show that the proposed scheme significantly improves system performance while reducing 68% of the feedback overhead. In addition, the power iterative strategy is suitable in practice due to low complexity.展开更多
We present a high-power, single-frequency, narrow linewidth fiber amplifier based on master oscillator power amplification chains in an all-fiber configuration. The effect of the delivery fiber on the maximum output p...We present a high-power, single-frequency, narrow linewidth fiber amplifier based on master oscillator power amplification chains in an all-fiber configuration. The effect of the delivery fiber on the maximum output power is studied. A home-made 1064-nm seed laser with a 20-kHz linewidth is boosted to 129 W, and limited by stimulated Brillouin scattering （SBS） when the delivery fiber is 1.2 m long By shortening the delivery fiber length to 0.7 m, the SBS threshold is increased efficiently and the maximum output power rises to 168 W with an 82.9% power conversion efficiency. The experimental results indicate that the output power can be further raised by shortening the delivery fiber length and increasing the pump power.展开更多
The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the re...The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the real-space Hamiltonian. The calculated results show that the probability of single photon frequency down-or up-conversion can reach a unit by choosing appropriate parameters in the non-dissipative system with perfect chiral coupling.We present a nonreciprocal single photon beam splitter whose frequency of the output photon is different from that of the input photon. The influences of dissipations and non-perfect chiral coupling on the single frequency conversion are also shown. Our results may be useful in designing quantum devices at the single-photon level.展开更多
This paper is part of a research under enhancement since 2001, in which the main objective is to measure small dynamic displacements by analysis of L1 GPS carrier frequency with 1575.42 MHz—wavelength 19.05 cm, under...This paper is part of a research under enhancement since 2001, in which the main objective is to measure small dynamic displacements by analysis of L1 GPS carrier frequency with 1575.42 MHz—wavelength 19.05 cm, under an adaptive method for collecting data and filtering techniques. This method, named Phase Residual Method (PRM) is based on the frequency domain analysis of the phase residuals resulted from the L1 double difference static data processing of two satellites in almost orthogonal elevation angle. In this work it is proposed to obtain the phase residuals directly from the raw phase observable collected in a short baseline during a limited time span, in lieu of obtaining the residual data file from regular GPS processing programs. In order to improve the ability to detect millimetric displacements, two filtering techniques are introduced. The first one is the autocorrelation that reduces the phase noise with random time behavior. The other one is the running mean to separate low frequency from the high frequency phase sources. Two trials are presented to verify the proposed method and filtering techniques applied. One simulates a 2.5 millimeter vertical GPS antenna displacement and the second using the data collected during a bridge dynamic load test. The results show a good consistency to detect millimetric oscillations from L1 frequency and filtering techniques.展开更多
High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies.However,the simul...High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies.However,the simultaneous achievement of kilowatt-level output power and diffraction-limited beam quality has remained elusive in all reported single-frequency fiber laser systems to date,primarily due to limitations imposed by the stimulated Brillouin scattering(SBS)effect and transverse mode instability(TMI)effect.In this study,we demonstrate the design and manufacturing of an ultra-low numerical aperture(NA)functional Yb-doped fiber featuring a bat-type refractive index distribution,specifically engineered for single-frequency laser amplification.In the fabrication,we implemented multiple chelate gas filling and particle deposition iterations,leading to an active fiber with a bat-type refractive index distribution.The unique capabilities of this large mode area and high-order modes leakage fiber(HOMLF)were demonstrated by stably amplifying the single-frequency laser with more than one kilowatt output power and near single mode beam quality(M_(x)^(2)=1.10,M_(x)^(2)=1.18)for the first time.This fiber design advances the leap forward in single-frequency fiber lasers,which could contribute as a novel and efficient laser amplification technique for the next generation of gravitational wave detection systems.展开更多
We report on the generation of self-oscillations from a continuously pumped singly resonant frequency doubler based on a periodically poled potassium titanyl phosphate crystal （PPKTP）. The sustained square-wave and ...We report on the generation of self-oscillations from a continuously pumped singly resonant frequency doubler based on a periodically poled potassium titanyl phosphate crystal （PPKTP）. The sustained square-wave and staircase curve of self-oscillations are obtained when the incident pump powers are below and above the threshold of subharmonic-pumped parametric oscillation （SPO）, respectively. The self-oscillations can be explained by the competition between the phase shifts induced by cascading nonlinearity and thermal effect, and the influence of fundamental nonlinear phase shift by the generation of SPO. The simulation results are in good agreement with the experiment data.展开更多
We present a high-power mid-infrared single-frequency pulsed fiber laser(SFPFL)with a tunable wavelength range from 2712.3 to 2793.2 nm.The single-frequency operation is achieved through a compound cavity design that ...We present a high-power mid-infrared single-frequency pulsed fiber laser(SFPFL)with a tunable wavelength range from 2712.3 to 2793.2 nm.The single-frequency operation is achieved through a compound cavity design that incorporates a germanium etalon and a diffraction grating,resulting in an exceptionally narrow seed linewidth of approximately 780 kHz.Employing a master oscillator power amplifier configuration,we attain a maximum average output power of 2.6 W at 2789.4 nm,with a pulse repetition rate of 173 kHz,a pulse energy of 15μJ and a narrow linewidth of approximately 850 kHz.This achievement underscores the potential of the mid-infrared SFPFL system for applications requiring high coherence and high power,such as high-resolution molecular spectroscopy,precision chemical identification and nonlinear frequency conversion.展开更多
We demonstrate a 202 W all polarization-maintaining(PM)single-frequency fiber amplifier operating at the C band.Simulations show that the length of the output fiber pigtail following the gain fiber critically has a gr...We demonstrate a 202 W all polarization-maintaining(PM)single-frequency fiber amplifier operating at the C band.Simulations show that the length of the output fiber pigtail following the gain fiber critically has a great impact on stimulated Brillouin scattering(SBS),posing a major obstacle for high-power single-frequency amplification.Optimizing the length to suppress the backward SBS by~10 d B,we experimentally achieved a maximum output power of 202 W,yielding an optical-to-optical efficiency of 42%.The signal-to-noise ratio(SNR)of signal light,relative to amplified spontaneous emission(ASE)in Er^(3+)and Yb^(3+)bands,was measured to be 23 and 32 dB,respectively,and it can be further improved by ASE suppression and filtering techniques during amplification.To the best of our knowledge,this is the all-PM single-frequency fiber amplifier with the highest power reported in the C band.展开更多
In this work,we report on the recent research progress on watt-level all-solid-state single-frequency Pr:LiYF_(4)(YLF)lasers in the orange spectral region.Combining dual-end pumping and ring-cavity technologies,we hav...In this work,we report on the recent research progress on watt-level all-solid-state single-frequency Pr:LiYF_(4)(YLF)lasers in the orange spectral region.Combining dual-end pumping and ring-cavity technologies,we have achieved a maximum single-frequency output of 1.19 W at 607 nm with a linewidth of about 20.3 MHz.Based on this study,by inserting a 0.15 mm etalon inside the ring cavity,we find that the 607 nm lasing can be completely suppressed and a single-frequency laser at 604 nm with a 0.69 W output power and a linewidth of about 16.7 MHz can also be obtained.Moreover,the wavelengths of the two single-frequency lasers can be tuned from 607.16 to 607.61 nm and from 603.99 to 605.02 nm,respectively.Furthermore,the single-frequency Pr:YLF laser can also operate in a state of the two orange wavelengths,simultaneously,with a maximum output power of 0.97 W.We believe that this is the highest output power of a direct generation of single-frequency orange lasers and the first demonstration of the wavelength-tuned operation of the achieved single-frequency orange lasers,which could bring opportunities for the application of single-frequency orange lasers.展开更多
Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimu...Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimulated Brillouin scattering effect.Nevertheless,over the past two decades much effort has been devoted to improving the power scaling and performance of high-power single-frequency fiber amplifiers.These amplifiers are mostly driven by applications,such as high precision detection and metrology,and have benefited from the long coherence length,low noise,and excellent beam quality of this type of laser source.In this paper,we review the overall development of high-power single-frequency fiber amplifiers by focusing on its progress and challenges,specifically,the strategies for circumventing the stimulated Brillouin scattering and transverse mode instability effects that,at present,are the major limiting factors of the power scaling of the single-frequency fiber amplifiers.These factors are also thoroughly discussed in terms of free-space and all-fiber coupled architecture.In addition,we also examine the noise properties of single-frequency fiber amplifiers,along with corresponding noise reducing schemes.Finally,we briefly envision the future development of high-power single-frequency fiber amplifiers.展开更多
基金supported by the Next Generation of Beidou Navigation Satellite(GFZX0301020104)
文摘Based on the theory of the passive hydrogen maser, along with the technology of frequency modulation and modulation transfer spectroscopy, the theoretical expression of the single frequency modulation for the passive hydrogen maser and the function of the cavity and H line error signals separation are derived, which are basically coincident with the experiment. The absorption and dispersion spectrum curves with different resonance widths show that the cavity and hydrogen transition serve as discriminators, and the two error signals can be separated. Through the calculations of the two error signals in the passive hydrogen maser, it analyzes the traditional method of the two error signals separation, and then describes a new improved method for the passive hydrogen servo loops consisting in the use of a single modulation frequency and frequency discrimination. A null interaction of the two error signals for the new selection of the phase setting is deduced theoretically and validated by the simulation. The preliminary experimental result confirms the feasibility of this new approach, which can reduce the influence from the cavity frequency variety on the crystal oscillator and contribute significantly to the long term performance of the passive hydrogen maser.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.YYYJ-1123)
文摘In the terahertz（THz） band, the inherent shake of the human body may strongly impair the image quality of a beam scanning single frequency holography system for personnel screening. To realize accurate shake compensation in imaging processing, it is quite necessary to develop a high-precision measure system. However, in many cases, different parts of a human body may shake to different extents, resulting in greatly increasing the difficulty in conducting a reasonable measurement of body shake errors for image reconstruction. In this paper, a body shake error compensation algorithm based on the raw data is proposed. To analyze the effect of the body shake on the raw data, a model of echoed signal is rebuilt with considering both the beam scanning mode and the body shake. According to the rebuilt signal model, we derive the body shake error estimated method to compensate for the phase error. Simulation on the reconstruction of point targets with shake errors and proof-of-principle experiments on the human body in the 0.2-THz band are both performed to confirm the effectiveness of the body shake compensation algorithm proposed.
基金supported by the National Natural Science Foundation of China (Grant No 60437010)
文摘This paper presents the anisotropic optical feedback of a single frequency intra-cavity He-Ne laser. A novel phenomenon was discovered that the laser output an elliptical polarized frequency instead of the initial linear polarized one. Two intensities with a phase difference were detected, both of which were modulated in the form of cosine wave and a fringe shift corresponds to a λ/2 movement of the feedback mirror. The phase difference can be continuously modulated by the wave plate in the external cavity. Frequency stabilization was used to stabilize the laser frequency so as to enlarge the measuring range and improve the measurement precision. This anisotropic optical feedback system offers a potential displacement measurement technology with the function of subdivision of λ/2 and in-time direction judgment. The three-mirror Fabry Perot cavity model is used to present the experimental results. Given the lack of need of lasing adjustment, this full intra-cavity laser can significantly improve the simplicity and stability of the optical feedback system.
基金Project (No. 2005EB040486) supported by the National Torch Program of China
文摘Former frequency-domain blind devolution algorithms need to consider a large number of frequency bins and recover the sources in different orders and with different amplitudes in each frequency bin,so they suffer from permutation and amplitude indeterminacy troubles. Based on sliding discrete Fourier transform,the presented deconvolution algorithm can directly recover time-domain sources from frequency-domain convolutive model using single frequency bin. It only needs to execute blind sepa-ration of instantaneous mixture once there are no permutation and amplitude indeterminacy troubles. Compared with former algorithms,the algorithm greatly reduces the computation cost as only one frequency bin is considered. Its good and robust per-formance is demonstrated by simulations when the signal-to-noise-ratio is high.
基金Supported by the International Cooperation Projects of Ministry of Science and Technology under Grant No 2012DFB10120the National Natural Science Foundation of China under Grant No 61177059
文摘By using a loop mirror filter, a novel wavelength-tunable single-frequency ytterbium-doped fiber laser is developed to select single longitudinal modes in a linear cavity. The output wavelength could be tuned 2.4 nm intervals range from 1063.3 to 1065.Tnrn with the temperature change of the fiber Bragg grating. The maximum output power could reach 32 m W while the pump power increases to 120 m W. The corresponding optical-to-optical conversion efficiency is 26.7% and the slope efficiency is 33.9%, respectively. The output power fluctuation is below 2%, and its highest signal-to-noise ratio is 60 dB.
基金Project supported by the National Natural Science Foundation of China(Grant No.11504389)the Funds of Key Lab of Function Crystal and Laser Technology,Technical Institute of Physics and Chemistry,Chinese Academy of Sciences
文摘Ways on energy enhancement for single frequency oscillator are reported in this paper.By quantitative analysis on gain and loss coefficients for each cavity mode with inserted etalons,a 37 mJ,100 Hz high energy single-frequency Nd:YAG oscillator is obtained.The pulse energy is promoted by enhancement of nearly 7 times for a single frequency oscillator reported.The result proves that this method does help for energy enhancement.It has attractive potential for high energy single frequency oscillator design,especially on condition of intensive side pumped or long cavity laser,where strong competitors exist and are hard to be suppressed.
基金supported by the National Key R&D Program of China (Grant No. 2020YFC2200500)the National Natural Science Foundation of China (Grant Nos. 12075325, 12005308, and 11605065)。
文摘In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.
基金the Ministerial Level Advanced Research Foundation (41302010107)
文摘Amplified spontaneous emission （ASE） in diode laser pumped double-clad fiber power amplifiers is studied experimentally, The dependences of ASE on fiber length and cross section of active core are discussed and the variations of ASE power as the function of pumping and signal power are investigated. There are indications that long fibers with large mode area need stronger input signals to suppress ASE. It is shown that a 150 mW input signal can suppress the ASE by 40 dB in a 4 m large mode area fiber, while to efficiently suppress the ASE in a 10 m fiber, stronger input signal is needed. 12.5 W and 16.1 W single frequency CW output power are obtained from 4 m fiber and 10 m fiber respectively. No stimulated Brillouin scattering （SBS） was observed
基金This work was supported by the Scientic Re-search Foundation of Harbin Engineering Univer-sity (HEUF04014)
文摘A diode-pumped single frequcncy Tm,Ho：YLF laser operating at an eye-safe wavelength of 2 μm has been developed. Temperature of the laser crystal was controlled at room temperature with a thermoelectric cooler. The line-width narrowing elements were two solid uncoated fused silica etalons whose thicknesses were 1 and 0.1 mm, respectively. Continuous wave single frequency power of 113 mW was obtained.
基金supported by the National Natural Science Foundation of China (Nos. 60972076 and 61072052)the National Science and Technology Major Project, China (No. 2010ZX03003-004-03)
文摘The single frequency network (SFN) can provide a multimedia broadcast multicast service over a large coverage area. However, the application of SFN is still restricted by a large amount of feedback. Therefore, we propose a multicast resource allocation scheme based on limited feedback to maximize the total rate while guaranteeing the quality of service (QoS) requirement of real-time services. In this scheme, we design a user feedback control algorithm to effectively reduce feedback load. The algorithm determines to which base stations the users should report channel state information. We then formulate a joint subcarrier and power allocation issue and find that it has high complexity. Hence, we first distribute subcarriers under the assumption of equal power and develop a proportional allocation strategy to achieve a tradeoff between fairness and QoS. Next, an iterative water-filling power allocation is proposed to fully utilize the limited power. To further decrease complexity, a power iterative scheme is introduced. Simulation results show that the proposed scheme significantly improves system performance while reducing 68% of the feedback overhead. In addition, the power iterative strategy is suitable in practice due to low complexity.
文摘We present a high-power, single-frequency, narrow linewidth fiber amplifier based on master oscillator power amplification chains in an all-fiber configuration. The effect of the delivery fiber on the maximum output power is studied. A home-made 1064-nm seed laser with a 20-kHz linewidth is boosted to 129 W, and limited by stimulated Brillouin scattering （SBS） when the delivery fiber is 1.2 m long By shortening the delivery fiber length to 0.7 m, the SBS threshold is increased efficiently and the maximum output power rises to 168 W with an 82.9% power conversion efficiency. The experimental results indicate that the output power can be further raised by shortening the delivery fiber length and increasing the pump power.
基金Supported by the Anhui Provincial Natural Science Foundation under Grant No 1608085MA09the National Natural Science Foundation of China under Grant Nos 11774262,61675006,11474003 and 61472282
文摘The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the real-space Hamiltonian. The calculated results show that the probability of single photon frequency down-or up-conversion can reach a unit by choosing appropriate parameters in the non-dissipative system with perfect chiral coupling.We present a nonreciprocal single photon beam splitter whose frequency of the output photon is different from that of the input photon. The influences of dissipations and non-perfect chiral coupling on the single frequency conversion are also shown. Our results may be useful in designing quantum devices at the single-photon level.
文摘This paper is part of a research under enhancement since 2001, in which the main objective is to measure small dynamic displacements by analysis of L1 GPS carrier frequency with 1575.42 MHz—wavelength 19.05 cm, under an adaptive method for collecting data and filtering techniques. This method, named Phase Residual Method (PRM) is based on the frequency domain analysis of the phase residuals resulted from the L1 double difference static data processing of two satellites in almost orthogonal elevation angle. In this work it is proposed to obtain the phase residuals directly from the raw phase observable collected in a short baseline during a limited time span, in lieu of obtaining the residual data file from regular GPS processing programs. In order to improve the ability to detect millimetric displacements, two filtering techniques are introduced. The first one is the autocorrelation that reduces the phase noise with random time behavior. The other one is the running mean to separate low frequency from the high frequency phase sources. Two trials are presented to verify the proposed method and filtering techniques applied. One simulates a 2.5 millimeter vertical GPS antenna displacement and the second using the data collected during a bridge dynamic load test. The results show a good consistency to detect millimetric oscillations from L1 frequency and filtering techniques.
基金support from the National Key Research and Development Program of China(2022YFB3606400).
文摘High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies.However,the simultaneous achievement of kilowatt-level output power and diffraction-limited beam quality has remained elusive in all reported single-frequency fiber laser systems to date,primarily due to limitations imposed by the stimulated Brillouin scattering(SBS)effect and transverse mode instability(TMI)effect.In this study,we demonstrate the design and manufacturing of an ultra-low numerical aperture(NA)functional Yb-doped fiber featuring a bat-type refractive index distribution,specifically engineered for single-frequency laser amplification.In the fabrication,we implemented multiple chelate gas filling and particle deposition iterations,leading to an active fiber with a bat-type refractive index distribution.The unique capabilities of this large mode area and high-order modes leakage fiber(HOMLF)were demonstrated by stably amplifying the single-frequency laser with more than one kilowatt output power and near single mode beam quality(M_(x)^(2)=1.10,M_(x)^(2)=1.18)for the first time.This fiber design advances the leap forward in single-frequency fiber lasers,which could contribute as a novel and efficient laser amplification technique for the next generation of gravitational wave detection systems.
基金supported by the National Basic Research Program of China (Grant No. 2010CB923101)the National Natural Science Foundation of China (Grant Nos. 61227015 and 61121064)
文摘We report on the generation of self-oscillations from a continuously pumped singly resonant frequency doubler based on a periodically poled potassium titanyl phosphate crystal （PPKTP）. The sustained square-wave and staircase curve of self-oscillations are obtained when the incident pump powers are below and above the threshold of subharmonic-pumped parametric oscillation （SPO）, respectively. The self-oscillations can be explained by the competition between the phase shifts induced by cascading nonlinearity and thermal effect, and the influence of fundamental nonlinear phase shift by the generation of SPO. The simulation results are in good agreement with the experiment data.
基金supported by the National Natural Science Foundation of China(Grant Nos.62375041,52203134 and 62075032)the Fundamental Research Funds for the Central Universities(Grant No.ZYGX2019J051).
文摘We present a high-power mid-infrared single-frequency pulsed fiber laser(SFPFL)with a tunable wavelength range from 2712.3 to 2793.2 nm.The single-frequency operation is achieved through a compound cavity design that incorporates a germanium etalon and a diffraction grating,resulting in an exceptionally narrow seed linewidth of approximately 780 kHz.Employing a master oscillator power amplifier configuration,we attain a maximum average output power of 2.6 W at 2789.4 nm,with a pulse repetition rate of 173 kHz,a pulse energy of 15μJ and a narrow linewidth of approximately 850 kHz.This achievement underscores the potential of the mid-infrared SFPFL system for applications requiring high coherence and high power,such as high-resolution molecular spectroscopy,precision chemical identification and nonlinear frequency conversion.
基金supported by the National Natural Science Foundation of China(Nos.U22A6003 and 62175122)。
文摘We demonstrate a 202 W all polarization-maintaining(PM)single-frequency fiber amplifier operating at the C band.Simulations show that the length of the output fiber pigtail following the gain fiber critically has a great impact on stimulated Brillouin scattering(SBS),posing a major obstacle for high-power single-frequency amplification.Optimizing the length to suppress the backward SBS by~10 d B,we experimentally achieved a maximum output power of 202 W,yielding an optical-to-optical efficiency of 42%.The signal-to-noise ratio(SNR)of signal light,relative to amplified spontaneous emission(ASE)in Er^(3+)and Yb^(3+)bands,was measured to be 23 and 32 dB,respectively,and it can be further improved by ASE suppression and filtering techniques during amplification.To the best of our knowledge,this is the all-PM single-frequency fiber amplifier with the highest power reported in the C band.
基金supported by the Natural Science Foundation of Xiamen City(No.3502Z20227166)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(No.KF202102)+2 种基金the Project of Advanced Laser Technology Laboratory of Anhui Province(No.AHL2022KF03)the Natural Science Foundation of Fujian Province(No.2023I0004)the National Natural Science Foundation of China(No.62275224).
文摘In this work,we report on the recent research progress on watt-level all-solid-state single-frequency Pr:LiYF_(4)(YLF)lasers in the orange spectral region.Combining dual-end pumping and ring-cavity technologies,we have achieved a maximum single-frequency output of 1.19 W at 607 nm with a linewidth of about 20.3 MHz.Based on this study,by inserting a 0.15 mm etalon inside the ring cavity,we find that the 607 nm lasing can be completely suppressed and a single-frequency laser at 604 nm with a 0.69 W output power and a linewidth of about 16.7 MHz can also be obtained.Moreover,the wavelengths of the two single-frequency lasers can be tuned from 607.16 to 607.61 nm and from 603.99 to 605.02 nm,respectively.Furthermore,the single-frequency Pr:YLF laser can also operate in a state of the two orange wavelengths,simultaneously,with a maximum output power of 0.97 W.We believe that this is the highest output power of a direct generation of single-frequency orange lasers and the first demonstration of the wavelength-tuned operation of the achieved single-frequency orange lasers,which could bring opportunities for the application of single-frequency orange lasers.
基金supported by the National Key R&D Program of China(No.2020YFC2200401)the National Natural Science Foundation of China(Nos.62005316 and 62035015)。
文摘Unlike conventional continuous-wave lasers with wide spectra,the amplification of single-frequency lasers in optical fibers is much more difficult owing to the ultra-high power spectral density induced nonlinear stimulated Brillouin scattering effect.Nevertheless,over the past two decades much effort has been devoted to improving the power scaling and performance of high-power single-frequency fiber amplifiers.These amplifiers are mostly driven by applications,such as high precision detection and metrology,and have benefited from the long coherence length,low noise,and excellent beam quality of this type of laser source.In this paper,we review the overall development of high-power single-frequency fiber amplifiers by focusing on its progress and challenges,specifically,the strategies for circumventing the stimulated Brillouin scattering and transverse mode instability effects that,at present,are the major limiting factors of the power scaling of the single-frequency fiber amplifiers.These factors are also thoroughly discussed in terms of free-space and all-fiber coupled architecture.In addition,we also examine the noise properties of single-frequency fiber amplifiers,along with corresponding noise reducing schemes.Finally,we briefly envision the future development of high-power single-frequency fiber amplifiers.
