Achillea species are known for their healing properties since ancient times.There is extensive literature on their pharmacological action due to their bioactive compounds.The present study aimed to investigate the ant...Achillea species are known for their healing properties since ancient times.There is extensive literature on their pharmacological action due to their bioactive compounds.The present study aimed to investigate the antioxidant and antimicrobial effects of hydroalcoholic extracts from the inflorescences and leaves of the species Achillea crithmifolia Waldst.and Kit.,A.grandifolia Friv.and A.millefolium L.The phytochemical profiles of all extracts were evaluated both by NMR spectroscopy and LC-MS analysis,and the results were consistent with the spectrophotometrically determined total phenolic(TP:125.42-191.98 mg/g)and total flavonoid(TF:47.34-180.02 mg/g)contents.All the extracts were tested for their antioxidant activity using DPPH and ABTS•+radical scavenging assay,as well as ferrous ion chelating ability and reducing power tests.All the extracts showed moderate antioxidant activity,compared to the reference substance BHT.Additionally,the antibacterial activity of the extracts was evaluated against major food-borne pathogens,showing moderate antimicrobial effects.展开更多
Recently,Prevotella spp.,a major genus of gram-negative commensal bacteria in humans,have emerged as a key microbial contributor to host metabolism due to its ability to ferment dietary fibers,produce beneficial short...Recently,Prevotella spp.,a major genus of gram-negative commensal bacteria in humans,have emerged as a key microbial contributor to host metabolism due to its ability to ferment dietary fibers,produce beneficial short-chain fatty acids,and influence immune responses.However,their diversity and functional differences have created challenges for their development and therapeutic use.Recent studies have shown that specific Prevotella species,such as P.copri,P.intestinalis,and P.histicola,can strengthen gut barrier integrity and reduce metabolic imbalances.Notably,Prevotella populations can be increased through high-fiber or herbal-based treatments.Traditional herbal medicines,including fiber-rich decoctions,also demonstrate the potential to boost endogenous Prevotella communities,enhance microbial fermentation,and improve glucose and lipid balance.This perspective examines the context-dependent roles of Prevotella spp.,with emphasis on the functional heterogeneity of key species such as P.copri,suggests a framework for combining herbal modulation with species-level microbiota profiling,and outlines a research plan to explore microbe-herb synergy in treating obesity,type 2 diabetes,and related metabolic disorders.This strategy offers a new,ecology-based approach to complement standard metabolic interventions.展开更多
Objective:To investigate the quantitative assessment efficacy of chest CT combined with serum Vanin-1 and SPP1 in determining the progression stage of chronic obstructive pulmonary disease(COPD).Methods:A total of 100...Objective:To investigate the quantitative assessment efficacy of chest CT combined with serum Vanin-1 and SPP1 in determining the progression stage of chronic obstructive pulmonary disease(COPD).Methods:A total of 100 COPD subjects from our hospital from January 2020 to December 2023 were included and randomly divided into a healthy control group and an experimental group(50 cases each).The healthy control group underwent slow vital capacity measurement using a spirometer,while the experimental group underwent high-resolution thin-slice CT scans and serum Vanin-1 and SPP1 concentration measurements.Pulmonary function parameters,symptom burden,biomarker concentrations,and imaging characteristics were compared between the two groups.Results:The FEV1/FVC ratio in the experimental group(58.3±7.2)was lower than that in the healthy control group(92.1±4.8);the total CAT score(22.4±3.5)was higher than that in the healthy control group(3.1±1.2);both Vanin-1(18.7±2.3μg/L)and SPP1(25.6±4.1μg/L)levels were higher than those in the healthy control group;LAA%-950(38.7±6.2%)and WA%(68.5±5.3%)were significantly higher than those in the healthy control group(all p<0.001).Conclusion:Chest CT combined with serum Vanin-1 and SPP1 can accurately quantify the pathological progression of COPD,providing a dual basis for clinical staging and individualized intervention.展开更多
Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolit...Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolithic nonplanar ring laser is designed. As a result, a laser of hundreds milliwatts cw single frequency output was built up, placed in a magnetic field and pumped by LD. The optical conversion efficiency was more than 15% and the slope efficiency more than 30%. The laser beam had a good quality, with M 2 about 1 2.展开更多
A novel Er:YAG laser system operating at 1645 nm with high pulse-repetition-frequency(PRF)of kHz level is demonstrated.A ring cavity with double gain medium end-pumped by two fiber lasers is utilized to obtain high pu...A novel Er:YAG laser system operating at 1645 nm with high pulse-repetition-frequency(PRF)of kHz level is demonstrated.A ring cavity with double gain medium end-pumped by two fiber lasers is utilized to obtain high pulse energy.A novel‘triple-reflection’configuration on a piezoelectric actuator(PZT)is adopted to achieve high-repetition-rate at 3-kHz operation with the ramp-fire locking method.Single frequency pulses with maximum average power of 18.3 W at 3 kHz are obtained,and the pulse duration time is 318 ns.The full line width at half maximum(FWHM)of the pulses measured by the heterodyne technique is 1.71 MHz at 3 kHz.To the best of our knowledge,this is the highest PRF single-frequency laser pulses achieved based Er:YAG gain medium.展开更多
We report a low noise continuous-wave （CW） single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO was ...We report a low noise continuous-wave （CW） single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO was pumped by a CW single-frequency Nd：YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit （SNL） at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.展开更多
A compact linearly polarized, low-noise, narrow-linewidth, single-frequency fiber laser at 1950nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3＋-doped germanate glass fiber. Over 100...A compact linearly polarized, low-noise, narrow-linewidth, single-frequency fiber laser at 1950nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3＋-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 195Ohm are achieved. The measured relative intensity noise is less than -135dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72dB, and the laser linewidth is less than 6kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.展开更多
We demonstrated a continuous wave(cw) single-frequency intracavity frequency-doubled Nd:YVO_4/LBO laser with 532 nm output of 7.5 W and 1.06 μm output of 3.1 W, and low intensity noise in audio frequency region.To su...We demonstrated a continuous wave(cw) single-frequency intracavity frequency-doubled Nd:YVO_4/LBO laser with 532 nm output of 7.5 W and 1.06 μm output of 3.1 W, and low intensity noise in audio frequency region.To suppress the intensity noise of the high power 532 nm laser, a laser frequency locking system and a feedback loop based on a Mach-Zehnder interferometer were designed and used.The influences of the frequency stabilization and the crucial parameters of the MZI, such as the power splitting ratio of the beam splitters and the locking state of the MZI, on the intensity noise of the 532 nm laser were investigated in detail.After the experimental optimizations, the laser intensity noise in the frequency region from 0.4 kHz to 10 kHz was significantly suppressed.展开更多
Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward tra...Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20dB from 0.2 to 5kHz and over lOdB from 5 to lOkHz. The relaxation oscillation peak is suppressed by 22dB. In addition, a long term （24h） laser instability of less than 0.05% is achieved.展开更多
A single-frequency retrievable phase modulated multi-tone fiber amplifier is presented in theory and demonstrated in experiment. A multi-tone seed laser generated by a sine wave phase modulated single-frequency laser ...A single-frequency retrievable phase modulated multi-tone fiber amplifier is presented in theory and demonstrated in experiment. A multi-tone seed laser generated by a sine wave phase modulated single-frequency laser is employed for stimulated Brillouin scattering suppression in an all-fiber amplifier. A demodulation signal which is π phase shifted with respect to the modulation signal is used to retrieve the single-frequency laser from the multi-tone laser. In experiment, we first optimize the all-fiber master-oscillator power-amplifier. With this amplifier, we demonstrate a single-frequency retrievable multi-tone laser with 330-W output when driven by the multi-tone seed, while the ultimate output power is only 130 W when driven by the single-frequency laser. Then, we carry out an experiment for retrieving the single-frequency laser from the amplified multi-tone laser. Results indicate that the single-frequency laser can be retrieved with a sideband suppression of more than 20 dB. Retrieving an even higher power single-frequency laser is possible if a high power demodulator is available.展开更多
In single-frequency precise-point positioning of a satellite,ionosphere delay is one of the most important factors impacting the accuracy. Because of the instability of the ionosphere and uncertainty of its physical p...In single-frequency precise-point positioning of a satellite,ionosphere delay is one of the most important factors impacting the accuracy. Because of the instability of the ionosphere and uncertainty of its physical properties, the positioning accuracy is seriously limited when using a precision-limited model for correction. In order to reduce the error, we propose to introduce some ionosphere parameter for real-time ionosphere-delay estimation by applying various mapping functions. Through calculation with data from the IGS（ International GPS Service） tracking station and comparison among results of using several different models and mapping functions, the feasibility and effectiveness of the new method are verified.展开更多
A 135 mW single-frequency distributed Bragg reflector fiber laser at 1.95μm was obtained based on a Tm:YAG ceramic-derived all-glass fiber.The fiber laser achieved an optical signal-to-noise ratio of~77 d B.Moreover,...A 135 mW single-frequency distributed Bragg reflector fiber laser at 1.95μm was obtained based on a Tm:YAG ceramic-derived all-glass fiber.The fiber laser achieved an optical signal-to-noise ratio of~77 d B.Moreover,the threshold and linewidth of the single-frequency laser were measured to be 15.4 mW and 4.5 kHz,respectively.In addition,the measured relative intensity noise was less than-140 d B·Hz^(-1)at frequencies of over 10 MHz.The results show that the as-drawn Tm:YAG ceramic-derived all-glass fiber is highly promising for~2μm single-frequency fiber laser applications.展开更多
Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-fre...Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-frequency receivers. However, user has to consider the resultant positioning accuracy. Since the evolution of low-cost single-frequency (LCSF) receivers is typically cheaper than single-frequency high grade receivers, it is possible to obtain comparable positioning accuracy if the corresponding observables are accurately modelled. In this paper, two LCSF GPS receivers are used to form short baseline. Raw GPS measurements are recorded for several consecutive days. The collected data are used to develop the stochastic model of GPS observables from such receivers. Different functions are tested to determine the best fitting model which is found to be 3 parameters exponential decay function. The new developed model is used to process different data sets and the results are compared against the traditional model. Both results from the newly developed and the traditional models are compared with the reference solution obtained from dual-frequency receiver. It is shown that the newly developed model improves the root-mean-square of the estimated horizontal coordinates by about 10% and improves the root-mean-square of the up component by about 39%.展开更多
Broadband ultrasound signals will produce distortion in viscoacoustic medium, which may influence the accuracy of time-of-flight (TOF) measurement. Under the condition of single-frequency acoustic source, the wave pro...Broadband ultrasound signals will produce distortion in viscoacoustic medium, which may influence the accuracy of time-of-flight (TOF) measurement. Under the condition of single-frequency acoustic source, the wave propagation process in viscoacoustic medium was analyzed and an approximate solution of the wave propagation was given. Instances of broadband ultrasound were analyzed and simulated based on the single-frequency results. A single-frequency matching pursuits (SFMP) algorithm was then introduced to solve the waveform distortion problem. Time-frequency decomposition was applied to extracting the single-frequency compositions from broadband ultrasound signals, and then these compositions were sent to the matching pursuits (MP) algorithm for calculating the TOF parameters. Compared with the broadband signals, the shapes of extracted single-frequency signals change more slightly as distance and attenuation coefficient increase. The residuals of SFMP were far less than those of MP algorithm. Experimental results show that the SFMP algorithm is able to eliminate waveform distortion of broadband ultrasound in viscoacoustic medium, which helps improve the accuracy of TOF measurement.展开更多
An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as ...An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as the seed source for the MOPA system and the Yb-doped fibers are employed as the gain medium or the saturable absorber. The SF operation is observed to be stable without mode hopping. The highest output power of 266 mW is obtained under the 400row pump power with the corresponding slope efficiency of 66.2-. The Hnewidth of the amplified output laser is approximately I kHz and its optical signal-to-noise ratio is over 45 dB.展开更多
An injection-seeded single-frequency Q-switched Nd：YAG laser is accomplished by using a phase modulated rampfire technique. A RbTiOPO4（RTP） electro-optic crystal is selected for effective optical path length modula...An injection-seeded single-frequency Q-switched Nd：YAG laser is accomplished by using a phase modulated rampfire technique. A RbTiOPO4（RTP） electro-optic crystal is selected for effective optical path length modulation of the slave self-filtering unstable resonator. This single-frequency laser is capable of producing 50 m J pulse energy at 1 Hz repetition rate with a pulse width of 16 ns. The standard deviation of laser pulse intensity for consecutive 100 shots from the mean pulse intensity is less than 1.05%. A spectral linewidth of less than 0.5 pm with a frequency jitter of about 14 fm over30 min is obtained.展开更多
We study the influence of the phase noises of far detuning single frequency lasers on the lifetime of Bose-Einstein condensation（BEC）of^（87）Rb in an optical dipole trap.As a comparison,we shine a continuous-wave s...We study the influence of the phase noises of far detuning single frequency lasers on the lifetime of Bose-Einstein condensation（BEC）of^（87）Rb in an optical dipole trap.As a comparison,we shine a continuous-wave singlefrequency Ti：sapphire laser,an external-cavity diode laser and a phase-locked diode laser on BEC.We measure the heating and lifetime of BEC in two different hyperfine states：｜F=2,m_F=2〉and｜F=1,m_F=1〉.Due to the narrow linewidth and small phase noise,the continuous-wave single-frequency Ti：sapphire laser has less influence on the lifetime of^（87）Rb BEC than the external-cavity diode laser.To reduce the phase noise of the external-cavity diode laser,we use an optical phase-locked loop for the external-cavity diode laser to be locked on a Ti：sapphire laser.The lifetime of BEC is increased when applfying the phase-Jocked diode laser in contrast with the external-cavity diode laser.展开更多
In this paper, we report a high power long-pulse single-frequency all-fiber amplifier at 1064 nm with near-diffraction-limited beam quality based on a polarization-maintaining tapered Yb-doped fiber (T-YDF). By applyi...In this paper, we report a high power long-pulse single-frequency all-fiber amplifier at 1064 nm with near-diffraction-limited beam quality based on a polarization-maintaining tapered Yb-doped fiber (T-YDF). By applying square wave pulse modulation to the diodes, with a frequency of 50 Hz and a pulse width of 668 μs, the peak power of the output laser reached 257 W with an average power of 8.65 W, linewidth of 10.6 kHz and M<sup>2</sup> < 1.5. .展开更多
基金supported by the Serbian Ministry of Education,Science and Technological Development(Agreements No.451-03-136/2025-03/200122 and 451-03-136/2025-03/200378).
文摘Achillea species are known for their healing properties since ancient times.There is extensive literature on their pharmacological action due to their bioactive compounds.The present study aimed to investigate the antioxidant and antimicrobial effects of hydroalcoholic extracts from the inflorescences and leaves of the species Achillea crithmifolia Waldst.and Kit.,A.grandifolia Friv.and A.millefolium L.The phytochemical profiles of all extracts were evaluated both by NMR spectroscopy and LC-MS analysis,and the results were consistent with the spectrophotometrically determined total phenolic(TP:125.42-191.98 mg/g)and total flavonoid(TF:47.34-180.02 mg/g)contents.All the extracts were tested for their antioxidant activity using DPPH and ABTS•+radical scavenging assay,as well as ferrous ion chelating ability and reducing power tests.All the extracts showed moderate antioxidant activity,compared to the reference substance BHT.Additionally,the antibacterial activity of the extracts was evaluated against major food-borne pathogens,showing moderate antimicrobial effects.
基金supported by the National Research Foundation of Korea(2020R1F1A1074155).
文摘Recently,Prevotella spp.,a major genus of gram-negative commensal bacteria in humans,have emerged as a key microbial contributor to host metabolism due to its ability to ferment dietary fibers,produce beneficial short-chain fatty acids,and influence immune responses.However,their diversity and functional differences have created challenges for their development and therapeutic use.Recent studies have shown that specific Prevotella species,such as P.copri,P.intestinalis,and P.histicola,can strengthen gut barrier integrity and reduce metabolic imbalances.Notably,Prevotella populations can be increased through high-fiber or herbal-based treatments.Traditional herbal medicines,including fiber-rich decoctions,also demonstrate the potential to boost endogenous Prevotella communities,enhance microbial fermentation,and improve glucose and lipid balance.This perspective examines the context-dependent roles of Prevotella spp.,with emphasis on the functional heterogeneity of key species such as P.copri,suggests a framework for combining herbal modulation with species-level microbiota profiling,and outlines a research plan to explore microbe-herb synergy in treating obesity,type 2 diabetes,and related metabolic disorders.This strategy offers a new,ecology-based approach to complement standard metabolic interventions.
基金Baoding Science and Technology Plan Project(Project No.:2341ZF214)。
文摘Objective:To investigate the quantitative assessment efficacy of chest CT combined with serum Vanin-1 and SPP1 in determining the progression stage of chronic obstructive pulmonary disease(COPD).Methods:A total of 100 COPD subjects from our hospital from January 2020 to December 2023 were included and randomly divided into a healthy control group and an experimental group(50 cases each).The healthy control group underwent slow vital capacity measurement using a spirometer,while the experimental group underwent high-resolution thin-slice CT scans and serum Vanin-1 and SPP1 concentration measurements.Pulmonary function parameters,symptom burden,biomarker concentrations,and imaging characteristics were compared between the two groups.Results:The FEV1/FVC ratio in the experimental group(58.3±7.2)was lower than that in the healthy control group(92.1±4.8);the total CAT score(22.4±3.5)was higher than that in the healthy control group(3.1±1.2);both Vanin-1(18.7±2.3μg/L)and SPP1(25.6±4.1μg/L)levels were higher than those in the healthy control group;LAA%-950(38.7±6.2%)and WA%(68.5±5.3%)were significantly higher than those in the healthy control group(all p<0.001).Conclusion:Chest CT combined with serum Vanin-1 and SPP1 can accurately quantify the pathological progression of COPD,providing a dual basis for clinical staging and individualized intervention.
基金Fundfor Research on Doctoral Programs in Institutions of Higher Learning
文摘Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolithic nonplanar ring laser is designed. As a result, a laser of hundreds milliwatts cw single frequency output was built up, placed in a magnetic field and pumped by LD. The optical conversion efficiency was more than 15% and the slope efficiency more than 30%. The laser beam had a good quality, with M 2 about 1 2.
基金the National Key Research and Development Program of China(Grant No.2017YFB0405203)the National Natural Science Foundation of China(Grant No.61627821).
文摘A novel Er:YAG laser system operating at 1645 nm with high pulse-repetition-frequency(PRF)of kHz level is demonstrated.A ring cavity with double gain medium end-pumped by two fiber lasers is utilized to obtain high pulse energy.A novel‘triple-reflection’configuration on a piezoelectric actuator(PZT)is adopted to achieve high-repetition-rate at 3-kHz operation with the ramp-fire locking method.Single frequency pulses with maximum average power of 18.3 W at 3 kHz are obtained,and the pulse duration time is 318 ns.The full line width at half maximum(FWHM)of the pulses measured by the heterodyne technique is 1.71 MHz at 3 kHz.To the best of our knowledge,this is the highest PRF single-frequency laser pulses achieved based Er:YAG gain medium.
基金supported by the National Natural Science Foundation of China(Grant No.60878003)the Science Fund for Excellent Research Team of the National Natural Science Foundation of China(Grant No.60821004)the National Basic Research Program of China(Grant No.2010CB923101)
文摘We report a low noise continuous-wave （CW） single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO was pumped by a CW single-frequency Nd：YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit （SNL） at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.
基金Supported by the National High-Technology Research and Development Program of China under Grant Nos 2013AA031502 and 2014AA041902the National Natural Science Foundation of China under Grant Nos 11174085,51132004,and 51302086+3 种基金the Natural Science Foundation of Guangdong Province under Grant Nos S2011030001349 and S20120011380the China National Funds for Distinguished Young Scientists under Grant No 61325024the Science and Technology Project of Guangdong Province under Grant No 2013B090500028the ’Cross and Cooperative’ Science and Technology Innovation Team Project of Chinese Academy of Sciences under Grant No 2012-119
文摘A compact linearly polarized, low-noise, narrow-linewidth, single-frequency fiber laser at 1950nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3＋-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 195Ohm are achieved. The measured relative intensity noise is less than -135dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72dB, and the laser linewidth is less than 6kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFA0301401)
文摘We demonstrated a continuous wave(cw) single-frequency intracavity frequency-doubled Nd:YVO_4/LBO laser with 532 nm output of 7.5 W and 1.06 μm output of 3.1 W, and low intensity noise in audio frequency region.To suppress the intensity noise of the high power 532 nm laser, a laser frequency locking system and a feedback loop based on a Mach-Zehnder interferometer were designed and used.The influences of the frequency stabilization and the crucial parameters of the MZI, such as the power splitting ratio of the beam splitters and the locking state of the MZI, on the intensity noise of the 532 nm laser were investigated in detail.After the experimental optimizations, the laser intensity noise in the frequency region from 0.4 kHz to 10 kHz was significantly suppressed.
基金Supported by the National High-Technology Research and Development Program of China under Grant Nos 2013AA031502 and 2014AA041902the National Natural Science Foundation of China under Grant Nos 11174085,51132004,and 51302086+3 种基金the Guangdong Natural Science Foundation under Grant Nos S2011030001349 and S20120011380the China National Funds for Distinguished Young Scientists under Grant No 61325024the Science and Technology Project of Guangdong Province under Grant No 2013B090500028the’Cross and Cooperative’Science and Technology Innovation Team Project of Chinese Academy of Sciences under Grant No 2012-119
文摘Effective multiple optoelectronic feedback circuits for simultaneously suppressing low-frequency and relaxation oscillation intensity noise in a single-frequency phosphate fiber laser are demonstrated. The forward transfer function, which relates the laser output intensity to the pump modulations, is measured and analyzed. A custom two-path feedback system operating at different frequency bands is designed to adjust the pump current directly. The relative intensity noise is decreased by 20dB from 0.2 to 5kHz and over lOdB from 5 to lOkHz. The relaxation oscillation peak is suppressed by 22dB. In addition, a long term （24h） laser instability of less than 0.05% is achieved.
基金Project supported by the New Century Excellent Talents in University, Ministry of Education of China and the Scientific Research Project in National University Defense of Technology
文摘A single-frequency retrievable phase modulated multi-tone fiber amplifier is presented in theory and demonstrated in experiment. A multi-tone seed laser generated by a sine wave phase modulated single-frequency laser is employed for stimulated Brillouin scattering suppression in an all-fiber amplifier. A demodulation signal which is π phase shifted with respect to the modulation signal is used to retrieve the single-frequency laser from the multi-tone laser. In experiment, we first optimize the all-fiber master-oscillator power-amplifier. With this amplifier, we demonstrate a single-frequency retrievable multi-tone laser with 330-W output when driven by the multi-tone seed, while the ultimate output power is only 130 W when driven by the single-frequency laser. Then, we carry out an experiment for retrieving the single-frequency laser from the amplified multi-tone laser. Results indicate that the single-frequency laser can be retrieved with a sideband suppression of more than 20 dB. Retrieving an even higher power single-frequency laser is possible if a high power demodulator is available.
基金supported by the National Natural Science Foundation of China(40902081,40774001,40841021)
文摘In single-frequency precise-point positioning of a satellite,ionosphere delay is one of the most important factors impacting the accuracy. Because of the instability of the ionosphere and uncertainty of its physical properties, the positioning accuracy is seriously limited when using a precision-limited model for correction. In order to reduce the error, we propose to introduce some ionosphere parameter for real-time ionosphere-delay estimation by applying various mapping functions. Through calculation with data from the IGS（ International GPS Service） tracking station and comparison among results of using several different models and mapping functions, the feasibility and effectiveness of the new method are verified.
基金Project supported by the Yunnan Fundamental Research Projects(Grant No.202201AU070065)Natural Science Foundation of China for Young Scholars(Grant No.52002131)+1 种基金Open Fund of the Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques(Grant No.2021-04)the Scientific Research Fund Project of Yunnan Provincial Department of Education(Grant No.2022J0591)
文摘A 135 mW single-frequency distributed Bragg reflector fiber laser at 1.95μm was obtained based on a Tm:YAG ceramic-derived all-glass fiber.The fiber laser achieved an optical signal-to-noise ratio of~77 d B.Moreover,the threshold and linewidth of the single-frequency laser were measured to be 15.4 mW and 4.5 kHz,respectively.In addition,the measured relative intensity noise was less than-140 d B·Hz^(-1)at frequencies of over 10 MHz.The results show that the as-drawn Tm:YAG ceramic-derived all-glass fiber is highly promising for~2μm single-frequency fiber laser applications.
文摘Typically, dual-frequency geodetic grade GNSS receivers are utilized for positioning applications that require high accuracy. Single-frequency high grade receivers can be used to minimize the expenses of such dual-frequency receivers. However, user has to consider the resultant positioning accuracy. Since the evolution of low-cost single-frequency (LCSF) receivers is typically cheaper than single-frequency high grade receivers, it is possible to obtain comparable positioning accuracy if the corresponding observables are accurately modelled. In this paper, two LCSF GPS receivers are used to form short baseline. Raw GPS measurements are recorded for several consecutive days. The collected data are used to develop the stochastic model of GPS observables from such receivers. Different functions are tested to determine the best fitting model which is found to be 3 parameters exponential decay function. The new developed model is used to process different data sets and the results are compared against the traditional model. Both results from the newly developed and the traditional models are compared with the reference solution obtained from dual-frequency receiver. It is shown that the newly developed model improves the root-mean-square of the estimated horizontal coordinates by about 10% and improves the root-mean-square of the up component by about 39%.
基金Supported by National Natural Science Foundation of China (No.30800240 and No.60901043)
文摘Broadband ultrasound signals will produce distortion in viscoacoustic medium, which may influence the accuracy of time-of-flight (TOF) measurement. Under the condition of single-frequency acoustic source, the wave propagation process in viscoacoustic medium was analyzed and an approximate solution of the wave propagation was given. Instances of broadband ultrasound were analyzed and simulated based on the single-frequency results. A single-frequency matching pursuits (SFMP) algorithm was then introduced to solve the waveform distortion problem. Time-frequency decomposition was applied to extracting the single-frequency compositions from broadband ultrasound signals, and then these compositions were sent to the matching pursuits (MP) algorithm for calculating the TOF parameters. Compared with the broadband signals, the shapes of extracted single-frequency signals change more slightly as distance and attenuation coefficient increase. The residuals of SFMP were far less than those of MP algorithm. Experimental results show that the SFMP algorithm is able to eliminate waveform distortion of broadband ultrasound in viscoacoustic medium, which helps improve the accuracy of TOF measurement.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61475125 and 61505162the Foundation of the Education Committee of Shaanxi Province under Grant Nos 16JK1769 and l4JK1756the Science Foundation of Northwest University under Grant Nos 15NW07 and 13NW14
文摘An efficient narrow=linewidth single-frequency （SF） Yb-doped all-fiber master oscillator power amplifier （MOPA） laser operating at 1064.3 nm is demonstrated experimentally. A ring cavity SF fiber laser is used as the seed source for the MOPA system and the Yb-doped fibers are employed as the gain medium or the saturable absorber. The SF operation is observed to be stable without mode hopping. The highest output power of 266 mW is obtained under the 400row pump power with the corresponding slope efficiency of 66.2-. The Hnewidth of the amplified output laser is approximately I kHz and its optical signal-to-noise ratio is over 45 dB.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFB1104500 and 2016YFB0701000)
文摘An injection-seeded single-frequency Q-switched Nd：YAG laser is accomplished by using a phase modulated rampfire technique. A RbTiOPO4（RTP） electro-optic crystal is selected for effective optical path length modulation of the slave self-filtering unstable resonator. This single-frequency laser is capable of producing 50 m J pulse energy at 1 Hz repetition rate with a pulse width of 16 ns. The standard deviation of laser pulse intensity for consecutive 100 shots from the mean pulse intensity is less than 1.05%. A spectral linewidth of less than 0.5 pm with a frequency jitter of about 14 fm over30 min is obtained.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301600 and 2016YFA0301602the National Natural Science Foundation of China under Grant Nos 11234008,11474188 and 11704234the Fund for Shanxi'1331 Project'Key Subjects Construction
文摘We study the influence of the phase noises of far detuning single frequency lasers on the lifetime of Bose-Einstein condensation（BEC）of^（87）Rb in an optical dipole trap.As a comparison,we shine a continuous-wave singlefrequency Ti：sapphire laser,an external-cavity diode laser and a phase-locked diode laser on BEC.We measure the heating and lifetime of BEC in two different hyperfine states：｜F=2,m_F=2〉and｜F=1,m_F=1〉.Due to the narrow linewidth and small phase noise,the continuous-wave single-frequency Ti：sapphire laser has less influence on the lifetime of^（87）Rb BEC than the external-cavity diode laser.To reduce the phase noise of the external-cavity diode laser,we use an optical phase-locked loop for the external-cavity diode laser to be locked on a Ti：sapphire laser.The lifetime of BEC is increased when applfying the phase-Jocked diode laser in contrast with the external-cavity diode laser.
文摘In this paper, we report a high power long-pulse single-frequency all-fiber amplifier at 1064 nm with near-diffraction-limited beam quality based on a polarization-maintaining tapered Yb-doped fiber (T-YDF). By applying square wave pulse modulation to the diodes, with a frequency of 50 Hz and a pulse width of 668 μs, the peak power of the output laser reached 257 W with an average power of 8.65 W, linewidth of 10.6 kHz and M<sup>2</sup> < 1.5. .
