A single-channel far-infrared （FIR） laser interferometer was developed to measure the line averaged electron density on the EAST tokamak. The structure of the single-channel FIR laser interferometer is described in ...A single-channel far-infrared （FIR） laser interferometer was developed to measure the line averaged electron density on the EAST tokamak. The structure of the single-channel FIR laser interferometer is described in detail. The evolution of density sawtooth oscillation was measured by means the FIR laser interferometer, and was identified by electron cyclotron emission （ECE） signals and soft X-ray intensity. The discharges with and without sawtooth were compared with each other in the Hugill diagram.展开更多
A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high si...A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high signal to noise ratio of interferometric intensity output and higher spectral resolution than traditional grating spectrophotometer.展开更多
A new multi-channel far infrared （FIR） laser interferometer was built up and ap- plied to HL-2A. The unique feature of real-time heterodyne interferometer is the combination of high power radiation source （300 mW）...A new multi-channel far infrared （FIR） laser interferometer was built up and ap- plied to HL-2A. The unique feature of real-time heterodyne interferometer is the combination of high power radiation source （300 mW）, lower noise room temperature detector （noise tempera- ture below 6000 K） with good spatial resolution of 7 cm. Various parameters are optimized for maximum laser output power. Zero crossings of the signals are counted with field programmable gate array （FPGA） digital circuitry yielding the resolution of 1/1000 fringe. The newly measured results including density fluctuation are also presented.展开更多
Accurate prediction of hypersonic boundary-layer transition plays an important role in thermal protection system design of hypersonic vehicles.Restricted by the capability of spatial diagnostics for hypersonic boundar...Accurate prediction of hypersonic boundary-layer transition plays an important role in thermal protection system design of hypersonic vehicles.Restricted by the capability of spatial diagnostics for hypersonic boundary-layer study,quite a lot of problems of hypersonic boundary-layer transition,such as nonlinearity and receptivity,remain outstanding.This work reports the application of focused laser differential interferometer to instability wave development across hypersonic boundary-layer on a flared cone model.To begin with,the focused laser differential interferometer is designed and set up in a Mach number 6 hypersonic quiet wind tunnel with the focal point in the laminar boundary-layer of a 5 degree half-angle flared cone model.Afterwards,instability experiments are carried out by traversing the focal point throughout the hypersonic boundary-layer and the density fluctuation along the boundary-layer profile is measured and analyzed.The results show that three types of instability waves ranging from 10 k Hz to over 1 MHz are co-existing in the hypersonic boundary-layer,indicating the powerful capability of focused laser differential interferometer in dynamic response resolution for instability wave study in hypersonic flow regime;furthermore,quantitative analyses including spectra and bicoherence analysis of instability waves throughout the hypersonic boundary-layer for both cold and heated cone models are performed.展开更多
A multichannel methanoic acid （HCOOH, λ=432.5 μm） laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide （HCN, λ=337 μm） laser interferometer in the HL-2A tokamak....A multichannel methanoic acid （HCOOH, λ=432.5 μm） laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide （HCN, λ=337 μm） laser interferometer in the HL-2A tokamak. A conventional Michelson-type interometer is used for the electron density measurement, and a Dodel-Kunz-type polarimeter is used for the Faraday rotation effect measurement, respectively. Each HCOOH laser can produce a linearly polarized radiation at a power lever of -30 mW, and a power stability 〈10% in 50 rain. A beam waist （diameter d0 ≈12.0 mm, about 200 mm away from the outlet） is finally determined through a chopping modulation technique. The latest optical layout of the interferometer/polarimeter has been finished, and the hardware data processing system based on the fast Fourier transform phase- comparator technique is being explored. In order to demonstrate the feasibility of the diagnostic scheme, two associated bench simulation experiments were carried out in the laboratory, in which the plasma was simulated by a piece of polytetrafluoroethene plate, and the Faraday rotation effect was simulated by a rotating half-wave plate. Simulation results agreed well with the initial experimental conditions. At present, the HCOOH laser interferometer/polarimeter system is being assembled on HL-2A, and is planned to be applied in the 2014-2015 experimental campaign.展开更多
Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely af...Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely affected by various error sources, including geometric imperfections, thermal deformations, load effects, and dynamic disturbances. The increasing demand for higher dimensional accuracy in various industrial applications has created the need to develop cost-effective methods for enhancing the overall performance of these mechanisms. Improving the accuracy of a MAS by upgrading the physical structure would lead to an exponential increase in manufacturing costs without totally eliminating geometrical deviations and thermal deformations of MAS components. Hence, the idea of reducing MAS’s error by a software-based alternative approach to provide real-time prediction and correction of geometric and thermally induced errors is considered a strategic step toward achieving the full potential of the MAS. This paper presents a structured approach designed to improve the accuracy of Cartesian MAS’s through software error compensation. Four steps are required to develop and implement this approach: (i) measurement of error components using a multidimensional laser interferometer system, (ii) tridimensional volumetric error mapping using rigid body kinematics, (iii) volumetric error prediction via an artificial neural network model, and finally (iv) implementation of the on-line error compensation. An illustrative example using a bridge type coordinate measuring machine is presented.展开更多
The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new ...The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new method to calibrate mirror map on ultraprecise movement stage （UPMS） with nanopositioning and to make a real-time compensation for the mirror surface error by using mirror map data tables with the software algorithm. Based on the mirror map test model, the factors affecting mirror map are analyzed through geometric method on the UPMS with six digrees of freedom. Dam processing methods including spline interpolation and spline offsets are used to process the raw sampling data to build mirror map tables. The linear interpolation as compensation method to make a real-time correction on the stage mirror unflatness is adopted and the correction formulas are illuminated. In this way, the measurement accuracy of the system is obviously improved from 40 nm to 5 nm.展开更多
In this paper,we present a phase multiplication algorithm(PMA)to obtain scalable fringe precision in laser self-mixing interferometer under a weak feedback regime.Merely by applying the double angle formula on the sel...In this paper,we present a phase multiplication algorithm(PMA)to obtain scalable fringe precision in laser self-mixing interferometer under a weak feedback regime.Merely by applying the double angle formula on the self-mixing signal multiple times,the continuously improved fringe precision will be obtained.Theoretical analysis shows that the precision of the fringe could be improved toλ/2^(n+1).The validity of the proposed method is demonstrated by means of simulated SMI signals and confirmed by experiments under different amplitudes.A fringe precision ofλ/128 at a sampling rate of 500 k S/s has been achieved after doing 6 th the PMA.Finally,an amplitude of 50 nm has been proved to be measurable and the absolute error is 3.07 nm,which is within the theoretical error range.The proposed method for vibration measurement has the advantage of high accuracy and reliable without adding any additional optical elements in the optical path,thus it will play an important role in nanoscale measurement field.展开更多
The method and experimental results of measuring a small vibrating displacement by laser interferometer are introduced in this paper. The dynamic response of a new kind of tiny piezoelectric driver is detected. Result...The method and experimental results of measuring a small vibrating displacement by laser interferometer are introduced in this paper. The dynamic response of a new kind of tiny piezoelectric driver is detected. Results show that this kind of PZN-PZT tiny driver not only has high voltage-displacement sensitivity, but also its frequency response approaches to 1 kHz.Therefore this kind of piezoelectric driver can be used widely in many fields.展开更多
A method is proposed to solve the problem of direction discrimination for laser feedback interferometers. By vibrating the feedback mirror with a small-amplitude and high-frequency sine wave, laser intensity is modula...A method is proposed to solve the problem of direction discrimination for laser feedback interferometers. By vibrating the feedback mirror with a small-amplitude and high-frequency sine wave, laser intensity is modulated accordingly. The modulation amplitude can be extracted using a phase sensitive detector （PSD）. When the feedback mirror moves, the PSD output shows a quasi-sine waveform similar to a laser intensity interference fringe but with a phase difference of approximately ±π/2. If the movement direction of the feedback mirror changes, the phase difference sign reverses. Therefore, the laser feedback interferometer offers a potential application in displacement measurement with a resolution of 1/8 wavelength and in-time direction discrimination. Without using optical components such as polarization beam splitters and wave plates, the interferometer is very simple, easy to align, and less costly.展开更多
Structure, improvements and experiment results of a vertical three-channel far- in- frared （FIR） hydrogen cyanide （HCN） laser interferometer, operated routinely in EAST to measure the electron density profile, are...Structure, improvements and experiment results of a vertical three-channel far- in- frared （FIR） hydrogen cyanide （HCN） laser interferometer, operated routinely in EAST to measure the electron density profile, are presented. Moreover, a five-channel deuterium cyanide （DCN） laser interferometer was developed successfully. Some key issues confronted in development, including the economization of working gas and the solution to atmospheric absorption, are resolved and described in detail.展开更多
We consider an extremely intense laser,enclosed by an atom interferometer.The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit.We com...We consider an extremely intense laser,enclosed by an atom interferometer.The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit.We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer.The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose-Einstein condensates.We push up the sensitivity limit of the interferometer with Bose-Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.展开更多
For the development of the aviation industry, machine tools are becoming large and travel long distances, making optical alignment setup difficult. An auto-tracking laser interferometer (ATLI) is proposed and research...For the development of the aviation industry, machine tools are becoming large and travel long distances, making optical alignment setup difficult. An auto-tracking laser interferometer (ATLI) is proposed and researched in this paper for the squareness error measurement of machine tools or coordinate-measuring machines (CMMs). The procedure involves measurement of only one line of an axis, and the measurement results provide us information about not only the positioning errors but also the squareness errors. This specially designed interferometer instrument can be useful in checking industrial machine tools in a short time.展开更多
A microwave photonic filter(MPF) with variable coefficient is proposed and demonstrated, which is constructed by a multi-wavelength fiber laser and Mach-Zehnder interferometer(MZI). Through changing the slope characte...A microwave photonic filter(MPF) with variable coefficient is proposed and demonstrated, which is constructed by a multi-wavelength fiber laser and Mach-Zehnder interferometer(MZI). Through changing the slope characteristics of Mach-Zehnder interference spectrum adjusted by optical variable delay line(OVDL), the conversion from phase modulation(PM) to intensity modulation(IM) is realized. The multi-wavelength fiber laser with Lyot-Sagnac optical filter has variable wavelength spacing. So the designed filter has a variable number of taps and tap weights. As a result, the tunable range of passband center frequency is 2.6 GHz. The reconfigurability of MPF can be also realized by adjusting the output of fiber laser.展开更多
In National Astronomical Observatory, Japan, Mitaka, a group of scientists has been constructing a laser interferometer with two Fabry Perot cavities 300m long, one in North South and one in East West directions. The ...In National Astronomical Observatory, Japan, Mitaka, a group of scientists has been constructing a laser interferometer with two Fabry Perot cavities 300m long, one in North South and one in East West directions. The interferomer is to detect any gravitational wave near 400Hz frequency and stronger than 10 -20 by autumn, 1998 all the instruments have been installed in the underground facilities and it will be operated for more than 30 days in April, 1999. Then a recycling device will be installed to increase the sensitivity by factor of 10. In this paper this system as well as other systems such as LIGOs in UAS and VIRGO in Europe will be reviewed.展开更多
In order to achieve high-accuracy measurement of radius of curvature of optical sphere, ultra-high accuracy radius of curvature testing device is developed by dual-frequency laser interferometer and Fizeau interferome...In order to achieve high-accuracy measurement of radius of curvature of optical sphere, ultra-high accuracy radius of curvature testing device is developed by dual-frequency laser interferometer and Fizeau interferometer based on cat’s eye and confocal method. Through analyzing the error source models of radius of curvature testing, optical configuration of the testing device has been optimized. Precise environment control and real-time monitoring system is also established to reduce the errors caused by environment. Through the above processes, the radius of curvature measurement relative accuracy is better than 2 ppm. One optical sphere, R88.5 mm, test aperture 59 mm, has been tested. Testing result is 88499.465 ± 0.176 μm, meeting the design requirement. The method has high accuracy and practical advantages.展开更多
Distributed fiber-optic sensing(DFOS)can turn the worldwide fiber network into a sensing array,which may immensely extend the sensing range and approaches for hazard assessment,earth observation,and human activity mea...Distributed fiber-optic sensing(DFOS)can turn the worldwide fiber network into a sensing array,which may immensely extend the sensing range and approaches for hazard assessment,earth observation,and human activity measurement.However,most existing DFOS schemes cannot simultaneously give dual attention to the detection ability(for example,sensing distance)and multipoint localizing function.A mirror-image correlation method is proposed and can precisely extract the time delay between two original signals from their composite detected signal.This method enables the distributed vibration sensing function of the laser interferometer and maintains its high detection ability.We demonstrate its feasibility by simultaneously localizing multiple knocking vibrations on a 250-km round-trip fiber and distinguishing traffic vibrations at two urban positions in a field test.The localizing precision is analyzed and satisfies the requirements for fiber network sensing.展开更多
In recent years, the high density plasma in the range of 10^19～ 10^20m^-3 have been operated in large or middle tokamak device in the world. A muhichannel far infrared interferometer for profile measurement of plasma...In recent years, the high density plasma in the range of 10^19～ 10^20m^-3 have been operated in large or middle tokamak device in the world. A muhichannel far infrared interferometer for profile measurement of plasma density on HL-2A divertor tokamak is being developed, however the design of the interferometer will appear many new problem in face of experimental environment of the HL-2A divertor device, such as how to make both transmission and arrangement of optics of the interferometer, the effect of electromo- tive force on device and how about the vibration etc. According to the eight windows setting on the largest flange of the device we have to design a Michelson-type FIR laser interferometer with 8 probing channels and eight concave mirrors must be attached it to the inner wall of the vacuum vessel of the device. Therefore, there are many problems should be taken into account to resolve, for example, （ 1 ） the vibration-proof consider for muhichannel interferometer and HCN laser, （2） the stabilization and reliability of the mirror frame uum vessel, the mirrors, hanging on internal wall of vachow to prevent the sputtering to （3） the vacuum seal of the windows and the design of mobile seal for the shutter to avoid the sputter coating of plasma,展开更多
Precision measurement tools are compulsory to reduce measurement errors or machining errors in the processes of calibration and manufacturing.The laser interferometer is one of the most important measurement tools inv...Precision measurement tools are compulsory to reduce measurement errors or machining errors in the processes of calibration and manufacturing.The laser interferometer is one of the most important measurement tools invented in the 20th century.Today,it is commonly used in ultraprecision machining and manufacturing,ultraprecision positioning control,and many noncontact optical sensing technologies.So far,the state-of-the-art laser interferometers are the ground-based gravitational-wave detectors,e.g.the Laser Interferometer Gravitational-wave Observatory(LIGO).The LIGO has reached the measurement quantum limit,and some quantum technologies with squeezed light are currently being tested in order to further decompress the noise level.In this paper,we focus on the laser interferometry developed for space-based gravitational-wave detection.The basic working principle and the current status of the key technologies of intersatellite laser interferometry are introduced and discussed in detail.The launch and operation of these large-scale,gravitational-wave detectors based on space-based laser interferometry is proposed for the 2030s.展开更多
This paper presents the estimation of three-dimensional volumetric errors of a machining center by using a tracking interferometer. A tracking interferometer is a laser interferometer with the mechanism to steer the l...This paper presents the estimation of three-dimensional volumetric errors of a machining center by using a tracking interferometer. A tracking interferometer is a laser interferometer with the mechanism to steer the laser direction to follow a target retroreflector. Based on the triangulation principle, the three-dimensional position of the target can be estimated from measured laser displacements. Its capability to measure three-dimensional positioning errors for arbitrary trajectories is important for the indirect measurement of the machine＇s kinematic model. This paper presents experimental investigation of the estimation accuracy of the multilateration-based measurement by a tracking interferometer. A tracking interferometer developed by a part of the authors is used in experiments. In the present experiment, the measured volume of target positions was 100 mm × 100 mm × 100 mm. The estimation accuracy of targets within this volume was not sufficiently high compared to the positioning error of the measured machine tool. The results of the experiment and simulation show that the estimation uncertainty is dependent on tracking interferometer locations relative to target locations. Error sensitivity analysis shows that wider distribution of tracker positions in XY improves the estimation accuracy.展开更多
基金National Natural Science Foundation of China(Nos.10475078,10675127,10675126,10675124,10605028)
文摘A single-channel far-infrared （FIR） laser interferometer was developed to measure the line averaged electron density on the EAST tokamak. The structure of the single-channel FIR laser interferometer is described in detail. The evolution of density sawtooth oscillation was measured by means the FIR laser interferometer, and was identified by electron cyclotron emission （ECE） signals and soft X-ray intensity. The discharges with and without sawtooth were compared with each other in the Hugill diagram.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.60677051 and No.10774193） and the National Key Basic Research Special Foundation （No.G2010CB923204）.
文摘A wide-range and phase-locked Michelson interferometer technique is described. This technique combined with femtosecond laser is used to measure the spectrum of the rare-earth ion Nd：YVO4, which presents very high signal to noise ratio of interferometric intensity output and higher spectral resolution than traditional grating spectrophotometer.
基金National Natural Science Foundation of China (Nos.10575030,10675043)the JSPS-CAS Core University Program in the field of Plasma and Nuclear Fusion
文摘A new multi-channel far infrared （FIR） laser interferometer was built up and ap- plied to HL-2A. The unique feature of real-time heterodyne interferometer is the combination of high power radiation source （300 mW）, lower noise room temperature detector （noise tempera- ture below 6000 K） with good spatial resolution of 7 cm. Various parameters are optimized for maximum laser output power. Zero crossings of the signals are counted with field programmable gate array （FPGA） digital circuitry yielding the resolution of 1/1000 fringe. The newly measured results including density fluctuation are also presented.
基金the State Key Laboratory for Turbulence&Complex Systems of Peking University for their support in this studysupport of National Numerical Wind-tunnel(No.2018-ZT1A03)+1 种基金National Natural Science Foundation of China grant(No.11702106)Fundamental Research Funds for the Central Universities(2019kfyXKJC001)。
文摘Accurate prediction of hypersonic boundary-layer transition plays an important role in thermal protection system design of hypersonic vehicles.Restricted by the capability of spatial diagnostics for hypersonic boundary-layer study,quite a lot of problems of hypersonic boundary-layer transition,such as nonlinearity and receptivity,remain outstanding.This work reports the application of focused laser differential interferometer to instability wave development across hypersonic boundary-layer on a flared cone model.To begin with,the focused laser differential interferometer is designed and set up in a Mach number 6 hypersonic quiet wind tunnel with the focal point in the laminar boundary-layer of a 5 degree half-angle flared cone model.Afterwards,instability experiments are carried out by traversing the focal point throughout the hypersonic boundary-layer and the density fluctuation along the boundary-layer profile is measured and analyzed.The results show that three types of instability waves ranging from 10 k Hz to over 1 MHz are co-existing in the hypersonic boundary-layer,indicating the powerful capability of focused laser differential interferometer in dynamic response resolution for instability wave study in hypersonic flow regime;furthermore,quantitative analyses including spectra and bicoherence analysis of instability waves throughout the hypersonic boundary-layer for both cold and heated cone models are performed.
基金supported by the National Magnetic Confinement Fusion Science Programs of China(Nos.2010GB101002 and 2014GB109001)National Natural Science Foundation of China(Nos.11075048 and 11275059)
文摘A multichannel methanoic acid （HCOOH, λ=432.5 μm） laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide （HCN, λ=337 μm） laser interferometer in the HL-2A tokamak. A conventional Michelson-type interometer is used for the electron density measurement, and a Dodel-Kunz-type polarimeter is used for the Faraday rotation effect measurement, respectively. Each HCOOH laser can produce a linearly polarized radiation at a power lever of -30 mW, and a power stability 〈10% in 50 rain. A beam waist （diameter d0 ≈12.0 mm, about 200 mm away from the outlet） is finally determined through a chopping modulation technique. The latest optical layout of the interferometer/polarimeter has been finished, and the hardware data processing system based on the fast Fourier transform phase- comparator technique is being explored. In order to demonstrate the feasibility of the diagnostic scheme, two associated bench simulation experiments were carried out in the laboratory, in which the plasma was simulated by a piece of polytetrafluoroethene plate, and the Faraday rotation effect was simulated by a rotating half-wave plate. Simulation results agreed well with the initial experimental conditions. At present, the HCOOH laser interferometer/polarimeter system is being assembled on HL-2A, and is planned to be applied in the 2014-2015 experimental campaign.
文摘Accuracy is one of the most important key indices to evaluate multi-axis systems’ (MAS’s) characteristics and performances. The accuracy of MAS’s such as machine tools, measuring machines and robots is adversely affected by various error sources, including geometric imperfections, thermal deformations, load effects, and dynamic disturbances. The increasing demand for higher dimensional accuracy in various industrial applications has created the need to develop cost-effective methods for enhancing the overall performance of these mechanisms. Improving the accuracy of a MAS by upgrading the physical structure would lead to an exponential increase in manufacturing costs without totally eliminating geometrical deviations and thermal deformations of MAS components. Hence, the idea of reducing MAS’s error by a software-based alternative approach to provide real-time prediction and correction of geometric and thermally induced errors is considered a strategic step toward achieving the full potential of the MAS. This paper presents a structured approach designed to improve the accuracy of Cartesian MAS’s through software error compensation. Four steps are required to develop and implement this approach: (i) measurement of error components using a multidimensional laser interferometer system, (ii) tridimensional volumetric error mapping using rigid body kinematics, (iii) volumetric error prediction via an artificial neural network model, and finally (iv) implementation of the on-line error compensation. An illustrative example using a bridge type coordinate measuring machine is presented.
文摘The accuracy and repeatability of the laser interferometer measurement system （LIMS） are often limited by the mirror surface error that comes from the mirror surface shape and distortion. This paper describes a new method to calibrate mirror map on ultraprecise movement stage （UPMS） with nanopositioning and to make a real-time compensation for the mirror surface error by using mirror map data tables with the software algorithm. Based on the mirror map test model, the factors affecting mirror map are analyzed through geometric method on the UPMS with six digrees of freedom. Dam processing methods including spline interpolation and spline offsets are used to process the raw sampling data to build mirror map tables. The linear interpolation as compensation method to make a real-time correction on the stage mirror unflatness is adopted and the correction formulas are illuminated. In this way, the measurement accuracy of the system is obviously improved from 40 nm to 5 nm.
基金supported by the Natural Science Foundation of Fujian Province(No.2020J01705)the School Foundation of Jimei University(No.C150345)。
文摘In this paper,we present a phase multiplication algorithm(PMA)to obtain scalable fringe precision in laser self-mixing interferometer under a weak feedback regime.Merely by applying the double angle formula on the self-mixing signal multiple times,the continuously improved fringe precision will be obtained.Theoretical analysis shows that the precision of the fringe could be improved toλ/2^(n+1).The validity of the proposed method is demonstrated by means of simulated SMI signals and confirmed by experiments under different amplitudes.A fringe precision ofλ/128 at a sampling rate of 500 k S/s has been achieved after doing 6 th the PMA.Finally,an amplitude of 50 nm has been proved to be measurable and the absolute error is 3.07 nm,which is within the theoretical error range.The proposed method for vibration measurement has the advantage of high accuracy and reliable without adding any additional optical elements in the optical path,thus it will play an important role in nanoscale measurement field.
文摘The method and experimental results of measuring a small vibrating displacement by laser interferometer are introduced in this paper. The dynamic response of a new kind of tiny piezoelectric driver is detected. Results show that this kind of PZN-PZT tiny driver not only has high voltage-displacement sensitivity, but also its frequency response approaches to 1 kHz.Therefore this kind of piezoelectric driver can be used widely in many fields.
文摘A method is proposed to solve the problem of direction discrimination for laser feedback interferometers. By vibrating the feedback mirror with a small-amplitude and high-frequency sine wave, laser intensity is modulated accordingly. The modulation amplitude can be extracted using a phase sensitive detector （PSD）. When the feedback mirror moves, the PSD output shows a quasi-sine waveform similar to a laser intensity interference fringe but with a phase difference of approximately ±π/2. If the movement direction of the feedback mirror changes, the phase difference sign reverses. Therefore, the laser feedback interferometer offers a potential application in displacement measurement with a resolution of 1/8 wavelength and in-time direction discrimination. Without using optical components such as polarization beam splitters and wave plates, the interferometer is very simple, easy to align, and less costly.
文摘Structure, improvements and experiment results of a vertical three-channel far- in- frared （FIR） hydrogen cyanide （HCN） laser interferometer, operated routinely in EAST to measure the electron density profile, are presented. Moreover, a five-channel deuterium cyanide （DCN） laser interferometer was developed successfully. Some key issues confronted in development, including the economization of working gas and the solution to atmospheric absorption, are resolved and described in detail.
基金the support by Ministry of Higher Education Malaysia under Long-Term Research Grant Scheme,LRGS/1/2020/UM/01/5/1。
文摘We consider an extremely intense laser,enclosed by an atom interferometer.The gravitational potential generated from the high-intensity laser is solved from the Einstein field equation under the Newtonian limit.We compute the strength of the gravitational force and study the feasibility of measuring the force by the atom interferometer.The intense laser field from the laser pulse can induce a phase change in the interferometer with Bose-Einstein condensates.We push up the sensitivity limit of the interferometer with Bose-Einstein condensates by spin-squeezing effect and determine the sensitivity gap for measuring the gravitational effect from intense laser by atom interferometer.
文摘For the development of the aviation industry, machine tools are becoming large and travel long distances, making optical alignment setup difficult. An auto-tracking laser interferometer (ATLI) is proposed and researched in this paper for the squareness error measurement of machine tools or coordinate-measuring machines (CMMs). The procedure involves measurement of only one line of an axis, and the measurement results provide us information about not only the positioning errors but also the squareness errors. This specially designed interferometer instrument can be useful in checking industrial machine tools in a short time.
基金supported by the National High Technology Research and Development Program of China(No.2013AA014200)the National Natural Science Foundation of China(No.61107052)+1 种基金the Natural Science Foundation of Tianjin in China(No.14JCYBJC16500)the Science and Technology Development Fund Project of Tianjin University(No.2012)
文摘A microwave photonic filter(MPF) with variable coefficient is proposed and demonstrated, which is constructed by a multi-wavelength fiber laser and Mach-Zehnder interferometer(MZI). Through changing the slope characteristics of Mach-Zehnder interference spectrum adjusted by optical variable delay line(OVDL), the conversion from phase modulation(PM) to intensity modulation(IM) is realized. The multi-wavelength fiber laser with Lyot-Sagnac optical filter has variable wavelength spacing. So the designed filter has a variable number of taps and tap weights. As a result, the tunable range of passband center frequency is 2.6 GHz. The reconfigurability of MPF can be also realized by adjusting the output of fiber laser.
文摘In National Astronomical Observatory, Japan, Mitaka, a group of scientists has been constructing a laser interferometer with two Fabry Perot cavities 300m long, one in North South and one in East West directions. The interferomer is to detect any gravitational wave near 400Hz frequency and stronger than 10 -20 by autumn, 1998 all the instruments have been installed in the underground facilities and it will be operated for more than 30 days in April, 1999. Then a recycling device will be installed to increase the sensitivity by factor of 10. In this paper this system as well as other systems such as LIGOs in UAS and VIRGO in Europe will be reviewed.
文摘In order to achieve high-accuracy measurement of radius of curvature of optical sphere, ultra-high accuracy radius of curvature testing device is developed by dual-frequency laser interferometer and Fizeau interferometer based on cat’s eye and confocal method. Through analyzing the error source models of radius of curvature testing, optical configuration of the testing device has been optimized. Precise environment control and real-time monitoring system is also established to reduce the errors caused by environment. Through the above processes, the radius of curvature measurement relative accuracy is better than 2 ppm. One optical sphere, R88.5 mm, test aperture 59 mm, has been tested. Testing result is 88499.465 ± 0.176 μm, meeting the design requirement. The method has high accuracy and practical advantages.
基金supported by the National Natural Science Foundation of China(Grant No.62171249)the National Key R&D Program of China(Grant No.2021YFA1402102)the Tsinghua Initiative Scientific Research Program.
文摘Distributed fiber-optic sensing(DFOS)can turn the worldwide fiber network into a sensing array,which may immensely extend the sensing range and approaches for hazard assessment,earth observation,and human activity measurement.However,most existing DFOS schemes cannot simultaneously give dual attention to the detection ability(for example,sensing distance)and multipoint localizing function.A mirror-image correlation method is proposed and can precisely extract the time delay between two original signals from their composite detected signal.This method enables the distributed vibration sensing function of the laser interferometer and maintains its high detection ability.We demonstrate its feasibility by simultaneously localizing multiple knocking vibrations on a 250-km round-trip fiber and distinguishing traffic vibrations at two urban positions in a field test.The localizing precision is analyzed and satisfies the requirements for fiber network sensing.
文摘In recent years, the high density plasma in the range of 10^19～ 10^20m^-3 have been operated in large or middle tokamak device in the world. A muhichannel far infrared interferometer for profile measurement of plasma density on HL-2A divertor tokamak is being developed, however the design of the interferometer will appear many new problem in face of experimental environment of the HL-2A divertor device, such as how to make both transmission and arrangement of optics of the interferometer, the effect of electromo- tive force on device and how about the vibration etc. According to the eight windows setting on the largest flange of the device we have to design a Michelson-type FIR laser interferometer with 8 probing channels and eight concave mirrors must be attached it to the inner wall of the vacuum vessel of the device. Therefore, there are many problems should be taken into account to resolve, for example, （ 1 ） the vibration-proof consider for muhichannel interferometer and HCN laser, （2） the stabilization and reliability of the mirror frame uum vessel, the mirrors, hanging on internal wall of vachow to prevent the sputtering to （3） the vacuum seal of the windows and the design of mobile seal for the shutter to avoid the sputter coating of plasma,
基金the National Natural Science Foundation of China(Grant Nos.11655001,11654004,91836104).
文摘Precision measurement tools are compulsory to reduce measurement errors or machining errors in the processes of calibration and manufacturing.The laser interferometer is one of the most important measurement tools invented in the 20th century.Today,it is commonly used in ultraprecision machining and manufacturing,ultraprecision positioning control,and many noncontact optical sensing technologies.So far,the state-of-the-art laser interferometers are the ground-based gravitational-wave detectors,e.g.the Laser Interferometer Gravitational-wave Observatory(LIGO).The LIGO has reached the measurement quantum limit,and some quantum technologies with squeezed light are currently being tested in order to further decompress the noise level.In this paper,we focus on the laser interferometry developed for space-based gravitational-wave detection.The basic working principle and the current status of the key technologies of intersatellite laser interferometry are introduced and discussed in detail.The launch and operation of these large-scale,gravitational-wave detectors based on space-based laser interferometry is proposed for the 2030s.
文摘This paper presents the estimation of three-dimensional volumetric errors of a machining center by using a tracking interferometer. A tracking interferometer is a laser interferometer with the mechanism to steer the laser direction to follow a target retroreflector. Based on the triangulation principle, the three-dimensional position of the target can be estimated from measured laser displacements. Its capability to measure three-dimensional positioning errors for arbitrary trajectories is important for the indirect measurement of the machine＇s kinematic model. This paper presents experimental investigation of the estimation accuracy of the multilateration-based measurement by a tracking interferometer. A tracking interferometer developed by a part of the authors is used in experiments. In the present experiment, the measured volume of target positions was 100 mm × 100 mm × 100 mm. The estimation accuracy of targets within this volume was not sufficiently high compared to the positioning error of the measured machine tool. The results of the experiment and simulation show that the estimation uncertainty is dependent on tracking interferometer locations relative to target locations. Error sensitivity analysis shows that wider distribution of tracker positions in XY improves the estimation accuracy.
