A white light spectral interferometry based on a Linnik type system was established to accurately measure the thin film thickness through transparent medium.In practical work,the equivalent thickness of a beam splitte...A white light spectral interferometry based on a Linnik type system was established to accurately measure the thin film thickness through transparent medium.In practical work,the equivalent thickness of a beam splitter and the mismatch of the objective lens introduce nonlinear phase errors.Adding a transparent medium also increases the equivalent thickness.The simulation results showthat the equivalent thickness has a significant effect on thin film thickness measurements.Therefore,it is necessary to perform wavelength correction to provide a constant equivalent thickness for beamsplitters.In the experiments,some pieces of cover glasses as the transparent medium were added to the measured beam and then a standard thin film thickness of 1052.2±0.9 nm was tested through the transparent medium.The results demonstrate that our system has a nanometer-level accuracy for thin film thickness measurement through transparent medium with optical path compensation.展开更多
Film thickness measurement can be realized using white light interferometry,but it is challenging to guarantee high precision in a large range of thicknesses.Based on scanning white light interferometry,we propose a s...Film thickness measurement can be realized using white light interferometry,but it is challenging to guarantee high precision in a large range of thicknesses.Based on scanning white light interferometry,we propose a spectral-temporal demodulation scheme for large-range thickness measurement.The demodulation process remains unchanged for either coatings or substrate-free films,while some adjustments are made according to the estimated optical thickness.Experiments show that the single-point repeatabilities for 500 nm SiO_(2) coating and 68μm substrate-free Si film are no more than 0.70 nm and 1.22 nm,respectively.This method can be further developed for simultaneous measurement of surface profile and film thickness.展开更多
A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended c...A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended cable or buried cable, a bi-directional optical path interrogator is built by using Michelson or Mach-Zehnder interferometer. A practical implementation of this technique is presented by using an amplified spontaneous emission （ASE） light source and standard single mode fiber, which are common in communication industry. The sensor loop topology is completely passive and absolute length measurements can be obtained for each sensing fiber segment so that it can be used to measure quasi-distribution strain perturbation. For the long distance perimeter monitoring, this technique not only extends the multiplexing potential, but also provides a redundancy for the sensing system. One breakdown point is allowed in the sensor loop because the sensing system will still work even if the embedded sensor loop breaks somewhere.展开更多
基金the support of The National Key Research and Development Program of China(Grant No.2017YFF0107001)the 111 Project fund(Grant No.B07014)
文摘A white light spectral interferometry based on a Linnik type system was established to accurately measure the thin film thickness through transparent medium.In practical work,the equivalent thickness of a beam splitter and the mismatch of the objective lens introduce nonlinear phase errors.Adding a transparent medium also increases the equivalent thickness.The simulation results showthat the equivalent thickness has a significant effect on thin film thickness measurements.Therefore,it is necessary to perform wavelength correction to provide a constant equivalent thickness for beamsplitters.In the experiments,some pieces of cover glasses as the transparent medium were added to the measured beam and then a standard thin film thickness of 1052.2±0.9 nm was tested through the transparent medium.The results demonstrate that our system has a nanometer-level accuracy for thin film thickness measurement through transparent medium with optical path compensation.
基金supported by the National Natural Science Foundation of China(Nos.62005062 and 61975040)the National Science Fund for Distinguished Young Scholars of China(No.61925501)the Open Fund of Guangdong Provincial Key Laboratory of Information Photonics Technology(No.GKPT20-02)。
文摘Film thickness measurement can be realized using white light interferometry,but it is challenging to guarantee high precision in a large range of thicknesses.Based on scanning white light interferometry,we propose a spectral-temporal demodulation scheme for large-range thickness measurement.The demodulation process remains unchanged for either coatings or substrate-free films,while some adjustments are made according to the estimated optical thickness.Experiments show that the single-point repeatabilities for 500 nm SiO_(2) coating and 68μm substrate-free Si film are no more than 0.70 nm and 1.22 nm,respectively.This method can be further developed for simultaneous measurement of surface profile and film thickness.
基金This work was supported by the key project of Nature Science Foundation of Heilongjiang Province （No. ZD200810） and Key Project Foster Program for University and College Science and Technology Innovation （No. 708030）, and partially supported by the National Nature Science Foundation of China, under grant number 60877046, 60707013, and 60807032, to the Harbin Engineering University.
文摘A loop topology based white light interferometric sensor network for perimeter security has been designed and demonstrated. In the perimeter security sensing system, where fiber sensors are packaged in the suspended cable or buried cable, a bi-directional optical path interrogator is built by using Michelson or Mach-Zehnder interferometer. A practical implementation of this technique is presented by using an amplified spontaneous emission （ASE） light source and standard single mode fiber, which are common in communication industry. The sensor loop topology is completely passive and absolute length measurements can be obtained for each sensing fiber segment so that it can be used to measure quasi-distribution strain perturbation. For the long distance perimeter monitoring, this technique not only extends the multiplexing potential, but also provides a redundancy for the sensing system. One breakdown point is allowed in the sensor loop because the sensing system will still work even if the embedded sensor loop breaks somewhere.
