Nanometer displacement measurement using Fresnel diffraction

Khorshad, Ali Akbar; Hassani, Khosrow; Tavassoly, Mohammad Taghi

doi:10.1364/ao.51.005066

Cited by 37 publications

(19 citation statements)

References 13 publications

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“…There is a growing demand for displacement measurement with nanometer-and subnanometer-scale resolution in nanoscience, material science, and biotechnology. Some typical micro-or nanometer-scale displacement sensors have been reported by many research groups [1][2][3][4][5][6]. Among these displacement sensors, capacitive sensors [7], piezoresistive sensors [8], eddy-current sensors [9], laser interferometers, and optical encoders [10,11] are considered to be most promising to address the issue.…”

Section: Introductionmentioning

confidence: 99%

Subnanometer resolution displacement sensor based on a grating interferometric cavity with intensity compensation and phase modulation

Wang

Bai

et al. 2015

Appl. Opt.

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A subnanometer resolution displacement sensor based on a grating interferometric cavity with intensity compensation and phase modulation is proposed and experimentally demonstrated in this paper. The grating interferometric cavity is composed of a frequency-stabilized laser source, a diffraction grating, and a mirror. To realize a subnanometer resolution, the intensity compensation and phase modulation technique are introduced, which are achieved by an intensity compensation light path, three closed placed photodetectors, a processing circuit and a piezoelectric ceramic transducer, and a lock-in amplifier. The intensity compensation technique can improve the stability of the output intensity signal greatly while the phase modulation technique can increase the signal-tonoise ratio dramatically. The detected signal is intensity modulated and processed by a particular arithmetic circuit. Experimental results indicate that the sensitivity of this displacement sensor is 44.75 mV/nm and the highest resolution can reach 0.017 nm, which is 27 times better than the one without intensity compensation and phase modulation. As a high-performance sensor with immunity to electromagnetic interference, this displacement sensor has potential to be used in nanoscience and technology.

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Section: Introductionmentioning

confidence: 99%

Subnanometer resolution displacement sensor based on a grating interferometric cavity with intensity compensation and phase modulation

Wang

Bai

et al. 2015

Appl. Opt.

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“…Using this technique, i.e., the visibility method, the step heights in the range of few tens nanometers up to several millimeters have been measured [23,24]. Also, the visibility change versus step height or incident angle in 1D FD from PS has been applied to the measurements of plate thickness, wavelength, and dispersion relation [23], nano displacement [25], refractive indices of solids and liquids [26][27][28], specification of the temperature profile around a very thin hot wire [29], refractive index of fiber [30], spectral modification by singular line [31], coherence length, correlations and shape of the spectrum [32], nonlinear refractive index [33] and refractive index of the transparent films [34], phase step diffractometer [35] and its application to wavemetery [36], focal/back-focal length measurement [37,38], measurement of thickness of thin film by white light diffractometry [39] and phase singularity [40]. Also, the FD from a step with two different materials on its both sides in the reflection mode has been theoretically formulated [41].…”

Section: Theoretical Approach a Theoretical Formulation Of Fd From Amentioning

confidence: 99%

Measurement of thickness of thin film by fitting to the intensity profile of Fresnel diffraction from a nanophase step

2018

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Diffraction of light beams from the phase steps due to the abrupt/sharp changes in the boundary of step leads to Fresnel fringes whose visibility and intensity profile depend on the change of the step height or light incident angle. The visibility has been utilized in measurements of different physical quantities. In this paper, for the first time to our knowledge by introducing the fitting method as a fast method we show that by fitting the theoretical intensity distributions on the experimental intensity profiles of the light diffracted from a step at different incident angles, one can specify the step height with few nanometers precision. In addition, we show that this approach provides accurate film thickness in a broad range of thicknesses using modest instrumentation. Furthermore, based on Fresnel diffraction from phase step we have manufactured and trademarked an optical device for measuring thickness of thin films.

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“…This pattern can be used to measure the phase difference on the two sides of the step or the amount of the sharp change in the wave-front. There are different setups and configurations developed based on this phenomena in recent years and they have been used for different applications including wavemetry [6], refractometry [7] and nanometer displacement measurement [8].…”

Section: Introductionmentioning

confidence: 99%

Application of Fresnel diffraction from a 2D array of reflective disks in optical profilometry of a flat surface

Darudi¹,

Asgari

Pourvais

2015

SPIE Proceedings

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Optical methods of three-dimensional profilometry have been of growing interest in both industrial and scientific applications. These techniques provide absolutely non-destructive measurement due to their non-contact nature and maintain their high precision in a large field of view. Most of these techniques however, are based on interferometry which happens to be considerably sensitive to environmental noises such as turbulence and vibration. We have used the phenomena of Fresnel diffraction from phase-steps instead of interferometry to maintain a higher precision and reduce sensitivity to environmental noises. This phenomena has been recently introduced as a method for precise measurement of wavelength, thickness and refractive index. A 2D array of reflective disks are placed above the test surface to provide the required phase-steps. In this paper, theoretical principles of Fresnel diffraction from phase-steps are discussed and the experimental results of testing an optical flat surface are presented. A flat mirror surface has been tested as an optical test surface and is been profiled. The results show that the method is precise and is not sensitive to environmental noises such as vibration and turbulence. Furthermore, the method seems to be a powerful means for testing of curved surfaces, too.

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Nanometer displacement measurement using Fresnel diffraction

Cited by 37 publications

References 13 publications

Subnanometer resolution displacement sensor based on a grating interferometric cavity with intensity compensation and phase modulation

Subnanometer resolution displacement sensor based on a grating interferometric cavity with intensity compensation and phase modulation

Measurement of thickness of thin film by fitting to the intensity profile of Fresnel diffraction from a nanophase step

Application of Fresnel diffraction from a 2D array of reflective disks in optical profilometry of a flat surface

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