Femtosecond digital in-line holography with the fractional Fourier transform: application to phase-contrast metrology |
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Authors: | M Brunel H Shen S Coetmellec D Lebrun K Ait Ameur |
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Institution: | (1) Coherent Optics Division, Central Scientific Instruments Organisation, Sector 30, Chandigarh, 160 030, India;(2) Department of Applied Physics, Guru Jambheshwar University of Science & Technology, Hisar, 125 001, India; |
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Abstract: | The possibility to analyze transparent phase objects using femtosecond digital in-line holography is demonstrated. We show
that the diffraction patterns produced by the diffraction of 20-fs pulses by pure phase objects can be advantageously processed
by using the fractional Fourier transform. The optimal fractional orders lead to the longitudinal location of the phase object
while the analysis of the reconstructed patterns leads to its diameter and to the value of the phase shift. Simulations and
experimental results are in good concordance. This work shows new important applications of these reconstruction techniques
in the domain of digital phase-contrast metrology. We further show that the use of femtosecond pulses results in a significant
reduction of coherent noise. |
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