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Wavefront error analysis in pinhole vector diffraction using the finite-difference time-domain method
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DOI：10.1117/1.oe.65.5.055108.png)
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Abstract
En 中文
Given that the accuracy of Shack-Hartmann wavefront sensor (SHWFS) calibration for high-numerical-aperture (NA) objectives depends critically on the precision of the spherical wavefront produced by a pinhole, we present an investigation into a method for generating such wavefronts via diffraction through a nanoscale pinhole. A vector diffraction model was established, and the finite-difference time-domain method was employed to simulate and analyze the influence of pinhole geometric parameters and alignment errors on energy transmittance, intensity uniformity, and diffracted wavefront quality. A quantitative relationship between pinhole parameters and wavefront error was derived. For a calibration system operating at a wavelength of 530 nm, the combination of a converging Gaussian beam with an NA of 0.6 and a chromium pinhole featuring a diameter of 1200 nm and a thickness of 100 nm has been demonstrated to generate a high-precision spherical wavefront in the far-field. Under the condition that the curvature radius of the spherical wave is no < 1.0 m , the diffracted wavefront error exhibits a peak-to-valley (PV) value below 1 & times; 10(-4) lambda and a root mean square value below 2 & times; 10(-5) lambda . To achieve an even higher accuracy with a PV value below 5 & times; 10 (-5) lambda , the axial positioning error of the pinhole relative to the ideal position must be strictly confined to the range of - 150 to 40 nm. These findings presented in this work establish a foundation for the precise control of SHWFS calibration techniques employed in high-NA objective lens measurement systems.
Keywords:
Shack-Hartmann wavefront sensor
wavefront error analysis
finite-difference time-domain
calibration.
Journal
O
IF:
1.2
Papers:
217
Citations:
1.1W
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