title: Study on a wideband, variable aperture, high resolution scatterometer for planar diffraction grating stray light measurement.
abstract: Stray light is one of the important factors for evaluating the quality of gratings. Therefore, it has become an important problem in the field of grating development to measure the stray light of planar diffraction gratings accurately. For that reason, a planar grating stray light testing instrument based on a Czerny-Turner (C-T) structure has been studied. On the premise of the low stray light of the instrument itself, the instrument is capable of measuring wideband, variable aperture, and high resolution stray light for planar gratings. A scatterometer dynamic range of over nine orders has been demonstrated. Based on the scalar diffraction theory and classical Fresnel-Kirchhoff diffraction theory, the optical and mechanical model of the scatterometer is designed, which is irradiated by parallel light, and the simulation results are analyzed. The instrument realizes the measurement of the grating distribution function (GDF). And with reference to the expression form of the bidirectional reflectance distribution function (BRDF), the measurement data of the instrument is associated with the power spectral density (PSD). Through the optical integrated design and stray light suppression design, full aperture (15  mm×15  mm-200  mm×200  mm) and wideband (380-900 nm) measurement for any number of lines grating is realized, and the efficiency of equipment usage is improved. Experimental results show that based on the attenuation method, the accuracy of measurement can be 10-9by the replacement of the neutral density filters.
authors.forename: Jin
authors.initials: J
authors.lastname: Yang
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Lu
authors.initials: L
authors.lastname: Yin
authors.forename: Ci
authors.initials: C
authors.lastname: Sun
authors.forename: Tianjiao
authors.initials: T
authors.lastname: Li