Diffraction grating is widely used in a variety of applications, and the grating must have good quality. In various methods of making large-sized gratings, laser direct writing has obvious advantages. Our research group uses the parallel direct laser writing technology to produce a sinusoidal grating with a size of 100×100mm and line number of 1780 per millimeter. Firstly, the grating is analyzed theoretically to find a groove depth where the sinusoidal grating can reach its highest efficiency, then the grating is produced by laser direct writing and finally coated with a layer of gold. In this paper, we introduce the fabrication and efficiency measurement of grating, and estimate its uniformity. We get 16×16 data points which is divided into 4×3 area from the measurement. For each small area, the efficiency is measured and processed by software, obtaining the efficiency distribution diagram. Most efficiencies are around 90%, which is close to the theoretical calculation. Meanwhile, the efficiency distribution is uniform. Experimental results demonstrated that the developed parallel direct laser writing technology is feasible for writing large-size grating.
Orthogonal crossed gratings, or two-dimensional (2D) gratings are key optical elements in plane optical encoders. In this paper, Scanning Dammann lithography (SDL) was implemented to fabricate gold-coated 2D gratings by stepping and scanning a 2D air-bearing stage and rotating Dammann gratings. A displacement measurement interferometer (DMI) was applied to monitor the 2D stage which ensured the positioning accuracy of exposing. A series of experiments by varying the exposure dose were conducted. The atomic force microscope (AFM) results indicted the duty cycle changed with the exposure dose. A 2D gold-coated grating with a size 100*100mm was also fabricated. Since it is straightforward to extend the size of the substrate up to hundreds of millimeters, SDL is a promising method to fabricate large-sized 2D gratings with controllable duty cycle.
In this paper, a non-contact, fast and high-precision optical 3D measurement method is proposed to provide a detection scheme for the processing of optical rough glass in the grinding stage. We first use a planar calibration board to map the phase-height of the optical rough glass in a certain spatial range, then use the phase-shifting method to obtain the heightmodulated phase distribution of the rough glass. Finally, the 3D profile of the whole rough glass is obtained based on the phase-height mapping. The whole detection process can be completed in a few minutes, and the accuracy is less than 100 microns.
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