Proceedings of the
9th International Conference of Nanomanufacturing (nanoMan2024)
December 1 – 4, 2024, Singapore

An Optical Head with Littrow Configuration for Measurement of the Pitch Deviation of a Diffraction Grating

Yuya Yamazaki1, Tomoki Kitazume1 and Yuki Shimizu2

1Graduate School of Engineering, Hokkaido University, Sapporo, Japan
2Division of Mechanical and Aerospace Engineering, Hokkaido University, Sapporo, Japan.

ABSTRACT

A method that utilizes positive and negative diffracted beams to measure pitch deviation in diffraction gratings demonstrates significant potential. However, conventional theory cannot measure pitch deviation when the grating's nominal pitch is narrower than the laser wavelength. In this paper, a new optical setup designed to overcome this limitation is presented. The setup uses laser autocollimation units to detect the diffraction angle of the first-order diffracted and reflected beams in a Littrow configuration. By applying arithmetic operations, pitch deviation can be evaluated while minimizing the effects of angular error and local slope in the grating. The basic characteristics of the setup have been evaluated using a grating with a nominal pitch of 556 nm and a laser with a wavelength of 785 nm.

Keywords: Diffraction grating, Littrow configuration, Pitch deviation, Calibration.


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