In-situ evaluation of the pitch of a reflective-type scale grating by using a mode-locked femtosecond laser

Dong Wook Shin, Lue Quan, Yuki Shimizu, Hiraku Matsukuma, Yindi Cai, Eberhard Manske, Wei Gao

Research output: Contribution to journalArticlepeer-review

Abstract

Major modifications are made to the setup and signal processing of the method of in-situ measurement of the pitch of a diffraction grating based on the angles of diffraction of the diffracted optical frequency comb laser emanated from the grating. In the method, the improvement of the uncertainty of in-situ pitch measurement can be expected since every mode in the diffracted optical frequency comb laser can be utilized. Instead of employing a Fabry-Pérot etalon for the separation of the neighboring modes in the group of the diffracted laser beams, the weight-of-mass method is introduced in the method to detect the light wavelength in the Littrow configuration. An attempt is also made to reduce the influence of the non-uniform spectrum of the optical comb laser employed in the setup through normalization operation. In addition, an optical alignment technique with the employment of a retroreflector is introduced for the precise alignment of optical components in the setup. Furthermore, a mathematical model of the pitch measurement by the proposed method is established, and theoretical analysis on the uncertainty of pitch measurement is carried out based on the guide to the expression of uncertainty in measurement (GUM).

Original languageEnglish
Article number8028
JournalApplied Sciences (Switzerland)
Volume11
Issue number17
DOIs
Publication statusPublished - 2021 Sep

Keywords

  • Diffraction equation
  • Diffraction grating
  • Grating pitch
  • Laser diffraction
  • Measurement uncertainty analysis
  • Mode-locked femtosecond laser

ASJC Scopus subject areas

  • Materials Science(all)
  • Instrumentation
  • Engineering(all)
  • Process Chemistry and Technology
  • Computer Science Applications
  • Fluid Flow and Transfer Processes

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