Measurement of grating groove density using multiple diffraction orders and one standard wavelength

Area of Science:

• Optics and Photonics
• Metrology
• Diffraction Grating Technology

Background:

• Accurate measurement of grating groove density is crucial for optical system performance.
• Traditional methods can be susceptible to errors from grating rotation, such as eccentricity.
• A need exists for precise and robust groove density measurement techniques.

Purpose of the Study:

• To develop a new method for measuring diffraction grating groove density.
• To eliminate eccentricity errors inherent in rotating diffraction gratings.
• To achieve high-accuracy groove density measurements using a single standard wavelength.

Main Methods:

• A Littman configuration for autocollimation was adapted.
• The method uses multiple diffraction orders and a single standard wavelength.
• Internal angles between diffracted beams were measured at a specific incident angle to calculate groove density.

Main Results:

• The proposed method successfully measured the groove density of a plane grating.
• A nominal 651 lines/mm grating was measured with a mean value of 650.76 lines/mm.
• A high relative measurement error of 3.8×10^-5 was achieved.

Conclusions:

• The new method effectively eliminates eccentricity errors in groove density measurements.
• This technique offers a precise and reliable approach for characterizing diffraction gratings.
• The method's high accuracy makes it suitable for demanding optical applications.