Grating periods measurement of multi-pitched grating using Littrow configuration external cavity diode laser

Abstract

A simple measurement technique is proposed for multi-pitched grating inserted in an external cavity diode laser. Measuring grating rotation and variation of multiple resonant wavelengths enables us to estimate grating periods and Littrow angles simultaneously. We experimentally determined that sufficient variation of resonant wavelength (i.e. ∼1.6 nm) could be obtained even with a grating rotation less than 0.05°. The grating periods and Littrow angles of two dual-period holographic gratings were successfully measured with less than 1% error. This technique can be applied to the motionless measurement of multi-pitched gratings, diffractive optics, and metasurfaces in the future.

Advances in wide-tuning and narrow-linewidth external-cavity diode lasers

“…Research on the Littrow-ECDL is relatively mature; therefore, in addition to more in-depth studies on the performance improvement of lasers, many reports on its applications have also been published. This laser type can achieve a wide wavelength-tuning range and high spectral resolution [61]; therefore, it is primarily used in gas-spectrum detection [7,62], industrial process control [63], and precision measurement calibration [64,65].…”

Longitudinal Mode Number Estimation of External Cavity Diode Laser Using Dual Periodic Grating for Optical Profiler System

“…While optical resonance typically requires precise alignment, such as in laser cavities [ 21 ], it is not commonly used for free-form metrology. However, it can achieve a high Q-value, leading to high measurement resolution when used for measurement purposes [ 22 , 23 , 24 , 25 ]. To enhance alignment robustness, an external resonator construction can be introduced [ 26 , 27 ].…”