Three-dimensional angular deviation and diffraction efficiency of a grating in Littrow-configuration ECDL

TL;DR

This paper analyzes the three-dimensional angular deviation and diffraction efficiency of reflection gratings in Littrow-configuration for external cavity diode lasers, providing a comprehensive framework for optimizing grating parameters to improve laser performance.

Contribution

It introduces a rigorous analysis of conical diffraction in 3D gratings and offers guidelines for parameter optimization in Littrow-configuration devices.

Findings

Angular tolerance derived for plane and conical diffraction

Diffraction efficiency calculated for a typical blazed grating

Parameter settings can significantly improve angular tolerance and efficiency

Abstract

We consider in this paper the angular deviation and diffraction efficiency of the reflection gratings in Littrow-configuration for applications of external cavity diode laser using the rigorous coupled-wave analysis method. We consider the three-dimensional diffraction case in general, where the incidence plane is un-parallel with the grating vector, i.e. conical diffraction. The angular tolerance of arbitrary gratings under plane and conical diffraction are thus derived and presented. A typical blazed grating is chosen as an example to calculate its diffraction efficiency using the rigorous coupled-wave analysis method. Furthermore, we point out that the angular tolerance and reflection efficiency can be improved if the appropriate parameter settings are selected for Littrow-configuration devices, including incidence angle, diffraction order, grating period and blazed angle. Otherwise, a tiny slanting angle of the grating vector deviated from the incidence plane will deviate the feedback light away from entering the laser-diode-chip and halt laser oscillation in the external cavity. Finally, a general rule for the parameter settings in Littrow-configuration is provided as a benchmark.