Orientation of Nd$^{3+}$ dipoles in yttrium aluminum garnet: A simple yet accurate model

TL;DR

This paper presents an experimental and theoretical study of Nd$^{3+}$ dipole orientations in Nd-YAG, demonstrating that transition dipoles are nearly collinear with crystallographic axes with high accuracy, and introduces a simple, accurate model.

Contribution

It provides the first experimental evidence that Nd$^{3+}$ transition dipoles in Nd-YAG are aligned with crystallographic axes, supported by a simple and accurate theoretical model.

Findings

Dipole ellipticity between 2% and 3%.

Transition dipoles are collinear with crystallographic axes within 1 degree.

Excellent agreement between experimental data and the proposed model.

Abstract

We report an experimental study of the 1064nm transition dipoles in neodymium doped yttrium aluminum garnet (Nd-YAG) by measuring the coupling constant between two orthogonal modes of a laser cavity for different cuts of the YAG gain crystal. We propose a theoretical model in which the transition dipoles, slightly elliptic, are oriented along the crystallographic axes. Our experimental measurements show a very good quantitative agreement with this model, and predict a dipole ellipticity between 2% and 3%. This work provides an experimental evidence for the simple description in which transition dipoles and crystallographic axes are collinear in Nd-YAG (with an accuracy better than 1 deg), a point that has been discussed for years.