Comments on "Amplifying magneto-optical photonic crystal, Appl. Phys. Lett. 97, 061116 (2010)"

TL;DR

This paper critiques an existing analytical method for predicting complex refractive indices of doped crystals, proposing an alternative approach and discussing limitations of the McCumber relation in this context.

Contribution

It introduces a new analytical solution for doped crystal refractive indices and clarifies the proper application of the McCumber relation.

Findings

Proposes an alternative analytical approach for doped crystal indices.

Highlights limitations of the McCumber relation in this context.

Applicable to various doped crystals beyond Erbium-doped Gadolinium Gallium Garnet.

Abstract

This report concerns analytical solutions predicting the complex refractive indices of doped crystals, based on empirical values of the refractive indices of the dopant and the undoped crystal. An analytical approach in calculating the refractive index of Erbium doped Gadolinium Gallium Garnet was reported by another author previously. My first comment is related to the proposed solution by the other author, where I have shown an alternative approach that leads to a different solution. Although my comments are made in relation to Erbium as the dopant and Gadolinium Gallium Garnet as the undoped lattice, the analytical solution I propose here may be applied to any doped crystals. My second comment concerns the limitations and mistreatment of McCumber relation in this context.