Comment on "Linear and passive silicon optical isolator" in Scientific Reports 2, 674

TL;DR

This paper critically examines Wang et al.'s claim of a silicon optical isolator based on symmetry breaking, clarifying that their approach conflicts with established Lorentz reciprocity principles.

Contribution

It provides a theoretical critique demonstrating that the proposed optical isolator violates fundamental reciprocity laws, challenging the validity of the original claim.

Findings

The proposed device contradicts Lorentz reciprocity.

Symmetry breaking alone cannot produce true optical isolation.

The claim in the original paper is physically inconsistent.

Abstract

Wang et al. [1] demonstrated different power transmission coefficients for forward and backward propagation in simulation and experiment. From such a demonstration, the central claim of their paper is that "the spatial inversion symmetry breaking diode can construct an optical isolator in no conflict with any reciprocal principle". Their claim contradicts the Lorentz reciprocity theorem, from which it is well known that one cannot construct an isolator this way.