# Electron g-factor engineering for non-reciprocal spin photonics

## TL;DR

This paper introduces a spintronic approach to engineer non-reciprocal photonic devices by tuning the electron g-factor in a ferromagnetically doped semiconductor, enabling reconfigurable control over photon spin and non-reciprocity.

## Contribution

It presents a novel method to control non-reciprocal photonics using gate-tunable Rashba spin-orbit coupling affecting the electron g-factor.

## Key findings

- Gate-controlled RSOC modifies magnetic permeability tensor.
- Non-reciprocal Kerr and Faraday rotations are tunable via g-factor.
- Enhanced Purcell factor for spin-polarized emitters near non-reciprocal media.

## Abstract

We study the interplay of electron and photon spin in non-reciprocal materials. Traditionally, the primary mechanism to design non-reciprocal photonic devices has been magnetic fields in conjunction with magnetic oxides, such as iron garnets. In this work, we present an alternative paradigm that allows tunability and reconfigurability of the non-reciprocity through spintronic approaches. The proposed design uses the high-spin-orbit coupling of a narrow-band gap semiconductor (InSb) with ferromagnetic dopants. A combination of the intrinsic and a gate-applied electric field gives rise to a strong external Rashba spin-orbit coupling (RSOC) in a magnetically doped InSb film. The RSOC which is gate alterable is shown to adjust the magnetic permeability tensor via the electron g-factor of the medium. We use electronic band structure calculations (k$\cdot$p theory) to show the gate-adjustable RSOC manifest itself in the non-reciprocal coefficient of photon fields via shifts in the Kerr and Faraday rotations. In addition, we show that photon spin properties of dipolar emitters placed in the vicinity of a non-reciprocal electromagnetic environment is distinct from reciprocal counterparts. The Purcell factor (F$_{p}$) of a spin-polarized emitter (right-handed circular dipole) is significantly enhanced due to a larger g-factor while a left-handed dipole remains essentially unaffected. Our work can lead to electron spin controlled reconfigurable non-reciprocal photonic devices.