Spontaneous emission modulation in biaxial hyperbolic van der Waals material

TL;DR

This paper demonstrates active modulation of spontaneous emission in a biaxial hyperbolic van der Waals material, { extalpha}-MoO3, through rotation, achieving significant tunability and providing insights into physical mechanisms and potential applications.

Contribution

First demonstration of active spontaneous emission modulation in { extalpha}-MoO3 via rotation, with theoretical analysis and extension to finite thickness films.

Findings

Modulation factor exceeds three orders of magnitude at 634 cm-1.

Rotation in y-z or x-y planes enables tunability, x-z plane shows angle independence.

Modulation factor can reach about 2000 in finite thickness films.

Abstract

As a natural van der Waals crystal, {\alpha}-MoO3 has excellent in-plane hyperbolic properties and essential nanophotonics applications. However, its actively tunable properties are generally neglected. In this work, we achieved active modulation of spontaneous emission from a single-layer flat plate using the rotation method for the first time. Numerical results and theoretical analysis show that {\alpha}-MoO3 exhibits good tunability when rotated in the y-z or x-y plane. A modulation factor of more than three orders of magnitude can be obtained at 634 cm-1. However, when the rotation is in the x-z plane, the spontaneous emission of the material exhibits strong angle independence. The theoretical formulation and the physical mechanism analysis explain the above phenomenon well. In addition, for the semi-infinite {\alpha}-MoO3 flat structure, we give the distribution of the modulation factor of spontaneous emission with wavenumber and rotation angle. Finally, we extended the calculation results from semi-infinite media to finite thickness films. We obtained the general evolution law of the peak angle of the modulation factor with thickness, increasing the modulation factor to about 2000. We believe that the results of this paper can guide the active modulation of spontaneous emission based on anisotropic materials.