Multilayer black phosphorus as a versatile mid-infrared electro-optic material

TL;DR

This paper explores the electro-optic properties of black phosphorus thin films for mid-infrared optical modulation, revealing tunable absorption shifts and proposing a BP-based modulator with improved efficiency over graphene.

Contribution

It introduces a detailed analysis of electro-absorption mechanisms in black phosphorus and demonstrates a BP-based modulator design with enhanced performance in the mid-infrared range.

Findings

Electric field induces tunable absorption edge shifts in BP.

BP-based modulator shows improved absorption and power efficiency.

Quantum-confined Franz-Keldysh effect is key to BP's electro-optic response.

Abstract

We investigate the electro-optic properties of black phosphorus (BP) thin films for optical modulation in the mid-infrared frequencies. Our calculation indicates that an applied out-of-plane electric field may lead to red-, blue-, or bidirectional shift in BP's absorption edge. This is due to the interplay between the field-induced quantum-confined Franz-Keldysh effect and the Pauli-blocked Burstein-Moss shift. The relative contribution of the two electro-absorption mechanisms depends on doping range, operating wavelength, and BP film thickness. For proof-of concept, simple modulator configuration with BP overlaid over a silicon nanowire is studied. Simulation result shows that operating BP in the quantum-confined Franz-Keldysh regime can enable improved maximal attainable absorption as well as power efficiency compared to its graphene counterpart.