A fundamental building block in nano-photonics is the ability to directionally excite highly squeezed optical mode dynamically, particularly with an electrical bias. Such capabilities would enable the active manipulation of light propagation for information processing and transfer. However, when the optical source is built-in, it remains challenging to steer the excitation directionality in a flexible way. Here, a mechanism is revealed for tunable directional excitation of highly squeezed polaritons in graphene-hexagonal boron nitride (hBN) heterostructures. The effect relies on controlling the sign of the group velocity of the coupled plasmon-phonon polaritons, which can be flipped by simply tuning the chemical potential of graphene (through electrostatic gating) in the heterostructures. Graphene-hBN heterostructures thus present a promising platform toward nano-photonic circuits and nano-devices with electrically reconfigurable functionalities.
Bibliographical noteFunding Information:
Y.J. and X.L. authors contribute equally to this work. This work was sponsored by the National Natural Science Foundation of China under Grants No. 61625502, No. 61574127, No. 61601408, No. 61775193 and No. 11704332, the ZJNSF under Grant No. LY17F010008, the Top-Notch Young Talents Program of China, the Fundamental Research Funds for the Central Universities, and the Innovation Joint Research Center for Cyber-Physical-Society System, Nanyang Technological University under NAP Start-Up Grant, Nanyang Research Award (Young Investigator), and Singapore Ministry of Education under Grants No. Tier 1 RG174/16(S), No. MOE2015-T2-1-070 and No. MOE2016-T3-1-006, National Science Foundation under grant number NSF/EFRI-1741660.
- directional excitation
- graphene-hBN heterostructures
- plasmon-phonon polaritons