Recently, a research group from the Center for Nanoscale Science and Technology at the National Institute of Standards and Technology (NIST), and the Massachusetts Institute of Technology in the United States has demonstrated a new type of quantum electro-optic phenomenon, whispering-gallery mode resonators.1 The resonators are generated by a scanning tunneling microscope (STM) in proximity to graphene devices (Figure 1). On the basis of the quantum effect of electron tunneling, STM is a powerful technique to investigate the local electronic properties of both metallic and semiconducting systems with atomic resolution. Graphene, the most acclaimed material of the last decade, has enabled new horizons for STM research. The graphene surface can be directly probed by the scanning tip, whereas remaining chemically stable and clean even exposure to ambient air for days. Charged carriers in graphene can be readily tuned from holes to electrons using an external gate electrode. Furthermore, the charge carriers in graphene, often called Dirac particles, behave like electromagnetic waves, setting the stage for graphene to realize quantum electro-optic phenomena such as Veselago lensing2 and Klein tunneling.3
