Size and edge dependence of two-photon absorption in rectangular graphene quantum dots

The size and edge-dependence of two-photon absorption (TPA) for rectangular graphene quantum dots (GQDs) is investigated theoretically in the framework of Dirac equation under hard wall boundary conditions. The TPA cross section associated with interband transitions around K point is derived and the transition selection rules are obtained. Results reveal that when the size of zigzag-edge M = 3M(0) +/- 1 (M-0 is an integer), the GQD exhibits a semiconductor while for M = 3M(0) it is metallic. For semiconducting rectangular GQDs, TPA is tuned by the sizes of both edges in GQDs and the armchair-edge dimension contributes more to TPA. While for metallic rectangular GQDs, zigzag-edge dimension affects TPA little and the position of absorption peak and the magnitude of the TPA coefficient are determined by the size of armchair-edge and the resonant enhancement occurs. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement