Nonlinear Optical Spectroscopy of Graphene Nanoribbons*

We investigate the optical response of graphene nanoribbons (GNRs) using the broadband nonlinear generation and detection capabilities of nanoscale junctions created at the LaAlO₃/SrTiO₃ interface [1]. Using the large non-resonant third-order nonlinear susceptibility in STO, strong difference frequency mixing occurs when the junction is biased, leading to an induced polarization that can also be detected at the junction [2,3]. Here we discuss an “inkwell” method we developed to deposit GNRs on the LAO surface with an atomic force microscope tip. We also review the results of experiments in which we interrogate few-GNR clusters with LAO/STO nanoscale junctions. Results show nearly 100% extinction of VIS-NIR light in the GNR clusters, agreeing with previous results on graphene [4].
[1] C. Cen, et al., Nature Mat 7, 298 (2008).
[2] Y. Ma, et al., Nano Lett 13, 2884 (2013).
[3] L. Chen, et al., Light: Science & Appl. 8, 24 (2019).
[4] E. Sheridan, et al., Nano Lett 20, 10 (2020).