Shape Enhancement of the Photothermal Interaction with Graphene Nanomechanical Resonators

The motion of suspended graphene can couple to light through photothermal interactions which shift the mechanical resonant frequency by tightening the graphene upon absorbing light. The applications of photothermal interactions are vast and include laser cooling, induced self-oscillations, and strain tuning. These photothermal interactions and many related applications depend strongly on the photothermal frequency shift and the characteristic thermal relaxation time. The effect of graphene device geometry on the photothermal interaction is expected to play a large role, but the study of this effect has been limited to simple drumhead geometries. Here, we show that a trampoline geometry consisting of a central suspended graphene structure supported by tethers exhibits an enhancement in the photothermal resonant frequency shift by two orders of magnitude. Furthermore, we find the photothermal relaxation time can be modified by the support tether width. We also present finite element simulations that suggest that these tethers act as thermal resistors to tune both the relaxation time and the frequency response.