Third-harmonic generation in the presence of classical nonlocal effects in gap-plasmon nanostructures

Classical nonlocality in conducting nanostructures has been shown to dramatically alter the linear optical response by placing a fundamental limit on the maximum field enhancement that can be achieved. This limit directly extends to all nonlinear processes, which depend on field amplitudes. A numerical study of third-harmonic generation in metal film-coupled nanowires reveals that for subnanometer vacuum gaps, the nonlocality may boost the effective nonlinearity by 5 orders of magnitude as the field penetrates deeper inside the metal than that predicted assuming a purely local electronic response. We also study the impact of a nonlinear dielectric placed in the gap region. In this case the effect of nonlocality could be masked by the third-harmonic signal generated by the spacer. By etching the dielectric underneath the nanowire, however, it is possible to muffle such contributions. Calculations are performed for both silver and gold nanowire.

Duke Scholars

Author David R. Smith Electrical and Computer Engineering