We study for the first time the effect of the geometry of quantum wire networks on their nonlinear optical properties and show that for some geometries, the first hyperpolarizability is largely enhanced and the second hyperpolarizability is always negative or zero. We use a one-electron model with tight transverse confinement. In the limit of infinite transverse confinement, the transverse wavefunctions drop out of the hyperpolarizabilities, but their residual effects are essential to include in the sum rules. The effects of geometry are manifested in the projections of the transition moments of each wire segment onto the 2D lab frame. Numerical optimization of the geometry of a loop leads to hyperpolarizabilities that rival the best chromophores. We suggest that a combination of geometry and quantum-confinement effects can lead to systems with ultralarge nonlinear response.
© 2012 Optical Society of America
Atomic and Molecular Physics
Original Manuscript: August 13, 2012
Revised Manuscript: October 20, 2012
Manuscript Accepted: October 24, 2012
Published: November 29, 2012
Shoresh Shafei, Rick Lytel, and Mark G. Kuzyk, "Geometry-controlled nonlinear optical response of quantum graphs," J. Opt. Soc. Am. B 29, 3419-3428 (2012)