Plasmon-enhanced second harmonic generation in semiconductor quantum dots close to metal nanoparticles

We report the enhancement of the optical second harmonic signal in non-centrosymmetric semiconductor CdS quantum dots, when they are placed in close contact with isolated silver nanoparticles. The intensity enhancement is about 1000. We also show that the enhancement increases when the incoming laser frequency $\omega$ is tuned toward the spectral position of the silver plasmon at $2\omega$, proving that the silver nanoparticle modifies the nonlinear emission.