# Fluorescence enhancement with the optical (bi-) conical antenna 

Ahmad Mohammadi 

Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland and Department of Physics, Persian Gulf University, 75196 Bushehr, Iran 

Franziska Kaminski, ∗ Vahid Sandoghdar, and Mario Agio † 

Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland 

## Abstract 

We investigate the properties of finite gold nanocones as optical antennas for enhancing molecular fluorescence. We compute the modification of the excitation rate, spontaneous emission rate, and quantum efficiency as a function of the nanocone base and length, showing that the maximum field and fluorescence enhancements do not occur for the same nanocone parameters. We compare the results with those for nanorods and nanospheroids and find that nanocones perform better. 

