Plasmonics and optical antennas

 Spontaneous emission plays a central role in the majority of optical phenomena in our world. The rate of this process is determined by the radiative decay of the excited state of the emitter and scales with the second and third powers of its dipole moment and transition frequency, respectively. Because optical emitters have nanometer or subnanometer extensions, the size of their dipole moments is restricted, giving rise to typical fluorescence lifetimes in the nanosecond range, which is orders of magnitude longer than an optical cycle. This long lifetime and the correspondingly slow decay restrict the optical power that can be extracted from a single emitter.

In this line of research, we devise “optical antennas” for changing the emission pattern and rate of quantum emitters such as molecules, semiconductor quantum dots or color centers in diamond. Here, we use a combination of theory and experiment to find (nano)structures that apply the optimal boundary conditions for the modification of spontaneous emission. The experiments build on the sophisticated use of scanning probe technology, single-photon detection and optical microscopy. We expect to enhance the power radiated by a single emitter by up to 10,000 times. You will be exposed to the state-of-the-art nanofabrication using a new generation of focused ion beam milling, will have the opportunity to learn single-molecule microscopy, and will get an insight into high-end scanning probe microscopy.

For more information, please feel free to contact Prof. Vahid Sandoghdar ( or consult our website and publications.

Some exemplary references:

1- Experimental realization of an optical antenna designed for collecting 99% of photons from a

quantum emitter

X.-L. Chu, T. J. K. Brenner, X.-W. Chen, Y. Ghosh, J. A. Hollingsworth, V. Sandoghdar, S. Götzinger

Optica 1, 203 (2014).

2- Metallo-dialectric hybrid antennas for ultrastrong enhancement of spontaneous emission

X. Chen, M. Agio, V. Sandoghdar

Phys. Rev. Lett. 108, 233001 (2012).

3- A planar dielectric antenna for directional single-photon emission and near-unity collection efficiency

K. G. Lee, X. Chen, H. Eghlidi, P. Kukura, R. Lettow, A. Renn, V. Sandoghdar, S. Götzinger

Nature Photonics 5, 166 (2011).

4- Spontaneous emission enhancement of a single molecule by a double-sphere nanoantenna across an interface

K.-G. Lee, H. Eghlidi, X.-W. Chen, A. Renn, S. Götzinger and V. Sandoghdar

Optics Express 20, 23331 (2011).

5- Enhancement of Single-Molecule Fluorescence Using a Gold Nanoparticle as an Optical Nanoantenna

S. Kühn, U. Hakanson, L. Rogobete, V. Sandoghdar 

Phys. Rev. Lett. 97, 017402 (2006).

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