Research

My research is focused on the electromagnetic interaction of a single emitter and a single optical antenna. My work supports two synergistic directions for the application of this science: enhancing the power of next-generation microscopy and developing methods for optical or quantum information and computing. I have developed new methods to study this subject, furthered its theoretical understanding, and made important experimental discoveries.

In this video I explain my research for a broad audience. It's a great starting point to understanding my work.

An optical antenna is a device to “convert free propagating optical radiation to localized energy, and vice-versa” [1]. Optical antennas are analogous to radio antennas, only optical antennas work for shorter wavelength, visible light. Unlike a radio antenna, an optical antenna cannot be a macroscopic object, but instead needs to be nanoscale. Thus it wasn’t until recently that nanotechnology matured enough for such devices to be fabricated and studied. Interest in optical antennas and associated effects has spawned an entire new field of study called nanophotonics, which researches light and its applications on the nanoscale. In addition to the rich new basic scientific directions to explore, there is immense interest in the multitudinous applications of nanophotonic technology, which range from single-photon transistors [2], to minimally-invasive cancer treatments [3], and to next-generation solar cells [4].

  Figure 1. (A) Simulation of a diffraction limited image of single emitter located at the red dot. (B) Real image of a single molecule (C) Computationally determining the location of an emitter with superresolution precision by Gaussian fitting [5].

Figure 1. (A) Simulation of a diffraction limited image of single emitter located at the red dot. (B) Real image of a single molecule (C) Computationally determining the location of an emitter with superresolution precision by Gaussian fitting [5].

My work utilizing single-molecule fluorescence super-resolution imaging to study optical antennas brings a novel method to bear on this rapidly evolving field. Super-resolution imaging refers to how the technique can obtain information from an optical microscope with a spatial resolution better than the diffraction limit of light (which in the visible is ~300 nm). The diffraction limit was thought to be the limit on attainable spatial information from a microscope. However, around the early 2000s, researchers realized that by computationally analyzing images of single fluorescent molecules they could recover location information beyond the diffraction limit (Fig. 1). Because super-resolution techniques have had such a tremendous scientific impact, in particular revolutionizing cellular imaging in biomedicine, the researchers who developed these techniques were awarded the 2014 Nobel Prize in Chemistry.

Single-molecule imaging is a truly incredible technique which has extended the power of the optical microscope to previously unimagined realms. However, this technique has not yet reached its full potential. In practice, experiments can rarely achieve resolution better than 30 nm [5], whereas theoretical limits are closer to 3 nm [6]. Because the resolution improves with more measured photons [6], having brighter emitters means better resolution.

My work on optical antennas aims to address this limitation. Coupling an emitter to an optical antenna can substantially increase brightness [7,8]. This strategy can improve the resolution, and thus the scope, of this already tremendously impactful technique by nearly an order magnitude. While developing this technology, we’re concomitantly leading the effort to study the basic science of optical antennas utilizing this novel method. Our discoveries and insights have been, and promise to continue to be, of fundamental importance to the nascent field of nanophotonics.

 

[1] P. Bharadwaj, B. Deutsch, L. Novotny. "Optical Antennas," Advances in Optics and Photonics, 1, 438, 2009.

[2] D.E. Chang, A.S. Sørensen, E.A. Demler,  M.D. Lukin. "A single-photon transistor using nanoscale surface plasmons." Nature Physics, 3, 807, 2007.

[3] E.B. Dickerson, et al. "Gold nanorod assisted near-infrared plasmonic photothermal therapy (PPTT) of squamous cell carcinoma in mice." Cancer Letters, 269, 57, 2008.

[4] K.R. Catchpole, A. Polman. "Plasmonic solar cells." Optics Express, 16, 21793, 2008.

[5] H.H. Tuson, J.S. Biteen. "Unveiling the inner workings of live bacteria using super-resolution microscopy." Analytical Chemistry, 87, 42, 2014.

[6] R.E. Thompson, D.R. Larson, W.W. Webb. "Precise nanometer localization analysis for individual fluorescent probes." Biophysical Journal, 82, 2775, 2002.

[7] M. Pelton. "Modified spontaneous emission in nanophotonic structures." Nature Photonics, 9, 427, 2015.

[8] K.A. Willets, R.P. Van Duyne. "Localized Surface Plasmon Resonance Spectroscopy and Sensing." Annual Review of Physical Chemistry, 58, 267, 2007.