1. Nanophotonic magnetic resonance spectroscopy
In this project, we apply the basic physics of color centers in diamond to create a device with unique properties desirable for chemical trace analysis. Unlike many magnetic-resonance (MR) systems, this spectrometer operates at ambient temperature, in a range of magnetic fields easily generated by small permanent magnets, and with nL sample volumes. 

The analyte is delivered via a microfluidic chip to a sensor region consisting of a nanostructured diamond doped with nitrogen-vacancy (NV) color centers [1-3]. By applying pulses of laser light and microwaves, the magnetic field from the analyte’s precessing magnetization becomes encoded in the NV fluorescence signal. Analysis of the fluorescence signal reveals the analyte's MR spectrum, from which the chemical composition can be extracted from established libraries. 

 

 Schematic of the microfluidic spectrometer  (top) Diamond NV center and nanophotonic structures. (bottom) Nazanin and Francisco with the setup at UNM.

1. V. M. Acosta, D. Budker, P. R. Hemmer, J. R. Maze, and R. L. Walsworth, "Optical magnetometry with nitrogen-vacancy centers in diamond", Cambridge University Press (2013).
2. V. M. Acosta, E. Bauch, M. P. Ledbetter, C. Santori, K. M. C. Fu, P. E. Barclay, R. G. Beausoleil, H. Linget, J. F. Roch, F. Treussart, S. Chemerisov, W. Gawlik, D. Budker, “Diamonds with a high density of nitrogen-vacancy centers for magnetometry applications.” Physical Review B 80, 115202 (2009). 
3. P. Kehayias, A. Jarmola, N. Mosavian, I. Fescenko, F. M. Benito, A. Laraoui, J. Smits, L. Bougas, D. Budker, A. Neumann, S. R. J. Brueck, V. M. Acosta, "Solution nuclear magnetic resonance spectroscopy on a nanostructured diamond chip." Nature Communications (2017).

2. Few-photon optical logic in scalable networks
What are the fundamental limits of optical computing? Is there a scalable platform that can be used to test them? In this project we seek to probe the fundamental limits of optical logic at both the nanometer and single-photon scales. Our platform for probing these limits uses all-optical circuits fabricated from color-center-doped diamond films. This approach to optical computing differs from previous failed attempts by using nanophotonics to perform logic with the lowest power consumption allowed by quantum mechanics--the single photon level.
All-optical logic requires that photons interact. This is a challenge, since photons lack charge, mass, etc., but the photon-photon interaction can be mediated by a third party, atoms. In our case, all-optical logical operations is performed by nonlinear optical addressing of color centers in diamond that are coupled to nanophotonic cavities [1-3]. Sequential logic is enabled by embedding these cavities into interacting networks of optical waveguides, beamsplitters, and other on-chip photonic elements.
     
A scalable nanophotonic network to test the fundamental quantum limits of classical optical computing. (courtesy of C. Santori, HP Labs.) SEM of diamond photonic resonators coupled to a waveguide with grating in/out-couplers (fabricated in the cleanrooms at UNM and CINT) Cryogenic confocal microscope featuring sub-micron spatial resolution, single photon detection, and home-built, high-resolution (~1 GHz) spectrometer.
1. V. M. Acosta, P. R. Hemmer, “Nitrogen-vacancy centers: Physics and applications.” MRS Bulletin 38,127 (2013).
2. V. M. Acosta, K. Jensen, C. Santori, D. Budker, R. G. Beausoleil, “Electromagnetically-induced transparency in a diamond spin ensemble enables all-optical electromagnetic field sensing.” Physical Review Letters 110, 213605 (2013).
3. A. Faraon, C. Santori, Z. Huang, V. M. Acosta, R. G. Beausoleil, “Coupling of Nitrogen-Vacancy Centers to Photonic Crystal Cavities in Monocrystalline Diamond.” Physical Review Letters 109, 033604 (2012).
4. A. Faraon, C. Santori, Z. Huang, K.-M. C. Fu, V. M. Acosta, D. Fattal, R. G. Beausoleil, “Quantum photonic devices in single-crystal diamond.” New Journal of Physics 15, 025010 (2013).

3. Nanodiamond molecular imaging
We are attempting to set a new record in resolution in super-resolution microscopy (2014 Nobel Prize, Chemistry) using recently-developed fluorescent nanodiamonds. This project combines nanomaterials synthesis, nonlinear optics, fluorescence microscopy, and bioimaging. More coming soon!

4. Bio-magnetic imaging

Identifying and localizing rare cells deep within tissue is a long-standing goal of biomedical imaging. For example, the ability to image small tumors or individual circulating tumor cells non-invasively could facilitate the early detection of cancer. However, this remains a major technical challenge. To create sufficient contrast for clinical relevance, target cells must be abundantly labeled with contrast agents with a high degree of specificity, and highly sensitive imaging modalities must be employed that retain sensitivity even when separated by thick tissue.

In this project we seek to label rare cell-bound biomarkers with magnetic nanoparticles and detect them noninvasively using ultrasensitive magnetic-field microscopes. Along the way, we are developing new tools for high-throughput sorting and characterization of individual magnetic nanoparticles. This project combines materials science, cancer nanotechnology, quantum sensing, and biomedical imaging.
5. Metasurfaces for Virtual Reality
This is a new project in collaboration with Adam Backer at Sandia National Labs and John Perreault at Google VR. Our goal is to make nanophotonic chips which can focus/bend light just as well as bulky traditional compound objectives. We are exploring facile ways to modulate the metasurface optical properties to realize dynamic optical displays for virtual and augmented reality applications.