Logo: University of Southern California

Andrea M Armani


Associate Professor



Research Topics

  • Biological and chemical sensors and microfluidics
  • Development of novel surface chemistries
  • Optical device design and characterization
  • Synthesis of optical materials
Research Images

An ultra-high-Q, whispering gallery mode, optical resonator fabricated using a combination of planar lithography, etching, and laser reflow. Among other accomplishments, these devices have demonstrated label-free, single molecule detection.
Artistic rendering (PovRay) of an array of toroid resonators surrounded by molecules. The whispering gallery is highlighted in red. These devices have demonstrated label-free, single molecule detection which is enabled by their 100 million quality factors.

Finite element model (FEM) of the whispering gallery mode in a toroidal resonant cavity with a polymer coating. The majority of the mode is located in the toroid (left), but part of the field extends into the polymer film and into the environment (right). Image from H.-S. Choi et al, Optics Letters, 35 4, (2010).

Research Topics

Integrated Photonics
We are actively engaged in both investigating new phenomena in optical microcavities as well as developing new types of non-resonant optical devices.  Optical microcavities have been crucial in studying many non-linear effects because of the resonant re-circulation of light within the microcavity.  They also can prove to be an integral component in many telecommunications platforms because of their very narrow linewidths.  However, there are many applications where a non-resonant device is preferred.  Example research thrusts include: inventing of novel, ultra-high performance devices for telecommunications and biodetection applications, improving our understanding of the behavior of planar optical cavities, and developing hybrid structures.
The ability to perform label-free experiments is an enabling technology for many biological systems studies.  However, currently the majority of label-free detection technologies require very high concentrations of molecules, ie they are not able to perform these potentially revolutionary experiments.  One active area of research is developing the techniques and methods which will allow many of the pivotal systems biology questions to be addressed.  This research involves improving all aspects of optical senors: specificity, sensitivity, sample collection, and data acquisition and analysis.  We are also investigating multiple biological materials, range from cells to single DNA. We are also investigating the development of entirely new methods of biodetection. By its very nature, this research is highly collaborative.  
Optical Materials
We are investigating multi-material or hybrid devices which are comprised of polymers and silica.  We are using polymers which have the ability to change or modify the optical properties of the optical device.  Additionally, we are studying the dynamic and often non-linear properties of polymeric materials by developing a realtime detection and monitoring technique.  One of the research topics is the development of such an instrument and its implementation in studying non-linear surface phenomena, such as catalysis and phase transformation. We are also working on developing materials based on silica sol-gels designed to alter the optical properties of our silica-based devices.  
FEM/FDTD Modeling
As a complementary effort to our experimental work, we perform a significant amount of FEM and FDTD modeling.  While the FDTD modeling (Lumerical) is primarily used for modeling the optical devices, the FEM modeling (COMSOL Multiphysics) is used for modeling the complex  interactions which occur in all of the systems we study, and include multiple physical parameters, such as mechanical, thermal, kinetic and optical behavior.

Selected Publications

1.       N. Deka, A. J. Maker, A. M. Armani, "Titanium enhanced Raman microcavity laser", Optics Letters 39 (6), 1354-1357 (2014).

2.       X. Zhou, L. Zhang, A. M. Armani, D. Zhang, X. Duan, J. Liu, H. Zhang, W. Pang, "On-chip biological and chemical detection with reversed Fano lineshape enabled by embedded microring resonators", IEEE Journal of Selected Topics in Quantum Electronics 20 (3), 5200110 (2014).

3.       C. Shi, S. Soltani, A. M. Armani, "Gold nanorod plasmonic upconversion microlaser", Nano Letters 13 (12), 5827-5831 (2013).

4.       R. M. Hawk, M. V. Chistiakova, A. M. Armani, "Monitoring DNA hybridization using optical microcavities", Optics Letters 38 (22), 4690-4693 (2013).

5.       X. Zhang, A. M. Armani, "Silica microtoroid resonator sensor with monolithically integrated waveguides", Optics Express 21 (20), 23592-23603 (2013).

6.       A. Harker, S. Mehrabani, A. M. Armani, "Ultra-violet light detection using an optical microcavity", Optics Letters 38 (17), 3422-3425 (2013).

7.       S. Mehrabani, A. M. Armani, "Blue upconversion laser based on thulium doped silica microcavity", Optics Letters 38 (21), 4346-4349 (2013).

8.       A. J. Maker, A. M. Armani, "NanoWatt threshold, alumina sensitized neodymium laser integrated on silicon", Optics Express 21 (22), 27238-27245 (2013).

9.       S. Mehrabani, P. Kwong, M. Gupta, A. M. Armani, “Hybrid microcavity humidity sensor”, Applied Physics Letters 102, 241101 (2013).

10.   C. R. Murthy,  A. M. Armani, “Mass transport effects in suspended waveguide biosensors integrated in microfluidic channels”, Sensors 12 (11), 14327-14343 (2012).

11.   X. Zhang, M. Harrison, A. Harker, A. M. Armani, “Serpentine low loss trapezoidal silica waveguides on silicon”, Optics Express 20 (20), 22298-22307 (2012).

12.   A. J. Maker, B. A. Rose, A. M. Armani, “Tailoring the behavior of optical microcavities with high refractive index sol-gel coatings”, Optics Letters 37 (14), 2844-2846 (2012).

13.   H. -S. Choi*, D. Neiroukh*, H. K. Hunt, A. M. Armani, “Thermo-optic coefficient of polyisobutylene ultrathin films measured with integrated photonic devices”, Langmuir 28 (1), 849-854 (2012). *authors contributed equally

14.   C. Shi, H. -S. Choi, A. M. Armani, “Optical microcavities with a thiol-functionalized gold nanoparticle polymer thin film coating”, Applied Physics Letters 100 (1), 013305 (2012).