Towards an Infrared Nanophotonic Nose: Ultracompact Spectroscopic Photodetection based on Plasmonic Nanoantenna-diodes

William Marsh Rice University, Houston TX

Investigators

Abstract

The identification of small molecules in our atmosphere, water supply, and exhaled breath or body fluids, is an extremely important capability with applications ranging from identification of dangerous environmental toxins to early-stage disease detection. The methods that are currently available to perform this type of chemical identification, however, require large, expensive and sensitive instruments, are available only in laboratory settings, and are based on decades-old technologies. The work enabled by this research grant aims to combine two recent research advances to develop a new approach for identifying small molecules. This work could ultimately provide chemical identification capabilities in ultracompact geometries that could be used in a variety of non-laboratory settings. The ability to rapidly detect and accurately identify molecules in the clinic or in the field has wide-ranging has applications in areas ranging from agriculture, pharmaceuticals, food quality control, and medical screening, including brain function. This approach could ultimately be used for identifying a plurality of molecules at a fully integrated, chip-based level of detection compatible, ultimately, with cloud-based processing and smart-phone-based data acquisition. The cross-cutting, multidisciplinary concepts central to this proposal provide a broad opportunity for student education at the high school, undergraduate, and graduate student level. Technical Description: The goal of this proposal is to develop highly compact infrared spectroscopic capabilities based on narrowband nanoantenna-diodes for near-infrared molecular spectroscopy. Two independent research advances in nanophotonics were recently pioneered which, when combined, are ideally suited to address this goal. They are: (1) the demonstration of optically active nanoantenna-diodes, where carriers are generated by the decay of photoexcited surface plasmons in resonant metallic nanoantennas, then injected into the conduction band of the adjacent semiconductor, and (2) the development of infrared nanoantennas tuned to the resonant vibration frequencies of specific chemical functional groups. By merging these two concepts, narrowband, infrared active nanoantenna-diodes for the spectroscopic identification of small molecules with direct electrical readout will be created. Efforts will focus on the development of nanoantenna-diodes with enhanced responsivities and quantum efficiencies, through the implementation of gain, and on lineshape control of the nanoantenna-diode spectral response, to ultimately resolve molecular spectral lines in the near-infrared region of the spectrum. This approach would ultimately eliminate the need for near-infrared photodetectors based on costly materials, along with the bulky dispersive optics and large optical path lengths required in conventional infrared spectroscopy for wavelength discrimination.