Tunable, Mid-Infrared Light Emitters

Srinivas Tadigadapa

ECE Professor and Chair Srinivas Tadigadapa was awarded a $110K NSF EAGER grant for “Gate tunable thermo-plasmonic mid-IR coherent light emitters.”

Abstract Source: NSF

The goal of this work is to demonstrate wavelength-tunable, laser-like, mid-infrared light emitters on a chip. This will be achieved, for the first time, by coupling of surface resonance in silicon carbide with plasmonic resonance in graphene films. The proposed tunable, mid-infrared source has many advantages over existing coherent infrared sources such as tunable lasers which include complete mechanical motion free tunability of wavelength, small size for various lightweight and mobile platforms, and extremely fast response for high speed applications. The small form factor, tunability and integration potential of these devices will usher a new generation of optical lab-on-chip devices where detection of relevant biomarkers, cells, and ligand chemistries can be spectroscopically realized and thus will enable the development of inexpensive, next generation point of care biosensors. The availability of frequency tunable emitters is likely to open opportunities in the area of on-chip optical communications and optical data transfer that are hitherto considered as cumbersome. The potential bandwidth afforded by such systems may revolutionize data transfer rates and volumes. A robust research and mentoring program consisting of a graduate and undergraduate student working on the project is proposed for this 1-year EAGER proposal.

This proposal aims to explore, investigate, and demonstrate the possibility of achieving tunable, coherent radiation sources in 11 – 12 ?m wavelength range. To accomplish this, we propose to hybridize the localized surface resonance of bulk thermo-plasmonic materials such as silicon carbide with gate-tunable surface plasmonic resonance of two-dimensional materials such as graphene to manipulate the emission characteristics of thermal radiation sources. The proposed experimental study will examine the relation between applied gate-voltage modulated optical properties of graphene, and the corresponding shift in coupled plasmonic and phononic resonance. The study is aimed at deepening the understanding of the coupling between surface phonon resonances of a radiating surface and gate tunable surface plasmon resonance of graphene sheets. The fact that surface phonons and surface plasmons are consequences of resonant ions and electrons respectively raises interesting questions of how momentum matching is balanced between particles of different rest masses. This study will present details of theoretical and the experimentally obtained emission/absorption properties at different temperatures and different wavelengths, specifically, the minimum resolution of wavelength shift that can be achieved with gate-voltage and temperature. From an experimental standpoint, the proposed work will systematically investigate plasmonic tuning of the emission characteristics. Heterogeneous integration techniques with novel micro and nanofabrication methods will be used. The electronic control will allow for programmability of the emitter to auto-sweep through a band of wavelength of interest, to determine the absorption spectrum of samples in spectroscopy applications. The wavelength sweep timeframes of the spectrometers can be potentially accomplished in the milli ? nano seconds allowing for the realization of ultrafast IR tunable sources. The fast, narrowband emission characteristics of the gate-tunable plasmonic emitters can provide nearfield infrared communication solutions in the context of next generation neuromorphic computing and sensing devices. Preliminary calculations show that these sources can generate an intensity of ~200 µW/mm2 and should be enough for spectroscopy and communication applications.

This award reflects NSF’s statutory mission and has been deemed worthy of support through evaluation using the Foundation’s intellectual merit and broader impacts review criteria.

Related Faculty: Srinivas Tadigadapa

Related Departments:Electrical & Computer Engineering