Jarrett H. Vella

Studies of the influence of deep subwavelength surface roughness on fields of plasmonic thin film based on Lippmann-Schwinger equation in the spectral domain

In this paper, we consider a line source over a plasmonic thin film with surface roughness. Using layered medium Green’s functions, we derive the Lippmann–Schwinger equation in the spectral domain with scattering potentials for the case of surface roughness over a layered medium. Because of deep subwavelength surface roughness, the scattering potentials are next approximated by the small potential approximation, so that the solutions of fields in the spectral domain can be readily computed. Numerical results are illustrated for the surface fields on the rough surface and the fields in the image plane. For periodic roughness, small periods, on the order of 0.1λ, and small heights, on the order of 0.01λ, are used. For the case of random roughness, we choose the correlation length to be much smaller than a wavelength, on the order of 0.1λ, and height on the order of 0.01λ. The results of the fields on the rough surface in the spectral domain show that subwavelength roughness creates fields with wave vector components that are many times larger than the free-space wavenumber (∼10k0 or larger). In the spatial domain, the imaging is enhanced by the deep subwavelength roughness. Results of the small roughness approximation are in good agreement with that of exact potential and that of the method of moments.

Emission of electric and magnetic dipoles in plasmonic systems

Spontaneous emission of Eu3+ is significantly modified in close vicinity of metal and nanostructured metal systems. The effects are different than those predicted by the “image model”, and ascribed to strong coupling with plasmonic modes.

High throughput, large scale, broadband, plasmonic nanostructure fabrication for optical sensors

Plasmonics have the potential to enhance the performance of detectors. A thermal metal dewetting process was developed which can be easily scaled for high throughput production. Through this process, plasmonic nanostructures were fabricated providing broadband plasmon resonance tunable over a 1000 nm wavelength range. The plasmonic media and their integration into fluorescence-based sensors will be described.

Black Aluminum: a novel anti-reflective absorbing coating

Black absorbing and antireflective coatings have many optical sensing applications. A process to deposit Black Aluminum, a novel anti-reflective coating has been discovered. Black Aluminum films with controlled thickness were deposited on silicon and their reflection spectra were investigated. In addition, to test the effectiveness of this new material at the device level, pyroelectric devices were fabricated with Black Aluminum acting as the absorbing layer. Significant enhancement in the pyroelectric response is reported for devices coated with Black Aluminum as compared to devices without the Black Aluminum absorbing layer.

Implementation of IR spectral target sensing algorithm in synthesizable logic

We report the implementation of an adaptive spectral sensing algorithm in hardware description language for IR target classification. The synthesized logic performs computation in digital domain between IR test input and a set of prescribed algorithmic weights to extract desired spectral information from targets as well as identifying its class.

Optical imaging over a plasmonic thin film with deep-subwavelength surface roughness

Subwavelength imaging has been reported for a layer of plasmonic thin film. In this paper, we investigate the enhancement of the sub-diffraction-limit imaging using subwavelength surface roughness. Full wave simulations are carried out based on Lippmann Schwinger equation with linearized scattering potentials. Progresses in experiment are also reported.

Surface plasmon enhanced rare earth fluorescence for increased imaging efficiency

Ions of rare earth metals are widely known for their versatile ultraviolet, visible, near infrared and middle infrared fluorescence; they can be excited by wavelengths ranging from the ultraviolet to near infrared. The preparation and optimization of infrared fluorescent ceramics will be discussed, as well as their thin film incorporation into plasmonic systems for fluorescent imaging with enhanced efficiency.

Nanoscale gradient index media fabrication for extreme control and tunability of optical wave propagation

Gradient Index Media have multiple applications for controlling the wave propagation and harvesting its received energy or processing its embedded data. A nanofabrication process was developed to produce a Luneburg lens on silicon, to operate in the optical regime, with feature sizes smaller than 100nm. The focused energy of the Luneburg lens is compared with lenses of non-spatially-varying index as well as a linear spatial variation, and its enhanced focusing is clearly demonstrated. In addition, a mechanism of thermal tunability of such devices is proposed and is supported by our results.

Optically Actuated MEMS Deformable Mirror Device

We propose a new design, fabrication procedures and the operating theory for a very low-power optically actuated deformable mirror device. The deformable mirror consists of an array of AlGaAs PIN photo detectors bonded onto a transparent substrate, a thin film resistor, and a suspended membrane