Nanofocusing of Ultraviolet Light in Aluminum V-Grooves

Jieying Mao Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah, USA Steve Blair Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah, USA

As significant progress has been accomplished in visible and infrared nanofocusing, the study of Ultraviolet (UV) plasmons are attracting interest due to their numerous applications such as label free detection of biological molecules. In this work, electromagnetic nanofocusing of UV light incident upon Aluminum (Al) V-groove nanostructures is simulated using the finite-difference time-domain (FDTD) method. A parametric study of the field enhancement around the V-groove tip area is conducted through the change of groove depth, width, and the tip angle. A short-wavelength threshold of about 200 nm, lying well above the plasma wavelength of Al, is identified, below which the electric field enhancement at the tip rapidly decreases. The adiabatic focusing condition and mode attenuation are taken into consideration as possible explanations. Through simplification of the V-groove model into a Metal-Dielectric-Metal (MDM) waveguide with gap width corresponding to V-groove width (based upon distance from the tip), modal solutions can be obtained for the complex propagation constant, from which the adiabatic parameter and propagation length are determined. These results suggest that the decrease in propagation length with decreasing wavelength is the underlying cause of the short-wavelength threshold.

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Blair@ece.utah.edu









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