Title :
Lightsabers (“laster swords”) for improving photodetector speed and responsivity
Author :
Hasan, I.M.M. ; Simpson, Jamesina J.
Author_Institution :
Electr. & Comput. Eng. Dept., Univ. of Utah, Salt Lake City, UT, USA
Abstract :
The micrometer scale of optics is significantly larger than the nanometer scale of modern electronic devices. To produce photodiodes yielding both superior speed and responsivity, a critical challenge is to confine the incident light efficiently to an active region having a small (subwavelength) area. In recent years, plasmonics has been applied as a means to confine light to subwavelength areas. In this case, the plasmonic structure converts the incident (far-field) light into near fields in order to achieve the sub-wavelength confinement. However, the surface plasmons are a near-field phenomenon such that the electromagnetic energy does not penetrate deeply. Further, surface plasmon resonances are generated only over narrow range of frequencies. Thus, the question arises: can we avoid the conversion to near fields and propagate the light into the semiconductor over a sub-wavelength area? When desired, can we propagate broadband electromagnetic energy into the sub-wavelength area to provide efficient broadband photodiodes? The latter may especially be desirable if the common silicon semiconductor is replaced with a more broadband semiconductor such as graphene. Here, it is proposed that a propagating sub-wavelength beam of light called a photonic nanojet and resembling a lightsaber or “laser sword” can be used to focus light onto the small active area of a photodiode. Exploratory three-dimensional, Maxwell´s equations finite-difference time-domain (FDTD) simulations are conducted and demonstrate that the nanojets can confine light to an area comparable to a nanostructured dipole antenna while propagating multiple wavelengths into the semiconductor, even over a broad range of frequencies when desirable.
Keywords :
Maxwell equations; elemental semiconductors; finite difference time-domain analysis; graphene; light propagation; nanophotonics; optical focusing; photodetectors; photodiodes; plasmonics; surface plasmon resonance; C; FDTD simulations; active region; broadband electromagnetic energy; broadband photodiodes; broadband semiconductor; far-field light; graphene; incident light confinement; laser swords; light focusing; light propagation; lightsabers; micrometer scale optics; near field light; near-field phenomenon; photodetector responsivity; photodetector speed; photodiodes; photonic nanojet; propagating sub-wavelength beam; sub-wavelength confinement; surface plasmon resonances; three-dimensional Maxwell equations finite-difference time-domain simulations; Broadband antennas; Broadband communication; Electromagnetics; Laser beams; Optical surface waves; Photodiodes; Plasmons;
Conference_Titel :
Radio Science Meeting (USNC-URSI NRSM), 2013 US National Committee of URSI National
Conference_Location :
Boulder, CO
Print_ISBN :
978-1-4673-4776-1
DOI :
10.1109/USNC-URSI-NRSM.2013.6525093