FDTD Analysis of Plasmonic and Nanojet Enhanced Photodetectors for Improved Performance
type: CreativeWork
description: The finite-difference time-domain (FDTD) technique is a very flexible and robust means to solve problems spanning a broad range of applications (defense, communication, computing, semiconductor devices and biomedicine), especially where geometrical complexities, nonlinearities and multiphysics dominate. In this thesis, novel photodetectors are developed via FDTD having sub-wavelength active areas that yield enhanced optical absorption at near-infrared (NIR) wavelengths by way of plasmonics or photonic nanojets. The response time of photodiodes is primarily limited by two factors: (1) the transit time of photo-generated carriers to the electrode and (2) depletion layer capacitance of the semiconductor. The former requires a thinner depletion layer, resulting in a large depletion layer capacitance. To suppress the increase of the depletion layer capacitance, it is necessary to decrease the active area of the photodiode with depletion layer thickness. However, the smaller the active area the lower the output of the photodiode under the constant optical power density. To overcome the trade-off between speed and responsivity, the incident light should be efficiently confined within a small active area. Surface plasmons play an important role in this phenomenon as surface plasmons can enhance the near-field when excited by a certain wavelength. Resonant surface plasmons can confine strong optical near fields in a sub wavelength volume, this has been demonstrated for near- infrared dipole antennas. As an alternative to plasmonics it is proposed here that photonic nanojets may be employed to focus light onto the small active region of a photodetector. A photonic nanojet is a narrow, high-intensity electromagnetic beam that propagates into the background medium from the shadow side surface of a plane-wave illuminated loss-less dielectric micro-cylinder or micro-sphere of diameter greater than the illuminating wavelength, λ. The transverse beam width of the nanojet can be as …
abstract: The finite-difference time-domain (FDTD) technique is a very flexible and robust means to solve problems spanning a broad range of applications (defense, communication, computing, semiconductor devices and biomedicine), especially where geometrical complexities, nonlinearities and multiphysics dominate. In this thesis, novel photodetectors are developed via FDTD having sub-wavelength active areas that yield enhanced optical absorption at near-infrared (NIR) wavelengths by way of plasmonics or photonic nanojets. The response time of photodiodes is primarily limited by two factors: (1) the transit time of photo-generated carriers to the electrode and (2) depletion layer capacitance of the semiconductor. The former requires a thinner depletion layer, resulting in a large depletion layer capacitance. To suppress the increase of the depletion layer capacitance, it is necessary to decrease the active area of the photodiode with depletion layer thickness. However, the smaller the active area the lower the output of the photodiode under the constant optical power density. To overcome the trade-off between speed and responsivity, the incident light should be efficiently confined within a small active area. Surface plasmons play an important role in this phenomenon as surface plasmons can enhance the near-field when excited by a certain wavelength. Resonant surface plasmons can confine strong optical near fields in a sub wavelength volume, this has been demonstrated for near- infrared dipole antennas. As an alternative to plasmonics it is proposed here that photonic nanojets may be employed to focus light onto the small active region of a photodetector. A photonic nanojet is a narrow, high-intensity electromagnetic beam that propagates into the background medium from the shadow side surface of a plane-wave illuminated loss-less dielectric micro-cylinder or micro-sphere of diameter greater than the illuminating wavelength, λ. The transverse beam width of the nanojet can be as …
author: Hasan, I.M. Mehdi
language: English
keywords: FDTD, Plasmonic, Photonic Nanojet
date published: 2012-08-27T07:00:00Z
date modified: 2026-07-24T05:27:19Z
provider: University of New Mexico
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of New Mexico