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Broadband Coherent Perfect Absorption in One-Dimensional Optical Systems

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Date Issued:
2015
Abstract/Description:
Absorption plays a critical role in a variety of optical applications (-) sometimes it is desirable to minimize it as in optical fibers and waveguides, or to enhance it as in solar cells and photodetectors. We describe here a new optical scheme that controllably produces high optical absorption over a broad wavelength range (hundreds of nm) in systems that have low intrinsic absorption over the same range. This effect, 'coherent perfect absorption' or CPA, arises from a subtle interplay between interference and absorption of two beams incident on a weakly absorbing medium. In the first part of this study, we present an analytical model that captures the relevant physics of CPA in one-dimensional photonic structures. This model elucidates an absorption-mediated interference effect that underlies CPA (-) an effect that is normally forbidden in Hermitian systems, but is allowed when conservation of energy is violated due to the inclusion of loss. As a concrete example, we consider a Fabry-P(&)#233;rot resonator containing a lossy dielectric and confirm this model through a computational study of a 1-micron-thick silicon layer in a cavity formed of dispersive mirrors with aperiodic multilayer design. We confirm that one may achieve 100% absorption in this thin silicon layer (whose intrinsic absorption is only ~ 3%) in the near-infrared. We then design two device models using few-micron-thick aperiodic planar dielectric mirrors and demonstrate (computationally, as well as experimentally) spectrally flat, coherently enhanced absorption at the theoretical limit in a 2-micron-thick film of polycrystalline silicon embedded in symmetric and asymmetric cavities. This coherent effect is observed over an octave-spanning wavelength range of ~800 (-) 1600 nm utilizing incoherent light in the near-infrared, exploiting mirrors that have wavelength-dependent reflectivity devised to counterbalance the decline in silicon's intrinsic absorption at long wavelengths. We anticipate that the design principles established here may be extended to other materials, broader spectral ranges, and large surface areas. Finally, we study the effect of the angle of incidence on CPA in planar structures. The results of this study point to a path for realizing CPA in such systems continuously over large bandwidths.
Title: Broadband Coherent Perfect Absorption in One-Dimensional Optical Systems.
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Name(s): Villinger, Massimo Maximilian, Author
Abouraddy, Ayman, Committee Chair
Dogariu, Aristide, Committee Member
Fathpour, Sasan, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2015
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Absorption plays a critical role in a variety of optical applications (-) sometimes it is desirable to minimize it as in optical fibers and waveguides, or to enhance it as in solar cells and photodetectors. We describe here a new optical scheme that controllably produces high optical absorption over a broad wavelength range (hundreds of nm) in systems that have low intrinsic absorption over the same range. This effect, 'coherent perfect absorption' or CPA, arises from a subtle interplay between interference and absorption of two beams incident on a weakly absorbing medium. In the first part of this study, we present an analytical model that captures the relevant physics of CPA in one-dimensional photonic structures. This model elucidates an absorption-mediated interference effect that underlies CPA (-) an effect that is normally forbidden in Hermitian systems, but is allowed when conservation of energy is violated due to the inclusion of loss. As a concrete example, we consider a Fabry-P(&)#233;rot resonator containing a lossy dielectric and confirm this model through a computational study of a 1-micron-thick silicon layer in a cavity formed of dispersive mirrors with aperiodic multilayer design. We confirm that one may achieve 100% absorption in this thin silicon layer (whose intrinsic absorption is only ~ 3%) in the near-infrared. We then design two device models using few-micron-thick aperiodic planar dielectric mirrors and demonstrate (computationally, as well as experimentally) spectrally flat, coherently enhanced absorption at the theoretical limit in a 2-micron-thick film of polycrystalline silicon embedded in symmetric and asymmetric cavities. This coherent effect is observed over an octave-spanning wavelength range of ~800 (-) 1600 nm utilizing incoherent light in the near-infrared, exploiting mirrors that have wavelength-dependent reflectivity devised to counterbalance the decline in silicon's intrinsic absorption at long wavelengths. We anticipate that the design principles established here may be extended to other materials, broader spectral ranges, and large surface areas. Finally, we study the effect of the angle of incidence on CPA in planar structures. The results of this study point to a path for realizing CPA in such systems continuously over large bandwidths.
Identifier: CFE0006059 (IID), ucf:50985 (fedora)
Note(s): 2015-05-01
M.S.
Optics and Photonics, Optics and Photonics
Masters
This record was generated from author submitted information.
Subject(s): Coherent Perfect Absorption -- CPA -- broadband -- one-dimensional photonic structure -- multilayer mirrors -- Fabry-Pérot resonator
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0006059
Restrictions on Access: campus 2018-11-15
Host Institution: UCF

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