KEYWORDS: Optimization (mathematics), Solar cells, Reflectivity, Refractive index, Transmittance, Information operations, Solar energy, Dielectrics, Chemical elements, Switches
A spectrum splitter can be used to spatially multiplex different solar cells that have high efficiency in mutually exclusive parts of the solar spectrum. We investigated the use of a grating, comprising an array of dielectric cylinders embedded in a dielectric slab, for specularly transmitting one part of the solar spectrum while the other part is transmitted nonspecularly and the total reflectance is very low. A combination of (1) the rigorous coupled-wave approach for computing the reflection and transmission coefficients of the grating and (2) the differential evolution algorithm for optimizing the grating geometry and the refractive indices of dielectric materials was devised as a design tool. We used this tool to optimize two candidate gratings and obtained definite improvements to the initial guesses for the structural and constitutive parameters. Significant spectrum splitting can be achieved if the angle of incidence does not exceed 15 deg.
The excitation of multiple surface-plasmon-polariton (SPP) waves and waveguide modes was experimentally demonstrated in a structure fabricated as a one-dimensional photonic crystal (PC) on top of a two-dimensional metal grating. The PC had two periods, each period comprising nine layers of silicon oxynitrides of different compositions. The individual excitations of the SPP waves and waveguide modes were also theoretically predicted using the Floquet theory, surface-multiplasmonics theory, and the transfer–matrix approach for multilayered waveguides. Both the theoretical and experimental results indicate broadband coupling of incident light of either linear polarization state to the guided waves of both types over a broad range of the angle of incidence.
Structurally chiral materials exhibit the circular Bragg phenomenon (CBP). These materials preferentially reflect
circularly polarized light of the same handedness while transmitting circularly polarized light of the opposite
handedness within a range of wavelengths called the circular Bragg regime. The CBP has been extensively
investigated experimentally for normal incidence, but not for oblique incidence. After fabricating a 20-periodthick
chiral sculptured thin film, we measured all of its circular remittances over a 60◦ range of the angle of
incidence and a 300-nm range of the free-space wavelength. Provided the incidence is not very oblique, the
obtained dependencies of the center wavelength and the bandwidth of the CBP on the angle of incidence match
theoretical estimates.
A spectrum splitter can be used to spatially multiplex different solar cells that have high efficiency in mutually exclusive parts of the solar spectrum. We investigated the use of a surface-relief grating made of dielectric materials for specularly transmitting one part of the solar spectrum while the other part is transmitted nonspecularly and the total reflectance is very low. A combination of (i) the rigorous coupled-wave approach for computing the reflection and transmission coeffients of the grating and (ii) the differential evolution algorithm for optimizing the grating shape was devised as a design tool. We used this tool to optimize two candidate gratings and obtained denite improvements to the initial guesses for the structural and constitutive parameters. Signicant spectrum splitting can be achieved if the angle of incidence does not exceed 15.
The Floquet theory and the transfer-matrix approach were used to investigate the excitation of surfaceplasmon-polariton (SPP) waves and waveguide modes in a structure comprising a one-dimensional photonic crystal (1D PC) of finite thickness on top of a planar thick metallic layer. The solutions of the relevant dispersion equations were used to predict the excitation of multiple SPP waves and waveguide modes when the metallic layer is patterned as a two-dimensional (2D) surface-relief grating. The same structure was experimentally fabricated and optically characterized to validate the theoretical approach. Both the theoretical and experimental results show broadband coupling of incident light of either linear polarization state over a broad range of the angle of incidence. This structure has potential applications in planar optical concentrators.
The excitation of multiple surface-plasmon-polariton (SPP) waves guided by the interface of a metal and a onedimensional photonic crystal in the grating-coupled configuration was studied both experimentally and theoretically. Only p-polarized incident light was considered in the visible and near-infrared regimes. When the absorptance was plotted against the angle of incidence, the excitation of an SPP wave was indicated by an absorptance peak whose angular location did not change with the number of periods (beyond a threshold) of the photonic crystal. A decrease in the period of the metal grating resulted in shifting the excitation of the SPP waves to smaller wavelengths.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.