Broadband Mid-IR superabsorption with aperiodic polaritonic photonic crystals

Devarapu, Ganga Chinna Rao; Foteinopoulou, Stavroula

doi:10.2971/jeos.2014.14012

Cited by 10 publications

(6 citation statements)

References 43 publications

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“…After obtaining the optimized structure for µc = 0.0 eV, the carrier density in graphene is increased by applying a positive DC bias, that corresponds to tuning the chemical potential to larger values. The increase in the chemical potential leads to modification of the optical properties of the structures [63,174], as explained in Section 3.5. The switchability can be inferred from the figure by looking at the dotted line that corresponds to the wavelength at which the structures are optimized.…”

Section: Effect Of Chemical Potential On Selectivity Tunability Andmentioning

confidence: 99%

Aperiodic multilayer graphene based tunable and switchable thermal emitter at mid-infrared frequencies

Sharifi

Banadaki

Nezhad

et al. 2018

Journal of Applied Physics

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for the continuous support of my thesis. I would like to thank Dr. Georgios Veronis for his comments, patience, motivation, and immense knowledge. His guidance and attention to detail helped me in all the time of research and this thesis could not have been written without his supervision. I am truly indebted to Jon for his meticulous comments and encouragements, as well as his innovative approach to develop and widen my research from various perspectives. Not only a great mentor, he has been a true father whose kindness will forever be of immense value to me. I could not have imagined having better advisors and mentors for my M.Sc. study than Dr. Georgios Veronis and Dr. Jonathan P. Dowling. My sincere thanks also go to Dr. Theda Daniels-Race for her insightful comments and suggestions to improve the quality of my research. Last but not the least, I would like to thank my lovely husband for supporting me spiritually throughout my study and my life in general. Without a doubt, this accomplishment would have never been possible without his continuous support, unconditional love, and prayers. iv

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Section: Effect Of Chemical Potential On Selectivity Tunability Andmentioning

confidence: 99%

Aperiodic multilayer graphene based tunable and switchable thermal emitter at mid-infrared frequencies

Sharifi

Banadaki

Nezhad

et al. 2018

Journal of Applied Physics

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“…After obtaining the optimized structure for µc = 0.0 eV, the carrier density in graphene is increased by applying a positive DC bias, that corresponds to tuning the chemical potential to larger values. The increase in the chemical potential leads to modification of the optical properties of the structures [63,174], as explained in Section 3.5. For the optimized thermal emitter with 8 graphene layers in Fig.…”

Section: Effect Of Chemical Potential On Selectivity Tunability Andmentioning

confidence: 99%

Aperiodic Multilayer Graphene Based Tunable and Switchable Thermal Emitter at Mid-Infrared Frequencies

Sharifi,

Banadaki,

You

et al. 2017

Meet. Abstr.

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Graphene has attracted an explosion of interest for photonic applications as it provides a degree of freedom to manipulate electromagnetic waves. In this work, we propose a new one-dimensional system composed of multiple graphene and hexagonal boron nitride (hBN) with varying aperiodic thicknesses in between the graphene layers. A hybrid optimization method, consisting of a micro-genetic global optimization algorithm coupled to a local optimization algorithm, indicates that absorption efficiency close to 100% can be achieved at very narrow frequency range under normal incidence. This efficiency can be significantly decreased by tuning the chemical potential and the corresponding carrier density in graphene. It thus enables a promising way to design electrically controllable thermal emitter. Fig. 1(a) shows the proposed device structure composed of 23 graphene layers and 22 alternating layers of hexagonal boron nitride (hBN) insulator, which sandwiches between two thick silicon carbide (SiC) layers. The hBN has two-dimensional atomic structure similar to graphene and has been proposed as its promising complementary insulator layer. The ambient temperature of 873 K is assumed, in which the semi-infinite tungsten substrate creates the thermal emission of black body radiation with maximum emission at infrared range. Since the tungsten substrate is taken to be semi-infinite, the transmittance is identically zero (Absorption = 1-Reflection) and the calculated absorption can be equated to emittance because of Kirchhoff’s second law and conservation of energy. The Kubo formula is used to extract the optical conductivity and consequently the refractive index of graphene while the experimental data is used for the wavelength-dependent indices of refraction of other materials. Fig. 1(b) shows the normalized power radiated per unit area and unit wavelength by the structure. In order to find the optimized structure with narrowband thermal emittance, the chemical potential initially set at the Dirac point of graphene layers (µg=0eV), thus introducing minimum insertion loss or signal attenuation. It can be seen that the proposed device can exhibit narrowband infrared emittance, leading to most prominent emission at λ=3340 nm with narrower wavelength range than black body curve. This wavelength corresponds with the λ/(4nSiC) of 538nm SiC layer, matched with the maximum thermal emission of black body radiation at T = 873 K. This indicates promising application of the proposed structure in design of thermophotovoltaic, in which the frequency of thermal radiation must be matched with the band gap of semiconductor. After obtaining the optimized structure, the dimensions are fixed and the carrier density in graphene is increased by tuning the chemical potential to larger values. It can be seen in Fig. 1(b) that the field effect tuning of carrier density in graphene reduces the normalized thermal emission from 100% at µg = 0eV to 64%, 43%, and 16% corresponding to the chemical potentials of µg = 0.4eV, 0.6eV, and 1.0eV, respectively. The intensity, width and the position of wavelength range is widely tunable, leading to electronic control of thermal emission. As the carrier density is increased, there is a decrease in intensity and a spectral shift toward smaller wavelength. When a bias is applied, two-dimensional electron gases are induced in the graphene layers, resulting in higher contribution of intraband transitions especially at high temperature of black body emitter. This manipulates the optical conductivity of graphene and alters the constructive and destructive interference of thermal incidences and reflections from the graphene/hBN layers, leading to different intensity, width, and position of thermal emittance. In this work, we present a 1D system composed of graphene/hBN heterostructure as a tunable and switchable thermal emitter. While the black-body thermal emission is a broadband and isotropic radiation, the proposed structure may contribute toward the realization of narrowband-wavelength selective thermal emitters with switchable intensity for sensing applications. Figure 1

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“…However, recent results with a compact one-dimensional SiC judicious PC design [21] show that it is possible to suppress such reflection and achieve near-perfect absorption within a narrow spectral band. This band can be extended to cover most of the SiC Reststrahlen spectral region, by employing a very thick, several wavelengths long, PC [36].…”

Section: The Silicon Carbide Platform For Broadband Superabsorp-tionmentioning

confidence: 99%

Broadband Near-Unidirectional Absorption Enabled by Phonon-Polariton Resonances in SiC Micropyramid Arrays

Devarapu

Foteinopoulou

2017

Phys. Rev. Applied

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Inspired by moth eyes, nature's most powerful antireflex, we present a sub-wavelength SiC micropyramid design, which operates in the Reststrahlen band of SiC, namely the spectral band of strong phonon-photon coupling in the SiC material. While within this band SiC repels EM waves, we observe here a broad low-reflectivity window with unique attributes, with distinct characteristics different from typical dielectric moth-eye-like structures. To be specific, while the latter systems are entirely symmetric, the reflection response of our SiC micropyramid system can be highly asymmetric. In particular, the SiC micropyramid system can be near-reflectionless for light impinging from the tip side of the micropyramids and exhibits more than 90% reflection for light impinging from the base side of the micropyramids, over a broad wavelength range in the SiC Reststrahlen band. This strongly asymmetric reflection response emanates from the cascaded coupling of vortex-like cavity modes at each of the SiC blocks comprising the micropyramids and translates into a strongly uni-directional absorber response. We discuss how, by virtue of Kirchhoff's law, this strongly uni-directional superabsorber behavior implies a strongly uni-directional emission profile that is important for one-way infrared sources and passive radiative-cooling systems.

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Broadband Mid-IR superabsorption with aperiodic polaritonic photonic crystals

Cited by 10 publications

References 43 publications

Aperiodic multilayer graphene based tunable and switchable thermal emitter at mid-infrared frequencies

Aperiodic multilayer graphene based tunable and switchable thermal emitter at mid-infrared frequencies

Aperiodic Multilayer Graphene Based Tunable and Switchable Thermal Emitter at Mid-Infrared Frequencies

Broadband Near-Unidirectional Absorption Enabled by Phonon-Polariton Resonances in SiC Micropyramid Arrays

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