Papers by Mehdi Afshari-Bavil
After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterne... more After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterned on a metal film have generated wide interest as they offer high optical transmission and strong localized electric near-field intensities. However, the large ohmic losses exhibited by SPs in the optical regime represent a fundamental limitation that reduces drastically the practical applicability of EOT properties. Furthermore, not compatible with silicon platform make it difficult for application purposes. As a possible solution to this fundamental problem, gain medium have been introduced to compensate the loss created by metallic film. But the most important yet challenging requirements for gain material are to be silicon compatible and working at telecommunication regime. The aim of this paper is to theoretically study optical amplification of EOT properties in periodic hole arrays incorporating optically pumped gain media. The gain media was selected Erbium/Ytterbium(Er/Yb) silicate...
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A circular slit-groove surface plasmon polaritons (SPPs) launcher surrounding a photodetector is ... more A circular slit-groove surface plasmon polaritons (SPPs) launcher surrounding a photodetector is employed theoretically to enhance the photocurrent of atypical Si-Ge pho-todetectors. The slit and grooves are designed such that the SPPs are focused at the center of the absorption layer of the photodetector to result in additional electric current. Fabry– Perot resonance condition accurately calculates the period of the groove, slit-groove distance, photodetector radius, and slit-photodetector distance. The manipulation leads to constructive interference between the incident light impinging from the top and the SPPs propagating toward the photodetector. Simulation result shows that photocurrent increases by approximately 13-fold when the SPPs are introduced.
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The enhanced light transmission through an I-shape aperture is studied by simulation and theory.... more The enhanced light transmission through an I-shape aperture is studied by simulation and theory. The transmission profile due to microcavities created in the entrance and exit of the aperture was modified and new peak was observed. By introducing a new formula the refractive index of layers is defined. The Fabry–Perot matrix method is employed to explore the role of Fabry–Perot resonator effect in modified slits, especially I-shape slit in the scope of this work. And the peaks correspond to this effect are determined. The effect of microcavity surface Plasmon polaritons is explored respectively. Both microcavity surface plasmons and Fabry–Perot resonator contribute in transmission enhancement and consider as the origin of extraordinary transmission for unsymmetrical slits.
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By embedding a nanocavity adjacent to one or both of slits in a subwavelength double-slit structu... more By embedding a nanocavity adjacent to one or both of slits in a subwavelength double-slit structure, frequency selective propagation through the slits is demonstrated. When the incident light wavelength corresponds to the cavity resonance mode, the electromagnetic wave passing through the slit will be trapped within the nanocavity. Therefore, the double slit operates as a single slit and light propagation is solely allowed through the partner slit. These wavelengths are determined by applying the Fabry—Perot resonance condition for the nanocavities. Various geometrical structures result in different effective refractive indexes. Thus, the effective refractive index and consequently the attenuation wavelength can be adjusted by choosing the appropriate parameters of the nanocavity. Our theoretical predictions are in good agreement with 2D finite-difference time-domain simulation.
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Here by introducing an I-shape structure to break the symmetry of a thin metallic film, the contr... more Here by introducing an I-shape structure to break the symmetry of a thin metallic film, the contributions of Fabry–Perot (FP) resonance-like modes and surface plasmon polariton (SPP) resonance-like are determined. The finite difference-time domain (FDTD) simulation is utilized to provide a clear picture of the electromagnetic field distribution and transmission profile. The FP matrix method is employed to specify the contribution of FP resonance. Some of the predicted resonances of the FP matrix method coincide with the simulation result which is labeled as FP resonance-like modes. The remaining resonance modes in transmission profile are considered as SPP resonance-like modes. Our results provide explicit evidence that both FP resonator modes and SPP resonance are responsible for extraordinary optical transmission (EOT) through a subwavelength aperture.
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By combining a Fabry–Perot (FP) cavity with a slot cavity, a compact filter structure is proposed... more By combining a Fabry–Perot (FP) cavity with a slot cavity, a compact filter structure is proposed. The peak resonance wavelength is determined by applying the FP resonance condition of the FP cavity. The relationship between filtering wavelength and cavity parameters is investigated. The results show that the filtering wavelength can be manipulated by changing the nanocavities' parameters. By using the finite difference time domain method, the theoretical predictions are confirmed. An intersection structure for nanoplasmonic waveguides is proposed and designed by utilizing two perpendicular filters. In addition to having compact dimensions, the proposed arrangement provides higher throughput and low cross talk. The proposed structure can be useful for designing compact integrated nanoplasmonic circuits.
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By utilizing a Fabry—Perot (FP) nanocavity adjacent to T-shaped gap waveguide ports, spectrally s... more By utilizing a Fabry—Perot (FP) nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry—Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.
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Extraordinary gain-assisted transmission in telecommunication regimes through circular nanohole a... more Extraordinary gain-assisted transmission in telecommunication regimes through circular nanohole arrays drilled on a metallic film is investigated theoretically. Silicon-compatible Er–Yb silicate, which has a photoluminescence peak in the telecommunication regime, was selected for optical amplification purposes. Geometrical parameters were optimized analytically in order to present transmission resonances at telecommunication regions. The required gain value for lossless propagation was determined by considering the surface-plasmon dispersion relation. Simulation results show that the predicted gain for lossless propagation cannot completely compensate the loss. By increasing gain value, absorption becomes zero and transmission approaches unit through a laser with a pumping power of 372 mW at 1480 nm.
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Books by Mehdi Afshari-Bavil
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After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterne... more After discovery of extraordinary transmission (EOT) subwavelength hole arrays structures patterned on a metal film have generated wide interest as they offer high optical transmission and strong localized electric near-field intensities. However, the large ohmic losses exhibited by SPs in the optical regime represent a fundamental limitation that reduces drastically the practical applicability of EOT properties. Furthermore, not compatible with silicon platform make it difficult for application purposes. As a possible solution to this fundamental problem, gain medium have been introduced to compensate the loss created by metallic film. But the most important yet challenging requirements for gain material are to be silicon compatible and working at telecommunication regime. The aim of this paper is to theoretically study optical amplification of EOT properties in periodic hole arrays incorporating optically pumped gain media. The gain media was selected Erbium/Ytterbium(Er/Yb) silicate that is silicon compatible with photoluminescence peak at telecommunication regime. Use of Er3+ ions has the advantages of proven, stable, and low-noise operation at the technologically important 1.54 m region. To excite the active material a laser with a maximum power of 372 mW at the wavelength of 1480 nm is applied. Geometrical parameters was obtained by solving the surface plasmon dispersion relation on periodic hole arrays. The condition for lossless propagation was obtained analytically. Simulation results shows that for lossless propagation we will need higher gain value. By considering higher gain values the absorption was approached to zero 30% transmission enhancements was observed at telecommunication wavelength.
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In this paper the capacitance-voltage characteristics of InN quantum dots embedded in AlGaN/GaN h... more In this paper the capacitance-voltage characteristics of InN quantum dots embedded in AlGaN/GaN heterostructure has been studied. This work has been done for the InN quantum dots with different quantum dot size, and energy dispersion and for the AlGaN/GaN heterostructures with different Al mole fraction and number of quantum wells in different temperatures. The presence of InN quantum dot will cause Gaussian shape in capacitance-voltage characteristics approximately, where the peak of curves can evidence the position of quantum dots in the structures. Our calculation results show the Gaussian shape (or negative differential capacitance) is much higher at low temperature and for quantum dots with low energy and higher size dispersion.
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Surface plasmon (SP) microcavity recently has been proposed to enhance transmission through a sub... more Surface plasmon (SP) microcavity recently has been proposed to enhance transmission through a subwavelength slit. Here we employed Fabry-Perot matrix method to predict the transmission profile of the structure. The result show good agreement with simulation result based on finite difference time domain (FDTD) method. The calculation shows that the SP microcavity standing waves and the Fabry-Perot resonance mode are responsible for transmission enhancement. For layered slits FP matrix method is a powerful method for prediction transmission behaviors.
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Papers by Mehdi Afshari-Bavil
Books by Mehdi Afshari-Bavil
Conference Presentations by Mehdi Afshari-Bavil