Two-dimensional Subwavelength Hole Array Research Articles

Tailoring the optical field enhancement in Si-based structures covered by nanohole arrays in gold films for near-infrared photodetection

We performed numerical simulations of plasmonic near-field enhancement in Si-based structures in near infrared region. Gold films perforated with periodic two-dimensional subwavelength hole arrays were used as the plasmonic couplers. The array periodicity was adjusted to excite the surface plasmon modes at the telecom wavelengths (between 1.3 and 1.55 μm). The field intensity enhancement factor and its spectral position, as a function of hole diameter, demonstrate the maximum at which the Bloch plasmon polariton waves propagating along the Au–Si interface change by a localized surface plasmon mode. The maximum peak wavelength and field intensity enhancement are reached at d/a = 0.5, where d is the hole diameter and a is the array periodicity. An over 14 times field intensity enhancement was obtained at λ = 1.54 μm for d = 200 nm and a = 400 nm. We found that the localized surface plasmon mode is confined mainly under the Au regions along the diagonals of the square lattice of holes. The lateral field distribution for propagating modes has either a hexagonal or square shape, reflecting in-pane symmetry of the grating. For structures with largest holes, the anticrossing of localized mode with the propagating one was observed implying coupling between the modes and formation of a mixed near-field state. The information acquired from the study is valuable for feasible device applications.

Room temperature plasmon-enhanced InAs0.91Sb0.09-based heterojunction n-i-p mid-wave infrared photodetector

Middle wavelength infrared (MWIR) photodetectors have a wide range of applications, but almost all of them operate at low temperature due to the limit of materials and device structures. The capability of plasmonic structures to localize electromagnetic wave on the deep subwavelength scale provides the possibility for MWIR photodetectors operating at room temperature. Here, we report a high sensitivity room temperature MWIR photodetector which is an InAs0.91Sb0.09-based heterojunction n-i-p photodiode integrated with a Au-based two-dimensional subwavelength hole array (2DSHA). A room temperature detectivity of 0.8 × 1010 cm Hz1/2 W−1 and a response time of 600 ns are achieved. The non-cooling high performance of 2DSHA-InAs0.91Sb0.09 based heterojunction photodetectors will make their applications easier, broader, and economic.

Single Plasmonic Structure Enhanced Dual-band Room Temperature Infrared Photodetection

Dual-band photodetection in mid- and near-wave infrared spectral bands is of scientific interest and technological importance. Most of the state-of-the-art mid-infrared photodetectors normally operate at low temperature and/or suffer from toxicity and high cost due to limitations of material properties and device structures. The capability of surface plasmons in confining electromagnetic waves into extremely small volume provides an opportunity for improving the performance for room temperature operation. Here, we report an n-InAsSb/n-GaSb heterostructure photodiode integrated with plasmonic two-dimensional subwavelength hole array (2DSHA) for room temperature two band photodetection. We demonstrate that with a properly designed 2DSHA, room temperature detectivities of the heterostructure device can be enhanced to ~1.4 × 109 Jones and ~1.5 × 1011 Jones for the two bands peaked at 3.4 μm and 1.7 μm, respectively. In addition, we study the photocurrent enhancement in both photoconductor and heterojunction modes in the same integrated structure. The demonstration of single 2DSHA enhanced heterojunction photodiode brings a step closer to high sensitivity room temperature devices and systems which require multiband absorption.

Quantum selection rule dependent plasmonic enhancement in quantum dot infrared photodetectors

In this paper, we analyze quantum selection rules of intersubband transitions in quantum dots (QDs) and determine their impact on plasmonic enhancement in quantum dot infrared photodetectors (QDIPs). Photoluminescence and photocurrent spectrum measurement were performed on QD samples with different doping levels to identify the QD energy levels and associate the photodetection peaks with the intersubband transitions. The quantum selection rules of the intersubband transitions are determined by the electric-dipole interaction. To determine the impact of quantum selection rules on the plasmonic enhancement, we fabricated metallic two-dimensional subwavelength hole array (2DSHA) plasmonic structures with different periods on QDIPs for specific plasmonic enhancement of individual intersubband transitions. We found that the plasmonic enhancement ratios of different intersubband transitions are not the same. The unequal enhancement ratios are attributed to the quantum selection rules in the intersubband transitions and the dominant electric field (E-field E→) vectors induced by the 2DSHA plasmonic structure.

Surface plasmonic resonance induced near-field vectors and their contribution to quantum dot infrared photodetector enhancement

In this paper, we analyse surface plasmonic resonance (SPR) induced near-field electric-field vector distribution in the quantum dot (QD) region and determine their roles in quantum dot infrared photodetector (QDIP) enhancement. SPR can be excited in metallic two-dimensional subwavelength hole arrays (2DSHAs) when illuminated at resonant wavelengths. The SPR induced near-field vectors (Ez, Ex and Ey) and their distributions and overlaps with the QD active region are simulated. A long-wave infrared (LWIR) QDIP is fabricated with the 2DSHA plasmonic structure to experimentally measure the SPR enhancement spectrum and compare it with the near-field vector components and their distribution in QDs. We found that QDIP enhancement is closely related to the near-field intensity overlap integral in the QD region. The large near-field overlap integral corresponds to high QDIP enhancement. Such near-field overlap integral dependent plasmonic enhancement is attributed to the interaction of and the electric-dipole interaction in QDs.

Optical transmission enhancement of two-dimensional subwavelength hole arrays in metallic films

Numerical simulation has been performed on the optical transmission enhancement of a metallic film with a two-dimensional subwavelength hole array- The results show that the ideal conducting film of the same array structure also presents a transmission enhancement, but the enhancement is not higher than that of the real one- Further analysis reveals that a complicated waveguide coupling effect is responsible for the enhanced transmission- The excitation of surface current on metallic surface transfers the light energy of incidence from metallic surfaces to the holes and then adjusts the optical transmission- We believe that the resonant excitation of surface plasmon is not necessary for the enhancement effect-

Enhanced light transmission by hole arrays

The extraordinary optical transmission of a metallic film pierced by a two-dimensional subwavelength hole array, observed by Ebbesen et al, is explained using rigorous electromagnetic analysis and a phenomenological approach. The analysis is based on Li's Fourier-modal method extended to crossed gratings, which reduces the diffraction problem to the search for eigenvalues and eigenvectors of a particular matrix. The computation of the eigenvalues allows us to find a new channel for light transmission through the subwavelength holes, which differs from the transmission channel in the one-dimensional case (lamellar or rectangular-rod grating). It is demonstrated that the enhanced transmission is due to the excitation of a surface plasmon on the lower metallic surface.

Theory of light transmission through subwavelength periodic hole arrays

The existing theories which aim to explain the extraordinary optical transmission of a metallic film pierced by a two-dimensional subwavelength hole array [T.W. Ebbesen, H.J. Lezec, H.F. Ghaemi, T. Thio, and P.A. Wolff, Natural (London) 391, 667 (1998)] all have in common the following feature: instead of studying the two-dimensional crossed grating resulting from the hole array, they consider a one-dimensional grating with infinite slits. We show that such a simplification introduces an efficient channel for light transmission in lamellar gratings, which does not exist for hole arrays. Therefore in order to explain the relatively high transmission observed by Ebbesen et al., it is necessary to take into account the existence of the holes in the array. In this paper we develop a two-dimensional analysis of the experiment performed by Ebbesen et al. No simplification is introduced. This allows us to obtain theoretically the long-wavelength peak reported by Ebbesen et al. with the same grating thickness as the one used by these authors. We also review and study in detail the various contributions devoted to this very surprising effect.