We propose that the operational wavelength of waveguided Si-based photonic integrated circuits and optoelectronic integrated circuits can be extended beyond the 1.55 µm telecom range into the wide infrared from 1.55 to 100 µm. The Si rib-membrane waveguide offers low-loss transmission from 1.2 to 6 µm and from 24 to 100 µm. This waveguide, which is compatible with Si microelectronics manufacturing, is constructed from silicon-on-insulator by etching away the oxide locally beneath the rib. Alternatively, low-loss waveguiding from 1.9 to 14.7 µm is assured by employing a crystal Ge rib grown directly upon the Si substrate. The Si-based hollow-core waveguide is an excellent device that minimizes loss due to silicon's 6-24 µm multi-phonon absorption. Here the rectangular air-filled core is surrounded by SiGe/Si multi-layer anti-resonant or Bragg claddings. The hollow channel offers less than 1.7 dB cm −1 loss from 1.2 to 100 µm.

We experimentally demonstrate a wide band near perfect light absorber in the mid-wave infrared region using multiplexed plasmonic metal structures. The wide band near perfect light absorber is made of two different size gold metal squares multiplexed on a thin dielectric spacing layer on the top of a thick metal layer in each unit cell. We also fabricate regular nonmultiplexed structure perfect light absorbers. The multiplexed structure IR absorber absorbs above 98% incident light over a much wider spectral band than the regular non-multiplexed structure perfect light absorbers in the mid-wave IR region.Anomalous light absorption in metal structures was first observed a century ago by Wood [1]. The interest of light absorption in structured metals resurfaced in the 1960s, 1970s, and 1990s [2-8]. Today, it is well understood that anomalous light absorption in metal structures is due to the excitation of surface plasmon-polaritons (SPPs). Recently, perfect electromagnetic energy absorptions in structured metamaterials have been demonstrated in the gigahertz and terahertz regimes [9][10]. Perfect absorbers at optical frequencies have also been reported by several groups [11][12][13][14][15][16]. However, all the metamaterial perfect absorbers reported have very narrow spectral widths limited by the line-widths of the electromagnetic resonances in the structures. In many applications, it is desirable to have perfect absorption over broader spectral bands. Expansion of absorption band has been proposed using structures combining multiplexed subwavelength apertures [13], however, the proposed structure is polarization dependent and experimentally has not been demonstrated. In this paper, we report an experimental demonstration of a wide spectral band perfect absorber using a multiplexed surface plasmon resonance structure. In the multiplexed surface plasmon resonance structure, two gold metal squares are multiplexed in the unit cell of the periodic structure. The multiplexed plasmonic structure metamaterial, operating in the mid-wave infrared regime, near perfectly absorbs photons over a wider spectral range than previously reported.Figure 1 (a) shows the regular non-multiplexed narrow band perfect light absorber structure. In this structure, gold thin film squares are patterned periodically on the top of a thin dielectric layer deposited on top of a thick gold metal layer. The thick metal layer is thick enough that no transmission can occur when light is incident from above the structure. Due to electromagnetic resonance in the metal-dielectric subwavelength structure, the effective impedance of the structured metamaterial surfaces can match the impedance of the vacuum; therefore reflections from the surface can be completely eliminated. Fig. 1 (b) shows the multiplexed perfect light absorber structure. The period of the multiplexed structure is the same as the period of the non-multiplexed perfect light absorber structure.However, in the multiplexed structure there are two metal squares of different sizes in the un...

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We study guided modes in a conductor-gap-dielectric (CGD) system that includes a low-index dielectric gap layer of deep sub-wavelength thickness sandwiched between a conductor and a high-index dielectric cladding. Analysis of the dispersion equation for CGD modes provides an analytical estimation for the cut-off thickness of the gap layer. This guided mode is unusual because it exists when the gap thickness is less than the cutoff thickness. In the direction normal to the interfaces, the modal electric field is tightly confined within the gap. Sub-wavelength lateral mode confinement is readily provided by a spatial variation of the gap-layer thickness: the modal field localizes at the narrowest gap. Various lateral confinement schemes are proposed and verified by numerical simulations. Possible applications of CGD modes include surface-plasmon nano-lasers (SPASERs) and sensors. If these plasmonic waveguides are scaled for operation at far infrared rather than telecomm wavelengths, then the propagation losses are dramatically reduced, thereby enabling the construction of practical chip-scale plasmonic integrated circuits or PLICs.

Conductors with infrared plasma frequencies are potentially useful hosts of surface plasmon polaritons (SPP) with sub-wavelength mode confinement for sensing applications. A challenge is to identify such a conductor that also has sharp SPP excitation resonances and the capability to be functionalized for biosensor applications. In this paper we present experimental and theoretical investigations of IR SPPs on doped silicon and their excitation resonances on doped-silicon gratings. The measured complex permittivity spectra for p-type silicon with carrier concentration 6Â10 19 and 1Â10 20 cm À3 show that these materials should support SPPs beyond 11 and 6 lm wavelengths, respectively. The permittivity spectra were used to calculate SPP mode heights above the silicon surface and SPP propagation lengths. Reasonable merit criteria applied to these quantities suggest that only the heaviest doped material has sensor potential, and then mainly within the wavelength range 6 to 10 lm. Photon-to-plasmon coupling resonances, a necessary condition for sensing, were demonstrated near 10 lm wavelength for this material. The shape and position of these resonances agree well with simple analytic calculations based on the theory of Hessel and Oliner (1965). V

We demonstrate the feasibility of fabricating heterojunctions of semiconductors with high mismatches in lattice constant and coefficient of thermal expansion by employing nanomembrane bonding. We investigate the structure of and electrical transport across the interface of a Si/Ge bilayer formed by direct, low-temperature hydrophobic bonding of a 200 nm thick monocrystalline Si(001) membrane to a bulk Ge(001) wafer. The membrane bond has an extremely high quality, with an interfacial region of ∼1 nm. No fracture or delamination is observed for temperature changes greater than 350 °C, despite the approximately 2:1 ratio of thermal-expansion coefficients. Both the Si and the Ge maintain a high degree of crystallinity. The junction is highly conductive. The nonlinear transport behavior is fit with a tunneling model, and the bonding behavior is explained with nanomembrane mechanics.

We investigate the electromagnetic response of the concentric multi-ring, or the bull's eye, structure as an extension of the dual-ring metamaterial which exhibits electromagnetically-induced transparency (EIT)-like transmission characteristics. Our results show that adding inner rings produces additional EIT-like peaks, and widens the metamaterial's spectral range of operation. Analyses of the dispersion characteristics and induced current distribution further confirmed the peak's EIT-like nature. Impacts of structural and dielectric parameters are also investigated.

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