Ruoxi Yang

Efficient light coupling between dielectric slot waveguide and plasmonic slot waveguide

An efficient coupler between a dielectric waveguide and a plasmonic metal-insulator-metal (MIM) waveguide is proposed, modeled, fabricated, and characterized. Based on the platform of a silicon slot waveguide, a quasi-MIM plasmonic junction is formed via e-beam lithography and lift-off process. Coupling efficiency between the silicon slot waveguide and plasmonic waveguide up to 43% is obtained after normalizing to reference waveguides at 1550 nm. This coupling scheme can be potentially used for fast optical switching and small-footprint optical modulation.

Efficiently squeezing near infrared light into a 21nm-by-24nm nanospot

Recent work demonstrated light transmission through deep subwavelength slits or coupling light into waveguides with deep subwavelength dimension only in one direction. In this paper, we propose an approach to squeeze light (lambda = 1550 nm) from a dielectric waveguide into a deep subwavelength spot. Vertical confinement is achieved by efficiently coupling light from a dielectric waveguide into a 20-nm metal-dielectric-metal plasmonic waveguide. The horizontal dimension of the plasmonic waveguide is then tapered into 20 nm. Numerical simulation shows that light fed from a dielectric waveguide can be squeezed into a 21 nm-by-24 nm spot with efficiency 62%.

Deep subwavelength waveguiding and focusing based on designer surface plasmons

We experimentally demonstrate focusing and guiding electromagnetic (EM) waves in a designer surface plasmonic waveguide with deep subwavelength mode cross section. Our experiments show that a metal grating with suitable parameters, functioning as a designer surface plasmonic waveguide, can support deep subwavelength surface modes and the width of the modes can be squeezed also into deep subwavelength by tapering the width of the waveguide. The results provide a new insight into deep subwavelength waveguiding and focusing.

Arbitrary Super Surface Modes Bounded by Multilayered Metametal

Abstract: The dispersion of the fundamental super mode confined along the boundary between a multilayer metal-insulator (MMI) stack and a dielectric coating is theoretically analyzed and compared to the dispersion of surface waves on a single metal-insulator (MI) boundary. Based on the classical Kretschmann setup, the MMI system is experimentally tested as an anisotropic material to exhibit plasmonic behavior and a candidate of “metametal” to engineer the preset surface plasmon frequency of conventional metals for optical sensing applications. The conditions to obtain artificial surface plasmon frequency are thoroughly studied, and the tuning of surface plasmon frequency is verified by electromagnetic modeling and experiments. The design rules drawn in this paper would bring important insights into applications such as optical lithography, nano-sensing and imaging. Keywords: surface waves; metal-insulator multilayer; effective surface plasmon frequency 1. Introduction The multilayer metal-insulator (MMI) stack system (also termed as metal-dielectric composite or MDC) has been widely used as an optically-anisotropic composite [1–3], utilized for imaging [4–8], optical lithography [9] and subwavelength sensing/detecting [10]. One of the most attractive features of this stratified medium is its ability to engineer the dispersion of engaged electromagnetic waves, and

Integration of 3D plasmonic devices with silicon-on-insulator-based optical circuitry

We demonstrate integrated plasmonic devices on silicon-on-insulator (SOI) substrate for photon-plasmon conversion and plasmonic mode transformation at near-infrared frequency. The plasmonic junction converts photons to surface plasmons and then back to photons with 7.35 dB conversion loss, and has successfully focused multimode plasmonic propagation to deep subwavelength (80 nm by 50 nm) single mode propagation with 2.28 dB/μm propagation loss. The integration approach leads to a robust and versatile platform for 3D nanoplasmonic gauges potentially functional in ultra-fast communications and optical sensing.

Semiconductor-coated deep subwavelength spoof surface plasmonic waveguide for THz and MIR applications

We propose integrated waveguides for terahertz (THz) and mid-infrared (MIR) applications on wafer platform. Based on the prototype of spoof plasmonic waveguides consisting of textured metallic surface, we explore the possibility of coating periodic metallic pattern with silicon (at 0.6 THz) or germanium (at MIR region of 30 THz) to further shrink the relative mode size of propagation spoof plasmonic waves. Numerical modeling via 3D finite-difference time-domain (FDTD) has shown deep sub-wavelength mode confinement in transverse directions to smaller than λ/50 by λ/50, with an estimated propagation loss of less than 0.1 dB for each repetitive unit.

Experimental demonstration of linear deep subwavelength spoof surface plasmonic waveguides

Due to the large transverse mode size in the frequency regime far below plasma frequency, some important applications of surface plasmons in the THz or microwave frequency regime have been limited where deep subwavelength optical devices are a critical technique. Here we experimentally demonstrated focusing and guiding electromagnetic (EM) waves in a 3D spoof surface plasmonic waveguide, which is a row of rectangular rods patterned on an aluminum slab. The maximum of the mode size can be mapped in the middle plane of two neighboring rods. The mode size slightly varies with different frequencies and minimizes at 0.04λ-by-0.03λ at 2.25 GHz. Moreover, due to the tight binding of surface waves, the decrease of the waveguide width does not significantly affect the dispersion of the guided modes. This fact enables the mode tapering in the transverse direction from a wide waveguide into deep subwavelength waveguide with high efficiency. To this end, a tapered spoof surface plasmonic waveguide was fabricated as the input is the uniform spoof surface plasmonic waveguide and its performance was investigated in experiments. From the experimental results, as the EM waves propagate in the taper, the mode size becomes smaller and smaller with the intensity gradually increasing, and eventually EM waves are coupled into the deep subwavelength mode.

Experimental Demonstration of Deep Subwavelength Waveguiding Based on Designer Surface Plasmons

We experimentally demonstrate squeezing and guiding electromagnetic (EM) waves in a designer surface plasmonic waveguide with mode cross section down to 0.04?-by-0.03?.