Nanoscale Metamaterial Optical Waveguides with Ultrahigh Refractive Indices

We propose deep-subwavelength optical waveguides based on metal-dielectric multilayer indefinite metamaterials with ultrahigh effective refractive indices. Waveguide modes with different mode orders are systematically analyzed with numerical simulations based on both metal-dielectric multilayer structures and the effective medium approach. The dependences of waveguide mode indices, propagation lengths and mode areas on different mode orders, free space wavelengths and sizes of waveguide cross sections are studied. Furthermore, waveguide modes are also illustrated with iso-frequency contours in the wave vector space in order to investigate the mechanism of waveguide mode cutoff for high order modes. The deep-subwavelength optical waveguide with a size smaller than {\lambda}0/50 and a mode area in the order of 10-4 {\lambda}02 is realized, and an ultrahigh effective refractive index up to 62.0 is achieved at the telecommunication wavelength. This new type of metamaterial optical waveguide opens up opportunities for various applications in enhanced light-matter interactions.Comment: 22 pages, 8 figure

5 x 20 Gb/s III-V on silicon electroabsorption modulator array heterogeneously integrated with a 1.6nm channel-spacing silicon AWG

We demonstrate a five-channel wavelength division multiplexed modulator module that heterogeneously integrates a 1.6nm channel-spacing arrayed-waveguide grating and a 20Gbps electroabsorption modulator array, showing the potential for 100 Gbps capacity on a 1.5x0.5 mm(2) footprint

Radio Frequency Exposure Compliance of Multiple Antennas for Cellular Equipment Based on Semidefinite Relaxation

Human exposure to radio frequency (RF) electromagnetic fields should not exceed the exposure limits set by the relevant regulatory guidelines. In this paper, we provide approaches to determine upper bounds of maximum exposure from multiple antennas. When the total transmitted power is fixed, the maximum exposure can be determined by an eigenvalue decomposition. If an individual antenna has additional power constraint, the exposure maximization problem can be relaxed to a semidefinite program. Two case studies are given to demonstrate the approaches to the maximum exposure of cellular equipment using multiple antennas. The methods and the obtained results provide valuable insights into RF compliance procedures of cellular equipment

Experimental demonstration of an ultracompact polarization beamsplitter based on a multimode interference coupler with internal photonic crystals

The fabrication and characterization of a compact InP-based polarization beamsplitter (PBS) is presented. A multimode interference (MMI) coupler with an internal air hole photonic crystal (PhC) section is utilized to separate the two polarizations. The PhC structure in the middle of the MMI is polarization dependent, so that one polarization is reflected and the other one is transmitted; both are collected by the respective output ports of the MMI coupler. The obtained experimental results show that the PBS as short as ∼400 μm has an extinction ratio as large as 15 dB