ABSTRACT
Ultra-compact, densely integrated optical components manufactured on a CMOS-foundry platform are highly desirable for optical information processing and electronic-photonic co-integration. However, the large spatial extent of evanescent waves arising from nanoscale confinement, ubiquitous in silicon photonic devices, causes significant cross-talk and scattering loss. Here, we demonstrate that anisotropic all-dielectric metamaterials open a new degree of freedom in total internal reflection to shorten the decay length of evanescent waves. We experimentally show the reduction of cross-talk by greater than 30 times and the bending loss by greater than 3 times in densely integrated, ultra-compact photonic circuit blocks. Our prototype all-dielectric metamaterial-waveguide achieves a low propagation loss of approximately 3.7±1.0 dB/cm, comparable to those of silicon strip waveguides. Our approach marks a departure from interference-based confinement as in photonic crystals or slot waveguides, which utilize nanoscale field enhancement. Its ability to suppress evanescent waves without substantially increasing the propagation loss shall pave the way for all-dielectric metamaterial-based dense integration.
ABSTRACT
We present a direct strip-slot waveguide mode coupler without any auxiliary structures. Contrary to popular belief, an apparent mode mismatch between strip and slot waveguide does not deteriorate conversion efficiency. Separated electric and magnetic field distributions in a slot waveguide lead to highly efficient modal coupling in the direct strip-slot coupler and result in high conversion efficiency. Accurate experimental characterization shows that the direct strip-slot waveguide mode coupler is capable of up to 96% conversion efficiency with a broad bandwidth. Being simplest and of high efficiency, the direct strip-slot waveguide mode coupler can encourage potential applications of slot waveguides.
ABSTRACT
The fundamental quasi-TE and quasi-TM modes of a sub-wavelength strip silicon waveguide are not purely TE or TM as the plane waves in free space. We investigate theoretically and experimentally the far-field polarization compositions of the two waveguide modes after they emanate from the waveguide facet. The measured polarization extinction ratios (PERs) of 31 dB for the quasi-TM mode and 26 dB for quasi-TE mode using free-space polarizers are consistent with our numerical analysis. Moreover, our far-field simulations show that the free-space measurement of PERs is influenced, and in many cases limited, by the sizes of various apertures in the experimental setup. This suggests a potential trade-off between achievable PERs and overall power detection/collection efficiency.
Subject(s)
Models, Theoretical , Refractometry/instrumentation , Refractometry/methods , Silicon/chemistry , Surface Plasmon Resonance/instrumentation , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Light , Scattering, RadiationABSTRACT
We demonstrate 40 dB nonreciprocal transmission at telecommunication wavelengths using an integrated all silicon optical diode. The nonreciprocal transmission ratio is the highest to date for CMOS compatible silicon integrated photonics.
ABSTRACT
An optical diode transmits forward 10Gbps data with less than 0.5dB power penalty, while suppressing and distorting backward data with a 11dB nominal power penalty. The nonreciprocal transmission is also demonstrated with a silicon modulator.
ABSTRACT
We demonstrate an all-optical transistor with the modulated output signal simultaneously having an output/input ratio > 3 dB and ON/OFF ratio > 20 dB. The microring based device is ultra-compact and CMOS compatible.