In this paper, we propose a modified platform for on-chip integrated photonics. The platform allows one to efficiently connect a tapered optical fiber or fiber lens to an on-chip waveguide with high alignment precision and to mechanically fix the fiber on the chip to prevent defocusing, lateral shift, and angular detuning during device operation. The metal screen of the connector-made of gold-prevents any penetration of the background radiation into the optical circuit, something which is not possible to achieve in all the cases using tapers or grating couplers. We performed impedance-matching analysis based on transmission line theory and numerically optimized the platform, allowing us to achieve a tapered fiber mode to on-chip waveguide mode transformation efficiency as high as 96% (−0.177 dB) at wavelengths of 785 and 1550 nm. The platform bandwidth (transformation efficiency ࣙ80%) is 151 nm. At the same time, transformation efficiency is stable (reduction less than 1%) in an offset range of ±2 nm-enough for modern on-chip and off-chip coherent light sources. The horizontal and vertical lateral alignment tolerances for the platform are 700 and 600 nm, respectively, at a transformation efficiency ࣙ80% while the longitudinal alignment tolerance is approximately 70 nm. Due to the relatively high lateral and longitudinal tolerances, it is possible to produce the platform at high efficiency using existing fabrication nanotechnologies. We believe that this platform accelerates the realization of fully on-chip Raman spectroscopes and may be of practical importance in other on-chip integrated photonic devices.

In this paper, we provide a detailed three-dimensional numerical analysis of the optical properties of common and modified bowtie aperture antennas integrated onto a silicon waveguide platform, to discuss the influence of geometrical parameters on the electric field enhancement factor and waveguide transmission when such antennas are excited by the evanescent field of the Si waveguide mode. We demonstrate that waveguide transmission is severely affected by the interference between Si waveguide modes and surface plasmon polariton modes excited in the antenna, while the antenna's field enhancement factor is mainly determined by the localized surface plasmon resonance occurring in its nano-gap. These mechanisms lead to a mismatch between the wavelength at which the antenna's field enhancement factor is maximized, and the wavelength at which transmission through the Si waveguide is minimized, suggesting that in some multi-mode cases, the optical properties of integrated nanoantennas determined through direct measurement of Si waveguide transmission may be misleading. Methods for improving the electric field enhancement (such that it has a bigger modulation depth) that have minimal impact on the resonant wavelength, and for improving the shape and location of the corresponding hot spot of the bowtie aperture antennas, are also discussed and analyzed. We believe that this analysis will be helpful in design of on-chip bowtie-type optical antennas for surface enhanced Raman spectroscopy, near-field optical microscopy, high sensitivity detection, and plasmonic optical tweezers.