Fiber-to-chip coupler designed using an optical transformation.

Department of Electrical Engineering and Computer Science, Vanderbilt University, 37235, USA.
Optics Express (Impact Factor: 3.53). 06/2012; 20(13):14705-13. DOI: 10.1364/OE.20.014705
Source: PubMed

ABSTRACT An integrated silicon photonics coupler for fiber to waveguide conversion was designed employing a transformation optics approach. Quasi-conformal mapping was used to obtain achievable material properties, which were realized by a distorted hexagonal lattice of air holes in silicon. The coupler, measuring only 10 μm in length and fabricated with a single-step lithography process, exhibits a peak simulated transmission efficiency of nearly 100% for in-plane mode conversion and a factor of 5 improvement over butt coupling for fiber to waveguide mode conversion in experimental testing.

  • [Show abstract] [Hide abstract]
    ABSTRACT: An integrated vertical coupler that transfers light from the lower passive waveguide to the upper active waveguide in an asymmetric twin-waveguide integration structure (in InGaAsP/InP material system) is designed using transformation optics (TO). The length of the coupler is as short as 3 μm, which is two orders of magnitude shorter than that of traditional tapered couplers. According to three-dimensional full-wave simulations, the designed optimized coupler has a high coupling efficiency of 94.9%, and a low reflection at the wavelength of 1.55 μm. Subsequently, quasi-conformal mapping is employed to reduce the material complexity and to make it possible to realize the coupler by purely using an isotropic dielectric material. Applying TO to integrated photonic devices may motivate new applications, and improve integration density on the InP platform.
    Applied Optics 11/2014; 53(33). DOI:10.1364/AO.53.007831 · 1.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this numerical study, a Gaussian beam-to-slab waveguide coupler for both modes of TM and TE has been studied. For this purpose, a concrete structure is suggested, in which the graded index photonic crystal lens and the slab waveguide are in the same structure composed of Si material, and can be fabricated with a single-step lithography process. For maximum power coupling, half-holes have been used as an input matching layer. Power coupling of 80% over a 450 nm bandwidth for the TM mode, and 60% over a 180 nm bandwidth for the TE mode is achieved.
    Journal of Optics 12/2013; 15(12):5502-. DOI:10.1088/2040-8978/15/12/125502 · 2.01 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The ommatidium of the butterfly's afocal apposition eye exhibits angular performance that can only be achieved by transforming the diffraction pattern of its corneal lens into the fundamental mode of its rhabdom waveguide. A graded index model of the ommatidium has been proposed and verified but the efforts to extract the transformation's underlying physics from it have been hindered by its extreme complexity. Here we numerically investigate the ommatidium model and reveal that the current model, involving only the graded index distribution, is insufficient for the transformation. We further find that adding spatially varying absorption to the existing model dramatically improves its transformation performance, producing near-perfect mode matching with overlap integral exceeding 0.96. Such a combined action of spatially varying index and absorption for microscale mode transformation is new to researchers in optics and biology and will benefit both disciplines.
    Scientific Reports 09/2014; 4:6291. DOI:10.1038/srep06291 · 5.08 Impact Factor