Etched Waveguide Grating Variable 1 2 Splitter/Combiner and Waveguide Coupler

Dept. of Electron. Eng., Chinese Univ. of Hong Kong, Shatin
IEEE Photonics Technology Letters (Impact Factor: 2.11). 04/2009; 21(5):268 - 270. DOI: 10.1109/LPT.2008.2010559
Source: IEEE Xplore


We propose and test a silicon waveguide grating which serves dual functions: as a 1 times 2 variable integrated beam splitter/combiner and as an out-of plane diffractive element for coupling light between a single-mode optical fiber and a 500-nm-wide silicon-on-insulator waveguide. An integrated Mach-Zehnder interferometer made with this novel functional element had over 20-dB extinction ratio. The splitting ratio can be tuned by changing the launch position of the optical fiber. The grating coupler had over 36% coupling efficiency and a 1-dB spectral bandwidth of 37 nm.

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    • "Thus this device can be used much like a Mach–Zehnder Interferometer (MZI). Similar phenomenon has also been demonstrated in [13]. If the two arms are equal in length, the light in the two arms is in the same phase, the output power will be doubled compared with that in one arm. "
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    ABSTRACT: A vertical grating coupler on silicon-on-insulator substrates has been designed and demonstrated. The light from a vertical fiber can be coupled in and split equally into two arms with the fiber placed in the grating center. An optical combiner is used to collect the transmission from the two arms. The measured peak coupling efficiency is 37%. Our device can also function like a Mach-Zehnder interferometer. In a device with an arm difference of 30 μm, the normalized transmission spectra of 20-nm free spectral range and more than 12-dB extinction ratio at 1567 nm are obtained.
    IEEE Photonics Technology Letters 02/2013; 25(3):224-227. DOI:10.1109/LPT.2012.2234099 · 2.11 Impact Factor
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    • "The device footprint can thus be significantly reduced without sacrificing the coupling efficiency. With further modification of chirped gratings, grating couplers can also be used as tunable beam splitters [27]. More applications can be found in [9]. "
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    ABSTRACT: We review our recent work on waveguide grating couplers, including an apodized grating coupler with engineered coupling strength to achieve Gaussian-like output profile, which greatly improves the fiber-chip coupling efficiency. We will also discuss a new class of grating couplers involving the use of sub-wavelength nanostructures to engineer the optical properties. Effective medium theory can be used in the design of sub-wavelength structures, which, when properly engineered, can offer broadband coupling and polarization independence. Other applications of waveguide gratings, for example bi-wavelength two dimensional gratings coupler for (de-)multiplexing two different wavelengths, fiber-waveguide hybrid lasers and mid-infrared grating couplers on silicon-on-sapphire wafer will also be briefly discussed.
    Conference on Silicon Photonics VII; 01/2012
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    ABSTRACT: We review our recent work on chirped waveguide gratings for efficient coupling between standard single mode optical fibers and silicon photonic wire waveguides. The use of a linear chirp in grating period reduces the second order Bragg reflection from the waveguide gratings and increases the coupling efficiency for perfectly vertical optical fibers. Measurement results obtained from devices fabricated using deep UV lithography yielded coupling efficiencies of over 34%. Techniques to further improve the coupling efficiency will be discussed. The use of chirped waveguide gratings for low cost photonic packaging and the application of waveguide gratings for splitting/combining light will also be presented.
    Optoelectronic Integrated Circuits Xi, 01/2009;
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