Metamaterials in waveguide to fiber couplers

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Citation (Scopus)


Coupling light into or out of a photonic integrated circuit is often accomplished by establishing a vertical link between a single mode optical fibre and a resonant waveguide grating, which is then followed by a tapered and a single mode waveguides. For a chip to fibre coupler, the period of the diffraction grating is often apodized to achieve an optimal beam profile at the input of the optical fibre. The tapered waveguide operates as a spot-size converter, expanding laterally the light beam in the single mode waveguide, to match the profile of the fundamental mode of the resonant waveguide grating. In this work, we propose using subwavelength structures to modulate the refractive index of the tapered waveguide for the lateral expansion of the light beam, when operating at the 1550 nm wavelength. The engineered graded index structure is simulated through adequate numerical methods and its performance is analysed in terms of efficiency and mode profile matching. With our proposed inverted taper waveguide, we were able to obtain an adiabatic power transfer and coupling efficiency with the TE fundamental mode of -0.26 dB and -0.92 dB, respectively. This performance has been achieved in a structure 11.1 μm long and 14.27 μm wide. Furthermore, the obtained fields were fed into a resonant waveguide grating to evaluate the coupling efficiency into the fundamental mode of an optical fibre, resulting in an expected performance decrease of 0.1 dB and ∼0.6 dB by comparing respectively with the power transfer and coupling efficiency of the resonant waveguide grating when propagating the calculated TE0 mode.

Original languageEnglish
Title of host publicationPhysics and Simulation of Optoelectronic Devices XXX
EditorsBernd Witzigmann, Marek Osinski, Yasuhiko Arakawa
PublisherSpie -- the Int Soc for Optical Engineering
Number of pages15
ISBN (Electronic)9781510648623
ISBN (Print)9781510648616
Publication statusPublished - 2022
EventPhysics and Simulation of Optoelectronic Devices XXX 2022 - Virtual, Online
Duration: 20 Feb 202224 Feb 2022

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferencePhysics and Simulation of Optoelectronic Devices XXX 2022
CityVirtual, Online


  • graded index taper waveguide
  • metamaterial
  • resonant waveguide grating
  • waveguide/fibre coupler


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