Effect of process parameters on mode conversion in submicron tapered silicon ridge waveguides

Zakriya Mohammed, Bruna Paredes, Mahmoud Rasras

Research output: Contribution to journalArticlepeer-review


The modal property and light propagation in tapered silicon ridge waveguides with different ridge heights are investigated for a silicon on insulator (SOI) platform with a 500 nm silicon (Si) thickness. Mode conversion between the transverse magnetic (TM) fundamental and higher-order transverse electric (TE) modes occurs when light is propagated in a waveguide taper. Such a conversion is due to mode hybridization resulting from the vertical asymmetry of the crosssection in the ridge waveguides. The influence of angled sidewalls and asymmetric cladding on mode conversion is also studied. It is shown that a very long taper length (adiabatic) is required for a complete conversion to take place. Conversely, such mode conversion could be suppressed by designing a short non-adiabatic taper. Our results show that significant improvement in performance metrics can be achieved by considering process parameters’ effect on mode conversion. With an optimum selection of the etching depth and accounting asymmetries due to angled sidewalls and cladding, we demonstrate an 84.7% reduction in taper length (adiabatic) for mode conversion and a 97% efficiency TM preserving taper (ultra-short). The analysis is essential for applications such as compact polarizers, polarization splitters/rotators, and tapers for TM devices.

Original languageEnglish (US)
Article number2366
Pages (from-to)1-12
Number of pages12
JournalApplied Sciences (Switzerland)
Issue number5
StatePublished - Mar 1 2021


  • Adiabatic tapers
  • Angled sidewalls
  • Mode converters
  • Mode hybridization
  • Photonic integrated circuits
  • Polarization splitter and rotators
  • Silicon photonics
  • Tapered waveguides

ASJC Scopus subject areas

  • General Materials Science
  • Instrumentation
  • General Engineering
  • Process Chemistry and Technology
  • Computer Science Applications
  • Fluid Flow and Transfer Processes


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