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Open Access Publications from the University of California

Giant birefringence silicon nanophotonic multi-slot waveguides for optical delay line applications

  • Author(s): Yang, Shun-Hui
  • et al.

With the vast increase in the amount of data transfer around the world each day, there has been a necessity for rapid development in optical communication and signal processing technologies. Using an all optical scheme to replace the current electronic format shows promise in the next generation of signal processing. In an optical processing system, the optical delay line buffer is a critical component. While significant research has been done on novel delay line schemes, it will be necessary to develop a CMOS compatible technology capable of integration onto a micro-chip. In this thesis, a multi- slotted waveguide has been studied as a novel element for optical delay line applications. Detailed simulations show large birefringence between the polarization modes in a multi-slot waveguide which enables the creation of a time delay. The birefringence was optimized by the use of fabricated structures with high refractive index contrast to create a compact single-mode waveguide, through the etching of deep sub-wavelength channels within the waveguide. The channels (comprising Si ribs and air gaps) are strongly coupled in the near field. The multi-slot waveguides were successfully fabricated and giant birefringence property was demonstrated. The obtained value of [Delta]ng was ̃1.6 at 1.55[mu]m. When used as a polarization-selective delay line element, the delay- bandwidth product was computed to be 40/mm which is comparable to existing delay line schemes. A mode shaping tool was also designed to shape the near field mode and achieve almost identical coupling to external optics. This reduces the polarization dependent loss. This work shows the potential of multi-slot waveguides for future optical communication applications

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