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Polarization-transparent microphotonic devices in the strong confinement limit


Microphotonic structures that strongly confine light, such as photonic crystals and micron-sized resonators, have unique characteristics that could radically advance technology1,2,3,4,5,6. However, such devices cannot be used in most applications because of their inherent polarization sensitivity; they respond differently to light polarized along different axes7,8,9. To take advantage of the distinctive properties of these structures, a general, integrated, broadband solution to their polarization sensitivity is needed. Here, we show the first demonstration of such a solution. It enables arbitrary, polarization-sensitive, strong-confinement (SC) microphotonic devices to be rendered insensitive (transparent) to the input polarization at all wavelengths of operation. To test our approach, we create the first polarization-transparent add–drop filter from polarization-sensitive microring resonators. It shows almost complete elimination of polarization sensitivity over the 60-nm bandwidth measured, while maintaining outstanding filter performance. This development is a milestone for SC microphotonics, allowing the applications of photonic-crystal and microring devices to several areas, including communications, spectroscopy and remote sensing.

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Figure 1: Integrated polarization diversity scheme.
Figure 2: Design of the polarization-transparent optical add–drop filter (OADF).
Figure 3: Fabricated polarization-transparent OADF.
Figure 4: Spectral response of a fabricated polarization-transparent OADF for 40 randomly chosen polarization states at each wavelength.


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This project resulted from the vision of Hermann A. Haus. We thank Minghao Qi for contributing to the development of the fabrication process. This work was supported by Pirelli Labs S.p.A (Milan, Italy) through the leadership of M. Romagnoli and made use of MIT's SEBL facility in the Research Laboratory of Electronics (SEBL at RLE).

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T.B. and M.R.W. contributed equally to this work. T.B. developed the nanofabrication techniques required for this work and created the polarization-transparent OADF. M.R.W. proposed the integrated-polarization-diversity approach, designed the PSR and the waveguide crossings, and co-designed the microring filters.

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Correspondence to Tymon Barwicz.

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The authors declare no competing financial interests.

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Barwicz, T., Watts, M., Popović, M. et al. Polarization-transparent microphotonic devices in the strong confinement limit. Nature Photon 1, 57–60 (2007).

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