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arXiv · 1806.08833

Coherency-broken Bragg filters: surpassing on-chip rejection limitations

D. Oser·F. Mazeas·X. Le Roux·D. Perez-Galacho·O. Alibart·S. Tanzilli·L. Labonte·D. Marris-Morini·L. Vivien·E. Cassan·C. Alonso-Ramos
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Abstract

Selective on-chip optical filters with high rejection levels are key components for a wide range of advanced photonic circuits. However, maximum achievable rejection in state-of-the-art on-chip devices is seriously limited by phase errors arising from fabrication imperfections. Due to coherent interactions, unwanted phase-shifts result in detrimental destructive interferences that distort the filter response, whatever the chosen strategy (resonators, interferometers, Bragg filters, etc.). Here we propose and experimentally demonstrate a radically different approach to overcome this fundamental limitation, based on coherency-broken Bragg filters. We exploit non-coherent interaction among modal-engineered waveguide Bragg gratings separated by single-mode waveguides to yield effective cascading, even in the presence of fabrication errors. This technologically independent approach allows seamless combination of filter stages with moderate performance, providing a dramatic increase of on-chip rejection. Based on this concept, we experimentally demonstrate on-chip non-coherent cascading of Si Bragg filters with a record light rejection exceeding 80 dB in the C-band.

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D. Oser, F. Mazeas, X. Le Roux, D. Perez-Galacho, O. Alibart, S. Tanzilli, L. Labonte, D. Marris-Morini, L. Vivien, E. Cassan, C. Alonso-Ramos. 2018-06-19. Coherency-broken Bragg filters: surpassing on-chip rejection limitations. https://arxiv.org/abs/1806.08833

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