Low-loss polysilicon subwavelength grating waveguides and narrowband Bragg reflectors in bulk CMOS

The performance of a photonic functional device in bulk CMOS has been limited by the high propagation loss in polysilicon strip waveguide. Based on the zero-process-change methodology, we successfully reduce the propagation loss of polysilicon waveguide from 112 dB/cm to only 38 dB/cm by solely engi...

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Veröffentlicht in:Optics express 2020-03, Vol.28 (6), p.7786-7798
Hauptverfasser: Hung, Yung-Jr, Tang, Cheng-Tse, Chen, Tse-Hung, Yen, Tzu-Hsiang, Tsai, Ming-Ju, Lee, San-Liang
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Sprache:eng
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Zusammenfassung:The performance of a photonic functional device in bulk CMOS has been limited by the high propagation loss in polysilicon strip waveguide. Based on the zero-process-change methodology, we successfully reduce the propagation loss of polysilicon waveguide from 112 dB/cm to only 38 dB/cm by solely engineering the waveguide geometry for the first time. Low propagation loss is attributed to a significantly reduced optical overlap factor of 0.09 to bulk polysilicon using subwavelength grating (SWG) waveguide design. These findings prompt us to demonstrate a narrowband SWG-based cladding-modulated Bragg reflector in bulk CMOS, which provides a full-width at half maximum (FWHM) of 1.63 nm, an extinction ratio of 24.5 dB, and a reduced temperature sensitivity of 27.3 pm/°C. Further reducing the FWHM to 0.848 nm is also achieved by decreasing the grating coupling strength. We believe the achievements made in this work validate a promising design path towards practical photonic-electronic applications in bulk CMOS.
ISSN:1094-4087
1094-4087
DOI:10.1364/OE.381894