14 March 2013 Highly efficient DBR in silicon waveguides with eleventh order diffraction
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Proceedings Volume 8629, Silicon Photonics VIII; 86290H (2013) https://doi.org/10.1117/12.2004071
Event: SPIE OPTO, 2013, San Francisco, California, United States
The distributed Bragg reflector (DBR) plays a major role in integrated optics. Because of the recent advances of silicon photonics and CMOS electronics in SOI platform, various types of DBR structures are being investigated for integrated optical couplers, filters, (de-)multiplexers, interleavers, Fabry-Perot micro-cavities, laser sources, etc. The first order diffraction gratings in SOI waveguide requires surface relief gratings of period Λ = 225 nm for a DBR response at Λ = 1550 nm. Fabrication of such sub-micron gratings with a uniform period over a length of several mm is really a challenging issue. Here we report the realization of an eleventh order Bragg grating (Λ = 2.6 μm, λB ~ 1564 nm, L = 2.62 mm) on the surface of single-mode rib waveguides. The DBRs and waveguide structures were defined by conventional photolithography and subsequent reactive ion etching processes. The waveguide end-facets were polished suitably before they were taken for characterizations using a tunable laser source (tunability 10 pm) in our free-space waveguide coupling set-up. The characterization results of the fabricated DBRs showed a reflectivity R = 88.32% and FWHM = 2.43 nm. Higher reflectivity and narrower grating response can be achieved by further increasing the grating length. The waveguide loss has been increased (~ 0.5 dB/mm) because of the enhanced surface roughness during the RIE process for grating fabrication. It can be reduced if conventional RIE is replaced by ICP RIE.
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S. Harish, S. Harish, D. Venkitesh, D. Venkitesh, B. K. Das, B. K. Das, } "Highly efficient DBR in silicon waveguides with eleventh order diffraction", Proc. SPIE 8629, Silicon Photonics VIII, 86290H (14 March 2013); doi: 10.1117/12.2004071; https://doi.org/10.1117/12.2004071

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