Broadband polarization independent nanophotonic coupler for silicon waveguides with ultra-high efficiency.

Coupling of light to and from integrated optical circuits has been recognized as a major practical challenge since the early years of photonics. The coupling is particularly difficult for high index contrast waveguides such as silicon-on-insulator, since the cross-sectional area of silicon wire waveguides is more than two orders of magnitude smaller than that of a standard single-mode fiber. Here, we experimentally demonstrate unprecedented control over the light coupling between the optical fiber and silicon chip by constructing the nanophotonic coupler with ultra-high coupling efficiency simultaneously for both transverse electric and transverse magnetic polarizations. We specifically demonstrate a subwavelength refractive index engineered nanostructure to mitigate loss and wavelength resonances by suppressing diffraction effects, enabling a coupling efficiency over 92% (0.32 dB) and polarization independent operation for a broad spectral range exceeding 100 nm.

[1]  T Pinguet,et al.  A Grating-Coupler-Enabled CMOS Photonics Platform , 2011, IEEE Journal of Selected Topics in Quantum Electronics.

[2]  Ultranarrow Silicon Inverse Taper Waveguide Fabricated with Double-Patterning Photolithography for Low-Loss Spot-Size Converter , 2012 .

[3]  Philippe Lalanne,et al.  High-order effective-medium theory of subwavelength gratings in classical mounting: application to volume holograms , 1998 .

[4]  A. Ortega-Moñux,et al.  Single etch grating couplers for mass fabrication with DUV lithography , 2012 .

[5]  Manfred Berroth,et al.  Bridging the gap between optical fibers and silicon photonic integrated circuits. , 2014, Optics express.

[6]  Siegfried Janz,et al.  Waveguide subwavelength structures : a review of principles and applications , 2014 .

[7]  Alireza Samani,et al.  Focusing-curved subwavelength grating couplers for ultra-broadband silicon photonics optical interfaces. , 2014, Optics express.

[8]  T. Tsuchizawa,et al.  Low loss mode size converter from 0.3 /spl mu/m square Si wire waveguides to singlemode fibres , 2002 .

[9]  F. Lederer,et al.  Closed-form expression for the scattering coefficients at an interface between two periodic media , 2011 .

[10]  Siegfried Janz,et al.  Waveguide sub‐wavelength structures: a review of principles and applications , 2015 .

[11]  P. Verheyen,et al.  High-efficiency fiber-to-chip grating couplers realized using an advanced CMOS-compatible silicon-on-insulator platform. , 2010, Optics express.

[12]  Xia Chen,et al.  Polarization-independent grating couplers for silicon-on-insulator nanophotonic waveguides. , 2011, Optics letters.

[13]  I Molina-Fernández,et al.  Fiber-chip grating coupler based on interleaved trenches with directionality exceeding 95. , 2014, Optics letters.

[14]  Ke Xu,et al.  Wideband subwavelength gratings for coupling between silicon-on-insulator waveguides and optical fibers. , 2012, Optics letters.

[15]  Siegfried Janz,et al.  Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure. , 2010, Optics letters.

[16]  H. Tsang,et al.  Apodized Waveguide Grating Couplers for Efficient Coupling to Optical Fibers , 2010, IEEE Photonics Technology Letters.

[17]  P. Cheben,et al.  Subwavelength waveguide grating for mode conversion and light coupling in integrated optics. , 2006, Optics express.

[18]  Yunhong Ding,et al.  Ultra-high-efficiency apodized grating coupler using a fully etched photonic crystal , 2013, 2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR).

[19]  Florian Merget,et al.  Edge Couplers With Relaxed Alignment Tolerance for Pick-and-Place Hybrid Integration of III–V Lasers With SOI Waveguides , 2014, IEEE Journal of Selected Topics in Quantum Electronics.

[20]  X. Le Roux,et al.  Design, Realization, and Characterization of 3-D Taper for Fiber/Micro-Waveguide Coupling , 2006, IEEE Journal of Selected Topics in Quantum Electronics.

[21]  Chao Li,et al.  CMOS-compatible high efficiency double-etched apodized waveguide grating coupler. , 2013, Optics express.

[22]  S. M. Rytov,et al.  Electromagnetic Properties of a Finely Stratified Medium , 2014 .

[23]  M. Lipson,et al.  Nanotaper for compact mode conversion. , 2003, Optics letters.

[24]  T. Krauss,et al.  Compact and Highly Efficient Grating Couplers Between Optical Fiber and Nanophotonic Waveguides , 2007, Journal of Lightwave Technology.

[25]  Pavel Cheben,et al.  Analysis of couplers between photonic nanowires and subwavelength grating waveguides , 2013, Europe Optics + Optoelectronics.

[26]  Tymon Barwicz,et al.  An o-band metamaterial converter interfacing standard optical fibers to silicon nanophotonic waveguides , 2015, 2015 Optical Fiber Communications Conference and Exhibition (OFC).

[27]  Siegfried Janz,et al.  Refractive index engineering with subwavelength gratings for efficient microphotonic couplers and planar waveguide multiplexers. , 2010, Optics letters.

[28]  J. Fédéli,et al.  Low-Loss ($<$ 1 dB) and Polarization-Insensitive Edge Fiber Couplers Fabricated on 200-mm Silicon-on-Insulator Wafers , 2010, IEEE Photonics Technology Letters.