Abstract

We report on a compact, ultra-broadband, $2\times 2$ adiabatic 3 dB coupler using silicon-on-insulator (SOI) strip waveguides assisted by sub-wavelength gratings (SWGs). In our device, two tapered SWG-assisted SOI strip waveguides achieve an adiabatic mode evolution of the two lowest-order transverse electric modes, in a two-waveguide system, for broadband 3 dB power splitting. Theory predicts that the proposed coupler will operate from 1200 nm to 1700 nm. We have been able to measure the performance of a device with a 15 μm long mode evolution region that achieves even, broadband power splitting over the 185 nm wavelength range of our tunable laser with an imbalance of less than $\pm 0.3\mathrm{dB}$ and with low average excess losses of $<0.11\mathrm{dB}$.

© 2018 Optical Society of America

Broadband 2 × 2 adiabatic 3 dB coupler using silicon-on-insulator sub-wavelength grating waveguides

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