Grating and ring based devices on SOI platform

Silicon is the dominant material in the electronics industry, and is emerging as a promising candidate for photonics.By taking advantage of existing complementary metal-oxide semiconductor (CMOS) foundries, low cost devices on the silicon-oninsulator platform are developed to address issues such as compactness, manufacturability, stability, and reliability.Active and passive photonic devices as well as integrated subsystems with high performance have been demonstrated.However, most components are under development, and various requirements need to be fulfilled before commercialization.Within the context of silicon photonics, we demonstrate several devices with improved performance using simple grating or ring structures.These devices can be used as fundamental building blocks for system level integration or individual packaged products.We start by reviewing the background of silicon photonics.A brief history of silicon photonics is introduced, followed by various fundamental building blocks designed on SOI platform.Two fabrication techniques used are described.A theoretical and experimental study of interferometric structure based filters is provided next, such as bandpass filters based on Michelson interferometers incorporating Bragg gratings, spectral shapers based on Bragg gratings in Sagnac loops, and OADMs based on Mach-Zehnder interferometers incorporating Bragg gratings (BGs).These filters can be used to provide wavelength selectivity in optical communications applications or in microwave photonics.For example, using the spectral shaper, we obtain chirped microwave pulses with central frequencies tuning range from ~10 GHz to ~30 GHz and an RF chirp rate of ~20 GHz/ns with both positive and negative signs.The OADMs exhibit transmission isolation as high as 45 dB and are tolerant to wavelength drift and misalignment between the transmitter and OADM.Multichannel OADMs are also demonstrated with similar low crosstalk performance.Finally, subwavelength gratings (SWG) are studied.SWGs have flexibility in tailoring the effective index, and SWG devices with breakthrough performance can be realized with reduced cost and footprint.We designed BGs, ring resonators, and delay lines based on SWG.We demonstrated SWG BGs with 3 dB bandwidths ~ 0.5 nm and a peak reflectivity as high as 94.4% in the C-band.The SWG ring resonators exhibit a Q-factor as high as 4,800 and the SWG race-track resonators exhibit an extinction ratio as large as 33 dB.For the SWG delay line demonstration, we achieve ~30 ps time-delay using the same length of SWG waveguides with the only difference being a 30% change in duty-cycle.These devices are compatible with other SWG building blocks and can be used to develop more complex devices with enhanced functionality for applications in communications and sensing.Life is not easy for any of us.But what of that?We must have perseverance and above all confidence in ourselves.We must believe that we are gifted for something, and that this thing, at whatever cost, must be attained.

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