Silicon-based technologies provide an ideal platform for the monolithic integration of photonics and microelectronics. In this context, a variety of passive and active silicon photonic devices have been developed to operate at telecom and datacom wavelengths, at which silicon has minimal optical absorption -due to its bandgap of 1.12 eV. Although in principle this transparency window limits the use of silicon for optical detection above 1.1 µm, in recent years tremendous advances have been achieved in the field of all-silicon subbandgap photodetectors at telecom and datacom wavelengths -by taking advantage of new emerging materials and structures. In this paper, a review of the state of the art is presented.Devices based on defect-mediated absorption, two-photon absorption and the internal photoemission effect are reported, their working principles are elucidated and their performance discussed and compared.

Abstract-The bandwidth bottleneck looming for traditional electronic interconnects has driven the consideration of optical communications technologies as realized through the complementary metal-oxide-semiconductor-compatible silicon nanophotonic platform. Within the silicon photonics platform, silicon microring resonators have received a great deal of attention for their ability to implement the critical functionalities of an on-chip optical network while offering superior energy-efficiency and small footprint characteristics. However, silicon microring-based structures have a large susceptibility to fabrication errors and changes in temperature. Integrated heaters that provide local heating of individual microrings offer a method to correct for these effects, but no largescale solution has been achieved to automate their tuning process. In this context, we present the use of dithering signals as a broad method for automatic wavelength tuning and thermal stabilization of microring resonators. We show that this technique can be manifested in low-speed analog and digital circuitry, lending credence to its ability to be scaled to a complete photonic interconnection network.Index Terms-Frequency locked loops, multi-processor interconnection, optical interconnects, optical resonators.

A defect-enhanced silicon photodiode and heater are integrated with and used to thermally stabilize a microring modulator. These optoelectronic components are interfaced with external control circuitry to create a closed-looped feedback system for thermally stabilizing the microring modulator. The thermal stabilization system enables the microring modulator to provide error-free 5-Gb/s modulation while being subjected to thermal fluctuations that would normally render it inoperable.

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