Wavelength-selective switches have been proposed for datacenter use to enhance datacenter scalability and to aid in meeting ever-increasing traffic demands and the resulting energy consumption. In silicon photonics, photonic integrated circuit (PIC) designers can take advantage of the high contrast between silicon and silicon dioxide---the latter of which acts as the cladding for the silicon nanowire waveguides---to design compact microring resonators with large free spectral ranges (FSRs). Furthermore, as commercial silicon photonics foundry offerings become more widely available, the ability to produce larger and more complicated PICs has become easier, as well as providing a clearer path towards large-scale manufacturability and adoption of such technologies. Thus, ring-based wavelength-selective switches are a particularly well-suited application for silicon photonics. Another major design consideration for PICs is low energy consumption.

A discussion of simulation results from a model for next generation energy efficient photonic links for data centers motivates and the two wavelength-selective switch designs that are presented in this thesis. The first design is an NxN crossbar switch with L ring pairs to route up to L wavelengths at each cross-point. The second design is an NxN ring-assisted Mach-Zehnder interferometer (RAMZI) switch with L ring pairs per switch element. In both designs, multiple ring pairs of differently sized rings were utilized to partition the FSR such that any one ring pair does not have to move far in the spectrum to complete the switching, thus saving in the power consumption.