The global market demand for higher-bandwidth communication is increasing exponentially. Although optical networks provide high transmission speed using light to transmit signals, a bottleneck-inducing conversion is often needed to perform the processing of optical signals in the electrical domain. Such processing imposes a major barrier that would limit the high transmission speed of fiber-optic communications. This bottleneck conversion may be mitigated by extending signal-processing capabilities directly into the optical domain itself. Thus, I have studied the dynamics of optical polarization in a nonlinear photonic resonator to understand a new optical physical behavior to enhance the capabilities of optical signal processing. I present a theoretical model and experimental investigation to study the simultaneous occurrence of two optical nonlinear processes---nonlinear polarization rotation (NPR) and dispersive optical bistability. These two optical nonlinear processes within a nonlinear photonic resonator produce an optical signal exhibiting hysteresis curves in its state of polarization (SOP). Bistable action accompanied with simultaneous NPR is a significant departure from traditional optical memory, where the optical signal only exhibits hysteresis curves in the output power. Bistable polarization rotation (BPR) term is used to refer to the new physical process of bistable action accompanied by simultaneous NPR. I have leveraged this new physical process of the bistable polarization rotation to realize a hysteresis-shape transformation and optimization. A diversity of hysteresis shapes are demonstrated in optical power including the canonical counter-clockwise (CCW) shape (S-shape), the clockwise (CW) shape (inverted S-shape), and butterfly shapes. The control of the shape is performed downstream of the nonlinear photonic resonator within which the bistable signal is generated. I have derived a mathematical model to study this transformation process. Critical to our model, a generalized Malus' law of a non-ideal linear polarizer and an elliptical input polarization. Since all hysteresis shapes originate from the same bistable signal, all shapes exhibit the same switching input powers. Moreover, the shape-control process is used to enhance the bistable switching contrast to surpass 20 dB for the CCW and CW shapes. Additionally, the new technique of hysteresis shape control enables the ability of simultaneous distribution of the bistable signal into multiple paths. In each path, the optical signal can be independently controlled to produce a hysteresis shape. For example, CCW and CW shapes can be configured in two locations using the same BPR signal. The theoretical and experimental work reported here is carried out for the case of a Fabry-Perot semiconductor optical amplifier as the nonlinear photonic resonator. Both the new physical process and the new control capability presented here are extendable to other nonlinear media (such as Kerr media) and other photonic resonators (such as ring and distributed feedback resonators). The dissertation outcomes detail processes and techniques to enhance the performance of all-optical combinational gates, such as photonic AND and XOR gates, as well as all-optical sequential devices, such as photonic flip-flops.
Library of Congress Subject Headings
Nonlinear optics; Polarization (Light); Optical rotation
Department, Program, or Center
Al Graiti, Saif A., "Polarization Dynamics in Nonlinear Photonic Resonators" (2021). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus