| In this dissertation, the results of theoretical investigations of the critical design concepts of novel optical devices used in photonic links for Radio Frequency (RF) transmission and processing are presented.; The first chapter provides an introduction to the basics of RF photonic links and lists the set of competitive advantages enjoined by them. Also in this chapter a detailed comparison of characteristics of frequency modulation (FM) and intensity modulation (IM) schemes is performed and conclusion is drawn that favors FM scheme due to its useful bandwidth, higher sensitivity, and link-gain. The crucial components in the FM photonic links are also reviewed in this chapter.; In Chapter Two, the design issues related to FM laser source are explored. Alternative methods of FM using density of carriers in the gain section or Quantum-confined Stark effect (QCSE) in separate phase section are investigated and the second scheme is shown to have an advantage. Both Distributed Feedback (DFB) and Distributed Bragg Reflector (DBR) schemes are shown to be able to attain single mode operation. Then we tackle two problems plaguing the FM lasers---how to increase the FM efficiency while maintaining the single mode operation and how to suppress spurious intensity modulation. We propose effective solutions for both problems and estimate the improvements achievable with these schemes.; Chapter Three is devoted to the second critical component of the FM RF link---frequency discriminator. To attain high slope, integrable, and linearized FM discrimination, we propose and model in detail three distinct discriminator schemes---one using the chirped Bragg gratings with loss, one using coupling to radiation modes in gratings and one based on combination of Mach-Zehnder interferometer with ring resonators.; In Chapter Four, possible enhancements of the external modulators used in RF photonic links are explored. One scheme involves linearization of Mach-Zehnder modulator using ring resonators; the other involves using slow wave propagation in traveling wave modulator. Experimental results are reported on the modification of the group velocity in the Ti-diffused LiNbO3 waveguides with dual Bragg gratings.; Chapter Five gives the summary of major contributions of this dissertation and outlines directions for the possible future work. |
