Browsing by Subject "Microwave photonics"

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Linearity analysis of microwave photonic links for analog signal processing
(2022-07-01) Mokhtari Koushyar, Farzad; Bank, Seth Robert; Vishwanath, Sriram; Campbell, Joe C; Wasserman, Daniel M; Nanzer, Jeffrey
Microwave photonics (MWP) provides wideband, programmable, and low-loss platforms for analog signal processing with high power handling and immunity to electromagnetic interference. Recent advancements in integrated photonics have enabled a variety of on-chip functions for signal processing including true-time delays, tunable switches, high-Q resonators, frequency combs, and so on which make MWP a promising solution for ever-increasing demand of high throughput signal processing. However, achieving the desired dynamic range (DR) from MWP links has remained elusive for signal processing applications. The nonlinear sources of MWP links are studied with a focus on integrated MWP for signal processing. The concept of interference induced distortions (IIDs) are introduced which are generated by passive structures in the link. As demonstrated by the presented theory, simulations, and measurement results, IIDs from passive components can dominate the nonlinear distortions of active components in the link by tens of dB. The impact of parasitic interferometric structures which are formed by design, fabrication, and packaging imperfections on IIDs are discussed along with mitigation solutions. The impact of frequency chirp in active devices on IIDs are studied by simulation and measurement results which shows a magnified sensitivity of IIDs to parasitic interferences when chirp increases. On-chip tap combination, however, is a desired interference in many applications which its implementation remains challenging due to instabilities and limited DR originating from IIDs. Incoherent combiners are proposed in the literature based on multiple PDs or wavelengths at the cost of limiting bandwidth, increasing insertion loss, and necessitating a frequency comb. A tapered-pitch array combiner (TPAC) is introduced here to break the trade-offs in the incoherent and off-chip solutions. TPAC is designed based on the rules derived from the theory and simulation presented for modeling IIDs. A SFDR₃ equal to 107.3 dBc.Hz [superscript 2/3] is measured for the fabricated TPAC combing taps of a 6-tap filter using one wavelength and one PD. A modified TPAC is proposed for further IID suppression using optical phase alignment (OPA) of taps where up to than 26.9 dB IMD₃ suppression is measured. Finally, the stability and tunability of OPA approach are discussed followed by suggestions for future research.
Silicon - polymer hybrid integrated microwave photonic devices for optical interconnects and electromagnetic wave detection
(2015-05) Zhang, Xingyu, 1986-; Chen, Ray T.; Willson, Grant; Alu, Andrea; Akinwande, Deji; Poggio, Enrico
The accelerating increase in information traffic demands the expansion of optical access network systems that require high-performance optical and photonic components. In short-range communication links, optical interconnects have been widely accepted as a viable approach to solve the problems that copper based electrical interconnects have encountered in keeping up with the surge in the data rate demand over the last decades. Low cost, ease of fabrication, and integration capabilities of low optical-loss polymers make them attractive for integrated photonic applications to support futuristic data communication networks. In addition to passive wave-guiding components, electro-optic (EO) polymers consisting of a polymeric matrix doped with organic nonlinear chromophores have enabled wide-RF-bandwidth and low-power active photonic devices. Beside board level passive and active optical components, on-chip micro- or nano-photonic devices have been made possible by the hybrid integration of EO polymers onto the silicon platform. In recent years, silicon photonics have attracted a significant amount of attentions, because it offers compact device size and the potential of complementary metal–oxide–semiconductor (CMOS) compatible photonic integrated circuits. The combination of silicon photonics and EO polymers can enable miniaturized and high-performance hybrid integrated photonic devices, such as electro-optic modulators, optical interconnects, and microwave photonic sensors. Silicon photonic crystal waveguides (PCWs) exhibit slow-light effects which are beneficial for device miniaturization. Especially, EO polymer filled silicon slotted PCWs further reduce the device size and enhance the device performance by combining the best of these two systems. The potential applications of these silicon-polymer hybrid integrated devices include not only optical interconnects, but also optical sensing and microwave photonics. In this dissertation, the design, fabrication, and characterization of several types of silicon-polymer hybrid photonic devices will be presented, including EO polymer filled silicon PCW modulators for on-chip optical interconnects, antenna-coupled optical modulators for electromagnetic wave detections, and low-loss strip-to-slot PCW mode converters. In addition, some polymer-based devices and silicon-based photonic devices will also be presented, such as traveling wave electro-optic polymer modulators based on domain-inversion directional couplers, and silicon thermo-optic switches based on coupled photonic crystal microcavities. Furthermore, some microwave (or RF) components such as integrated broadband bowtie antennas for microwave photonic applications will be covered. Some on-going work or suggested future work will also be introduced, including in-device pyroelectric poling for EO polymer filled silicon slot PCWs, millimeter- or Terahertz-wave sensors based on EO polymer filled plasmonic slot waveguide, low-loss silicon-polymer hybrid slot photonic crystal waveguides fabricated by CMOS foundry, logic devices based on EO polymer microring resonators, and so on.