Browsing by Subject "Crystal optics"
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Item Photonic crystal waveguides based active and passive devices for phased array antenna systems(2006) Jiang, Yongqiang; Chen, Ray T.Photonic crystals are a new class of artificial optical materials with periodic dielectric structures, which promise to miniaturize photonic devices. Optical true-time delay techniques are an emerging technology for the squint-free beam steering of phased array antennas with wide bandwidth, reduced system weight and size, and low electromagnetic interference. In this dissertation, highly dispersive photonic crystal fibers based optical true time delay modules were designed, integrated and characterized. An ultra-compact optical modulator based on silicon photonic crystal waveguides for phased array antenna systems was designed, fabricated and characterized. A true-time delay controlled X-band phased array antenna system was designed, integrated, and characterized. The continuously tunable optical true time delay module employ highly dispersive photonic crystal fibers connected with various lengths of nondispersive telecom fiber. A highly dispersive silica photonic crystal fiber using dual-core structure was developed to achieve high chromatic dispersion. By employing photonic crystal fibers to increase the dispersion, the true time delay module size can be proportionally reduced. A 4-element linear X-band phased array antenna system using photonic crystal fibers based true-time delay modules was developed and demonstrated. The beam steering angle of the phased array antenna system was scanned by tuning the optical wavelength. Squint-free operation is experimentally confirmed. An optical modulator based on silicon photonic crystal waveguides was developed, which could be implemented in phased array antenna systems to replace conventional optical modulators. Silicon photonic crystal waveguides were firstly developed and demonstrated. Photonic crystal line-defect waveguides showed high group velocity dispersion and slow photon effect near the transmission band edge. An ultra-compact silicon electro-optic modulator based on silicon photonic crystal waveguides was proposed, developed and demonstrated for the first time. Modulation operation was demonstrated by carrier injection into an 80 µm-long silicon photonic crystal waveguide of a Mach-Zehnder interferometer structure.Item Photonic crystal-based passive and active devices for optical communications(2008-08) Chen, Xiaonan, 1980-; Chen, Ray T.With the progress of microfabrication and nanofabrication technologies, there has been a reawakened interest in the possibility of controlling the propagation of light in various materials periodically structured at a scale comparable to, or slightly smaller than the wavelength. We can now engineer materials with periodic structures to implement a great variety of optical phenomena. These include well known effects, such as dispersing a variety of wavelength to form a spectrum and diffracting light and controlling its propagation directions, to new ones such as prohibiting the propagation of light in certain directions at certain wavelengths and localizing light with defects in some artificially synthesized dielectric materials. Advances in this field have had tremendous impact on modern optical and photonic technologies. This doctoral research was aimed at investigating some of the physics and applications of periodic structures for building blocks of the optical communication and interconnection system. Particular research emphasis was placed on the exploitation of innovative periodic structure-based optical and photonic devices featuring better functionality, higher performance, more compact size, and easier fabrication. Research topics extended from one-dimensional periodic-structure-based true-time delay module, to two-dimensional periodic-structure-based silicon photonic-crystal electro-optic modulators. This research was specifically targeted to seek novel and effective solutions to some long-standing technical problems, such as slow switching speed, large device size, and high power consumption of silicon optical modulators, among others. For each subtopic, research challenges were presented and followed by the proposed solutions with extensive theoretical analysis. The proposals were then verified by experimental implementations. Experimental results were carefully interpreted and the future improvements were also discussed.