Polymer-based electro-optical modulators are, generally, applicable to many fields but their applications to analog optical links and silicon photonic integrated circuits are specifically emphasized in this dissertation. This dissertation aims to improve the linearity characteristics of polymer-based electro-optic modulators for their practical application in high speed analog optical links. Domain-inversion technique is employed to linearize a two-section Y-fed directional coupler modulator. The spurious free dynamic range as high as 119dB/Hz2/3 has been demonstrated with 11dB enhancement over the conventional Mach-Zehnder modulator at low frequency. For high speed modulation, a traveling wave electrode with low RF loss and large bandwidth is designed and installed in a linearized Y-fed directional coupler modulator. The spurious free dynamic range has been measured in the range of 110±3dB/Hz2/3 at 2~8GHz frequency. For digital application of polymer-based electro-optic modulators, a hybrid silicon photonic crystal waveguide modulator was investigated with focus on size-reduction and electro-optic efficiency enhancement. The slow group velocity of photonic crystal waveguides promises two orders of magnitude size-reduction in device footprint compared with the conventional strip waveguide. Infiltration of an electro-optic polymer into the slot waveguide can infuse silicon with nonlinear optical properties. To actualize these benefits of a hybrid silicon photonic crystal waveguide modulator, nano-fabrication process was developed and optimized in this work. / text

Bandwidth demands in global telecommunication infrastructures continue to rise and new optical techniques are needed to deal with massive data flows. Generating high bandwidth signals (> 40 GHz) using conventional modulation techniques is hindered by material limitations and fabrication complexities. Similarly, controlling such high bandwidths in both the temporal and spectral domain becomes more problematic using conventional electronic processes. Advances in electro-optic organic materials, fibers/micro-fluidics integration, and nonlinear optics have significant potential for higher bandwidth modulation and temporal/spectral control. The work presented in this dissertation demonstrates the use of various nonlinear optical effects in new photonic device and system designs towards the generation and manipulation of highspeed optical pulses. First, an all fiber-based system utilizing an integrated carbon disulfide-filled liquidcore optical fiber (i-LCOF) and co-propagating pulses of comparable temporal lengths is presented. The slow light effect was observed in 1-meter of i-LCOF, where 18 ps pulses were delayed up to 34 ps through the use of stimulated Raman scattering. Delays greater than a pulse width indicate a potential application as an ultrafast controllable delay line for time division multiplexing in multi-Gb/s telecommunication systems. Similarly, an optically tunable frequency shift was observed using this system. Pulses experienced a full spectral bandwidth shift at low peak pump powers when utilizing the Raman-induced frequency shift and slow light effects. Numerical simulations of the pulse-propagation equations agree well with the observed shifts. Included in our simulations are the contributions of both the Raman cross-frequency shift and slow light effects to the overall frequency shift. These results make the system suitable for numerous applications including low power wavelength converters. Second, a silica/electro-optic (EO) polymer phase modulator with an embedded bowtie antenna is proposed for use as a microwave radiation receiver. The detection of high-frequency electromagnetic fields has been heavily studied for wireless data transfer. Recently there has been growing interest in the field of microwave photonics. We present the design and optimization of a waveguide with an EO polymer core and silica/sol-gel cladding. The effect of electrodes on the insertion losses and poling efficiency are also analyzed, and conditions for low-loss and high poling efficiency are established. Experimental results for a fabricated device with microwave-response between 10 - 14 GHz are presented. Finally, we present the design for a fast optical switch incorporating silicon as the passive waveguide structure and EO polymer as the active material. The design uses a simple directional coupler with coplanar electrodes and promises to have low cross-talk and high switching speed (on the order of nanoseconds). An initial design for a 1x2 switch is fabricated and tested, and future optimization processes are also presented.

Fabry-Perot interferometer (FPI) devices are designed based on the electro-optic (EO) activities of nonlinear optical (NLO) polymer materials for tunable optical filters (TOFs) and spatial light modulators (SLMs). The performance of the EO polymer based FPI devices is theoretically modeled with first order approximation on the FPI cavity interface phase dispersion. NLO materials including TCBD coupled hybrid sol-gel, AJL8/amorphous polycarbonate (APC), and AJLS102/APC are incorporated in FPI structures with distributed Bragg reflector mirrors and transparent conducting oxide electrodes for TOFs. High finesse (over 200), low drive voltage (10 dB isolation ratio with 5 V), and fast settling time (about sub-millisecond) are achieved. The physical origin of the large tunabilities is explored and the contributions from EO effect and inverse piezoelectric effect are analyzed. EO polymer SWOHF3ME/APC is employed in FPI devices with simplified structures for SLMs. Modulation beyond megahertz level is achieved with constant modulation ratio from DC frequency to high operation speed. The operation speed can be potentially over gigahertz with improved device and drive circuit design. When the EO polymer based SLM is configured to work at near the resonance band of the NLO material, the spectral tunability is increased due to resonance enhanced EO activity and the SLM performance is significantly improved. The EO polymer based FPI devices can be further optimized and are promising candidates for many optoelectronic applications.

Silicon is the dominant material in Microelectronics. Building photonic devices out of silicon can leverage the mature processing technologies developed in silicon CMOS. Silicon is also a very good waveguide material. It is highly transparent at 1550nm, and it has very high refractive index of 3.46. High refractive index enables building high index contrast waveguides with dimensions close to the diffraction limit. This provides the opportunity to build highly integrated photonic integrated circuit that can perform multiple functions on the same silicon chip, an optical parallel of the electronic integrated circuit. However, silicon does not have some of the necessary properties to build active optical devices such as lasers and modulators. For Example, silicon is an indirect band gap material that can’t be used to make lasers. The centro-symmetric crystal structure in silicon presents no electro-optic effect. By contrast, electro-optic polymer can be engineered to show very strong electro-optic effect up to 300pm/V. In this research we have demonstrated highly compact and efficient devices that utilize the strong optical confinement ability in silicon and strong electro-optic effect in polymer. We have performed detailed investigations on the optical coupling to a slow light waveguide and developed solutions to improve the coupling efficiency to a slow light photonic crystal waveguides (PCW). These studies have lead to the demonstration of the most hybrid silicon modulator demonstrate to date and a compact chip scale true time delay module that can be implemented in future phased array antenna systems. In the future, people may be able to realize a photonic integrated circuit for optical communication or sensor systems using the devices we developed in our research. / text

No description available.

Optical interconnects based on CMOS compatible photonic integrated circuits are regarded as a promising technique to tackle the issues traditional electronics faces, such as limited bandwidth, latency, vast energy consumption and so on. In recent years, plasmonic integrated components have gained great attentions due to the properties of nano-scale confinement, which may potentially bridge the size mismatch between photonic and electronic circuits. Based on silicon nanowire platform, this thesis work studies the design, fabrication and characterization of several integrated plasmonic components, aiming to combine the benefits of Si and plasmonics. The basic theories of surface plasmon polaritons are introduced in the beginning, where we explain the physics behind the diffraction-free confinement. Numerical methods frequently used in the thesis including finite-difference time-domain method and finite-element method are then reviewed. We summarize the device fabrication techniques such as film depositions, e-beam lithography and inductively coupled plasma etching as well as characterization methods, such as direct measurement method, butt coupling, grating coupling etc. Fabrication results of an optically tunable silicon-on-insulator microdisk and III-V cavities in applications as light sources for future nanophotonics interconnects are briefly discussed. Afterwards we present in details the experimental demonstrations and novel design of plasmonic components. Hybrid plasmonic waveguides and directional couplers with various splitting ratios are firstly experimentally demonstrated. The coupling length of two 170 nm wide waveguides with a separation of 140 nm is only 1.55 µm. Secondly, an ultracompact polarization beam splitter with a footprint of 2×5.1 μm2 is proposed. The device features an extinction ratio of 12 dB and an insertion loss below 1.5 dB in the entire C-band. Thirdly, we show that plasmonics offer decreased bending losses and enhanced Purcell factor for submicron bends. Novel hybrid plasmonic disk, ring and donut resonators with radii of ~ 0.5 μm and 1 μm are experimentally demonstrated for the first time. The Q-factor of disks with 0.5 μm radii are                         , corresponding to Purcell factors of . Thermal tuning is also presented. Fourthly, we propose a design of electro-optic polymer modulator based on plasmonic microring. The figure of merit characterizing modulation efficiency is 6 times better comparing with corresponding silicon slot polymer modulator. The device exhibits an insertion loss below 1 dB and a power consumption of 5 fJ/bit at 100 GHz. At last, we propose a tightly-confined waveguide and show that the radius of disk resonators based on the proposed waveguide can be shrunk below 60 nm, which may be used to pursue a strong light-matter interaction. The presented here novel components confirm that hybrid plasmonic structures can play an important role in future inter- and intra-core computer communication systems. / <p>QC 20140404</p>