This study uses vertical mirror optical waveguide reflector and bending waveguide to fabricate semiconductor ring resonators. By using multimode interference couplers with specific width and length that generate distinctive energy distribution to achieve the power splitting of 85:15. We integrate vertically deep etching turning mirror to reflect optical mode, and reduce the component size to 37.6%. In fabrication process, this study applies multiple wet etching technique to form the waveguide structure. First, we use wet etching technique to etch ridge waveguide and turning mirror, and then perform deep etching in the periphery of bending and turning region to reduce the bending loss. Finally, the etching mask is lifted off, and the wafer is polished and sliced for measurement. After measuring the signal, we can compute waveguide loss by Fabry-perot resonant situation. The waveguide loss is 59.6dB/cm. Power splitting of 90:10 is achieved. The free spectral range (FSR) is 72GHz for the ring resonators.

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In this dissertation, the development of an experimental prototype for on-board optical-to-electrical signal broadcasting at 10 Gb/s per channel over an interconnect distance of 10 cm was presented. The optical distribution network was implemented using a polymer-based 1-by-4 multimode interference (MMI) splitter with linearly tapered output facet. A 1-by-8 MMI splitter with input/output waveguides of 10 microns in width was first fabricated using standard photolithography and characterized at 40 Gb/s in NRZ format and PRBS = 2^7-1. The pulse response of MMI devices was further quantified from the time-dependent, pulse-modulated field propagation perspective incorporated with various dispersion mechanisms. The results predict their operating limitations and investigate why and how such devices become non-functional in the ultrashort-pulse limit that is far beyond the most present-day optical systems. The guided-mode attenuation associated with polymer waveguides fabricated on FR-4 printed-circuit boards was also investigated for the first time. The rigorous transmission-line network approach was applied and the FR-4 substrate was treated as a long-period substrate grating with rectangular corrugations. The peaks of attenuation were shown to occur near the Bragg conditions that were recognized as the leaky-wave stop bands. As the buffer layer thickness increases, the attenuation becomes negligibly small that is attributed to the weak grating-induced perturbation to the mode behavior. The prototype was then developed on the basis of both experimental verifications to the devices and theoretical investigations. An improved 1-by-4 MMI splitter at 1550 nm with linearly tapered output facet was heterogeneously integrated with four p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself was then hybrid integrated onto an FR-4 printed-circuit board with four receiver channels composed of transimpedance amplifiers, limiting amplifiers, and surface-mounted components. The innovative integration approach demonstrated the simultaneous alignment between multiple waveguides and multiple PDs during the MMI fabrication process that is a complete radical departure from the conventional assembly method inherent from the telecommunication industry. The entire system was fully functional at 10 Gb/s per channel.

Multimode interference (MMI) in optical fibers has been studied and its applications in optical fiber lasers and amplifiers have been proposed and demonstrated in this thesis. When a single-mode fiber is spliced onto a multimode fiber, quasi-reproduction of the field from the single-mode fiber, also called “self-imaging”, occurs periodically along the multimode fiber where the phase differences between the strongly excited modes are very small. The properties of self-imaging in multimode optical fibers have been investigated experimentally and theoretically in this thesis. Key parameters for the design of MMI-based fiber devices have been defined and their corresponding values have been provides for the 50 μm and 105 μm multimode fibers. By use of the self-imaging effect, a fiber laser with single-transverse-mode output while using a multimode rare-earth-doped fiber has been demonstrated as an alternative route to overcome the constraints of an active single-mode fiber. The first MMI-based fiber laser in the world has provided a perfect beam quality (M² = 1.01) and an inherent narrow spectrum (Δλ(3dB) < 0.5 nm). Linearly-polarized narrow-linewidth single-transverse-mode emission has also been obtained from a MMI fiber laser utilizing a single-mode fiber inscribed with a polarization-maintaining fiber Bragg grating. Moreover, high power MMI fiber lasers and amplifiers utilizing rare-earth doped silica large-core multimode fibers have been proposed and their critical features, such as efficiency, optical spectrum, and beam quality, have been investigated. On the other hand, because exclusively excited LP₀, n modes inside the multimode fiber segment are represented by apertured Bessel fields that have long propagation invariant distances, nondiffracting beams can be generated from the MMI-based fiber devices. In this thesis, the principle of generating nondiffracting beams from multimode optical fibers has been described and the propagation characteristics of the generated beams have been investigated. Active MMI fiber devices to generate tens of watts or even hundreds of watts nondiffracting beams have also been proposed.

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The design, simulation, and initial fabrication of a novel ultra-compact 2x2 silicon multimode-interference device evanescently coupled to a dual germanium metal-semiconductor-metal (MSM) photodetector is presented. For operation at the standard telecom wavelength of 1.5 µm, the simulations demonstrate high-speed operation at 30 GHz, low dark current in the nanoamp range, and external quantum efficiency of 80%. Error analysis was performed for possible tilt error introduced by hybrid integration of the MSM layer on top of the MMI waveguides by use of surface mount technology (SMT) and direct wafer bonding.

Compact high power fiber lasers and the vertical-external-cavity surface-emitting lasers (VECSELs) are promising candidates for high power laser sources with diffraction-limited beam quality and are currently the subject of intensive research and development. Here three large mode area fiber lasers, namely, the photonic crystal fiber (PCF) laser, the multicore fiber (MCF) laser, and the multimode interference (MMI) fiber laser, as well as the VECSEL are modeled and designed.For the PCF laser, the effective refractive index and the effective core radius of the PCF are investigated using vectorial approaches and reformulated. Then, the classical step-index fiber theory is extended to PCFs, resulting in a highly efficient vectorial effective-index method for the design and analysis of PCFs. The new approach is employed to analyze the modal properties of the PCF lasers with depressed-index cores and to effectively estimate the number of guided modes for PCFs.The MCF laser, consisting of an active MCF and a passive coreless fiber, is modeled using the vectorial mode expansion method developed in this work. The results illustrate that the mode selection in the MCF laser by the coreless fiber section is determined by the MMI effect, not the Talbot effect. Based on the MMI and self-imaging in multimode fibers, the vectorial mode expansion approach is employed to design the first MMI fiber laser demonstrated experimentally.For the design and modeling of VECSELs, the optical, thermal, and structural properties of common material systems are investigated and the most reliable material models are summarized. The nanoscale heat transport theory is applied for the first time, to the best of my knowledge, to design and model VECSELs. In addition, the most accurate strain compensation approach is selected for VECSELs incorporating strained quantum wells to maintain structural stability. The design principles for the VECSEL subcavity are elaborated and applied to design a 1040nm VECSEL subcavity that has been demonstrated for high power operation of VECSELs where near diffraction-limited output over 20 W is obtained. Physical modeling of the VECSEL is also discussed and used to compare VECSEL subcavity designs on the laser level.

Silicon-on-insulator (SOI) technology has become increasingly attractive because of the strong light confinement, which significantly reduces the footprint of the photonic components, and the possibility of monolithically integrating advanced photonic waveguide circuits with complex electronic circuits, which may reduce the cost of photonic integrated circuits by mass production. This thesis is dedicated to numerical simulation and experimental performance measurement of passive SOI waveguide devices. The thesis consists of two main parts. In the first part, SOI curved waveguide and corner turning mirror are studied. Propagation losses of the SOI waveguide devices are accurately measured using a Fabry-Perot interference method. Our measurements verify that the SOI corner turning mirror structures can not only significantly reduce the footprint size, but also reduce the access loss by replacing the curved sections in any SOI planar lightwave circuit systems. In the second part, an optical 90o hybrid based on 4 × 4 multimode interference (MMI) coupler is studied. Its quadrature phase behavior is verified by both numerical simulations and experimental measurements.

Silicon-on-insulator (SOI) technology has become increasingly attractive because of the strong light confinement, which significantly reduces the footprint of the photonic components, and the possibility of monolithically integrating advanced photonic waveguide circuits with complex electronic circuits, which may reduce the cost of photonic integrated circuits by mass production. This thesis is dedicated to numerical simulation and experimental performance measurement of passive SOI waveguide devices. The thesis consists of two main parts. In the first part, SOI curved waveguide and corner turning mirror are studied. Propagation losses of the SOI waveguide devices are accurately measured using a Fabry-Perot interference method. Our measurements verify that the SOI corner turning mirror structures can not only significantly reduce the footprint size, but also reduce the access loss by replacing the curved sections in any SOI planar lightwave circuit systems. In the second part, an optical 90o hybrid based on 4 × 4 multimode interference (MMI) coupler is studied. Its quadrature phase behavior is verified by both numerical simulations and experimental measurements.

The Multimode Interference (MMI) mechanism is a powerful toool used in the analysis and design of a certain class of optical, microwave and millimeter wave devices. The principles of the MMI method and the self-imaging principle is described. Using this method, NXM MMI couplers, MMI splitter/combiners are analyzed. Computer simulations for illustrating the &quot / Multimode Interference Mechanism&quot / are carried out. The MMI approach is used to analyze overmoded &#039 / rectangular metallic&#039 / and &#039 / dielectric slab&#039 / type of waveguides and devices. The application of the MMI technique is investigated experimentally by using a metallic waveguide structure operating in the X-band. The construction of the related structure and the related experimental work are reported.