The purpose of this thesis is to develop ring resonators with simple processes and integration. We used loop mirror as a reflector in the semiconductor lasers. In the material, a 1.55£gm symmetric quantum well InGaAsP epi-layer is used to fabricate the lasers. In device design, we designed four kinds of semiconductor lasers by using loop mirror and cleaved facet. The curvature radiuses are 160 and 260£gm that are presented to investigate bending loss and material loss. In the input/output we had an inclined 7 degree to avoid interference. We also designed another two semiconductor lasers by using ring resonator and cleaved facet. Applying the resonance characteristic of ring resonator can achieve wavelength selection and filtering. In fabrication process, we developed new etching technique. The ICP-RIE dry etching and wet etching method were used in the process. Fist we etched half of the total depth by ICP-RIE dry etching. And then the multi-step technique was used to approach the expecting depth. Beside, we had extra deep wet etching process in MMI. Finally, we used the etching solution HBr:HCl:H2O2:H2O =5:4:1:70 to smooth the sidewall and reduce the scattering loss. In device characteristic, we obtained differential quantum efficiency of 20£gW/mA for the 1000£gm straight waveguide laser. We can not observe laser characteristics for the loop mirror laser, partly because of the high loss in bending section.

We present design and fabrication of ring cavity semiconductor lasers and single ring filter with simple fabrication processes. A 1.55-£gm symmetric quantum well InGaAlAs epi-layer wafer is used to fabricate the lasers. In device design, we apply loop mirror to obtain reflection instead of cleaved facet and take 1x2, and 2x2 Multi-Mode Interference (MMI) with different splitting ratio(50%:50%¡F15%:85%) as a coupler. Then we combine MMI couplers with ring cavities to control the output of specific wavelength. Therefore we can obtain filter and lasers with the property of wavelength selection. We also design two kinds of special waveguides to achieve low reflectivity. One is a tapered spiral waveguide tail. The other waveguide is expanded in a curve and then cut off at the Brewster¡¦s angle. In loop mirror, two curvature radius(260,160£gm) were introduced to study bending loss and material loss. In single ring filter, we design two kinds of resonator lengths(1479,1385£gm) and the corresponding Free Spectrum Range (FSR) are 63.4, 67.75GHz, respectively. In fabrication, owing to the unstable dry etch condition for InGaAlAs, we adopted multi-step etch technology. In the part of curved waveguide, we also use this method to make deep-etching to increase the difference of refractive index between waveguide and the outside part. Finally, we use the etch solution (HBr:HCl:H2O2:H2O=5:4:1:70) to smooth the sidewall of the waveguide, and to reduce scattering loss of the device.

The purpose of this research is to present design and fabrication of resonant loop-mirror Fabry-Perot lasers. Single filter has simple fabrication processes and good potential for intergration. A 1.55-£gm symmetric quantum well InGaAlAs epi-layer wafer is used to fabricate the laser. In device design, we apply loop mirror to obtain reflection instead of cleaved facet and take 1x2, 2x2 Multi-Mode Interference (MMI) with different splitting ratio (50%:50%¡F15%:85%) as a coupler. Then we combine MMI couplers with ring cavities to reflect specific wavelength at particular position. Therefore we can obtain semiconductor laser with property of wavelength-selection filter. In this design of the mask, we add a mask of deep-etch around MMI in order to decrease the loss of higher mode inside MMI. In the part of devices design, we apply multi-step technology for wet etch to obtain necessary depth. Finally, we use the etch solution (HBr¡GHCl¡GH2O2¡GH2O¡×5¡G4¡G1¡G70) to smooth the sidewall of the waveguide, and to reduce scattering loss of the device. In the part of planarization, we can adhere dummy wafers to surround the main sample and extend the total area. If we can fill the gap flat, the problem of high edge by spinning will be solved. However, we were not able to fill the gap.

This paper presents design and fabrication of ring cavity semiconductor lasers and optical filters with simple fabrication process. A 1.55

<p> The modeling, design and simulation of optical waveguides and integrated optical triplexer filters are presented. The work includes two subjects. One is application of improved three-point fourth-order finite-difference method and the other is design of triplexer optical filter for fiber-to-the-home passive optical network.</p> <p> The improved three-point fourth-order finite-difference method utilizes special format of one dimensional Helmholtz Equation and adopts generalized Douglas scheme and boundary conditions matching at interface. The modal analysis of dielectric slab waveguides and metal slab waveguides that support Surface Plasmon Plaritons by using this improved fourth-order finite-difference method is compared by using traditional first-order central difference method. The application of using improved three-point fourth-order finite-difference method in modal analysis of optical fiber waveguide is also provided.</p> <p> The modeling, design and simulation of monolithically integrated triplexer optical filter based on silicon wire waveguide are presented in detail. The design of this device facilitates multi-mode interference device (MMI) and arrayed waveguide grating (AWG) device to function as coarse wavelength division multiplexing and dense wavelength division multiplexing respectively. The MMI is used to separate downstream signs for upstream signal and AWG is used to further separate two down-stream signals with different bandwidths required. This design is validated by simulation that shows excellent performance in terms of spectral response as well as insertion loss.</p> / Thesis / Master of Applied Science (MASc)

Large on-chip bandwidths required for high performance electronic chips will render optical components essential parts of future on-chip interconnects. Silicon photonics enables highly integrated photonic integrated circuit (PIC) using CMOS compatible process. In order to maximize the bandwidth density and design flexibility of PICs, vertical integration of electronic layers and photonics layers is strongly preferred. Comparing deposited silicon, single crystalline silicon offers low material absorption loss and high carrier mobility, which are ideal for multi-layer silicon PIC. Three different methods to build multi-layer silicon PICs based on single crystalline silicon are demonstrated in this dissertation, including double-bonded silicon-on-insulator (SOI) wafers, transfer printed silicon nanomembranes, and adhesively bonded silicon nanomembranes. 1-to-12 waveguide fanouts using multimode interference (MMI) couplers were designed, fabricated and characterized on both double-bonded SOI and transfer printed silicon nanomembrane, and the results show comparable performance to similar devices fabricated on SOI. However, both of these two methods have their limitations in optical interconnects applications. Large and defect-free silicon nanomembrane fabricated using adhesive bonding is identified as a promising solution to build multi-layer silicon PICs. A double-layer structure constituted of vertically integrated silicon nanomembranes was demonstrated. Subwavelength length based fiber-to-chip grating couplers were used to couple light into this new platform. Three basic building blocks of silicon photonics were designed, fabricated and characterized, including 1) inter-layer grating coupler based on subwavelength nanostructure, which has efficiency of 6.0 dB and 3 dB bandwidth of 41 nm, for light coupling between layers, 2) 1-to-32 H-tree optical distribution, which has excess loss of 2.2 dB, output uniformity of 0.72 dB and 3 dB bandwidth of 880 GHz, 3) waveguide crossing utilizing index-engineered MMI coupler, which has crossing loss of 0.019 dB, cross talk lower than -40 dB and wide transmission spectrum covering C-band and L-band. The demonstrated integration method and silicon photonic devices can be integrated into the CMOS back-end process for clock distribution and global signaling. / text

A MBS (Multi-port beamsplitter) for higher dimensional quantum communication has been designed and constructed and the theory and method for this is presented in this thesis. It uses optical fibers in a heterogeneous structure with a single-mode fiber spliced to a multi-mode fiber and then spliced to a few-mode fiber. Three MBS:s were constructed and tested to see if superpositions between spatial modes could be generated. One with 5.65cm multi-mode fiber, one with 9cm of multi-mode fiber and one with just the single-mode fiber spliced to the few-mode fiber. The optical modes that where focused on for the superposition were the linear polarized LP01, LP11a and LP11b modes. Simulations of superpositions between these modes were performed and experiments were done to see if these simulations could be realised. The shapes of these superpositions could be seen with a camera and the stability of the different modal powers and the stability of the phases between the modes where also tested. The last experiment tested the tunability of the modes by finding their maximum and minimum output power for each individual mode. The results of these experiments show that the stability of power and relative phases are high and testing of the tunability shows that the 9cm MBS is the most tunable, the 5.65cm MBS the second best and the SMF-FMF MBS the worst. Even though the shapes of the superpositions, the stability and tunability shows very positive results, the conclusion is that more experiments are required in order to identify the superpositions and for this to be used in a quantum communication system. / En Multi-port stråldelare (MSD) för kvantkommunikation med hjälp av rumsliga optiska moder har blivit designad och konstruerad. Teorin, metoden och resultatet av detta arbete presenteras i denna uppsats. Denna konstruktion använder sig av optiska fiber i heterogena strukturer med en single-mode fiber svetsad till en multi-mode fiber som i sin tur är svetsad till en few-mode fiber. Tre stycken MSD blev konstruerade och testade för att se om superpositioner mellan rumsliga moder kunde bli genererade, en med 5.65cm multi-mode fiber, en med 9cm multi-mode fiber och en med bara en single-mode fiber svetsad till en few-mode fiber. De moder som fokuserades på för superpositionerna var de linjärpolariserade moderna LP01, LP11a och LP11b. Superpositionerna simulerades och sen genomfördes experiment för att se ifall de kunde bli genererade. Formerna av dessa superpositioner kunde hittas och synliggöras med en kamera. Stabiliteten av modernas energi och stabiliteten av faserna mellan moderna testades också. Det sista experimentet som gjordes testade justerbarheten av moderna genom att hitta den minimala samt maximala intensiteten för varje mod. Experimenten visar att intensiteterna och de relativa faserna har hög stabilitet för alla konstruerade MSD, men i justerbarhets experimentet visar det sig att 9cm MSD:en presterar bäst, 5.65cm MSD:en presterar näst bäst och SMF-FMF strukturen presterar sämst. Trots att formerna av superpositionerna kunde hittas för alla tre konstruktioner, och att testen i stabiliteten visar goda resultat så krävs mer experiment för att identifiera superpositionerna mellan moderna och ifall denna konstruktion går att implementera i ett kvantkommunikationssystem.