The goal of the thesis is to fabricate the integrated asymmetric Mach-Zehnder Interferometer and Optical waveguide Ring Resonator with simple fabrication process. A 1.49£gm symmetric quantum well InGaAlAs epitaxial wafer is used to fabricate the devices. In the asymmetric Mach-Zehnder Interferometer design, we design asymmetric straight waveguides with difference of optical path, and asymmetric bend waveguides with difference of curvature radius. By this design, we can observe the interference variation of output light by difference of optical path. Using these properties, it will get the index change caused by electric field and the loss of bend waveguide. In optical waveguide ring resonator design, we improve the problem of the length of original K=0.15 Multi-Mode Interference (MMI) by stepped-width waveguide. And we obtain different transmission spectrum by adjusting the splitting ratio of MMI couplers (K=0.85, 0.5, and 0.15) and cascading doudle rings. We apply K0=0.5, K1=0.15 and K2=0.5 MMIs to design and fabricate optical filters with square transmission spectrum. In fabrication process, we get smooth sidewall and highly perpendicularity waveguide by multi-step wet etch method. In order to reduce waveguide loss, we make deep etching for the outside of curve waveguide and MMI. Finally, we use polyimide to smooth out the sides of the ridge waveguides and evaporate metal pad over the polyimide.

Abstract This thesis is composed of three models that imply the impact of managers¡¦ characteristics on investment under asymmetric information. The first one regards insider as managers and formulates a model to explain the positive relationship between cash flow and capital expenditure of a firm, and tries to synthesize the ¡§asymmetric information hypothesis¡¨(Myers and Majluf, 1984) and the ¡§free cash flow hypothesis¡¨(Jensen, 1986) by insider ownership. The finding demonstrates that in instances with low percentage of insider ownership, the free cash flow hypothesis will better explain the positive relationship between cash flow and capital expenditure and will have the phenomenon of over-investment. On the other hand, when the percentage of insider ownership is high, the asymmetric information hypothesis is better suited to explain this relationship and will have the phenomenon of the under-investment. The second one formulates a model to synthesize the ¡§reputation effect¡¨ and ¡§asymmetric information hypothesis¡¨ through considering the outsider investors¡¦ evaluation of the firms in terms of firms¡¦ reputation and firms¡¦ private information. This study concludes that the good type firms with low reputation will show the behavior of under-investment and the bad type firms with high reputation will have the phenomenon of over-investment. Moreover, the model demonstrates that both the phenomena of under-investment and of over-investment are caused by the conflict between the firms and the outsider investors. At last, this study implies that the effect of reputation has an influence on the choice of financial tools for the good type firms but does not have an influence on that of the bad ones. This study presents a general model to explain two types of investment inefficiency under the effect of reputation in a reasonable mode. The last one formulates a model to synthesize the ¡§bias effect¡¨ and ¡§reputation effect¡¨ through considering the fact that the CEO in the interest of firm is in favor of a certain project and that junior managers concern their reputation. This study concludes that the CEO¡¦s bias will influence the project that the managers suggest and does not necessarily lead to the direction of bias. The untalented managers will be affected more seriously than talented managers. Moreover, the model combines ¡§bias effect¡¨ with ¡§asymmetric information hypothesis¡¨ and implies that the bias can alleviate the problem of under-investment under certain circumstances. This finding shows that the bias is not always a negative factor of investment efficiency.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 196-207). Also available in electronic version. Access restricted to campus users.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 107-111). Also available in electronic version. Access restricted to campus users.

Changes in big companies resulting in new organizational structures and cost cutting are pushing more and more of the knowledge and information handling to sub-units in a multi-national structure. For big knowledge-intensive companies that act in the global market place, internal information handling is becoming a challenge. The study and reflections are based on experiences from Ericsson, a knowledge-intensive global telecommunication company. This company delivers complex cross-functional products (solutions) and has a decentralized organization. It faces the cost of managing distributed product information and the challenge to gather relevant information in the sales departments. One can easily characterize the company’s complex and unique product offerings as having multiple dependencies. The solutions are composed by building blocks, i.e. different sub products, delivered by different product units. The different sub products suffer from limitations in how they can be combined into solutions. This study addresses the information gaps in a decentralized organization regarding this specific issue. It focuses on identifying vital information without driving cost and requiring organizational changes. Stakeholder identification was done from a value chain perspective. The type of information that would give the most profitable solutions was identified during group sessions and individual interviews. An asymmetric compatibility matrix (ACM) was developed to fit the purpose of keeping low maintenance cost and without requiring organizational changes. The ACM was applied and process maturity improvements were evaluated with the use of the Process Enterprise and Maturity Model. The Ericsson specific study shows that the use of an ACM for product compatibility information makes it possible to define information responsibility that is sustainable over time. Thereby the maintenance cost for this information can be brought down to a minimum. Furthermore, the study shows that the effort of gathering information for the sales organizations to provide customer solutions can be reduced by the use of an ACM offering generic compatibility information. Users of the ACM would be able to re-use its information and focus on customer specific sales and deployment issues rather than re-do what others already have done. Cost of sales as well as business risks would thereby likely decrease, affecting the bottom line positively. Furthermore new business opportunities are assumed to be addressed better since relevant generic information is made available up front. Other positive expected benefits are prevention of network malfunctions and increased customer satisfaction. From this study it can be concluded that an ACM can be a powerful tool for gathering cross-functional product information in large decentralized organizations at a low cost, without any organizational changes, and with a high process maturity. Further research would be needed if one would consider validating the general applicability of the ACM in other processes.

Asymmetric nitrene transfer reactions via metalloradical catalysis (MRC) with azides has attracted research interest because of its fundamental and practical importance. The resulting nitrogen-containing units are recurrent motifs in biologically important molecules and can serve as versatile precursors in organic synthesis. The [Co(D2-Por*)] have emerged as a new class of catalysts for asymmetric aziridination and C-H amination. These metalloradical catalysts have been shown to be highly effective for the asymmetric intermolecular aziridination of a broad scope of substrates with different classes of azides with excellent to good enantioselectivity. The intramolecular C-H amination utilizing various azides can allow for the construction of diverse nitrogen containing heterocyclic compounds.

Upon making an optimal timing decision, a player takes into consideration not only the actions of the other players, but also the uncertainty of the environment. I use the real options approach to study the strategic timing decisions of asymmetric firms in an environment with uncertainty. When firms make timing decisions, they take into account the opportunity cost of immediate action today. The second chapter studies the identification in an asymmetric duopoly. The two potential entrants contemplate entering a new market where the demand follows a geometric Brownian motion. I show that under certain parameter conditions there will be an equilibrium triggered by preemption, and both firms could preempt. Moreover, the equilibrium may no longer be only triggered by preemption. I identify the joint distribution of the unobserved investment costs and find the probability of the first entry being triggered by preemption. Given the observation of the first entrant, I can predict the probability of observing the second entrant. The third chapter studies the spillover effect of exit in a vertical relationship. I extend the methodology of irreversible investment under uncertainty to consider exits in a vertical market structure. When the exogenous demand shock is low, one party of the supply chain wants to exit first and will thus lead to the exit of the remaining party. The firm which wants to exit later strategically acts to delay the exit of its counterpart and therefore prevents its own exit. When the state level drops below the unique equilibrium exit threshold, both firms will exit simultaneously. The expected delay in exit timing is derived. The fourth chapter studies the strategic optimal timing of entry in the competition between one-way essential complements under demand uncertainty. The value of a new add-on to its consumers is uncertain. While the rational essential good producing firm recognizes the value of waiting under uncertainty when it contemplates entering the add-on market and endogenously self-selects between the two entry options- to produce or to acquire, the add-on producing firm strategically decides when to agree on acquisition. The impact of profit sharing in the case of acquisition and relative fixed costs of entry on the size and form of the waiting region and the responses of both firms are analyzed. / text

Two syntheses of non-cross-linked polystyrene-supported TADDOL-based phosphoric acid organocatalyst have been developed. The optimal polymer-supported catalyst 2.29d exhibited comparable catalytic activity to its small molecule counterpart in asymmetric Mannich-type reactions, and the syntheses of several chiral β-amino esters were demonstrated using 2.29d as catalyst. However, when this TADDOL-based phosphoric acid was immobilized on a polystyrene cross-linked with 1,4-bis(4-vinylphenoxy)butane, ie. JandaJelTM, the catalytic activity diminished in the first recycling and reuse of the catalyst. Building on the success of the immobilization of chiral phosphoric acid, a more robust phase-tagged BINOL-based phosphoric acid organocatalyst was developed. By taking advantage of a tetraarylphosphonium salt as a solubility-controlling group, a widely-used BINOL-based phosphoric acid, TRIP (3.1), was introduced onto a tetraphenylphosphonium salt to produce a phosphonium salt-tagged phosphoric acid catalyst 3.3e. After systematic optimizations of reaction conditions, it was found that the catalyst 3.3e with PF6 as counteranion exhibited the best performance in terms of enantioselectivity. Catalyst 3.3e was proved to be highly effective in asymmetric Friedel-Crafts reaction of indoles because it was shown to be recyclable and reusable after six cycles without loss of catalytic activity. Based on our previous studies on the reduction of unsaturated thioesters catalyzed by (BDP)CuH, further investigation of ligand effects revealed that in addition to BDP, dppf was also an effective ligand for the simple reduction of 5.8. In the stoichiometric reduction of unsaturated thioester 5.8, dppe and dppf were both efficient ligands for copper hydride that could convert 5.8 to aldehyde 5.18 in the presence of TMSCl, without the formation of the undesired enol ester 5.17, which was a major product when stoichiometric amounts of Stryker’s reagent was employed. When 5.30 bearing both a saturated and unsaturated thioester was reduced under these conditions, only the enethioate functional group underwent reaction to yield the mono-reduced product 5.31 while the saturated thioester functional group remained inert. The desymmetrizing reductive aldol reactions of symmetrical keto-enethioates 6.19, 6.22, 6.24 and 6.26 catalyzed by in situ generated chiral copper hydride were investigated. After a screening of the reaction conditions, TaniaPhos L8 was found to be the most effective chiral ligand to achieve high ee and yields. Under the optimum reaction condition (5 mol% Cu(OAc)-H2O and L8 with 2.0 eq. PhSiH3), a range of keto-enethioates smoothly underwent desymmetrizing reductive aldol cyclizations, offering bicyclic or polycyclic β-hydroxythioesters (6.28a-6.32a, 6.37a-6.47a) in 35- 84% yield and 30-97% ee with high diastereoselectivity. The addition of 5 mol% of bipyridine as additive resulted in an accelerated reaction rate in all of the reductions of keto-enethioates. The crystal structure of the L8-copper bromide complex allowed the rationalization of the major enantiomer (eg. 6.48a), in which all of the substituents are cis, to be a result of a reductively generated (Z)-thioester enolate reacting through a Zimmerman-Traxler transition state. This stereochemical outcome is in contrast to the reduction of the analogous oxoesters, which yield trans β-hydroxyesters, (eg. 6.54b), as the major products. Several proposals to explain the divergent stereochemistry, including the predominance of a Zimmerman-Traxler transition state of (E)-enolates or subsequent retroaldol rearrangements, were discussed. The retroaldol rearrangement has been observed in the conversion of 6.48a to 6.57c, in which there was retention of the configuration at C5 and a perfect conservation of enantiomeric purity. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The synthesis of useful chiral skeletons from simple achiral starting materials is always the dream of organic chemists. In the past decades, organocatalysis has been rapidly developed and has become one of the most important methods in asymmetric catalysis. The aim of this thesis is to develop asymmetric methods for the construction of useful chiral skeletons based on organocatalytic chemistry. Many natural products and biologically important compounds contain the hydrogenated dibenzofuran (Figure 1) as a common sub-structure. In the first part of this thesis, the first amine-catalysed asymmetric synthesis of a dihydrodibenzofuran species from bisenal substrates has been demonstrated. After a systematic screening of various reaction parameters, the optimal conditions have been found to be as follows: 0.1 M of substrate in solution with toluene with 0.2 equiv of (S)-di(2-naphthyl)pyrrolinol TMS ether (C2.8) and 0.2 equiv of 2-nitrobenzoic acid at 50 ℃ for 7 h under an argon atmosphere (Scheme 1). The first step product, an aldehyde, can be reduced in one pot to an alcohol by NaBH4. This two-step protocol gives exclusive cis selectivity. Many chiral cis-dihydrodibenzofuran species have been synthesized from the corresponding bisenal substrates in moderate to good yield with good to excellent ee (Scheme 1). The resulting cis-dihydrodibenzofuran species have promising synthetic applications. As shown in Scheme 2, the less hindered face of the newly formed C ring is more reactive and highly regioselective functionalizations of the C ring have been achieved. In the second part of this thesis, the first asymmetric aziridination of trans-α-nitroalkenes via a phase-transfer catalysis strategy has been systematically studied. The chiral phase-transfer catalysts screened are derivatives of the cinchona alkaloids. The new cinchonidine-derived phase-transfer catalyst CD17 has been found to be optimal for the aziridination (Figure 2). Addition of a small amount of water is crucial to achieve complete conversion of the reaction. Both trans-1-nitro-2-arylalkenes and trans-1-nitro-2-alkylalkenes are suitable substrates (Scheme 3). The reaction can be run on the gram-scale without significant loss of efficiency and ee. Mechanistic studies have revealed that the aziridination proceeds through an aza-Michael addition followed by an intramolecular SN 2 type three-membered ring formation (Scheme 4). / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The research on asymmetric organocatalysis has been intensifying since the beginning of 2000. The growing interest in this research area is driven by the importance of the chemical synthesis of enantiomerically pure products. While the general field of asymmetric organocatalysis has been explored intensively, the recyclability of organocatalysts has not really been considered. The attachment of phosphonium ion phase tags to chiral binaphthyl-based phosphoric acid catalyst and the use of these materials in a range of organocatalytic asymmetric Friedel-Crafts reactions of indoles have been studied. Placement of tags at the 3 and 3’ positions of the binaphthyl core, so that they could serve as steric blocking groups, failed to produce an active catalyst. However, moving the phosphonium ion groups to the 6 and 6’ positions produced an efficient and enantioselective catalyst. Aided by the presence of the phase tags, the chiral catalyst was easily recovered at the end of the reactions, and could be reused several times, albeit with somewhat decreased efficiency and enantioselectivity. Furthermore, the synthesis of 1,1’-spirobiindane-7,7’-diol and their spiroindane-based derivatives have been explored. The (R)-1,1’-spirobiindane- 7,7’-diamine was successfully applied in exo selective asymmetric Diels-Alder reactions of -unsaturated aldehyde with cyclopentadiene. However, moderate results aspire further studies in assay of (R)-1,1’-spirobiindane-7,7’-diamine derivatives, which bear various bulky groups at the 6 and 6’ positions. Moreover, the conversion of the SPINOL into a spiroindane ketone unfortunately failed, which was caused by the sterically crowded structure of the SPINOL skeleton. / published_or_final_version / Chemistry / Master / Master of Philosophy