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The overall efficiency of photovoltaics is dictated by processes occurring within it. These processes include exciton formation, diffusion, dissociation and charge collection. This dissertation will focus around the fundamental issue of charge collection. In organic photovoltaics (OPVs) the rate of charge injection is dominated by the interaction between dissimilar materials, usually organic compound interacting with inorganic ones. In order to improve this rate of injection and, by direct consequence the efficiency of this process, fundamental knowledge of this organic-inorganic interface must be gained. In this work the focus will reside solely on creating molecules capable of probing the interface between the indium tin oxide (ITO) and the donor layer. At this interface, the usual charge transfer being transferred is the hole. Chapters 2 and 3 detail the synthesis and photophysical characterization of porphyrin-perylene diimide (Por-PDI) and porphyrin-fullerene (Por-C₆₀) molecular dyads. The idea behind these moieties is that covalent attachment of these species to ITO should lead to a robust ohmic contact. Since these molecular dyads are capable of producing charge-separated states after photoexcitation, they should have the capacity to produce a radical-cation in close proximity to the ITO. This will translate to a capacity for probing the dynamics of the hole injection at this interface. Studies performed demonstrate that in fact these dyads are capable of producing a charge-separated state upon photo-excitation. The lifetimes of these states were determine to be 35 ps and 3 ns for the Por-PDI and Por-C₆₀ respectively. Chapter 4 takes a different turn. It is focused on the application and extension of a solvent-free synthesis of metallated phthalocyanines (Pcs). Shown in chapter 4 is the synthesis of a series of metallated Pcs using various transition metals and group 3 elements. Photophysical and electrochemical investigation of these materials shows that the

In the past year, the PI s research on the fundamental properties and applications of nanoclusters has been centered around gold and silver, and many different models have been developed to address the core packing, electron configurations and to explain some of the observed optical properties. Gold and silver in their atomic state shares the same number of valence electrons and bulk packing distance. In this report, we summarize our recent work on silver based nanoclusters. Recent work produced stable silver nanoclusters in the condensed phase, purified by gel separation. The basic synthetic approach is similar to that of gold nanoclusters. However, the silver nanoclusters have not been optimized like some other nanoclusters, where high purity can be achieved in a single-pot synthesis. Moreover, the stability of silver nanoclusters is also a major concern. By utilizing gel separation methods in their synthesis, our coworkers have been able to purify the nanocluster mixtures to produce highly pure mono-disperse nanoclusters. The result of this work leads to the synthesis of stable silver nanoclusters in high purity, which allows for the identification of silver nanoclusters by mass spectrometry. Due to the very small size of nanocluster and the difficulty in obtaining crystal structures, mass spectrometry has become essential in the identification of nanocluster formula. In this report we focus on the Ag32(SG)19, cluster. The initial interested in silver based system was not solely based on synthetic exploration. One of the most interesting optical property of gold system is its emission and it has tremendous potential in imagining. The larger bandgap of silver (compare to gold) should leads to stronger emission, which would further demonstrate the possibility of using nanoclusters as imaging agents on a cellular level. Ag32(SG)19 also offers an unexplored area in the ultrafast spectroscopy of nanoclusters.

This project was directed toward the generation of long wavelength visible optical limiting materials that respond via a combination of reverse saturable absorption and two-photon absorption processes. The particular wavelength range we have focused on initially is the 600- 900 nm range, covering frequencies of regeneratively amplified Ti:sapphire lasers. The chromophores all have two relatively independent chromophoric systems as a part of their structure. One system is optimized to exhibit one or two photon absorption in the long wavelength visible region and the other, accessed by population of the first, allows optimization of the transient absorption of light that will provide the optical limiting effect. This report discusses our work in three areas: (a) the design and synthesis of ligands and metal complex systems that approach optimization of the two chromophoric components, (b) photophysical characterization and evaluation of the figures of merit for the chromophores and (c) the study of vibrational energy dissipation in model systems excited in the infrared and involving relaxation assisted two-dimensional infrared spectroscopy., The original document contains color images.

This research was a comprehensive science and engineering program to develop a new generation of nanophotonic materials, structures, and devices exhibiting large, high-speed nonlinear optical (NLO) changes, as needed to enable new capabilities in all-optical switching for imaging applications. In particular, the problem of passive optical limiting and switching without using focusing optics is an extremely challenging task. The goal of this research was to tackle lensless optical limiting by determining the ultimate possibilities and limits on materials, materials structures, and device configurations. The approach we adopted combined three methodologies to achieve this goal: (1) to enhance the NLO response of the molecules through a variety of molecular engineering approaches, (2) to use surface plasmon field enhancements in nano-engineered clusters and arrays of metal and/or dielectric nanoparticles coupled to the organic NLO materials; and (3) to integrate the first two methodologies in systems having weakly resonant structures, including 3-D and/or 1-D photonic crystal structures (i.e. nonlinear Bragg mirrors). We made significant progress in all three areas and have observed orders of magnitude enhancement of NLO absorption; however, we have not been able to fully harness this enhancement for devices due to the transient nature of the effects., Prepared in cooperation with Georgia Institute of Technology, University of Arizona, and Purdue University.

Photo-physical properties relevant for optical power limiting in the near-visible and visible regions of the spectrum are reported for a series of substituted diarylalkynyl chalcogenophenes (furans, thiophenes, selenophenes, and tellurophenes). The linear ground and excited state absorption as well as the nonlinear (two-photon) absorption were determined at the time-dependent density functional theory level with use of the hybrid exchange-correlation functionals B3LYP and CAM-B3LYP. A selected number of the theoretically studied molecules were synthesized and characterized experimentally with the use of absorption and luminescence spectroscopy. The photo-physical data are compared to the results from optical power limiting measurements performed in THF solution at a wavelength of 532 nm, with a laser pulse length of 5 ns and pulse energies up to 150 J. The best compounds in the present investigation display an energy damping by approximately a factor of 10 at a concentration of 0.010 M., References: Prasad, P.N., Reinhardt, B.A., (1990) Chem. Mater, 2, p. 660; Bredas, J.L., Adant, C., Tackx, P., Persoons, A., Pierce, B.M., (1994) Chem. Rev, 94, p. 243; Stegeman, G.I., (1997) Nonlinear Optical Organic Molecular Polymers, p. 799. , edited by H.S. Nalwa and S. Miyata CRC Press, Boca Raton; Hollins, R.C., (1999) Curr. Opi. Solid State Mater. Sci, 4, p. 189; Kaino, T., (2000) J. Opt. A, Pure Appl. Opt, 2, pp. R1; Zhou, G.J., Wong, W.Y., Ye, C., Lin, Z.Y., (2007) Adv. Funct. Mater, 17, p. 963; He, G.S., Tan, L.-S., Zheng, Q., Prasad, P.N., (2008) Chem. Rev, 108, p. 1245; Ramos-Ortiz, G., Cha, M., Thayumanavan, S., Mendez, J., Marder, S.R., Kippelen, B., (2004) Appl. Phys. Lett, 85, p. 3348; Lee, K.S., Yang, D.Y., Park, S.H., Kim, R.H., (2006) Polym. Adv. Technol, 17, p. 72; Perry, J.W., (1997) Nonlinear Optical Organic Molecular Polymers, p. 813. , edited by H.S. Nalwa and S. Miyata CRC Press, Boca Raton; Spangler, C.W., (1999) J. Mater. Chem, 9, p. 2013; Dini, D., Barthel, M., Hanack, M., (2001) Eur. J. Org. Chem, 2001, p. 3759; Ehrlich, J.E., Wu, X.L., Lee, I.Y.S., Hu, Z.Y., Rockel, H., Marder, S.R., Perry, J.W., (1997) Opt. Lett, 22, p. 1843; Reinhardt, B.A., Brott, L.L., Clarson, S.J., Dillard, A.G., Bhatt, J.C., Kannan, R., Yuan, L.X., Prasad, P.N., (1998) Chem. Mater, 10, p. 1863; Rogers, J.E., Hall, B.C., Hufnagle, D.C., Slagle, J.E., Ault, A.P., McLean, D.G., Fleitz, P.A., Cooper, T.M., (2005) J. Chem. Phys, 122, p. 214708; Nalwa, H.S., (1997) Nonlinear Optical Organic Molecular Polymers, p. 611. , edited by H.S. Nalwa and S. Miyata CRC Press, Boca Raton; Badaeva, E., Tretiak, S., (2008) Chem. Phys. Lett, 450, p. 322; Xing, X.J., Li, J., Sun, Y.P., Wang, C.K., (2008) Theochem-J. Mol. Struct, 849, p. 116; Ogawa, K., Kobuke, Y., (2006) J. Photochem. Photobiol. C, 7, p. 1; Lind, P., Lopes, C., Öberg, K., Eliasson, B., (2004) Chem. Phys. Lett, 387, p. 238; Lind, P., Eriksson, A., Lopes, C., Eliasson, B., (2005) J. Phys. Org. Chem, 18, p. 426; Vestb

Photo-physical properties relevant for optical power limiting in the near-visible and visible regions of the spectrum are reported for a series of substituted diarylalkynyl chalcogenophenes (furans, thiophenes, selenophenes, and tellurophenes). The linear ground and excited state absorption as well as the nonlinear (two-photon) absorption were determined at the time-dependent density functional theory level with use of the hybrid exchange-correlation functionals B3LYP and CAM-B3LYP. A selected number of the theoretically studied molecules were synthesized and characterized experimentally with the use of absorption and luminescence spectroscopy. The photo-physical data are compared to the results from optical power limiting measurements performed in THF solution at a wavelength of 532 nm, with a laser pulse length of 5 ns and pulse energies up to 150 J. The best compounds in the present investigation display an energy damping by approximately a factor of 10 at a concentration of 0.010 M.

We cover five general areas: (1) optical limiting (2) organic multiphoton absorber (AFX) (3) numerical methods (4) relationship between the building blocks/decay rate matrix and the coupled propagation/rate equations and (5) semiconductor quantum dots., The original document contains color images.

In this review paper we showcase recent activities on silicon photonics science and technology research in Hong Kong regarding two important topical areas - microresonator devices and optical nonlinearities. Our work on silicon microresonator filters, switches and modulators have shown promise for the nascent development of on-chip optoelectronic signal processing systems, while our studies on optical nonlinearities have contributed to basic understanding of silicon-based optically-pumped light sources and helium-implanted detectors. Here, we review our various passive and electro-optic active microresonator devices including (i) cascaded microring resonator cross-connect filters, (ii) NRZ-to-PRZ data format converters using a microring resonator notch filter, (iii) GHz-speed carrier-injection-based microring resonator modulators and 0.5-GHz-speed carrier-injection-based microdisk resonator modulators, and (iv) electrically reconfigurable microring resonator add-drop filters and electro-optic logic switches using interferometric resonance control. On the nonlinear waveguide front, we review the main nonlinear optical effects in silicon, and show that even at fairly modest average powers two-photon absorption and the accompanied free-carrier linear absorption could lead to optical limiting and a dramatic reduction in the effective lengths of nonlinear devices. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.

In this review paper we showcase recent activities on silicon photonics science and technology research in Hong Kong regarding two important topical areas - microresonator devices and optical nonlinearities. Our work on silicon microresonator filters, switches and modulators have shown promise for the nascent development of on-chip optoelectronic signal processing systems, while our studies on optical nonlinearities have contributed to basic understanding of silicon-based optically-pumped light sources and helium-implanted detectors. Here, we review our various passive and electro-optic active microresonator devices including (i) cascaded microring resonator cross-connect filters, (ii) NRZ-to-PRZ data format converters using a microring resonator notch filter, (iii) GHz-speed carrier-injection-based microring resonator modulators and 0.5-GHz-speed carrier-injection-based microdisk resonator modulators, and (iv) electrically reconfigurable microring resonator add-drop filters and electro-optic logic switches using interferometric resonance control. On the nonlinear waveguide front, we review the main nonlinear optical effects in silicon, and show that even at fairly modest average powers two-photon absorption and the accompanied free-carrier linear absorption could lead to optical limiting and a dramatic reduction in the effective lengths of nonlinear devices. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.

In this review paper we showcase recent activities on silicon photonics science and technology research in Hong Kong regarding two important topical areas - microresonator devices and optical nonlinearities. Our work on silicon microresonator filters, switches and modulators have shown promise for the nascent development of on-chip optoelectronic signal processing systems, while our studies on optical nonlinearities have contributed to basic understanding of silicon-based optically-pumped light sources and helium-implanted detectors. Here, we review our various passive and electro-optic active microresonator devices including (i) cascaded microring resonator cross-connect filters, (ii) NRZ-to-PRZ data format converters using a microring resonator notch filter, (iii) GHz-speed carrier-injection-based microring resonator modulators and 0.5-GHz-speed carrier-injection-based microdisk resonator modulators, and (iv) electrically reconfigurable microring resonator add-drop filters and electro-optic logic switches using interferometric resonance control. On the nonlinear waveguide front, we review the main nonlinear optical effects in silicon, and show that even at fairly modest average powers two-photon absorption and the accompanied free-carrier linear absorption could lead to optical limiting and a dramatic reduction in the effective lengths of nonlinear devices. Copyright © 2008 The Institute of Electronics, Information and Communication Engineers.

The demand for protection of eyes and various types of optical sensors from laser-beam pulses has resulted in the search for optical limiting devices that have the property of being transparent at low intensity of light (normal light), but non-transparent towards high intensity (laser) light. This type of protection may be obtained by using an organic material that displays nonlinear optical (NLO) properties. Examples of NLO effects that can be used for optical limiting are reverse saturable absorption (RSA), two-photon absorption (TPA) and nonlinear refraction. The advantage of using compounds that show such NLO effects is that they can have very fast response and are self-activating, that is, there is no need for externally controlled switching to obtain optical limiting. In this work, several dialkynyl substituted thiophenes and some thiophenyl-alkynyl-platinum(II)-complexes were synthesized and tested for nonlinear absorption of light. A palladium-copper mediated coupling (Sonogashira coupling) was utilized for all reactions between terminal alkynes and aryl halides. Molecular orbital calculations were used in order to screen for suitable properties, such as the second hyperpolarizability, in compounds of interest. A quantitative structure-activity relationship (QSPR) study using a PLS approach were performed in order to identify important molecular electronic variables for optical limiting of organic compounds.

The demand for protection of eyes and various types of optical sensors from laser-beam pulses has resulted in the search for optical limiting devices that have the property of being transparent at low intensity of light (normal light), but non-transparent towards high intensity (laser) light. This type of protection may be obtained by using an organic material that displays nonlinear optical (NLO) properties. Examples of NLO effects that can be used for optical limiting are reverse saturable absorption (RSA), two-photon absorption (TPA) and nonlinear refraction. The advantage of using compounds that show such NLO effects is that they can have very fast response and are self-activating, that is, there is no need for externally controlled switching to obtain optical limiting. In this work, several dialkynyl substituted thiophenes and some thiophenyl-alkynyl-platinum(II)-complexes were synthesized and tested for nonlinear absorption of light. A palladium-copper mediated coupling (Sonogashira coupling) was utilized for all reactions between terminal alkynes and aryl halides. Molecular orbital calculations were used in order to screen for suitable properties, such as the second hyperpolarizability, in compounds of interest. A quantitative structure-activity relationship (QSPR) study using a PLS approach were performed in order to identify important molecular electronic variables for optical limiting of organic compounds.

Two novel poly(1-alkyne)s containing azobenzene nonlinear optical chromophoric group, poly(4-(4-[4-(n-dodecyloxy)phenylazophenyl]carbonyl)oxy-1-butyne) (P1) and poly(11-(4-[4-(n-dodecyloxy)phenylazophenyl]carbonyl)oxy-1-undecyne) (P2), were synthesized by [Rh(nbd)Cl](2)-Et3N catalysts and characterized by FTIR, H-1 NMR, GPC and UV-vis techniques. Their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm. The results show that these soluble functional poly(1-alkyne)s possess good optical limiting properties and large nonlinear optical properties. (c) 2006 Elsevier Ltd. All rights reserved.

Two functional polyurethanes (P1 and P2) bearing a large pi electron conjugated chromophoric pendant were synthesized and characterized by FT-IR, H-1-NMR and UV-Vis absorption spectra. Their optical limiting properties were evaluated. The results show that P1 and P2 show novel optical limiting properties, which are assigned to a long pi electron conjugated chromophoric pendant. It was found that their optical limiting properties were affected simultaneously by solution concentration and P2 displays a better optical limiting property than P1 at the same solution transmittance, although that P1 has larger chi((3)) (4.28 x 10(-11) esu) than P2 (0.87 x 10(-11) esu), and their optical limiting mechanism is investigated.

A novel soluble functional polyacetylene copolymer (poly(EAAB-co-PA)) of 4-ethynyl-4'-[N,N-diethylamino]azobenzene (EAAB) and phenylacetylene (PA) was synthesized. The structures and properties of the polymers were characterized and evaluated by FTIR, UV-vis, H-1 NMR GPC, optical limiting, and nonlinear optical analyses. The results show that poly(EAAB-co-PA) has the large third-order nonlinear susceptibility, which are two orders of magnitude larger than those of poly(PA) and novel optical limiting property. (c) 2005 Elsevier Ltd. All rights reserved.

Two novel poly(1-alkyne)s containing azobenzene nonlinear optical chromophoric group, poly(4-(4-[4-(n-dodecyloxy)phenylazophenyl]carbonyl)oxy-1-butyne) (P1) and poly(11-(4-[4-(n-dodecyloxy)phenylazophenyl]carbonyl)oxy-1-undecyne) (P2), were synthesized by [Rh(nbd)Cl](2)-Et3N catalysts and characterized by FTIR, H-1 NMR, GPC and UV-vis techniques. Their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm. The results show that these soluble functional poly(1-alkyne)s possess good optical limiting properties and large nonlinear optical properties. (c) 2006 Elsevier Ltd. All rights reserved.

Two functional polyurethanes (P1 and P2) bearing a large pi electron conjugated chromophoric pendant were synthesized and characterized by FT-IR, H-1-NMR and UV-Vis absorption spectra. Their optical limiting properties were evaluated. The results show that P1 and P2 show novel optical limiting properties, which are assigned to a long pi electron conjugated chromophoric pendant. It was found that their optical limiting properties were affected simultaneously by solution concentration and P2 displays a better optical limiting property than P1 at the same solution transmittance, although that P1 has larger chi((3)) (4.28 x 10(-11) esu) than P2 (0.87 x 10(-11) esu), and their optical limiting mechanism is investigated.

A novel soluble functional polyacetylene copolymer (poly(EAAB-co-PA)) of 4-ethynyl-4'-[N,N-diethylamino]azobenzene (EAAB) and phenylacetylene (PA) was synthesized. The structures and properties of the polymers were characterized and evaluated by FTIR, UV-vis, H-1 NMR GPC, optical limiting, and nonlinear optical analyses. The results show that poly(EAAB-co-PA) has the large third-order nonlinear susceptibility, which are two orders of magnitude larger than those of poly(PA) and novel optical limiting property. (c) 2005 Elsevier Ltd. All rights reserved.

The demand for protection of eyes and various types of optical sensors from laser-beam pulses has resulted in the search for optical limiting devices that have the property of being transparent at low intensity of light (normal light), but non-transparent towards high intensity (laser) light. This type of protection may be obtained by using an organic material that displays nonlinear optical (NLO) properties. Examples of NLO effects that can be used for optical limiting are reverse saturable absorption (RSA), two-photon absorption (TPA) and nonlinear refraction. The advantage of using compounds that show such NLO effects is that they can have very fast response and are self-activating, that is, there is no need for externally controlled switching to obtain optical limiting. In this work, several dialkynyl substituted thiophenes and some thiophenyl-alkynyl-platinum(II)-complexes were synthesized and tested for nonlinear absorption of light. A palladium-copper mediated coupling (Sonogashira coupling) was utilized for all reactions between terminal alkynes and aryl halides. Molecular orbital calculations were used in order to screen for suitable properties, such as the second hyperpolarizability, in compounds of interest. A quantitative structure-activity relationship (QSPR) study using a PLS approach were performed in order to identify important molecular electronic variables for optical limiting of organic compounds.

Two functional polyurethanes (P1 and P2) bearing a large pi electron conjugated chromophoric pendant were synthesized and characterized by FT-IR, H-1-NMR and UV-Vis absorption spectra. Their optical limiting properties were evaluated. The results show that P1 and P2 show novel optical limiting properties, which are assigned to a long pi electron conjugated chromophoric pendant. It was found that their optical limiting properties were affected simultaneously by solution concentration and P2 displays a better optical limiting property than P1 at the same solution transmittance, although that P1 has larger chi((3)) (4.28 x 10(-11) esu) than P2 (0.87 x 10(-11) esu), and their optical limiting mechanism is investigated.

A novel soluble functional polyacetylene copolymer (poly(EAAB-co-PA)) of 4-ethynyl-4'-[N,N-diethylamino]azobenzene (EAAB) and phenylacetylene (PA) was synthesized. The structures and properties of the polymers were characterized and evaluated by FTIR, UV-vis, H-1 NMR GPC, optical limiting, and nonlinear optical analyses. The results show that poly(EAAB-co-PA) has the large third-order nonlinear susceptibility, which are two orders of magnitude larger than those of poly(PA) and novel optical limiting property. (c) 2005 Elsevier Ltd. All rights reserved.

Two novel poly(1-alkyne)s containing azobenzene nonlinear optical chromophoric group, poly(4-(4-[4-(n-dodecyloxy)phenylazophenyl]carbonyl)oxy-1-butyne) (P1) and poly(11-(4-[4-(n-dodecyloxy)phenylazophenyl]carbonyl)oxy-1-undecyne) (P2), were synthesized by [Rh(nbd)Cl](2)-Et3N catalysts and characterized by FTIR, H-1 NMR, GPC and UV-vis techniques. Their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm. The results show that these soluble functional poly(1-alkyne)s possess good optical limiting properties and large nonlinear optical properties. (c) 2006 Elsevier Ltd. All rights reserved.

The demand for protection of eyes and various types of optical sensors from laser-beam pulses has resulted in the search for optical limiting devices that have the property of being transparent at low intensity of light (normal light), but non-transparent towards high intensity (laser) light. This type of protection may be obtained by using an organic material that displays nonlinear optical (NLO) properties. Examples of NLO effects that can be used for optical limiting are reverse saturable absorption (RSA), two-photon absorption (TPA) and nonlinear refraction. The advantage of using compounds that show such NLO effects is that they can have very fast response and are self-activating, that is, there is no need for externally controlled switching to obtain optical limiting. In this work, several dialkynyl substituted thiophenes and some thiophenyl-alkynyl-platinum(II)-complexes were synthesized and tested for nonlinear absorption of light. A palladium-copper mediated coupling (Sonogashira coupling) was utilized for all reactions between terminal alkynes and aryl halides. Molecular orbital calculations were used in order to screen for suitable properties, such as the second hyperpolarizability, in compounds of interest. A quantitative structure-activity relationship (QSPR) study using a PLS approach were performed in order to identify important molecular electronic variables for optical limiting of organic compounds.

The demand for protection of eyes and various types of optical sensors from laser-beam pulses has resulted in the search for optical limiting devices that have the property of being transparent at low intensity of light (normal light), but non-transparent towards high intensity (laser) light. This type of protection may be obtained by using an organic material that displays nonlinear optical (NLO) properties. Examples of NLO effects that can be used for optical limiting are reverse saturable absorption (RSA), two-photon absorption (TPA) and nonlinear refraction. The advantage of using compounds that show such NLO effects is that they can have very fast response and are self-activating, that is, there is no need for externally controlled switching to obtain optical limiting. In this work, several dialkynyl substituted thiophenes and some thiophenyl-alkynyl-platinum(II)-complexes were synthesized and tested for nonlinear absorption of light. A palladium-copper mediated coupling (Sonogashira coupling) was utilized for all reactions between terminal alkynes and aryl halides. Molecular orbital calculations were used in order to screen for suitable properties, such as the second hyperpolarizability, in compounds of interest. A quantitative structure-activity relationship (QSPR) study using a PLS approach were performed in order to identify important molecular electronic variables for optical limiting of organic compounds.

Optical limiting materials are developed for applications in protection of optical sensors against laser aggressions. We have studied functionalised macrocycles (thiacalixarenes) and alkynylplatinum(H) derivatives for optical limiting applications. Glass materials based on alkynylplatinum(H) derivatives and macrocycles were prepared through the sol-gel process. The molecular species were grafted to the matrix in order to maximise the concentration and the stability of the final solid-state material. The glass materials were cut and polished to approximately 1.5 mm. The glass materials show broadband optical limiting in the visible wavelength region, for nanosecond laser pulses., QC 20101025

Two novel polyacetylenes bearing nonlinear optical chromophoric group poly(3-(4-[4-(n-butyloxy) phenylazophenyl]carbonyl)oxy-1-propyne) (poly(la)) and poly(3-(4-[4-(n-heptyloxy)phenylazophenyl]carbonyl)-oxy-1-propyne) (poly(1b)) were synthesized with [Rh(nbd)Cl](2)-Et3N as catalysts. These polyacetylenes are soluble by using an alkyl spacer and an alkyloxyl group as a substituent. They were characterized by FTIR, NMR, GPC and UV-Vis and their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm wavenumber. The results show that these soluble functional polyacetylenes possess optical limiting properties and large nonlinear optical properties and poly(1b) possesses better optical limiting and nonlinear optical properties than poly(1a).

High molecular weight functional polyurethanes bearing large pi electron conjugated chromophoric pendants with different conjugation bridge structure, poly(1a), poly(1b), and poly(1e), were synthesized and characterized by FTIR, H-1 NMR and UV-vis absorption spectra. Their optical properties were evaluated by optical limiting and nonlinear optical analyses. The results show that these polymers possess good optical limiting and large nonlinear optical properties, which are attributed to the long D-pi-A conjugated pi electron structure of the NLO-chromophoric segment. Poly(la) with C=C double bond as pi electron conjugation bridge shows better optical limiting property than poly(1b) and poly(1c) with C=N or N=N double bond as conjugation bridge structure under the same linear transmittance, while poly(le) with N=N double bond as pi electron conjugation bridge of the NLO-chromophoric segment is superior on nonlinear optical properties to poly(la) and poly(1b) with C=C and C=N double bonds as pi electron conjugation bridge structure, respectively. (c) 2006 Elsevier Ltd. All rights reserved.

Two novel polyacetylenes bearing nonlinear optical chromophoric group poly(3-(4-[4-(n-butyloxy) phenylazophenyl]carbonyl)oxy-1-propyne) (poly(la)) and poly(3-(4-[4-(n-heptyloxy)phenylazophenyl]carbonyl)-oxy-1-propyne) (poly(1b)) were synthesized with [Rh(nbd)Cl](2)-Et3N as catalysts. These polyacetylenes are soluble by using an alkyl spacer and an alkyloxyl group as a substituent. They were characterized by FTIR, NMR, GPC and UV-Vis and their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm wavenumber. The results show that these soluble functional polyacetylenes possess optical limiting properties and large nonlinear optical properties and poly(1b) possesses better optical limiting and nonlinear optical properties than poly(1a).

Two novel polyacetylenes bearing nonlinear optical chromophoric group poly(3-(4-[4-(n-butyloxy) phenylazophenyl]carbonyl)oxy-1-propyne) (poly(la)) and poly(3-(4-[4-(n-heptyloxy)phenylazophenyl]carbonyl)-oxy-1-propyne) (poly(1b)) were synthesized with [Rh(nbd)Cl](2)-Et3N as catalysts. These polyacetylenes are soluble by using an alkyl spacer and an alkyloxyl group as a substituent. They were characterized by FTIR, NMR, GPC and UV-Vis and their optical limiting and nonlinear optical properties were investigated using 8 ns pulse at 532 nm wavenumber. The results show that these soluble functional polyacetylenes possess optical limiting properties and large nonlinear optical properties and poly(1b) possesses better optical limiting and nonlinear optical properties than poly(1a).

High molecular weight functional polyurethanes bearing large pi electron conjugated chromophoric pendants with different conjugation bridge structure, poly(1a), poly(1b), and poly(1e), were synthesized and characterized by FTIR, H-1 NMR and UV-vis absorption spectra. Their optical properties were evaluated by optical limiting and nonlinear optical analyses. The results show that these polymers possess good optical limiting and large nonlinear optical properties, which are attributed to the long D-pi-A conjugated pi electron structure of the NLO-chromophoric segment. Poly(la) with C=C double bond as pi electron conjugation bridge shows better optical limiting property than poly(1b) and poly(1c) with C=N or N=N double bond as conjugation bridge structure under the same linear transmittance, while poly(le) with N=N double bond as pi electron conjugation bridge of the NLO-chromophoric segment is superior on nonlinear optical properties to poly(la) and poly(1b) with C=C and C=N double bonds as pi electron conjugation bridge structure, respectively. (c) 2006 Elsevier Ltd. All rights reserved.

Three diarylalkynyl-substituted thiophenes were synthesized and the optical power limiting (OPL) effect at 532 nm was investigated for solutions of these compounds. The relationship between the OPL and parameters obtained from molecular-orbital-based calculations is discussed. Semi-empirical calculations indicate that the compounds can have a broad distribution of conformations due to inter-ring twisting, but that the second hyperpolarizability (gamma) can be significant despite a ring twist. The calculations imply that substitution by alkyl groups can lead to enhanced gamma values. The measurements and calculations show a greater increase of the OPL and gamma effects from compound 5 to 6 than from 6 to 7. For these compounds, which differ mainly by the length of the pi-electron system, the magnitude of non-linear absorption seems to be well correlated with several properties of the electronic ground state estimated by standard ab initio molecular orbital calculations, as well as with gamma values from the semi-empirical calculations.

The reverse saturable absorption and the optical limiting (OL) property of fullerene-functionalized polycarbonates (C60-PCs) which were synthesized by a direct reaction of C60 and PC in the presence of AIBN using 1, 1, 2, 2-tetrachloroethane as the solvent under microwave irradiation (MI) was investigated by z-scan technique in femtosecond scale. Its reverse saturable absorption behavior was believed to being caused by the covalently attached fullerene to the polymer chain and was found to be of the same order as C60. The measured OL results revealed that the absorption cross-section of the photo-excited singlet state was larger than that of the ground state, and the ratio of the absorption cross-section of the photo-excited singlet state to that of the ground state was determined by fitting the experimental data to the numerical integration by using the rate equation treatment. These new synthesized materials which are soluble in common organic solvents can be considered as potential sources for further optical applications, especially in ultrashort scale. © 2005 Elsevier B.V. All rights reserved.

Poly(1-alkyne)s containing azobenzene pendants with different spacer lengths and ring substitutents -{HC=C(CH2)(m)COO-C6H4-N=N-C6H4-NO2])(n)- P1(m) m = 3, 8 and -\{HC=C[(CH2)(m)COO-C6H3-o-Br-N=N-C6H4 NO2]}(n)- P2(m) m = 3, 8] are designed and synthesized. The polymers are prepared in satisfactory yields with high molecular weights (M-w up to 3.3 X 10(4) Da) by [Rh(nbd)Cl](2)-Et3N in THF or dioxane. Their structures and properties are characterized and evaluated by IR, UV, NMR, TGA, nonlinear optical and optical limiting analyses. All the polymers are completely soluble in common organic solvents and lose 5\% of their weights at temperatures of similar to 270 degrees C. The spacer length and the pendant substitutent affect the nonlinear optical and optical limiting properties of the polymers, with 1(3) showing superior properties than its counterparts 1(8) and 2(3) with long methylene spacers and bromide substitutents on the azobenzene pendants, respectively. (c) 2005 Elsevier Ltd. All rights reserved.

High molecular weight polyacetylenes hearing nonlinear chromophoric pendants poly [4-ethynyl-4'-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl](2)-Et3N. The azo unit in the copolymers call be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility. all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7\%. The structures and properties of the polymers were characterized and evaluated by UV. NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability ( 300 degrees C). They can attenuate intense laser pulses, With Solutions of high concentrations showing better performances. The third-order nonlinear Susceptibility of the copolymers was as high as 4.62 X 10(-11) esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene). (c) 2005 Elsevier Ltd. All rights reserved.

Alkyne copolycyclomerizations of aromatic diynes 2,7-bis(4-ethynylphenylethynyl)-9,9-diliexylfluorene (1) and I 4-bis(4-ethynylphenylethynyl) benzene (11) with an aliphatic moncyne 1-dodecyne (A) were effected by CPCO(CO)(2)-hv in THF, producing hyperbranched poly(aryleneethynylene)s 1 and 2) Of high molecular weights (M, up to 4.4 x 10(4) Da) in high isolation yields (up to 97\%). The polymers possessed outstanding thermal stability and emitted strong deep blue light of; 400 nm when their solutions were photoexcited. The polymers effectively limited the light of a 532 nm laser, with the performance of 2 being better than that Of C-60, a well-known optical limiter, under similar linear transmittance.

The reverse saturable absorption and the optical limiting (OL) property of fullerene-functionalized polycarbonates (C60-PCs) which were synthesized by a direct reaction of C60 and PC in the presence of AIBN using 1, 1, 2, 2-tetrachloroethane as the solvent under microwave irradiation (MI) was investigated by z-scan technique in femtosecond scale. Its reverse saturable absorption behavior was believed to being caused by the covalently attached fullerene to the polymer chain and was found to be of the same order as C60. The measured OL results revealed that the absorption cross-section of the photo-excited singlet state was larger than that of the ground state, and the ratio of the absorption cross-section of the photo-excited singlet state to that of the ground state was determined by fitting the experimental data to the numerical integration by using the rate equation treatment. These new synthesized materials which are soluble in common organic solvents can be considered as potential sources for further optical applications, especially in ultrashort scale. © 2005 Elsevier B.V. All rights reserved.

High molecular weight polyacetylenes hearing nonlinear chromophoric pendants poly [4-ethynyl-4'-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl](2)-Et3N. The azo unit in the copolymers call be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility. all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7\%. The structures and properties of the polymers were characterized and evaluated by UV. NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability ( 300 degrees C). They can attenuate intense laser pulses, With Solutions of high concentrations showing better performances. The third-order nonlinear Susceptibility of the copolymers was as high as 4.62 X 10(-11) esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene). (c) 2005 Elsevier Ltd. All rights reserved.

Poly(1-alkyne)s containing azobenzene pendants with different spacer lengths and ring substitutents -{HC=C(CH2)(m)COO-C6H4-N=N-C6H4-NO2])(n)- P1(m) m = 3, 8 and -\{HC=C[(CH2)(m)COO-C6H3-o-Br-N=N-C6H4 NO2]}(n)- P2(m) m = 3, 8] are designed and synthesized. The polymers are prepared in satisfactory yields with high molecular weights (M-w up to 3.3 X 10(4) Da) by [Rh(nbd)Cl](2)-Et3N in THF or dioxane. Their structures and properties are characterized and evaluated by IR, UV, NMR, TGA, nonlinear optical and optical limiting analyses. All the polymers are completely soluble in common organic solvents and lose 5\% of their weights at temperatures of similar to 270 degrees C. The spacer length and the pendant substitutent affect the nonlinear optical and optical limiting properties of the polymers, with 1(3) showing superior properties than its counterparts 1(8) and 2(3) with long methylene spacers and bromide substitutents on the azobenzene pendants, respectively. (c) 2005 Elsevier Ltd. All rights reserved.

Alkyne copolycyclomerizations of aromatic diynes 2,7-bis(4-ethynylphenylethynyl)-9,9-diliexylfluorene (1) and I 4-bis(4-ethynylphenylethynyl) benzene (11) with an aliphatic moncyne 1-dodecyne (A) were effected by CPCO(CO)(2)-hv in THF, producing hyperbranched poly(aryleneethynylene)s 1 and 2) Of high molecular weights (M, up to 4.4 x 10(4) Da) in high isolation yields (up to 97\%). The polymers possessed outstanding thermal stability and emitted strong deep blue light of; 400 nm when their solutions were photoexcited. The polymers effectively limited the light of a 532 nm laser, with the performance of 2 being better than that Of C-60, a well-known optical limiter, under similar linear transmittance.

The reverse saturable absorption and the optical limiting (OL) property of fullerene-functionalized polycarbonates (C60-PCs) which were synthesized by a direct reaction of C60 and PC in the presence of AIBN using 1, 1, 2, 2-tetrachloroethane as the solvent under microwave irradiation (MI) was investigated by z-scan technique in femtosecond scale. Its reverse saturable absorption behavior was believed to being caused by the covalently attached fullerene to the polymer chain and was found to be of the same order as C60. The measured OL results revealed that the absorption cross-section of the photo-excited singlet state was larger than that of the ground state, and the ratio of the absorption cross-section of the photo-excited singlet state to that of the ground state was determined by fitting the experimental data to the numerical integration by using the rate equation treatment. These new synthesized materials which are soluble in common organic solvents can be considered as potential sources for further optical applications, especially in ultrashort scale. © 2005 Elsevier B.V. All rights reserved.

High molecular weight polyacetylenes hearing nonlinear chromophoric pendants poly [4-ethynyl-4'-(N,N-diethylamino)azobenzene-co-phenylacetylene]s [poly(EAAB-co-PA)s] were synthesized in moderate yields by [Rh(nbd)Cl](2)-Et3N. The azo unit in the copolymers call be effectively controlled by the monomer feed ratio. Whereas the homopolymer of EAAB possessed low solubility. all the copolymers, however, dissolved readily in common organic solvents when the poly(EAAB) molar content was less than 41.7\%. The structures and properties of the polymers were characterized and evaluated by UV. NMR, optical limiting, and nonlinear optical analyses. All the copolymers possessed high stereoregularity and thermal stability ( 300 degrees C). They can attenuate intense laser pulses, With Solutions of high concentrations showing better performances. The third-order nonlinear Susceptibility of the copolymers was as high as 4.62 X 10(-11) esu, which are two orders of magnitude larger than those of poly(PA), and larger than that of poly(N-carbazoylacetylene), and poly(1-naphthylacetylene). (c) 2005 Elsevier Ltd. All rights reserved.

Poly(1-alkyne)s containing azobenzene pendants with different spacer lengths and ring substitutents -{HC=C(CH2)(m)COO-C6H4-N=N-C6H4-NO2])(n)- P1(m) m = 3, 8 and -\{HC=C[(CH2)(m)COO-C6H3-o-Br-N=N-C6H4 NO2]}(n)- P2(m) m = 3, 8] are designed and synthesized. The polymers are prepared in satisfactory yields with high molecular weights (M-w up to 3.3 X 10(4) Da) by [Rh(nbd)Cl](2)-Et3N in THF or dioxane. Their structures and properties are characterized and evaluated by IR, UV, NMR, TGA, nonlinear optical and optical limiting analyses. All the polymers are completely soluble in common organic solvents and lose 5\% of their weights at temperatures of similar to 270 degrees C. The spacer length and the pendant substitutent affect the nonlinear optical and optical limiting properties of the polymers, with 1(3) showing superior properties than its counterparts 1(8) and 2(3) with long methylene spacers and bromide substitutents on the azobenzene pendants, respectively. (c) 2005 Elsevier Ltd. All rights reserved.

Alkyne copolycyclomerizations of aromatic diynes 2,7-bis(4-ethynylphenylethynyl)-9,9-diliexylfluorene (1) and I 4-bis(4-ethynylphenylethynyl) benzene (11) with an aliphatic moncyne 1-dodecyne (A) were effected by CPCO(CO)(2)-hv in THF, producing hyperbranched poly(aryleneethynylene)s 1 and 2) Of high molecular weights (M, up to 4.4 x 10(4) Da) in high isolation yields (up to 97\%). The polymers possessed outstanding thermal stability and emitted strong deep blue light of; 400 nm when their solutions were photoexcited. The polymers effectively limited the light of a 532 nm laser, with the performance of 2 being better than that Of C-60, a well-known optical limiter, under similar linear transmittance.

The FCS Laser-Hardened Vision STO seeks to develop an electro-optic targeting vision system that utilizes a combination of nonlinear and sacrificial materials to provide protection from damage by frequency-agile battlefield lasers at both long and short range. Evidently, the selection of sensor protection technologies for incorporation into the final targeting system will be based on their optical limiting performance under field conditions. While few optical limiting devices perform as well in the field as in the laboratory, some, notably an otherwise extremely promising prototype sacrificial mirror, exhibit a discrepancy that is particularly striking. In the case of a thin, passive limiting component (e.g. ablative mirror or dye cell) situated at a focal plane, the decrease in performance can be attributed to the randomly fluctuating axial displacement of the focal plane that is known to arise from the effects of atmospheric turbulence on a propagating laser beam. I present the results of a quantitative study of the effects of turbulence-induced focal shift on the performance of passive optical limiting devices. The results apply not only to the FCS targeting system, but to all laser eye and sensor protection devices that employ a thin, passive component whose optical limiting performance depends strongly on the input irradiance or the input fluence., See also ADM001736, Proceedings for the Army Science Conference (24th) held in Orlando, FL on 29 Nov-2 Dec 2005. The original document contains color images.

The objective of this Trident project is to study the optical properties of single mode waveguide systems that exhibit an absorption that increases with the intensity of the light incident upon them. In this way these devices limit the transmission of optical energy and are referred to as optical limiters . Such systems are of great value to both the military and the telecommunications industry because of their ability to protect sensitive equipment from exposure to high intensity light. Experiments were performed using very small glass capillaries filled with materials that exhibit a nonlinear absorption. In this case, the materials absorb a greater amount of light as the intensity increases. These systems act as waveguides, confining the light to a small core region where the nonlinear material resides. Furthermore, only one intensity distribution (or mode ) is allowed if the index of refraction of the core is very close to that of the surrounding glass. In this case, the waveguide is called single mode. Single mode behavior was achieved by controlling the temperature of the waveguide in order to tune the index of refraction of the core material. Pulses of visible light (wavelength = 532 nm, pulse width = 4ns) were coupled into single mode waveguides and the input and output intensities were measured. These results were compared to optical limiting observed in multi-mode waveguides. It was observed that multi-mode waveguides exhibit better optical limiting than single-mode waveguides. This is because the entire mode structure is confined to the core in a multi-mode waveguide. However, a portion of the mode extends into the cladding in a single-mode waveguide. In addition, single-mode waveguides show a decreased ability to limit at higher temperatures where the difference in index of refraction is smallest., The original document contains color images.

A series of dendritic 2,3,4,5-tetraphenylsiloles (1-8) are prepared. Polymerizations of 4-8 are effected by transition-metal catalysts, giving linear (9-12) and hyperbranched polymers (14) in high yields. Whereas the silole polymers axe practically nonluminescent when molecularly dissolved, they become emissive when aggregated in poor solvents or cooled to low temperatures. The light-emitting diodes using linear poly(silolylacetylene)s as active layers emit blue and green lights with current efficiency up to 1.45 cd/A. The hyperbranched poly(siloleneaxylene) s are nonlinear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that Of C-60, a well-known optical limiter.

A series of dendritic 2,3,4,5-tetraphenylsiloles (1-8) are prepared. Polymerizations of 4-8 are effected by transition-metal catalysts, giving linear (9-12) and hyperbranched polymers (14) in high yields. Whereas the silole polymers axe practically nonluminescent when molecularly dissolved, they become emissive when aggregated in poor solvents or cooled to low temperatures. The light-emitting diodes using linear poly(silolylacetylene)s as active layers emit blue and green lights with current efficiency up to 1.45 cd/A. The hyperbranched poly(siloleneaxylene) s are nonlinear optically active and strongly attenuate the optical power of intense laser pulses, whose optical limiting performances are superior to that Of C-60, a well-known optical limiter.

This program is focused on understanding recent discoveries of the optical nonlinearities of the metaphases of liquid crystals, and novel nonlinear optical phenomena enabled by the extremely large nonlinearities in these material systems. Both collective and individual molecular optical properties have been investigated experimentally. Quantitative theories of the basic physics as well as novel phenomena and the working principles of multifunctional optical devices have also been developed. Specifically, (i) the large optical nonlinearities of nematic liquid crystals in the optical communication wavelength regime (1 .55 microns) as well as the visible region have been quantitatively established. (ii) All-optical self-action processes such as stimulated scattering and polarization switching, and self-starting optical phase conjugation using thin (microns) nematic films with very low power cw infrared lasers have been demonstrated, along with the development of quantitative theories. (iii) Novel optical elements/devices such as liquid-crystal photonic crystals, nonlinear optical fibers and fiber arrays were developed using nematic as well as isotropic phase liquid crystals. (iv) Quantitative theoretical descriptions of their tunable and nonlinear transmission/ reflection properties, and optical limiting actions and practical devices; feasibility demonstration of the nonlinear fiber array limiting devices. (v) Demonstration of the feasibility of optical soliton formation in nematic liquid crystals. (vi) Synthesis of a new class of extremely nonlinear liquid with superior optical limiting performance, wide temperature stability and very fast (picosecond - nanosecond) nonlinear electronic absorption properties suitable for limiting applications against agile frequency lasers.

High molecular weight, hyperbranched polyarylenes were synthesized in high isolation yields by the copolycyclotrimerizations of 2,5-diethynylthiophene (1), 4,4'-biphenyldiyne (2), and 2,7-diethynylfluorenes (3) with I-heptyne (4) and 1-dodecyne (5) using TaCl5-Ph4Sn as the catalyst in toluene. The structures of the polymers were characterized by IR, NMR, TGA, and UV analyses. All the polymers exhibited outstanding thermal stability and emitted strong blue light, whose intensities are higher than that of poly(l-phenyl-l-octyne), a well-known highly emissive polyacetylene. Little red shift was observed in the photoluminescence of the polymer thin films. The polymers strongly attenuated intense pulses of 532 nm laser pulses. (C) 2002 Elsevier Science B.V. All rights reserved.

Alkyne polycyclotrimerizations are effected by tantalum- and cobalt-based catalysts, giving soluble hyperbranched polyarylenes (HPAs) with high molecular weights (M-w up to similar to2 X 10(5)) in high yields (up to 99.9\%). All the HPAs exhibit excellent thermal stability. losing little of their weights when heated to > 400 degreesC. The HPAs graphitize when pyrolyzed at 800 degreesC in high yields (up to 86\%). Upon photoexcitation, the HPAs efficiently emit strong deep-blue and blue-green light with fluorescence quantum yields LIP to 98\%. The HPAs strongly attenuate intense laser pulses, with their limiting performances being superior to that of C-60, a well-known optical limiter. (C) 2003 Academie des sciences. Published by Editions scientifiques et medicales Elsevier SAS. All rights reserved.