Here we demonstrate a 40% increase in the nonlinearity, or electro-optic (EO) coefficient, of the nonlinear optic (NLO) polymer SEO100 with the addition of a thin guanine nucleobase buffer layer deposited between the NLO polymer and the cathode electrode. We suggest that the high lowest unoccupied molecular orbital of guanine flattens the field distribution at the high injection barrier reducing leakage current during poling. This has the potential to realize higher EO coefficients without the need to synthesize new NLO polymer materials, as well as an increase in device yield due to less failure during poling.

Brittlestars (Echinoderms) are a large group of marine invertebrates, from which many species are able to produce bioluminescence. The light is used for ecological functions associated with defense. Hence, the larger and more intense the bioluminescent display the more effective it would be. Here, we report on our study to determine whether ossicles, making the arms of brittlestars, play a role in increasing the luminous display. We compared ossicles from three brittlestar species, two luminous and one not, and found no striking difference between the ossicles, in terms of structure, or calcium and magnesium content.

Novel microdisk optical 3D structure fabrication was demonstrated in a room temperature and atmospheric condition with tens-seconds processing duration. This additive manufacturing scheme of polymeric microdisk was based on the ink-jet technique with hyperbranched polymer TZ-001. And whispering-gallery mode (WGM) lasing with a low threshold was confirmed by doping LDS798 or Rhodamine 590 dyes. The diameters both 75 µm were archived. The WGM lasing at around 800 nm wavelength by the LDS798, and at around 600 nm by the Rhodamine 590. Low lasing threshold about 2~3 µJ/mm² were confirmed. And shift of peak wavelength was observed on the Rhodamine590:TZ-001 disk.

Diatoms are single cellular algae encapsulated in an external wall of micro-structured porous silica called the frustule. Diatoms are present in all water environments and contribute with 20-25 % of the global primary production of oxygen by photosynthesis. The appearance of the frustule is very species dependent with huge variety in size, shape, and microstructure. We have experimentally investigated optical properties of frustules of several species of diatoms to further understand light harvesting properties together with common traits, effects and differences between the different frustules. We have observed, when incident light interacts with the micro-structured frustule it is multiple diffracted giving rise to wavelength dependent multiple focal points and other optical effects. Experimental results have been simulated and well confirmed by free space FFT propagation routine analysis software. The software uses parameters which are extracted from experimental images as basis for simulation and allows us to extract the influence of the different elements of the frustule. The information could be used both for predicting optical properties of diatoms and by changing frustule parameters, maybe by altering growth conditions of the diatoms tailor their optical properties.

Triphenylmethyl and triphenylsilyl structural fragments can be used to obtain glass forming, solution processable materials from polar chromophore molecules. Large number of compounds has been synthesized taking advantage of this approach, making it possible to identify some structure-property relations. Regarding the non-linear optical (NLO) properties of the given materials it is evident that triphenylmethyl groups help shielding unwanted NLO efficiency limiting dipolar interactions between polar chromophores in solid films. Chromophore stacking is still observed for compounds with large dipole momentum values. The glass transition temperatures of the compounds increase with the molecular weight for the studied material class, reaching values up to 130°C.

Time-resolved circular dichroism (CD) measurements can yield relevant information on the dynamics of conformational changes in molecules on the condition that some a priori knowledge is obtained. This can be the use of simple models such as the excitonic coupling or the octant rule or the phenomenological relationship between far-UV CD and secondary structures in proteins for example. This article describes such experiments where CD has brought relevant conformational information.

In this era of novel technological materials, inorganic-organic (IO) materials has emerged as new class of materials for their application in photonic materials, miniaturized sensors, optoelectronic devices, non-linear optical apparatus by exploiting the properties of both constituents in a single entity. Here we present the formation and growth mechanism of two dimensional Inorganic-organic (IO) perovskite structures from anisotropically grown PbO hexagonal nanosheets, in three steps: Fabrication of hexagonal PbO nanosheets by the versatile bottom-up electrochemical deposition technique, iodinization of PbO into PbI₂, followed by conversion of PbI₂ into IO hybrid by the intercalation of organic moiety. A systematic and detailed structural study reveals that PbO nanosheet formation is more likely to result from an oriented attachment mechanism, in which the sheets formed by the reduction in surface area that happens during aggregation of small nanoparticle that each has a net dipole moment, which tends to form a self-assembled structure. Intercalation of organic moiety into the PbI₂ layers yielded a selfassembled quantum-wells system of one of the IO hybrid, i.e. (C₆H₉C₂H₄NH₃)₂PbI₄ (CHPI), sustaining the hexagonal shape.

The RMS surface roughness of an optical polymer waveguide end facet cut by a milling router and measured by AFM is investigated for a range of rotation speeds and translation speeds of the router. It was found that 1 flute (cutting edge) routers gave significantly less rough surfaces than 2 or 3 flute routers. The best results were achieved for a 1 flute router when the milling bit was inserted from the copper layer side of the board with a rotation speed of 15,000 rpm and a translation speed of 0.25 m/min which minimized the waveguide core end facet RMS roughness to 183 ± 8 nm and gave input optical coupling loss of 1.7 dB ± 0.5 dB and output optical coupling loss of 2.0 dB ± 0.7 dB. The relationship between optical coupling loss at the input and output of the waveguides and waveguide end facet roughness is also investigated in this paper. The ratio of RMS roughness to autocorrelation length of the roughness is shown to have a quantified linear relationship with experimental measurements of optical insertion loss, input optical coupling loss and output optical coupling loss. A new fabrication technique for cut waveguide end facet treatment has been proposed and demonstrated which reduces the insertion loss by 2.60 dB ± 1.3 dB which is more than that achieved by the closest available index matching fluid which gave 2.23 dB ± 1.2 dB and which is far more robust for use in commercial products.

Development of passive and active polymer based optical materials for high data rate waveguide routing and interconnects has gained increased attention because of their excellent properties such as low absorption, cost savings, and ease in fabrication. However, optical polymers are typically limited in the range of their refraction indices. Combining polymeric and inorganic optical materials provides advantages for as development of nano-composites with higher refractive indices with the possibility of being used as an active optical component. In this paper a new composite material is proposed based on polymer-metal oxide nano-composites for use as optical wave guiding structures and components. PDMS (Polydimethylsiloxane) is utilized for the polymer portion while the inorganic material is titanium dioxide. Refraction indices as high as 1.74 have been reported using these composites. For PDMS-TiO₂ hybrids, the higher the ratio of titanium dioxide to PDMS, the higher the resulting refractive index. The index of refraction as a function of the PDMS:TiO₂ ratio is reported with an emphasis on use as optical waveguide devices. Absorption spectrum of the nano-composites is measured showing low absorption at 850 nm and high absorption in the UV regime for direct UV laser/light curing. Prototype multimode waveguides are fabricated using soft imprint embossing that is compatible with the low viscosity nano-composite material. Cross dimensional shape and profile show the potential for full scale development utilizing the material set.

This study addresses a unique degradation mechanism in organic electronic devices occurring due to combined effects of electric field and temperature. A simple polymer diode structure consisting of a semiconducting polymer sandwiched between two electrodes (ITO and Al) is considered for degradation studies. It is observed that voltages beyond a certain value lead to fracture of polymer and aluminium films. As characterized, these defects show that the degradation nucleates in the form of a chain-like pattern consisting of alternating polymer fracture sites (hinges) and aluminium rupture sites (links). A mechanism is hypothesized based on experimental observations to explain the phenomenon. This is further validated by an analytical model for stress at degradation sites due to electric field and temperature. The model is used to develop a failure criteria based on device geometry, operating voltage and temperature. Experiments and modelling predict that this mechanism might be unique to soft thin film electronic devices.

Second Harmonic Generation (SHG) was employed to study phase transition in molecular films formed at the air/water interface. Studies were performed at biomimetic lipid monolayers by simultaneous surface tension and SHG measurements. Light polarization analysis of the SHG intensities was performed with different lipid interfaces. A comparison between these interfaces provided lipid condensed state-dependent data. An optical signature was observed in the polarization plots for the transition from the Liquid-Expanded (LE) to the Liquid-Condensed (LC) state.

We present photophysical properties of functionalized anthradithiophene (ADT) and pentacene (Pn) derivatives, as well as charge and energy transfer properties of donor-acceptor (D/A) pairs of these derivatives. All molecules studied were fluorescent and photostable enough to be imaged on the single-molecule level in a variety of polymeric and in a functionalized benzothiophene (BTBTB) crystalline host using room-temperature wide- field epifluorescence microscopy. Flexibility of functionalization of both guest (ADT, Pn) and host (BTBTB or polymer) molecules can be used for systematic studies of nanoscale morphology and photophysics of D/A organic semiconductor bulk heterojunctions, as well as in applications relying on FRET, using single-molecule fluorescence microscopy.

Recently, bilayer resist processing combined with development in hydrofluoroether (HFE) solvents has been shown to enable single color structuring of vacuum-deposited state-of-the-art organic light-emitting diodes (OLED). In this work, we focus on further steps required to achieve multicolor structuring of p-i-n OLEDs using a bilayer resist approach. We show that the green phosphorescent OLED stack is undamaged after lift-off in HFEs, which is a necessary step in order to achieve RGB pixel array structured by means of photolithography. Furthermore, we investigate the influence of both, double resist processing on red OLEDs and exposure of the devices to ambient conditions, on the basis of the electrical, optical and lifetime parameters of the devices. Additionally, water vapor transmission rates of single and bilayer system are evaluated with thin Ca film conductance test. We conclude that diffusion of propylene glycol methyl ether acetate (PGMEA) through the fluoropolymer film is the main mechanism behind OLED degradation observed after bilayer processing.

Geminate recombination of photo-generated excitons represents a considerable loss mechanism in polymer solar cells. We apply time-resolved photoluminescence (TRPL) to study the radiative recombination which accompanies the process of charge generation. A streak camera is used, which is sensitive for both the photoluminescence (PL) from the initially excited singlet excitons and the weaker emission from charge transfer (CT) states. The latter are formed at internal interfaces when the polymer is blended with a fullerene acceptor. We draw a comparison between our results for two polymers, P3HT and PTB7, respectively, which were studied in blends with the fullerene derivative PCBM. In addition, pristine films were investigated, allowing for the identification of interfacial features in the blends. For both polymers, the PL of the singlet states was rapidly quenched in blends with PCBM. In P3HT, time constants of about 40 ps were recorded for the singlet exciton decay and related to exciton diffusion, whereas the PL of PTB7 was almost completely quenched within the first 3 ps. The decay rates of the emissive CT excitons were 2-3 orders of magnitude smaller than those of the singlet state. Yet, due to their slower dynamics (~ 500 ps), they could be separated from the superimposed singlet emission. The CT decay times in blends with P3HT exhibited no significant temperature dependence, indicating that thermally driven dissociation of emissive excitons is unlikely. For blends with PTB7, however, a faster decay of the CT emission was obtained at room temperature.

Because charge transport in a single crystal is anisotropic in nature, directional growth of single crystals would enhance device performance and reduce its variation among devices. For an organic thin film, a method based on a temperature gradient would offer advantages in throughput and cleanliness. In experiments, a temperature gradient was established in a spin-coated film of 2,7-dioctyl [1]benzothieno[3,2-b]benzothiophene (C₈-BTBT) by two methods. First, a sample was placed on a metal plate bridging two heat stages. When one of the heat stages was cooled, the material started to solidify from the colder region. The melt-solid interface proceeded along the temperature gradient. Cracks were formed perpendicular to the solidification direction. Second, a line-shaped region on the film was continuously exposed to the light from a halogen lamp. After the heat stage was cooled, cracks similar to the first experiment were observed, indicating that the melt-solid interface moved laterally. We fabricated top-contact, bottom-gate transistors with these films. Despite the cracks, field-effect mobility of the transistors fabricated with these films was close to 6 cm² /Vs and 4 cm² /Vs in the first and second experiment, respectively. Elimination of cracks would improve charge transport and reduce performance variation among devices. It should be noted that the intense light from the halogen lamp did not damage the C₈-BTBT films. The vast knowledge on laser annealing is now available for directional growth of this type of materials. The associated cost would be much smaller because an organic thin film melts at a low temperature.

Second Harmonic Generation (SHG) was used to investigate the two enantiomers of a chiral bridged binaphthol derivative 1(+) and 1(-) at the air-water interface under lateral compression in a Langmuir trough. For each enantiomer, surface pressure and SH intensity were measured simultaneously during compression and decompression cycle of the molecular film. S polarized output SHG intensity as a function of the input polarization angle of the fundamental beam demonstrated the supramolecular origin for the chirality. The formation of 1(+) and 1(-) aggregates in the film was deduced from the non-vanishing SHG intensities collected for the 90° input and S output polarization angles.

We present a technique to study the (dis)charging of organic semiconductor films at microscopic scales, and in various environments, using an optical tweezers-based method combined with fluorescence spectroscopy. The 1 µm silica spheres were coated with either pristine organic semiconductor or a donor-acceptor blend, trapped using optical tweezers, and their fluorescence was measured concurrently with the effective surface charge. The effective surface charge in uncoated silica spheres suspended in water was a factor of ∼70 higher as compared to that from similar spheres in a nonpolar toluene. In contrast, the coated silica spheres exhibited low effective charge densities in both environments, which is indicative of minimal interaction of organic semiconductors under study with these environments. This serves as a proof-of-principle experiment towards systematic studies of nanoscale photoinduced charge-based interactions between organic semiconductor molecules, with a resolution down to an elementary charge, and depending on the dielectric environment.

One of the issues that affects the performance of plastic optical fibers (POFs) is the light scattering caused by the presence of inhomogeneities in the polymer, which is responsible for the optical energy loss and for the mode coupling in POFs. The aim of this work is to compare two different methods for measuring light scattered in step index polymer optical fibers (SI-POF) by using the side-illumination technique. On the one hand, scattered intensity and far-field patterns at single wavelength have been measured by varying the launching conditions: position of the excitation spot in the fiber and incidence angle. On the other hand, we have measured the spectral distribution of the scattered light in SIPOFs by exciting the fiber with a supercontinuum source. A theoretical model based on Mie theory has been used to analyze the obtained experimental results. From this analysis, the size and position of the most influential scattering centers in step-index POFs can be estimated. The results obtained employing both methods have been compared, resuming the advantages and drawbacks of each one for characterizing the optical quality on SI-POFs.