A three-dimensional micro-object was fabricated by two-photon initiated photopolymerization (TPIP) of soft-resin with the efficient two-photon absorbing multi-branched chromophore, EPS-3arm, which possesses high two-photon absorption cross-section of 5.21×10-47 cm4s/photons at 700 nm. The structural stability of the fabricated micro-objects could be achieved with aid of sol-gel process. The two-photon absorbing stilbazolium-cored dendrimer was also synthesized. The stillbazolium chromophore was covalently linked with the dendrimer chains so as to restrict free conformation motion. The hindered molecular twisting motion of the stilbazolium dye within the dendrimer is responsible for 5 to 16 times of enhancement in fluorescence emission along with the increased emission lifetime. The steady-state and time-resolved fluorescence emission study of the solid-state film indicate an efficient site-isolation and restriction of conformation motion of the active two-photon chromophore.

We have performed a critical analysis of optical limiting materials exhibiting the two typical absorption mechanisms of reverse saturable absorption (RSA) and two-photon absorption (TPA). The limiting characteristics of beam propagation in nonlinear liquids that exhibit RSA and TPA are discussed, and guidelines for materials and parameter optimization that will result in practical large dynamic range devices are given.

The development of an instrument measuring the age of a fingerprint could raise the effectiveness and reliability of the dactyloscopy and lower the expenses of unnecessary fingerprint analysis. The purpose of the presented investigation is to determine the compounds in a fingerprint residue, which can be used as a time relevant indicator. The identification of the information carrier inside the secreted substance shall determine the main components, which allow age-related statements. A multiphoton excitation is used to determine the age without degenerating or changing samples in any way, so that the evidence is usable for further examination and documentation. Non-invasive fluorescence analysis on the basis of the surface concentration of fingerprint components is presented.

This report presents preliminary optical limiting and spectroscopic characterization of dendrimer capped Pt-ethynyls. Preliminary OPL and spectroscopic characterization revealed that these have better OPL properties than the non-capped analogue. The excited state properties in terms of luminescence for emission at ca 400 nm and 525 nm is in the nanosecond and microsecond range, respectively. The site isolation provided by the dendrimer capping also give rise to strong phosphorescence involving the same emission bands near 525 nm. The decay time for this was found to be in the range 0.2 ms, considerably longer than for other similar Pt-complexes, and we tentatively assign this to a site-isolation effect that prevents quenching of the triplete state. It was shown how the dendron capping also makes it feasible to blend the dye with e.g. MMA monomers and carry out polymerization to obtain a solid OPL device with good performance.

The series of (tert-butyl)catechol-substituted fluorinated naphthalocyanines 1, 2 and 3 displays limiting of the optical power generated with nanosecond light pulses simultaneously at 532 and 1064 nm. Limiting thresholds of 1-3 fall in the range 1.5-2.7 J cm^-2 at 532 nm and 2.6-3.7 J cm^-2 at 1064 nm when linear transmittance is 0.75 at both wavelengths of analysis. Compared to other unsubstituted naphthalocyanines, 1-3 show a relatively large window of high linear optical transmission between the characteristic Q- and B- absorption bands (above 0.75 for a 250 nm-wide window when 1-3 concentration is in the order of few millimoles per liter in 1 cm thick cells). A general enhancement of photostability in 1-3 is observed for the presence of electron-withdrawing fluorine substituents. The optical limiting effect produced by these systems is evaluated for the protection of optical sensors which operate in both visible and NIR spectral ranges, e.g. the human eye and night vision devices.

Compound semiconductors, in the form of GaAs and InP have achieved major commercial significance in areas of application such as mobile communications, displays and telecoms and offer a versatility of function beyond the capabilities of Si. III-V compounds, and in particular GaAs, have since their early development been the subject of defence related interest. Support from this sector established the basic materials technologies and nurtured development up until their commercial breakthrough into consumer products. GaAs, for example, now provides essential components for mobile phones and CD / DVD players. An overview is presented of the crystal growth and processing methods used in the manufacture of these materials. Current state of the art characteristics on crystal form and quality are discussed, together with the evolution of single crystal growth techniques. Consideration is given to how these principal compounds together with the minor materials, InSb, GaSb and InAs are employed in diverse applications over a broad spectral range, together with information on markets and future perspectives.

High Resistivity (HiRes(TM)) silicon (Resistivity ≥ 8000 Ohm-cm) is demonstrated as the best choice of microwave substrate for emerging radio frequency (RF) MEMS devices operating at GHz/THz frequencies. The potential combination of active devices with passive MEMS structures allows single-chip realization of complete and cost effective microwave and millimeter wave systems. High Transparency (HiTran) silicon is demonstrated as the best choice of infrared material for systems working in the 3-5 micron region and for some type of systems working in the 8-12 micron region provided than thickness of the HiTran material does not exceed 2 mm.

In this work is presented a study on the surface microdomain formation in quasi-SLN Z-cut 3" crystals, with an accurate control on both the composition and on the wafering process. The UV absorption edge has been measured and correlated with the crystal composition, showing the edge shift towards shorter wavelengths. The coercive field has been measured as a function of temperature and it has been found lower in the quasi-SLN substrate if compared with the congruent crystals. The microdomain formation at wafer level can be controlled and avoided by appropriate composition choice as well as wafer mechanical and thermal treatments, and is checked by chemical etching and subsequent optical inspection. It has been found that quasi-SLN crystals with 49.82 Li₂O mol% content could present microdomains formation even after the photoresist process. On the other side, quasi-SLN crystals with 49.72 Li₂O mol% content seem to be more stable for both photoresist and Ti diffusion process for waveguide fabrication. A careful control on LiNbO₃ composition and wafer surface quality allows one to find the proper compositional window for the realization of various advanced optical and electro-optical devices.

Non-linear optical (NLO) devices for wavelength conversion of laser sources into the mid-infrared waveband (such as optical parametric oscillators) require the provision of non-linear materials. Quasi-phase matched (QPM) gallium arsenide crystals represent a promising alternative NLO material (high non-linear coefficient, low-optical loss) to conventional birefringent chalcopyrite crystals for use in the mid to far-infrared. To date, several approaches have been investigated to produce QPM GaAs crystals, including diffusion and fusion wafer bonding, orientation patterned growth and total internal reflection techniques. However, these require ultra-clean processing environments, relatively high bonding temperatures or are limited in crystal aperture. We present an approach to developing QPM GaAs crystals based on bonding using an index-matched chalcogenide glass. The glass-bonding (GBGaAs) technique forms low-loss bonds at moderate temperature and has several advantages over existing approaches. In particular, the technique is tolerant to GaAs wafer thickness variations and surface defects, and has the potential to produce large-aperture crystals. The glass-bonding process involves coating individual GaAs wafers with a thin-film of glass, deposited by RF sputtering, and then bonding assembled stacks of coated wafers in a vacuum oven under carefully controlled temperature and pressure conditions to form a single composite structure. To date, GBGaAs crystals consisting of up to 40 layers have been produced and optical losses per layer of less than 0.1% have been achieved. An outline of the production process for manufacturing GBGaAs crystals will be described together with details of optical assessment procedures. The impact of glass purity, sputtering conditions and pressing conditions on optical absorption levels will be reported. Techniques to minimise optical loss in fabricated crystals will be discussed.

The potential of organic electro-optic materials for large electro-optic activity and fast response to applied electric fields (leading to 100 GHz device bandwidths) is important and increasingly well-recognized. In this communication, we demonstrate how quantum and statistical mechanical calculations can be used to guide the systematic improvement of both molecular first hyperpolarizability (β) and macroscopic electro-optic activity (r). Femtosecond time-resolved, wavelength-agile Hyper-Rayleigh Scattering (HRS) measurements have been used to measure β values relative to chloroform and to avoid confusion associated with two photon contributions. Electro-optic coefficients have been characterized by simple reflection (Teng-Man method), attenuated total reflection (ATR), and Mach Zehnder interferometry. "Constant bias" modifications of these techniques have been used to permit investigation of optimized poling conditions. Organic electro-optic materials also afford unique advantages for the fabrication of conformal and flexible devices, for the integration of disparate materials, and for exploitation of novel manufacturing technologies such as soft lithography. Both stripline and ring microresonator structures have been fabricated by soft lithography. The integration of organic electro-optic materials with silicon photonics (both split ring microresonators and photonic bandgap circuitry) has been demonstrated.

Self-assembled superlattices (SASs) are intrinsically acentric and highly cross-linked structures. For organic electro-optics, they offer great advantages such as not requiring electric field poling for creating an acentric, EO-active microstructure and having excellent chemical, thermal, and orientational stabilities. In this paper, a greatly improved two-step all "wet-chemical" self-assembly (SA) approach is reported. Excellent radiation hardness of the SAS films is demonstrated by high-energy proton irradiation experiments. By introducing metal oxide nanolayers during SA, we show that the refractive indices of SAS films can be tuned over a wide range. Through special chromophore design, the optical absorption maxima of SAS films can also be greatly blue-shifted. Prototype waveguiding electro-optic modulators have been fabricated using the SAS films integrated with low-loss polymeric materials functioning as partial guiding and cladding layers. EO parameters such as the half-wave voltage and the effective electro-optic coefficient are reported.

The absorption spectra of Congo red (CR) in aqueous solution and PVA film are measured, respectively. With the Z-scan method, the nonlinear optical properties of CR are investigated, and experimental data on the nonlinear refractive index and the change of refractive index are obtained. As a result, the intensity dependent index n₂ of CR has been determined to be in the range from 10^-10 to 10^-9 m²/W. The nonlinear absorption of CR aqueous film and CR-doped PVA film for three wavelengths is measured respectively. Under the condition of that the two samples are irradiated by 443nm or 535nm, the characteristics of absorption as function of the power of 633nm are determined. Finally, the experimental results are analyzed.

Optical materials for waveguiding applications must possess the desired optical and electromagnetic properties for optimal device performance. Purified deoxyribonucleic acid (DNA), derived from salmon sperm, has been investigated for use as an optical waveguide material. In this paper we present the materials processing and optical and electromagnetic characterization of this purified DNA to render a high quality, low loss optical waveguide material.

We report on asymmetric two-beam coupling and the ways of controlling it in liquid crystals cells with photoconducting polymer layers. The cells had one of the substrates covered with a photoconductive polymer layer, namely PVK, photosensitised with C₆₀ to respond to visible light. Efficient gain was measured in 30 micron thick cells with two incident beams having the same intensity. We present a model of two-beam coupling gain based on the build-up and discharge of surface charge screening layers, spatially modulated due to the photoconductivity of doped PVK. The simulation of electric field distribution inside a liquid crystal cell for different two-beam coupling grating spacing showed different penetration of field into the liquid crystal bulk. The characteristics of dynamics, magnitude of two-beam coupling and the efficiency of diffraction were determined for different values of applied DC field, cell configuration and liquid crystals. We found that the direction of energy flow was determined just by the cell tilt and not by the DC field bias.

Thiol-ene photopolymerization reactions initiated by a UV Argon laser line were used to write Bragg reflection gratings in polymer dispersed liquid crystals. Thiol-ene polymers are well suited as hosts for grating formation as they exhibit good long-term stability in their optical and electro-optical properties. Gelation in thiol-enes occur at high conversions (> 50%) and phase separation leads to formation of spherically shaped nematic droplets. For conventional photopolymerization using acrylates, high molecular weight polymer is formed very early in the reaction and therefore gelation occurs at low conversions. In this study, we have observed the effect of adding a multifunctional acrylate to the commercially available Norland thiol-ene precursors on the formation of Bragg reflection gratings. The results suggest a preferential homopolymerization of acrylate leading to early gelation that adversely affects the performance of the reflection gratings. A decrease of diffraction efficiency, an increase of switching voltage, and higher levels of shrinkage of the polymerizing film was observed. Morphology studies indicate with increasing addition of acrylate, a progressive transition from spherical nematic droplets to elongated droplets occurs with decrease of droplet density.