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Purposely tailored thin film stacks sustaining surface waves have been utilized to create a unique link between emission angle and wavelength of fluorescent dye molecules. The knowledge of the thin film stack’s properties allows us to derive the intrinsically emitted luminescence spectrum as well as to gain information about the orientation of fluorophores from angularly resolved experiments. This corresponds to replacing all the equipment necessary for polarized spectroscopy with a single smart thin film stack, potentially enabling single shot analyses in the future. The experimental results agree well with those from other established techniques, when analyzing the Rubrene derivative in a 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T) host used for the fabrication of optimized organic light-emitting diodes. The findings illustrate how resonant layered stacks can be applied to integrated spectroscopic analyses.

We report on the detection of an angiogenic molecule Vascular Endothelial Growth Factor (VEGF) in different biological matrices by means of a new integrated biosensing platform exploiting the properties of Bloch surface waves. The new platform takes advantage of a tandem configuration, in which both label-free and enhanced fluorescence detection are implemented. Specifically designed one dimensional photonic crystals were deposited directly on disposable and low cost plastic biochips. A direct sandwich immunoassay was used to detect VEGF in buffer, cell culture supernatant and human plasma at low concentration (ng/mL). The platform enabled the detection of VEGF in all three matrices with high resolution, fast turnaround time (30 min) and in close agreement with the results of enzyme linked immunosorbent assays.

The combination of fiber-optic–based platforms for biosensing with nanotechnologies is opening up the chance for the development of in situ, portable, lightweight, versatile, reliable and high-performance optical sensing devices. The route consists of the generation of lossy mode resonances (LMRs) by means of the deposition of nm-thick absorbing metaloxide films on special geometric-modified fibers. This allows measuring precisely and accurately the changes in surface refractive index due to the binding interaction between a biological recognition element and the analyte, with very high sensitivity compared to other optical technology platforms, such as fiber gratings or surface plasmon resonance. The proposed methodology, mixed with the use of specialty fiber structures such as D-shaped fibers, allows improving the light-matter interaction in a strong way. The shift of the LMR has been used to monitor in real-time the biomolecule interactions thanks to a conventional wavelength-interrogation system and an ad-hoc developed microfluidics. A big leap in performance has been attained by detecting femtomolar concentrations in real samples of human serum. The biosensor regeneration has been also studied by using a solution of sodium dodecyl sulphate (SDS), proving the device reusability. Therefore, this technology possibly represents a paradigm shift in the development of a simple, high-specificity and label-free biosensing platform, which can be applied to speed up diagnostic healthcare processes of different diseases toward an early diagnostic and personalized treatment system.

Optical biosensors based on one-dimensional photonic crystals sustaining Bloch surface waves are proposed to study antibody interactions and perform affinity studies. The presented approach utilizes two types of different antibodies anchored at the sensitive area of a photonic crystal-based biosensor. Such a strategy allows for creating two or more on-chip regions with different biochemical features as well as studying the binding kinetics of biomolecules in real time. In particular, the proposed detection system shows an estimated limit of detection for the target antibody (anti-human IgG) smaller than 0.19 nM (28 ng/mL), corresponding to a minimum surface mass coverage of 10.3 ng/cm2. Moreover, from the binding curves we successfully derived the equilibrium association and dissociation constants (KA = 7.5 &times, 107 M&minus, 1, KD = 13.26 nM) of the human IgG&ndash, anti-human IgG interaction.

A combined label-free and fluorescence surface optical technique was used to quantify the mass deposited in binary biomolecular coatings. These coatings were constituted by fibronectin (FN), to stimulate endothelialization, and phosphorylcholine (PRC), for its hemocompatibility, which are two properties of relevance for cardiovascular applications. One-dimensional photonic crystals sustaining a Bloch surface wave were used to characterize different FN/PRC coatings deposited by a combination of adsorption and grafting processes. In particular, the label-free results permitted to quantitatively assess the mass deposited in FN adsorbed (185 ng/cm2) and grafted (160 ng/cm2). PRC binding to grafted FN coatings was also quantified, showing a coverage as low as 10 and 12 ng/cm2 for adsorbed and grafted PRC, respectively. Moreover, desorption of FN deposited by adsorption was detected and quantified upon the addition of PRC. The data obtained by the surface optical technique were complemented by water contact angle and X-ray photoelectron spectroscopy (XPS) analyses. The results were in accordance with those obtained previously by qualitative and semiquantitative techniques (XPS, time-of-flight secondary ion mass spectrometry) on several substrates (PTFE and stainless steel), confirming that grafted FN coatings show higher stability than those obtained by FN adsorption.

A biosensor platform based on Bloch Surface Waves and operating in angular interrogation mode is applied to the detection of a clinical biomarker (HER2-neu/ERBB2) related to breast cancer initiation/progression. Preparing regions for specific recognition of different proteins as well as a reference on the biochip enables to correct the signal for nonspecific effects. Additionally, label-free analysis and surface wave enhanced fluorescence detection can be applied and compared directly on the platform. Cell lysates with high and low expression levels of ERBB2 are analyzed. Comparing the signals of such ERBB2 positive and negative samples estimates the limit of detection at 1.7 ng/mL. This is well below the threshold of 15 ng/mL set by the FDA for clinically useful ERBB2 detection in human serum, demonstrating that 1DPC-based biochips are attractive candidates for breast cancer detection/monitoring.

We report on the use of one-dimensional photonic crystals to detect clinically relevant concentrations of the cancer biomarker ERBB2 in cell lysates. Overexpression of the ERBB2 protein is associated with aggressive breast cancer subtypes. To detect soluble ERBB2, we developed an optical set-up which operates in both label-free and fluorescence modes. The detection approach makes use of a sandwich assay, in which the one-dimensional photonic crystals sustaining Bloch surface waves are modified with monoclonal antibodies, in order to guarantee high specificity during the biological recognition. We present the results of exemplary protein G based label-free assays in complex biological matrices, reaching an estimated limit of detection of 0.5 ng/mL. On-chip and chip-to-chip variability of the results is addressed too, providing repeatability rates. Moreover, results on fluorescence operation demonstrate the capability to perform high sensitive cancer biomarker assays reaching a resolution of 0.6 ng/mL, without protein G assistance. The resolution obtained in both modes meets international guidelines and recommendations (15 ng/mL) for ERBB2 quantification assays, providing an alternative tool to phenotype and diagnose molecular cancer subtypes.

We report on the use of one-dimensional photonic crystals to detect clinically relevant concentrations of ERBB2/neu/Her2 in cell lysates. ERBB2 is a pivotal breast cancer biomarker and targetable oncogenic driver associated with aggressive breast cancer subtypes. To quantitate soluble ERBB2, we developed an optical platform that combines label-free and fluorescence detection modes. Such platform makes use of a sandwich assay in which the one-dimensional photonic crystals sustaining Bloch surface waves are tailored with a monoclonal antibody for highly specific biological recognition (BSW biochip). In a second step, a second antibody to ERBB2 quantitatively detects the bound analyte. The strategy of the present approach takes advantage of the combination of label-free and fluorescence techniques, making bio-recognition more robust and sensitive. In the fluorescence operation mode, the platform can attain the limit of detection 0.3 ng/mL (1.5 pM) for ERBB2 in cell lysates. Such resolution meets the international guidelines and recommendations (15 ng/mL) for diagnostic ERBB2 assays that in the future may help to more precisely assign therapies counteracting cancer cell proliferation and metastatic spread.

n this work we report on the characterisation of multimode rectangular ridge waveguides fabricated by Plasma Enhanced Chemical Vapor Deposition and anisotropic etching using different cores, consisting of hydrogenated amorphous silicon and amorphous silicon nitride. The propagation losses have been measured at several wavelengths by an end-fire coupling set-up and compared to intrinsic absorption of the core materials. Two-dimensional photonic crystal structures have been carved onto the channel waveguides by Focused Ion Beam lithography demonstrating the possibility to fabricate complex optical elements merging the consolidated amorphous silicon growth technology with ion-beam nanomachining

We perform a near-field mapping of Bloch Surface Waves excited at the truncation interface of a planar silicon nitride multilayer. We directly determine the field distribution of Bloch Surface Waves along the propagation direction and normally to the surface. Furthermore, we present a direct measurement of a near-field enhancement effect under particular coupling conditions. Experimental evidence demonstrates that a ∼ 102 near-field intensity enhancement can be realistically attained, thus confirming predictions from rigorous calculations. © 2008 Optical Society of America.

Polarization sensitive electroreflectance was used to study a typical hybrid photoconducting polymer–liquid crystal (LC) structure. Similar structures serve as optically addressed liquid crystalline spatial light modulators in real-time holography. It was shown that this technique might be used for the evaluation of internal electric-field changes in the vicinity of LC layer due to light-induced photogeneration and transport of charge carriers in the photoconducting polymer layer. A simplified theory presented in this work clarifies the experimental technique and the obtained results for the planar nematic LC panel. Employing the formalism of nonlinear optics for a particular type of LC (seven-component nematic mixture), we measured that the low-frequency (Ω/2π=1680 Hz) main component of a cubic optical susceptibility tensor χijkl(3)(−ω;0,Ω,ω) along the director direction is χa(3)=(7.4±1.5)×10−16 m2/V2.

Waveguiding light-emitting strips have been written in a blank LiF crystal with a femtosecond laser, by translating the sample under the pulsed focused beam. Light guiding through these buried micro-structures was observed at several wavelengths between 458 and 1550 nm. Visible photoluminescence spectra of aggregate F2 and F3 + laser active color centers were measured. The refractive index increase, estimated of the order of 10-4 in the visible and near-infrared spectral intervals, is consistent with the stable formation of electronic point defects in LiF. These results are promising for the realization of miniaturized optical waveguiding solid-state amplifiers and lasers based on color centers. © 2014 AEIT.

We report on the design, manufacturing and testing of Alq 3 /polyvinylcarbazole (PVK) light emitting devices. The devices were obtained by spin coating PVK films on indium tin oxide coated glass substrates. Alq 3 films were then deposited by high vacuum thermal evaporation. The devices were topped by depositing magnesium/silver electrodes by thermal evaporation. After deposition, the samples were stored and operated under a nitrogen atmosphere in order to prevent damage due to oxidation. The thickness of the active layers was purposely chosen to be large in order to study the device with an electro-optic reflectometric technique.

The intensity dependent complex character of the photodarkening of virgin As2S3 samples exposed to continuous wave (CW) and pulsed laser radiation has been measured. Excitation in the CW and pulsed (picosecond) regime for the same irradiation doses leads to significant differences in the photodarkening curves. It is shown that the kinetics of the photodarkening can be decomposed into several processes related to structural transformations in As2S3: defect elimination and stabilization, polymerization of the structural entities, decomposition followed by arsenic clustering and arsenic oxidation.

We report on the measurement of the electro-optic properties of poled polymers at λ=1.55 μm via the Teng and Man technique. Measurements of the electro-optic coefficient obtained for two different sandwich structures, using either indium tin oxide (ITO) or aluminum doped zinc oxide (ZnO:Al) semitransparent electrodes, are compared. The experimental results show that the use of ITO electrodes can lead to a largely wrong evaluation of the electro-optic coefficient r33, with respect to that obtained when using ZnO:Al electrodes, whose plasma resonance is shifted to longer wavelengths. Results on the disperse red 1/methyl-metacrylate based sidechain benchmark system are reported.

We exploit the properties of surface electromagnetic waves propagating at the surface of finite one dimensional photonic crystals to improve the performance of optical biosensors with respect to the standard surface plasmon resonance approach. We demonstrate that the hydrogenated amorphous silicon nitride technology is a versatile platform for fabricating one dimensional photonic crystals with any desirable design and operating in a wide wavelength range, from the visible to the near infrared. We prepared sensors based on photonic crystals sustaining either guided modes or surface electromagnetic waves, also known as Bloch surface waves. We carried out for the first time a direct experimental comparison of their sensitivity and figure of merit with surface plasmon polaritons on metal layers, by making use of a commercial surface plasmon resonance instrument that was slightly adapted for the experiments. Our measurements demonstrate that the Bloch surface waves on silicon nitride photonic crystals outperform surface plasmon polaritons by a factor 1.3 in terms of figure of merit.

The optical properties of Rhodamine 6G doped silica-titania glassy thin films deposited onto soda-lime glass substrates, have been studied by changing the relative concentrations of SiO 2 and TiO 2 . The guided light propagation properties of the films in the planar waveguide configuration have been investigated at λ = 632.8 nm, by means of a single prism geometry.

We report on time resolved sensing experiments demonstrating the direct, label-free and specific binding of an antibody/antibody system probed by means of Bloch surface waves on silicon-based one-dimensional photonic crystals.

Lithium Fluoride (LiF) presents interesting optical properties and it has been proposed as an active optical material for colour centre (CC) lasers and amplifiers. The use of a grating to reduce the laser threshold and to narrow the line-width has also been demonstrated. More recently, LiF gained increased attention due to its unique characteristics as x-ray imaging detector for high resolution microscopy and for the development of CC lasers using gratings induced by high energy femtosecond laser pulses. We present a review of our recent work in the production of photonic structures, like photo-induced Bragg gratings and wave-guides either by laser CW illumination or by femtosecond laser irradiation. CW laser illuminated gratings were written in both coloured LiF crystals and films. Gratings and wave-guides are characterized using confocal microscopy, optical absorption and emission spectroscopy, near field scanning, scattering and insertion loss measurements.

After the introduction in 1991 by B. O’Regan and M. Gratzel, Dye Solar Cells (DSCs) have reached power conversion efficiency values over small area device as high as 11%. Being manufactured with relatively easy fabrication processes often borrowed from the printing industry and utilizing low cost materials, DSC technology can be considered nowadays a proper candidate for a large scale production in industrial environment for commercial purposes. This scenario passes through some challenging issues which need to be addressed such as the set-up of a reliable, highly automated and cost-effective production line and the increase of large area panels performances, in terms of efficiency, stability and life-time of the devices. In this work, an overview of the most utilized DSCs materials and fabrication techniques are highlighted, and some of the most significant characterization methods are described. In this direction, different approaches used to improves devices performances are presented. In particular, several methods and techniques known as Light Management (LM) have been reported, based to the ability of the light to be confined most of the time in the cell structure. This behavior contributes to stimulate higher levels of charge generation by exploiting scattering and reflection effects. The use of diffusive scattering layers (SLs), nanovoids, photonic crystals (PCs), or photoanodes co-sensitization approaches consisting in the use of two Dyes absorbing in two different parts of the visible range, have been demonstrated to be effective strategies to carry out the highest values of device electrical parameters. Finally, to increase the light path inside the DSCs active layer, the use of refractive element on the topside (a complementary approach to SL) has been shown a promising possibility to further improve the generated photocurrent.

We report on the experimental characterization of the thermal sensitivity of biosensors based on the coupling of Bloch surface waves (BSW) on amorphous silicon nitride/silicon one dimensional photonic crystals (1DPC). The results show that the silicon alloys compensate the thermo-optic effect taking place in the external medium and indicate that a class of temperature insensitive biosensors can be fabricated by properly designing the layout of the 1DPC. The experimental results are in very good agreement with numerical simulations based on a transfer matrix approach. Moreover, the BSW biosensors show a resolution of 0.03 °C for the measurement of temperature.

The coupling of optical Bloch surface waves at the truncated end of one dimensional porous silicon photonic crystals is exploited for fast vapour sensing. Self-standing multilayered membranes bound to transparent substrates were fabricated by electrochemical etching and used in an attenuated total reflection configuration to resonantly excite the surface waves and perform real-time sensing.

The Rhodamine 6G fluorescence enhanced by the surface electromagnetic waves coupled on surface of 1D photonic crystals is studied. The fluorescence-mediated surface electromagnetic waves (SEW) distribution is visualized by means of far-field fluorescence microscopy. The kinetics of Rhodamine 6G bleaching due to SEW is studied. The way of SEW visualization in reflectivity spectra via fluorescence process is shown. The prospective for SEW application in the optical sensors field is tested via direct spectroscopy of the photonic crystal covered by the ethanol and R6G thin film. Spectral flexibility of the SEW excitation depending on the effective photonic crystal dispersion controlled by its design rather than on material dispersion opens prospectives for the application of SEW-enhanced fluorescence microscopy in biocensing with increased spatial and concentration sensitivity and spectral selectivity.

We describe the use of one-dimensional porous silicon (p-Si) photonic crystals for guiding TE-polarized surface electromagnetic waves (SEWs). Although bulk and interface roughnesses might deteriorate the optical response of photonic structures, we observed reflection spectra presenting narrow (≲6nm) reflectivity anomalies associated with SEWs. In analogy with surface plasmons, SEWs are strongly sensitive to surface modifications. As a proof of principle for a sensor, we provide a direct real-time monitoring of the reversible interactions of organic vapors with the p-Si multilayer. We highlight the higher sensitivity of the SEW-based detection scheme as compared to a method exploiting perturbations of waveguide modes.

We report on an original technique for poling polymeric thin films, which allowed us to obtain a second-order nonlinear inverted domain structure, which could be used for frequency-doubling waveguides under quasi-phase-matching condition. Measurements of the local value and orientation of the electro-optic r33 tensor component were performed by a reflection microscopic electro-optic ellipsometer. The measured parameters for the nonlinear structure induced in the polymeric film result to be consistent with the expected values.

In this work the authors investigated the second order nonlinear optical properties of a group of Disperse Red 1 based electro-optic fluorinated copolymers, synthesized with two fluorinated monomers: the -fluoroacrylate monomer bearing an adamantane side group and the -fluoroacrylate monomer bearing the Disperse Red 1 chromophore. By means of nonlinear ellipsometry at =1550 nm, the poling induced electro-optic tensor main component r33 was determined. The polymer's thermostability was investigated by means of the temperature scanning and isothermal relaxation techniques, leading to the determination of the depolarization temperature Tdep=136 °C, corresponding to an activation energy for the relaxation of the orientational distribution of the active chromophores EA=105 kcal/mol. The increased thermostability of the copolymer, given by the adamantane side group, is then compared with that of other two groups of fluorinated copolymers. ©2006 American Institute of Physics

In this work we investigated the second-order nonlinear optical properties of a group of Disperse-Red-1-based electro-optic fluorinated copolymers, synthesized with two fluorinated monomers: the hexafluoroisopropyl alphafluoroacrylate monomer and the alphafluoroacrylate monomer bearing the Disperse Red 1 chromophore. Copolymers, with a concentration of chromophore substituted groups ranging from 46% to 75% molar, were synthesized and deposited as single films on glass substrates, for second-harmonic generation, and as sandwich structures with electrodes, for nonlinear ellipsometry measurements. For large concentrations of substituted groups, cracking of the films was observed and did not allow for any electro-optic characterization by nonlinear ellipsometry. The second-harmonic generation tensor main component d33 was retrieved by means of second-harmonic generation at λ=1064nm for each concentration. The results obtained for the copolymer with the lowest concentration are compared with those obtained by ...

Measurements of the second and third order electro‐optic response of side‐chain copolymer films are reported and discussed in the frame of an extended model taking into account the dependence of the nonlinearity on the orientational distribution of poled copolymers, charge injection and trapping in the films upon application of large voltage drops and screening of the electric field in the mesoscopic films.

We report the results of the morphological, electrical and optical characterisation of double-layer Alq3-based organic emitting diodes with a lithium fluoride (LiF)/Al cathode. A detailed electron microscopy investigation of their cross-section shows the presence of LiF isolated grains underneath the Al film. Due to the introduction of the LiF layer, luminance was larger than 30,000 cd/m2 at a bias voltage VB=25 V with a maximum external luminous efficiency as large as 46 lm/W at VB=20 V. Performing on/off VB cycles at a very low frequency, each time a recovery of the initial electric and luminous performance was observed. The non-exponential decay of both electric current and luminance during each on-cycle has been interpreted as the signature of dispersive transport controlled by multiple trapping on localised states in an amorphous system.

We report on the measurement of the electro-optic properties of poled side-chain copolymer films by means of a time-resolved ellipsometric version of the Teng and Man experiment. The polymer is a side-chain Disperse Red 1 substituted poly(methyl methacrylate). The technique makes use of polymer layers sandwiched between indium tin oxide and metal electrodes. We show that the technique can give a good evaluation of the real electro-optic properties if operated in a wavelength range outside the absorption bands of the indium tin oxide layers. In this case we evaluated the temperature dependence of the relaxation time constant and found that it is described by an Arrhenius like dependence as a function of temperature. The activation energies and the time constants are in agreement with data reported in literature.

We report on the measurement of the Kerr electro-optic susceptibility in DPOP-poly-phenylene-vinylene films sandwiched between indium tin oxide and metal electrodes. Such a polymer was designed and used for the application in third-order non-linear optical integrated devices. The results, obtained by means of non-linear reflectance ellipsometry, indicate the presence of charge injected and trapped in the polymer films under application of a dc voltage. The values of the Kerr χ (3) susceptibility and of the total voltage drop on the film are evaluated.

We present experimental results on the electro-optic response of electroluminescent polymer films, pertaining to the family of the poly-phenylene-vinylenes. The samples used in the experiments were obtained by sandwiching polymer films between chromium-gold and indium tin oxide electrodes. The technique that was adopted is based on the Teng and Man setup, that is usually adopted for the determination of the electro-optic Pockels coefficient in poled polymers. As the structure of the polymer used is not provided with polar groups and, moreover, is completely disordered and therefore centrosymmetric, as expected, only quadratic electro-optical effects were observed (Kerr), which are connected to the presence of third-order optical nonlinearities (χ(2)≡0, χ(3)≠0). The existence of charge injection and trapping in the samples, giving rise to built-in static electric fields in the polymer layers, is put into evidence. The experimental data show the presence of a third-order susceptibility for Kerr electro-optic effect which is comparable to values reported in literature, namely χ(3)(−ω;ω,0,0)=7.9×10−21 m2/V2 at the wavelength λ=0.6328 μm. The possibility that the measured signals are due to a mechanical compression of the films is taken into account and discarded on the basis of the experimental results. The technique can be usefully applied in order to perform charge injection and trapping measurements in electroluminescent devices. Moreover, the results show that in the case of measurements performed on poled polymers for χ(2) applications, the measured values for the electro-optic coefficient can be offset by a third-order contribution, even in those cases when usually one assumes it may be neglected. In the article, the main models reported in literature, describing the effects contributing to the electro-optic response, are critically reviewed. The measurement on the centrosymmetric polymer films were used in order to check those models and permit us to evaluate.We present experimental results on the electro-optic response of electroluminescent polymer films, pertaining to the family of the poly-phenylene-vinylenes. The samples used in the experiments were obtained by sandwiching polymer films between chromium-gold and indium tin oxide electrodes. The technique that was adopted is based on the Teng and Man setup, that is usually adopted for the determination of the electro-optic Pockels coefficient in poled polymers. As the structure of the polymer used is not provided with polar groups and, moreover, is completely disordered and therefore centrosymmetric, as expected, only quadratic electro-optical effects were observed (Kerr), which are connected to the presence of third-order optical nonlinearities (χ(2)≡0, χ(3)≠0). The existence of charge injection and trapping in the samples, giving rise to built-in static electric fields in the polymer layers, is put into evidence. The experimental data show the presence of a third-order susceptibility for Kerr electro-opti...

The interest to the study of the nonlinear propagation of laser radiation in non-crystalline semiconductors (NS) is determined not only by the new fundamental physical mechanisms present in these materials, but also by a wide spectrum of possible applications in high speed optoelectronic devices and photonic switching. This report illustrates the present state of knowledge and some problems of the nonlinear interaction of micro-, nano-, pico-, and femtosecond laser pulses with NS (chalcogenide glasses: As2S3, As2Se3, AsSe, GeSe2, As22S33Ge45, and a-Si:H; 0.2 - 5 μm thick).

The electro‐optic properties of polymer films are measured by an original technique whereby a periodic sequence of poling and probing steps permits alternation of the application of orientation and dephasing potentials. Relaxation dynamics of the electro‐optic coefficient of Red–Acid–Magly crosslinkable polymer films is studied as a function of the temperature of the samples. The time constant of the decay τ as measured at several temperatures is found to follow a Vogel–Fulcher–Tamann—Hesse dependence, for temperatures above glass transition. Poling the samples in the presence of a pulsed electric field leads to a r33 electro‐optic coefficient as high as 6 pm/V.

The lateral confinement of Bloch surface waves on a patterned multilayer is investigated by means of leakage radiation microscopy (LRM). Arrays of nanometric polymeric waveguides are fabricated on a proper silicon-nitride/silicon-oxide multilayer grown on a standard glass coverslip. By exploiting the functional properties of the polymer, fluorescent proteins are grafted onto the waveguides. A fluorescence LRM analysis of both the direct and the Fourier image plane reveals that a substantial amount of emitted radiation couples into a guided mode and then propagates into the nanometric waveguide. The observations of the mode are supported by numerical simulations.

Experimental evidence that organic semiconductors show some of the highest figures of merit among all the nonlinear optical materials of χ(3) type has increased the interest in these materials during the last few years1. Due to charge conjugation along the polymer backbone or to the presence of side chains constituted of organic molecules with high hyperpolarizabilities, the third order nonlinear response can be strongly enhanced.

The non-linear change of refractive index and absorption coefficient of a-Si:H films has been measured through the Z -scan technique using a picosecond ( τ FWHM = 1 ps) high repetition rate ( ƒ rep = 3.8−9.5 MHz ) laser. The films were prepared by the radiofrequency glow discharge technique. A reversible increase of the optical absorption under high-intensity illumination conditions has been measured, indicating an increase of dangling bond states concentration up to N r ≈ 10 19 cm −3 . In order to explain the experimental results, a theoretical model has been developed which takes into account the change of absorption, due to light-induced metastable changes, during a Z -scan measurement. Non-linear changes of the refractive index as large as Δn = −0.07 have been detected.

We describe the production and optical characterization of planar dielectric waveguides of the organic polymers Poly-(alpha) -Methyl-Styrene and Poly-Phenyl-Acetylene. Single mode waveguides, at (lambda) equals 1.064 micrometers , were obtained by the use of the spin-coating technique. Propagation losses were measured through detection of the out of plane scattered light are as low as 0.7 dB/cm. The waveguiding films were spun over fused silica substrates that were previously etched in order to obtain two grating couplers with a 0.55 micrometers period. Nonlinear grating coupling was investigated in the case of Poly-Phenyl-Acetylene, with a 70 ps pulsed source at (lambda) equals 1.064 micrometers at high repetition rate (frep equals 76 MHz).© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The thermal diffusivity measurement through pulsed photodeflection in a modified collinear configuration is presented and discussed; comparison between theory and experiment is also shown.

When properly designed, a dielectric multilayer can sustain Bloch surface waves (BSWs). Using a multiheterodyne scanning near-field optical microscope that resolves phase and polarization, we will show that a thin dielectric structure deposited on the multilayer deflects the BSW propagation according to Snell's law. Moreover, the mechanism involved in this process is a transfer of energy from the BSW state in the bare multilayer to the new BSW state generated by the presence of the thin dielectric structure. No relevant radiative counterpart occurs. This characteristic validates the treatment of BSWs at the surface of dielectric multilayers as a two-dimensional phenomenon.

Nonlinear properties of chalcogenide glasses (ChG) are very interesting both from the point of view of potential application in photonic devices ( as planar waveguides, fibers, coating films ) and new basic mechanisms in the field of short laser pulses. Recently the measurements of optical hysteresis in thin films of ChG were performed, showing the effect at fight intensities lower than those reported in the case of crystalline semiconductors [1].

Dynamics of optical nonlinearity are investigated experimentally in different time scales, from microsecond to nano-, pico-, and femtosecond domains. In addition Z-Scan measurements carried out the competition between permanent photodarkening and electronic nonlinearities in photoinduced absorption and refraction.

Crosslinking of polymers with dipoles can be followed by means of dielectric, pyroelectric, and in situ electro-optic measurements. All three techniques provide similar insights as to the cross-linking process. In addition, electro-optic measurements allow for the determination of the resulting optical nonlinearity. After crosslinking is completed the polymer behaves like a side-chain polymer. In addition, photoinduced poling of an already cross-linked dipolar polymer network is demonstrated.

Detection of glucose in water solution for several different concentrations has been performed with the purpose to determine the sensitivity of Near Infrared Bloch Surface Waves (lambda = 1.55 mu m) upon refractive index variations of the outer medium. TE-polarized electromagnetic surface waves are excited by a prism on a silicon nitride multilayer, according to the Kretschmann configuration. The real-time reflectance changes induced by discrete variations in glucose concentration has been revealed and analyzed. Without using any particular averaging strategy during the measurements, we pushed the device detection limit down to a glucose concentration of 2.5mg/dL, corresponding to a minimum detectable refractive index variation of the water solution as low as 3.8.10(-6). (c) 2010 Optical Society of America