Review and comparison of experimental techniques used for determination of thin film electro-optic coefficients
The results of electro-optic coefficient measurements performed with three commonly applied techniques used to assess electro-optic coefficients: the Mach–Zehnder, the Teng–Man, and the attenuated total reflectance technique are reported. It is shown that the signal obtained by the Mach–Zehnder and Teng–Man techniques is strongly influenced by the multiple internal reflection and piezo- and electrostrictive thickness change effects, which in our opinion have not been addressed sufficiently in the literature. A novel approach based on using Abeles matrix formalism is implemented for the retrieval of electro-optic coefficients from experimental data. The measurement results, errors, and compa…
All-organic electro-optic waveguide modulator comprising SU-8 and nonlinear optical polymer
Institute of Solid State Physics, University of Latvia (SJZ/2016/26); Ministry of Education and Science, Republic of Latvia (MultIfunctional Materials and composItes, photonicS and nanotechnology (IMIS2)). We acknowledge Dr. Anatolijs Sarakovskis at Institute of Solid State Physics for the XPS measurements.
Evaluation of performance of a hybrid electro-optic directional coupler and a Mach–Zehnder switch
The efficiency of an electro-optic (EO) directional coupler (DC) and a Mach–Zehnder (MZ) switch is discussed. The specific designs employ a passive waveguide core and an EO cladding. The performance of a DC switch was evaluated by numerical methods, namely coupled mode theory (CMT), eigenmode expansion (EME) method, and beam envelope method. Using the CMT and EME methods, it is shown that in the DC with a passive waveguide core and EO cladding at certain waveguide parameters the switching effect does not take place. The effect is demonstrated for the first time and suggests that careful optimization of the DC switch should be done before experimental realization of the device. The efficienc…
Asymmetrical all-organic waveguide gas sensor
An all-organic waveguide sensor for volatile solver detecting was presented. Device consists of SU-8 waveguide with novel organic material used as sensitive cladding. Created device was tested in isopropanol and N2 vapor mixture.
Dendronized azochromophores with aromatic and perfluoroaromatic fragments: Synthesis and properties demonstrating Ar ArF interactions
Abstract Syntheses of four new dendronized azochromophores were performed from 2-(2-amino-5-nitrophenoxy)ethanol, 2-[methyl(phenyl)amino]ethanol, 3,5-bis(benzyloxy)benzoic acid and 3,5-bis[(pentafluorophenyl)methoxy]benzoic acid using azo coupling reaction and ester formation reaction in presence of N,Nʹ-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine. Arene-perfluoroarene (Ar ArF) interactions are demonstrated in single crystal structure of dendronized azochromophore between pentafluorophenyl fragment and acceptor part of the azochromophore. The effect of Ar ArF interactions becomes apparent in thermal and nonlinear optical properties of the chromophores. Glass transition temperatur…
Optical phase retrieval using four rotated versions of a single binary mask – simulation results
In signal processing one often faces the phase problem, i.e., when an image is formed information about the phase is lost so that only information about intensity is available. This is often an issue in astronomy, biology, crystallography, speckle imaging, diffractive imaging where the phase of the object must be known. While there have been many approaches how to find a solution to the phase problem, numerical algorithms recovering the phase from intensity measurements become more and more popular. One of such algorithms called PhaseLift has been recently proposed. In this study, we show that even 4 masks may be sufficient for reasonable recovery of the phase. The original wavefront and th…
Photoluminescence in Er-doped 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 solid solutions
Photoluminescence and optical second harmonic generation in Er-doped 0.4Na0.5Bi0.5TiO3-(0.6-x)SrTiO3-xPbTiO3 solid solutions is studied. Earlier, it was shown that upon increasing of PbTiO3 concent...
Determination of Kerr and two-photon absorption coefficients of ABI thin films
This material is based upon work supported by the ERDF 1.1.1.1 activity project Nr. 1.1.1.1/16/A/046 “Application assessment of novel organic materials by prototyping of photonic devices”
Optical propagation loss measurements in electro optical host-guest waveguides
Thin organic waveguiding layers are applied more and more frequently as optical components in novel optoelectronic devices. For development of such devices it is important to know the optical properties of the used waveguides. One of the most important parameters is optical propagation loss in the waveguide. In this paper we present optical propagation loss measurements in planar electro optical waveguides using travelling fiber method. Using this method attenuation coefficient α at 633 nm as a function of chromophore concentration for the first two guiding modes in the slab waveguide was determined.
Determination of refractive index of submicron-thick films using resonance shift in a four-layer slab waveguide
The measurement of refractive index of very thin films at the order of ten to hundred nanometers is cumbersome and usually requires employing sophisticated techniques such as the spectral ellipsometry. In this paper we describe a simple contact method for measuring the refractive index of thin films. Here we have used the prism-coupling technique for characterizing samples prepared as four-layer slab waveguides. The waveguide resonance condition can be calculated by solving simple analytic transcendental equations for the slab waveguide. Then the captured mode position as a function of cladding thickness is used for probing the refractive index of cladding layer. We used indium-tin-oxide la…
Simple method for measuring bilayer system optical parameters
A simple method for measuring bilayer system refractive indexes and thicknesses in the low absorbing part of spectra is demonstrated. The method is based on application of Savitzky - Golay smoothing filters and interference fringe separation in the reflected or transmitted spectra of the bilayer system. The refractive indexes and thicknesses are extracted from the wavelengths corresponding to extreme points in the spectrum. Due to the fact that wavelength difference of extreme points in the analyzed spectrum is defined by the product of both, the layer thickness and refractive index, one must generate an appropriate initial guess of these parameters. For refractive index approximation two d…
Mach-Zehnder interferometer implementation for thermo-optical and Kerr effect study
Scientific Research Project for Students and Young Researchers Nr. SJZ/2016/10; National Research Program “Multifunctional Materials and Composites, Photonics and Nanotechnology” (IMIS2) project “Photonics and materials for photonics”.
EFFECTS OF THE MULTIPLE INTERNAL REFLECTION AND SAMPLE THICKNESS CHANGES ON DETERMINATION OF ELECTRO-OPTIC COEFFICIENT VALUES OF A POLYMER FILM
New nonlinear optical (NLO) active organic materials are appealing candidates for optoelectronic and photonic technologies. For the evaluation of new NLO polymer materials for applicability in the mentioned technologies, the most important criteria are their electro-optic (EO) coefficients. We have implemented the Mach–Zehnder interferometric (MZI) method for the determination of EO coefficients of thin organic films. Despite the fact that other multiple optical methods for the determination of thin film EO coefficients are known, the MZI method has been chosen because this particular technique has high sensitivity to phase and intensity modulations in the sample arm of an interferometer an…
Hybrid silicon on insulator/polymer electro-optical intensity modulator operating at 780 nm
Currently inorganic materials prevail as the nonlinear active medium for light modulation in electro-optical (EO) device technology. A recent promising trend is to consider organic nonlinear optical materials for application in EO modulators due to their multiple advantages including low costs and high EO coefficients. In this paper, we proposed a new type of polymer EO modulator whose fabrication is compatible with the currently used silicon on insulator technology. Our numerical optimization of the proposed structure demonstrates that it is theoretically possible to achieve a half-wave voltage as low as 1.56 V for a 1 cm long modulator structure operating at 780 nm. Based on the results o…
Determination of Kerr and two-photon absorption coefficients of indandione derivatives
This material is based upon work supported by the ERDF 1.1.1.1 activity project Nr. 1.1.1.1/16/A/046 “Application assessment of novel organic materials by prototyping of photonic devices” as well as by National Research Program “Multifunctional Materials and Composites, Photonics and Nanotechnology” (IMIS2) project “Photonics and materials for photonics”.
Poling Induced Mass Transport in Thin Polymer Films
In this study we report investigation of the polymer film morphology modifications during their corona poling for fabrication of nonlinear optically (NLO) active materials. We demonstrate that at certain poling conditions surface and spatial inhomogeneities in the poled area of the sample appear. Densities of the inhomogeinities depend on the strength of the poling field, the sample temperature during the poling, and the prepoling conditions. Optimization of the poling conditions directed toward avoiding surface modifications enables us to increase the overall observable effective nonlinearity of the sample up to 10 times. To investigate, understand, and eventually explain the formation of …
NIR tracking assists sports medicine in junior basketball training
We recorded eye movements of eight elite junior basketball players. We hypothesized that a more stable gaze is correlated to a better shot rate. Upon preliminary testing we invited male juniors whose eyes could be reliably tracked in a game situation. To these ends, we used a head-mounted video-based eye tracker. The participants had no record of ocular or other health issues. No significant differences were found between shots made with and without the tracker cap, Paired samples t-test yielded p= .130 for the far and p=.900 > .050 for the middle range shots.The players made 40 shots from common far and middle range locations, 5 and 4 meters respectively for aged 14 years As expected, a st…
Stereoselective synthesis and properties of 1,3-bis(dicyanomethylidene)indane-5-carboxylic acid acceptor fragment containing nonlinear optical chromophores
A series of organic push–pull type chromophores using indane-1,3-dione 5-carboxylic acid (IDCA) and novel 1,3-bis(dicyanomethylidene)indane 5-carboxylic acid (CICA) electron acceptor fragments have been synthesized and characterized. NMR and X-ray analysis revealed that condensation reactions with the CICA fragment were stereoselective and yielded benzylidenes and azomethines with E double bond configurations. Due to the non-planar geometry these compounds are chiral and were acquired as a racemic mixture. The subsequent functionalization of the carboxylic acid group with 5,5,5-triphenylpentan-1-ol yielded solution-processable glass forming materials (6, 8, 10, 13) with glass transition tem…
Electric breakdown of dielectric thin films for high-voltage display applications
Smectic A liquid crystal is one of the most promising material for smart glass application due to infinite bistability and low haze at clear state. Voltage is needed to switch from scattering to transparent and it is likely for dielectric breakdown to occur. In order to reduce the probability of dielectric breakdown to occur, a dielectric insulating coating is usually employed. In this work we have compared electrical and optical properties of SiO2 thin films with thickness up to 500 nm coated by flexographic printing and reactive magnetron sputtering. IV characteristics and dielectric breakdown values show sputtered coatings to have higher dielectric strength. For sputtered coatings with t…
Numerical 2D And 3D Simulations of a Spherical Fabry–Pérot Resonator for Application as a Reference Cavity for Laser Frequency Stabilisation
Abstract We report on the results of a numerical study of deformations of a spherical Fabry-Pérot cavity that can be used for laser frequency stabilisation. It is demonstrated that for a precise simulation of the cavity deformations a 3D model has to be used instead of a simpler 2D model, which employs simulation on the symmetry plane of the cavity. To lower the sensitivity to environmental perturbations, it is suggested to use a material with a low density and a high Young’s modulus. We also show that the mechanical resonance frequencies of the cavity are mainly determined by the size of the cavity.
Study of Tetragonal Phase in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3Solid Solutions by Second-Harmonic Generation
Description of the local symmetry of relaxor ferroelectrics, especially in connection with nature of polar nanoregions, is one of the key questions in research of relaxor ferroelectrics. Unlike such well-known relaxor ferroelectrics as PbMg1/3Nb2/3O3 and (Pb,La)(Zr0.65Ti0.35)O3, ternary solid solutions 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 show clear coexistence of phases of tetragonal and cubic symmetry, which is established by x-ray diffractometry. Since the second-harmonic generation spectroscopy is a sensitive tool in determination of deviation from symmetry, containing a centre of inversion, it is used as an additional method in characterization of structure in 0.4Na1/2Bi1/2TiO3-(0.6…
Study of Structure–Third-Order Susceptibility Relation of Indandione Derivatives
By using the Z-scan method we studied the third-order nonlinear optical parameters of several aminobenziliden-1,3-indandione (ABI) derivatives that have previously been shown to own second-order nonlinear optical properties. Measurements were carried out using two 1064 nm Nd:YAG lasers with picosecond (ps) and nanosecond (ns) pulse widths, respectively. When ns laser was employed in the Z-scan setup, a strong thermal lensing took place resulting in severe overestimation of optical Kerr coefficients. Due to this reason the ps laser was employed to evaluate correct magnitude of Kerr effect. For investigated organic molecules, experimental results show that two-photon absorption at 1064 nm is …
All-Organic Waveguide Sensor for Volatile Solvent Sensing
This work was supported by ERDF 1.1.1.1 Activity Project Nr. 1.1.1.1/16/A/046 “Application assessment of novel organic materials by prototyping of photonic devices”. We acknowledge Igors MIHAILOVS for valuable discussions.
Dielectric breakdown of fast switching LCD shutters
Fast liquid crystal optical shutters due to fast switching, vibrationless control and optical properties have found various applications: substitutes for mechanical shutters, 3D active shutter glasses, 3D volumetric displays and more. Switching speed depends not only on properties of liquid crystal, but also on applied electric field intensity. Applied field in the shutters can exceed >10 V/micron which may lead to dielectric breakdown. Therefore, a dielectric thin film is needed between transparent conductive electrodes in order to reduce breakdown probability. In this work we have compared electrical and optical properties of liquid crystal displays with dielectric thin films with thickne…
Wavefront Recovery: Shack-Hartmann Aberrometry vs PhaseLift Using a Single Binary Amplitude Modulating Mask
We investigate whether a wavefront can be recovered by using a single mask rotated in four different positions. Results show that PhaseLift can recover the wavefront from intensity measurements using such a kind of modulation.
Poling dynamics of an EO active material using parallel-plate electrodes
We describe the sample preparation and experimental setup for second harmonic generation measurement of electro-optical (EO) chromophore/polymer system at the time of contact-poling. Different types of spacers for avoiding electric breakdown due to avalanche multiplication are compared. Electric field threshold values for second harmonic generation are observed in all samples.
Optical phase retrieval using four rotated versions of a single binary amplitude modulating mask
In recent years, phase retrieval methods recovering the phase of an object from coded diffraction patterns have gained popularity. A numerical phase retrieval method called PhaseLift that recovers the phase of an object from a very limited number of coded diffraction patterns was recently proposed. Performance of PhaseLift has been analyzed for different types and the number of masks modulating an object. We present a unique application of PhaseLift that uses four rotations of a single mask, modulating only the amplitude of an object. In simulations, a phase screen with the root-mean-square (RMS) value 0.294 μm was used as the test object. The RMS value of the retrieved phase screen after …
Cavity Ring-Down Spectroscopy measurements of Acetone concentration
This research has been partly supported by the National Research Programme "The next generation of information and communication technologies" (NexIT).
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