GROWTH OF K 2 CO 3 -DOPED KDP CRYSTAL FROM AN AQUEOUS SOLUTION AND AN INVESTIGATION OF ITS PHYSICAL PROPERTIES RAST KDP KRISTALOV Z DODATKOM K 2 CO 3 IZ VODNE RAZTOPINE IN PREISKAVA NJIHOVIH FIZIKALNIH LASTNOSTI

In this present work, KDP and 2M%-K2CO3-doped KDP crystals were grown by a slow-evaporation solution technique. The grown crystals were characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray diffractometry (XRD), UV-Vis spectroscopy, and laser damage threshold (LDT) analysis. The presence of the functional groups of the grown crystals was identified from the FT-IR spectra. The XRD tests showed that the grown crystals had a tetragonal structure. A comparison of the optical transmission of the grown crystals revealed that the K2CO3-doped KDP crystal had a higher transmission than the pure KDP crystal for the entire UV and visible region. Keywords: growth from solution, slow-evaporation solution technique, KDP crystal, K2CO3 additive V predstavljenem delu so KDP in z 2M % K2CO3 dopirani KDP kristali rasli s tehniko po~asnega izhlapevanja teko~ine. Dobljeni kristali so bili karakterizirani iz infrarde~o spektroskopijo s Fourierjevo transformacijo (FT-IR), z rentgensko difrakcijo (XRD), z UV-Vis spektroskopijo in s pragom po{kodbe z laserjem (LDT). Prisotnost funkcionalnih skupin kristalov v rasti je bila dolo~ena s FT-IR spektrom. XRD je pokazal, da imajo rasto~i kristali tetragonalno zgradbo. Primerjava prepustnosti svetlobe v rasto~ih kristalih je odkrila, da imajo KDP kristali, dopirani s K2CO3, bolj{o prepustnost kot pa~isti KDP v celotnem UV in v vidnem podro~ju. Klju~ne besede: rast iz raztopine, tehnika po~asnega izparevanja raztopine, KDP kristal, dodatek K2CO

The physical and electrochromic properties of Prussian Blue thin films electrodeposited on ITO electrodes

In this article, a set of Prussian Blue (PB) thin films with different electrodeposition times (25 s, 50 s, 75 s, 100 s and 150 s) in air at ambient temperature was prepared. The layers were characterized by a variety of techniques which include, field effect scanning electron microscopy, energy-dispersive X-ray spectrometer, X-ray diffraction, Fourier transform infared spectroscopy, UV-Vis spectrophotometry, and electrochemical analysis. A simple and exact electrochemical method was used to estimate the optimal voltages for coloring and bleaching of different PB layers. Controlling electrodeposition time along with applying suitable voltage enabled us to investigate and improve electrochromic properties of PB layer. The sample prepared under 75 s deposition time showed probably a composition intermediate between the insoluble and soluble form. Furthermore, this sample (S75) shows a better electrochromic properties. High value of electrochromic contrast 55.36% at 555 nm and well stability of ion exchange by cycling are the characteristics of this layer. The control of the deposition time resulted in an increase of 9.38 times of the contrast ratio and corresponding values for optical density (Delta OD) of the PB layers.The authors also acknowledgement FEDER, through COMPETE and Fundacao para a Ciencia e a Tecnologia (FCT) Pest-OE/QUI/UI0616/2014 and the project LUMECD (POCI-01-0145-FEDER-016884)

All-optical signal processing and microwave photonics using nonlinear optics

Processing of high speed optical signals in the optical domain, referred to as optical signal processing, is required for many applications in the telecommunication systems and networks. Many optical signal processing techniques have been studied in the literature where most of them are based on nonlinear optics such as 2nd order and 3rd order nonlinear effects. A wide range of nonlinear media are used for performing these nonlinear optical signal processing applications such as optical fibres, semiconductor optical amplifiers, and different types of optical waveguides. In this thesis, we use nonlinear optics to perform nonlinear optical signal processing and microwave photonics applications. First we propose and experimentally demonstrate an optical signal processing module that will be used for recognition of spectral amplitude code (SAC) labels in optical packet-switched networks. We use the nonlinear effect FWM in a highly nonlinear fibre (HNLF) for generation of a unique FWM idler for each SAC label referred to as a label identifier (LI). A serial array of fibre Bragg gratings is then used to reflect the LI wavelengths. Each LI is associated with a unique amount of delay between two optical signals received at two photodiodes. Label recognition is then achieved by measuring this unique time delay. An experiment is conducted where two variable-length data packets are transmitted over a 50-km dispersion-compensated span of fibre and switched at a forwarding node. The SAC labels are successfully recognized, and we obtain error-free transmission for the switched packets with less than 0.3-dB penalty. Then using FWM in a HNLF and also a programmable planar lightwave circuit (PLC) we propose and experimentally demonstrate the all-optical reconfigurable time slot interchange (TSI) of individual bits at 40 Gb/s. The PLC is used to generate different control signals (masks) that determine which bits undergo TSI. By programming the PLC to generate two different masks, two different TSI patterns are obtained. TSI is achieved using FWM between the data signal and the desired mask with bidirectional propagation in the HNLF. Error-free operation is obtained for both of the TSI patterns, with a power penalty of less than 5.2 dB, at a bit error rate of 10-9.Next, we use a low-stress silicon-rich nitride waveguide as the nonlinear medium to perform two different applications based on XPM. The waveguide is engineered to display flat and low dispersion over the entire C+L bands. First, we demonstrate wavelength conversion of 10 Gb/s signals across the C band and obtain error free operation. We also demonstrate ultra broadband wavelength conversion over 300 nm from the O-band to the L-band. Second, we highlight the use of SixNy waveguides for nonlinear MWP. We report the first demonstration of an XPM-based radio-frequency (RF) spectrum analyzer of optical signals using an integrated silicon nitride waveguide. Measurements show a bandwidth of at least 560 GHz for our RF-spectrum analyzer. RF-spectra measurements for pulse trains at rates from ~ 10 GHz to ~ 160 GHz are demonstrated. These results show that the silicon nitride technology has a competitive performance for realizing high-speed optical processing of telecom signals.De nombreuses techniques du traitement du signal optique ont été étudiées dans la littérature, dont la plupart sont basés sur l'optique non linéaire telle que le deuxième ordre et troisième ordre des effets non linéaires. Une large gamme de moyens non linéaires sont utilisés pour l'exécution de ces applications du traitement du signal optique non linéaire tels que les fibres optiques, les amplificateurs optiques à semi-conducteurs, et différents types de guides d'ondes optiques. Dans cette thèse, nous utilisons l'optique non linéaire pour effectuer des applications d'un traitement du signal optique et d'un photonique appliquée aux micro-ondes. Nous proposons et démontrons expérimentalement un module de traitement du signal optique qui sera utilisé pour la reconnaissance des étiquettes correspondent à des codes d'amplitude spectrale (SAC) dans les réseaux de paquets optiques commutés. Nous utilisons l'effet non linéaire FWM dans une fibre hautement non linéaire (HNLF) pour générer une longueur d'onde FWM unique pour chaque étiquette de SAC désignée comme un identificateur d'étiquette. Une série de réseau de fibres Bragg est ensuite utilisée pour refléter les longueurs d'ondes de ces identificateurs d'étiquette. Chaque identificateur d'étiquette est associé à un temps unique de retard entre deux signaux optiques reçus au niveau de deux photodiodes. La reconnaissance de l'étiquette est ensuite obtenue en mesurant ce délai unique. Une expérience est effectuée lorsque deux paquets de données de longueur variable sont transmis sur une fibre à dispersion compensée sur 50 km et ensuite commutés à un nœud de transmission. Les étiquettes de SAC sont reconnues avec succès et on obtient une transmission sans erreur pour les paquets commutés avec une pénalité inférieure à 0,3 dB. Ensuite, en utilisant le FWM dans une HNLF ainsi qu'un circuit d'onde lumineuse planaire (PLC) programmable, nous proposons et démontrons expérimentalement l'échange entre les intervalles de temps tout-optique reconfigurable (TSI) de bits individuels à 40 Gb /s. Le PLC est utilisé pour générer différents signaux de commande (masques) qui déterminent quels bits subissent un TSI. En programmant le PLC pour générer deux masques différents, deux modèles différents TSI sont obtenus. Le TSI est réalisé en utilisant un FWM entre le signal de données et le masque souhaité avec la propagation bidirectionnelle dans le HNLF. Le fonctionnement sans erreur est obtenu pour les deux modèles TSI avec une pénalité de puissance inférieure à 5,2 dB et à un taux d'erreur de bit de 10-9.Ensuite, nous utilisons un guide d'onde optique de nitrure riche en silicium avec une faible contrainte en tant que milieu non linéaire pour effectuer deux applications différentes basées sur la XPM. Le guide d'onde optique est conçu pour afficher une dispersion plate et basse sur les bandes entières de C + L. Tout d'abord, nous démontrons la conversion des signaux de longueur d'onde de 10 Gb /s tout au long de la bande C et on obtient une opération sans erreur. Nous démontrons également la conversion d'une bande de longueur d'onde ultra large supérieure à 300 nm de la bande O à la bande L. Deuxièmement, nous mettons en évidence l'utilisation de guides d'ondes SixNy pour le photonique appliquée aux micro-ondes non linéaire. Nous rapportons la première démonstration d'un XPM basée sur un analyseur de spectre de radiofréquence (RF) de signaux optiques à l'aide d'un guide d'onde de nitrure de silicium intégré. Les mesures montrent une bande d'au moins 560 GHz pour notre analyseur de spectre RF. Les mesures des spectres RF pour les trains d'impulsions à taux de ~ 10 GHz à 160 GHz ~ sont démontrées. Ces résultats montrent que la technologie de nitrure de silicium a un rendement concurrentiel pour la réalisation de traitement optique à haute vitesse des signaux de télécommunications

Growth and characterization of TGS single crystal doped with NiSO₄ grown by Sankaranarayanan-Ramasamy method

234-238Unidirectional NiSO4 doped triglycine sulphate (TGS) single crystal of 15 mm in diameter and 150 mm in length was successfully grown in aqueous solution by Sankaranarayanan-Ramasamy (S-R) method. The characterization of the grown crystal was made by powder X-ray diffraction, UV-Vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), Vicker’s microhardness studies. The X-ray diffraction analysis revealed a monoclinic structure for the grown crystal. UV–Vis. analysis showed high transmittance for the doped TGS crystal in the entire visible region. FTIR spectrum verified the presence of various functional groups in the grown specimen. Vicker's microhardness studies of the doped TGS crystal showed that it is harder than pure TGS crystal. The density of the doped crystal was found to be higher than that of the undoped one

Growth and characterization of TGS single crystal doped with NiSO4 grown by Sankaranarayanan-Ramasamy method

Unidirectional <001> NiSO4 doped triglycine sulphate (TGS) single crystal of 15 mm in diameter and 150 mm in length was successfully grown in aqueous solution by Sankaranarayanan-Ramasamy (S-R) method. The characterization of the grown crystal was made by powder X-ray diffraction, UV-Vis. spectroscopy, Fourier transform infrared spectroscopy (FTIR), Vicker’s microhardness studies. The X-ray diffraction analysis revealed a monoclinic structure for the grown crystal. UV–Vis. analysis showed high transmittance for the doped TGS crystal in the entire visible region. FTIR spectrum verified the presence of various functional groups in the grown specimen. Vicker's microhardness studies of the doped TGS crystal showed that it is harder than pure TGS crystal. The density of the doped crystal was found to be higher than that of the undoped one

Thickness Dependence of Structural and Optical Properties of CdTe Films

In this work, Cadmium Telluride (CdTe) thin films were deposited on glass substrates at room temperature by vacuum evaporation technique. The deposited CdTe thin films were characterized by X-ray diffraction, UV-Visible spectroscopy and Field emission scanning electron microscope (FESEM) techniques. Structural studies revealed that the CdTe films deposited at various thicknesses are crystallized in cubic structure. The results showed the improvement of the film crystallinity upon grain size increment. Optical constants such as refractive index (n), extinction coefficient (k), real and imaginary parts of dielectric constant, volume energy loss function (VELF), and surface energy loss function (SELF) were calculated using UV-Vis spectra. In addition, band gap and Urbach energies were calculated by Tauc and ASF methods. The band gap energy of the specimens was found to decrease from 1.8 to 1.4eV with increasing the thickness of films. The absorption coefficient, computed and plotted versus the photon energy (hν) and tailing in the optical band gap, was observed which is understood based on Urbach law. Urbach energy variation from 0.125 to 0.620 eV in the samples with higher thicknesses is concluded. &nbsp

Oxygen doping effect on wettability of diamond-like carbon films

DLC films were deposited on Ge substrates using direct ion beam deposition method, followed by investigating the influence of O _2 doping on their morphological, electrical, and structural properties. The films were doped with oxygen under flow rates of 5, 10, 20, and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy. Result showed that by increasing oxygen incorporation, sp ^2 content decreases, sp ^3 content increases, and the C-C bonding loses its order. The hydrophilicity of the layers was analyzed by the contact angle measuring experiment. The results showed that by increasing the O _2 flow ratio from 5 to 40 sccm, the percentage of O _2 increases from 1.1 to 3.9%. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°

All-Optical Radio Frequency Spectrum Analyzer Based on Cross-Phase Modulation in a Silicon-Rich Nitride Waveguide

We report RF-spectrum analysis of optical signals based on cross-phase-modulation in a silicon-rich nitride waveguide. Measurements show a bandwidth of at least 560 GHz for our RF-spectrum analyzer. RF-spectra measurements for pulse trains at rates from ~ 10 GHz to ~ 160 GHz are demonstrated