Direct ultrafast laser written C-band waveguide amplifier in Er-doped chalcogenide glass

This paper reports the fabrication and characterization of an ultrafast laser written Er-doped chalcogenide glass buried waveguide amplifier; Er-doped GeGaS glass has been synthesized by the vacuum sealed melt quenching technique. Waveguides have been fabricated inside the 4 mm long sample by direct ultrafast laser writing. The total passive fiber-to-fiber insertion loss is 2.58 +/- 0.02 dB at 1600 nm, including a propagation loss of 1.6 +/- 0.3 dB. Active characterization shows a relative gain of 2.524 +/- 0.002 dB/cm and 1.359 +/- 0.005 dB/cm at 1541 nm and 1550 nm respectively, for a pump power of 500 mW at a wavelength of 980 nm. (C) 2012 Optical Society of Americ

Nanoindentation studies on waveguides inscribed in chalcogenide glasses using ultrafast laser

Optical straight waveguides are inscribed in GeGaS and GeGaSSb glasses using a high repetition-rate sub-picosecond laser. The mechanical properties of the glasses in the inscribed regions, which have undergone photo induced changes, have been evaluated by using the nanoindentation technique. Results show that the hardness and elastic modulus of the photo-modified glasses are significantly lower as compared to the other locations in the waveguide, which tend to be similar to those of the unexposed areas. The observed mechanical effects are found to correlate well with the optical properties of the waveguides. Further, based on the results, the minimum threshold values of hardness and elastic modulus for the particular propagation mode of the waveguide (single or multi), has been established

Observation of high pressure o-GeTe phase at ambient pressure in Si-Te-Ge glasses

Te-rich Si15Te85-xGex (1 <= x <= 11) glasses are found to exhibit an anomalous phase separations with germanium composition. The structural transformation of o-GeTe crystalline phase from o-GeTe with a = 11.76 angstrom, b = 16.59 angstrom, c = 17.44 angstrom, to high pressure o-GeTe with a new reduced lattice parameters a = 10.95 angstrom, b = 4.03 angstrom, c = 4.45 angstrom, is observed at T-c3 in the composition range 6 <= x <= 11. Raman studies support the possible existence of high pressure o-GeTe phase which is observed in X-ray diffraction experiments. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. http://dx.doi.org/10.1063/1.3696862

FBG Tactile Sensor for Surface Thickness and Shape Measurement

In recent years, numerous measurement techniques have been employed to characterize surface textures in the micrometer and nanometer range. Although these techniques have enabled significant advances in surface metrology, larger surface details are not easily measurable with such techniques. We propose a simple and reliable fiber Bragg grating (FBG) based tactile displacement sensor to measure a wide range of displacements that vary from 0.2 mu m to 2mm. The device adopts a novel multi-pivot mechanical lever-based amplification mechanism to achieve a wide measurement range. Experimental results show that the sensor can measure both 219nm thick, thin-film coating and 1.22mm glass slide by selecting an appropriate pivot position. Further, the device is employed to identify topographies of three different surfaces of different dimensions. The sensor's optimized configuration demonstrates an excellent displacement sensitivity of 63926pm/mm with a high resolution of 15.64nm. The repeatability of the sensor in this configuration is 2.44%

Thermodynamic, Raman and electrical switching studies on Si15Te85-xAgx (4 <= x <= 20) glasses

We have investigated thermal properties of bulk Si15Te85-xAgx (4 <= x <= 20) glasses in detail, through alternating differential scanning calorimetry experiments. The composition dependence of thermal parameters reveal the signatures of rigidity percolation and chemical threshold at compositions x = 12 and x = 19, respectively. The stability and glass forming ability of these glasses have also been determined using the data obtained from different thermodynamic quantities and it is found that the Si15Te85-xAgx glasses in the region 12 <= x <= 17 are more stable when compared to other glasses of the same series. Further, the blueshift observed in Raman spectroscopy investigations, in the composition range 12 <= x <= 13, support the occurrence of stiffness threshold in this composition range. All Si15Te85-xAgx (4 <= x <= 20) glasses are found to exhibit memory type switching (for sample thickness 0.25 mm) in the input current range 3-9 mA. The effect of rigidity percolation and chemical thresholds on switching voltages are observed at x = 12 and 19, respectively. (C) 2012 American Institute of Physics. [doi:10.1063/1.3682759

Switching behavior of bulk, fast ion conducting, vitreous AgI-Ag2O-MoO3 solids with inert electrode

Developing efficient, fast performing and thermally stable Silver iodide-based fast ion conducting solids are of great interest for resistive switching applications, but still remain a challenge. Metallization in bulk, behavior of threshold voltage profile over composition, and corrosion reactions are few of the challenges. In this work, the switching behavior of bulk, fast ion conducting, vitreous (AgI)(x)-(Ag2O)(25)-(MoO3)(75-)(x), for 60 <= x <= 40 solids, has been investigated in order to understand the switching mechanism with the inert electrodes. By using inert electrodes, the switching becomes irreversible, memory type. The switching mechanism is the electrochemical metallization process. The inert electrodes restrain ionic mass transfer but exhibit low barrier to electron transfer allowing the cathodic metallization reaction to reach Nernst equilibrium faster. Cations involved in this process transport through the free volume within the solid structure and follows Mott-Gurney model for electric field-driven thermally activated ion hopping conductivity model. This model along with the thermal stability profile provides a narrow region within composition with better switching performance based on swiftness to reach threshold voltage and less power loss. Traces of anionic contribution to metallization are absent. Moreover, anodic oxidation involves reactions that cause bubble formation and corrosion

Thermodynamic, kinetic and electrical switching studies on Si(15)Te(85-x)In(x) glasses: Observation of Boolchand intermediate phase

An interesting topic for quite some time is an intermediate phase observed in chalcogenide glasses, which is related to network connectivity and rigidity. This phenomenon is exhibited by Si-Te-In glasses also. It has been addressed here by carrying out detailed thermal investigations by using Alternating Differential Scanning Calorimetry technique. An effort has also been made to determine the stability of these glasses using the data obtained from different thermodynamic quantities and crystallization kinetics of these glasses. Electrical switching behavior by recording I-V characteristics and variation of switching voltages with indium composition have been studied in these glasses for phase change memory applications. (C) 2011 Elsevier Inc. All rights reserved

Design and Validation of a Novel High Sensitivity Self-Temperature Compensated Fiber Bragg Grating Accelerometer

Fiber Bragg Grating-based accelerometers are being used in structural health monitoring as they offer several advantages over their electrical counterparts. In this paper, the concept of a novel T-shaped cantilever-based mechanical sensor head is proposed on which the two Fiber Bragg Gratings are integrated in a differential sensing configuration to realize an optical accelerometer. This elegant design simultaneously achieves the dual goals of sensitivity enhancement, and self-temperature compensation. A mathematical model of the accelerometer is developed, and numerical simulations are carried out for three mechanical sensor head designs. A prototype is fabricated and characterized to prove the design. The sensitivity of 821 pm/g of is achieved with a linearity of 99.7%, cross-axis sensitivity of 0.3%, and natural frequency of 64 Hz; self-temperature compensation is achieved with an error of 0.07 pm/degrees C