Multimaterial multifunctional fiber devices

Transcription

1 Multimaterial multifunctional fiber devices The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation As Published Publisher Sorin, Fabien, and Yoel Fink. "Multimaterial Multifunctional Fiber Devices." In European Conference on Optical Communication, ECOC 2009, September, 2009, Vienna, Austria. Institute of Electrical and Electronics Engineers Version Final published version Accessed Fri Oct 05 12:58:30 EDT 2018 Citable Link Terms of Use Detailed Terms Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.

2 Multimaterial Multifunctional Fiber Devices Fabien Sorin (1), Yoel Fink (2) (1) Department of Materials Science and Engineering, Research Laboratory of Electronics and Institute for Soldier Nanotechnology, Massachusetts Institute of Technology, Cambridge, MA (USA), (2) Department of Materials Science and Engineering, Research Laboratory of Electronics and Institute for Soldier Nanotechnology, Massachusetts Institute of Technology, Cambridge, MA (USA), Abstract Recent discoveries have enabled the integration of metals, insulators and semiconductors structures into extended length of polymer fibers. The challenges and opportunities associated with this new class of fiber devices will be presented. The recent development of fiber devices integrating a prescribed assembly of conducting, semiconducting and insulating materials into specific geometries with intimate interfaces and microscopic feature dimensions has heralded a novel path to large area, flexible and light weight electronic and optoelectronic systems 1. For the first time, functionalities such as optical transport 2,3, external reflection 4, lasing 5, but also optical 6-9 and thermal 10 detection may be delivered at length scales and uniformity typically associated with optical fibers. While these fibers share the basic device attributes of their traditional electronic and optoelectronic counterparts, they are fabricated using conventional preform-based fiber-processing methods, yielding kilometers of functional, thin and flexible fiber devices. This renders these fibers systems a compelling candidate for applications such as remote and distributed sensing, large-area optical-detection arrays, and functional fabrics 1,6-10. This presentation provides a review of the recent progress in multimaterial fibers research aimed to enhance fiber-systems functionalities by increasing device density and complexity. We will first describe the fabrication approach of multimaterial fiber devices, and briefly present Photonic Band Gap fibers for medical applications our group has developped. The latest results on photodetecting fibers will then be presented. Especially, two complementary approaches towards realizing sophisticated functions are explored: on the single-fiber level, the integration of a multiplicity of functional components into one fiber, and on the multiplefiber level, the assembly of large-scale two- and three-dimensional geometric constructs made of many fibers. Finally, recent progressses on Fig. 1: (a) A chalcogenide semiconducting glass rod is assembled with an insulating polymer shell and four metal electrodes; and (b) a polymer sheet is rolled around the structure to form a protective cladding. (c) The high-index chalcogenide glass is evaporated on both sides of a lowindex thin polymer film before (d) being rolled around the cylinder prepared in (a-b). A polymer layer is wrapped around the coated film for protection. (e) The preform is consolidated in a vacuum oven and is thermally drawn to mesoscopic-scale fibers. The cross-section of the resulting fibers retains the same structure and relative sizes of the components at the preform level. in-fiber device complexity will be presented as well as an overview of the different projects and future direction for this emerging technology. The fabrication of multimaterial fibers involves the construction of macroscale preforms that are subsequently stretched into long (hundreds of meters), thin, flexible, and light-weight fibers that deliver prescribed functionalities 1. In order to give an outline of the steps involved in fiber fabrication, we consider an integrated device that consists of both a cylindrical omnidirectional mirror structure and a metal-semiconductor-insulator optoelectronic device as depicted in Figure 1. Fabricating the device fiber begins with synthesizing a

3 chalcogenide glass rod using standard sealedampoule techniques. A hollow polymer tube is prepared having an inner diameter that exactly matches the outer diameter of the glass rod, and a thickness exactly equal to that of thin metallic ribbons. The glass rod is then slid into the tube, the electrodes are inserted into pockets cut in the tube (Fig. 1a), and finally a protective polymer cladding is wrapped around the structure (Fig. 1b). In this way, the metal electrodes are completely enclosed between the polymer and the glass rod, preventing any leakage when it melts during drawing. The electrodes may be contacted to thin glass films with this method as well. Fabrication of hollow multilayer structures in fibers begin by thermally evaporating a high-index chalcogenide glass on both sides of a free-standing low-index thin polymer film. To create a hollow fiber, the film is wrapped around a silicate glass tube and consolidated through heating in a vacuum oven. The silicate tube is then removed from the preform core by etching with hydrofluoric acid. When the structure is placed on the external surface of the fiber, no quartz tube is needed. Instead, the coated film is rolled directly around a polymer cylinder with a thin protective polymer layer wrapped around it. Both procedures are combined in preparing the preform shown in Fig. 1, where an external multilayer structure surrounds the optoelectronic device. The preform is then consolidated under vacuum at a high temperature (typically 10-3 Torr and 260 Cº). The resulting fiber preform is thermally drawn into extended lengths of fiber using the tower draw procedure common in the fiber-optic industry. During the draw process, the mirror layers are reduced in thickness by a factor of ~ and the nominal positions of the PBGs are determined by laser micrometer monitoring of the fiber outer diameter during the draw process. The end result of this fabrication process is 100 s of meters of uniform fibers. We now turn to recent development in codrawn metal-insulator-semiconductor photodetecting fiber-based devices with mesoscopic-scale cross-sectional features enabled by this fabrication approach. These new class of fibers have heralded a novel path to optical radiation detection, allowing device-like performance at length scales and in a mechanically flexible form hitherto associated Fig. 2: Top: SEM micrographs of a dual-ring fiber where the position of the electrodes contacting the inner layer are rotated by 45o with respect to those contacting the outer layers (scale bar 100 microns). Bottom left: a semiconducting film (scale bar 1 micron). Bottom right: intimate contact between the film and an electrode (scale bar 1 micron). with optical fibers. Until recently, however, a limitation of these novel fiber devices has been the challenge of integrating multiple optoelectronic components into a single fiber cross-section. This is in fact a common problem in nanotechnology where the drive towards smaller and smaller nanoscale devices complicates the ability to integrate and individually address many of them, especially over very large-area coverage. Integration of multiple devices to work collectively, however, is key to the delivery of complex functionality. The fabrication approach described above however, espsecially for thin-film structures, allows for great flexibility in the number of films to be integrated, their composition, thickness (from a few microns down to below 100 nm), and radial position, as well as the number of electrodes and their placement around the film circumference. This is exemplified in Figure 2, in which the precise alignment of the electrodes between layers, the semiconducting film and the intimate contact between the semiconductor and an electrode are shown. Here, the metallic electrodes are typically tens of microns in size which renders trivial electrical contact of each individual device, while the film is uniformly maintained down to below 100 nm in thickness, illustrating the fine level of control over the fiber crosssectional structure that can be achieved.

4 Fig. 3: Principle of single grid lensless imaging: An object (smiley face) is illuminated by polychromatic radiation. The two diffracted patterns are obtained at the grid location. The phase-retrieval algorithm is used to reconstruct the object. The first row shows theoretical calculations while the second shows the experimental results. This prescribed arrangement of multiple nanometer scale components in a single fiber enables the exploitation of their collective response to impart complex functionalities to fiber devices. We will show that a tandem arrangement of sub-wavelength photodetecting devices integrated in a single fiber enables the extraction of information on the direction, wavelength and potentially even color of incident radiation over a wide spectral range in the visible regime. The remarkable increase in functionality of polymer fibers integrating novel arrangements of nanometer devices is best exploited when one considers the potential coverage area of these systems and the opportunities associated with their assemblies into constructs and fabrics 1,6-10. In Figure 3, we demonstrate how a single wavelength discriminating fiber web can image a complex object with polychromatic light, noninterferometrically and without lenses, by taking an intensity measurement at a single diffraction plane 8. Finally we will present recent development and direction for multimaterial fibers. One example is the incorporation of electronic junctions having build-in potential is a necessity for the realization of transistors, photovoltaics, LEDs, and many other electronic and optoelectronic devices. Until recently, the length and complexity of fiber devices showing rectification behavior have been limited by the processing methods. Their cylindrical geometry is ideal for single device architectures but not amenable to building multiple devices into a single fiber, a requirement for more complex tasks such as signal processing. The multimaterial preform-to-fiber approach addresses the challenges of device density, complexity, and length simultaneously, but the performance of these fiber devices has also been limited by the relatively small set of materials compatible with the drawing process and use of low mobility amorphous inorganic semiconductors. From a processing standpoint, non-crystallinity is necessary to ensure that the preform viscosity during thermal drawing is large enough to extend the time-scale of breakup driven by surface tension effects in the fluids to times much longer than that of the actual drawing. The structured preform cross-section is maintained into the microscopic fiber only when this requirement is met. Unfortunately, the same disorder that is integral to the fabrication process is detrimental to the semiconductors electronic properties. As a result, multimaterial fiber devices built to date are limited to ohmic metalsemiconductor contacts and suffer from problems common to photoconductor devices including high noise currents, continuous power consumption, and reduced sensitivity. The recent incorporation of phase-changing semiconductors 11, those that may be easily converted between the amorphous and crystalline states, into composite fibers offers a path towards reduction of these defects and the ability to introduce spatially extended internal fields within the device. Indeed, by proper selection of the semiconductor and metallic contacts the synthesis of a crystalline compound semiconductor in fiber can be achieved. This opens the way toward arbitrarily long rectifying junction or field effect devices embedded in polymer fibers 12. It is safe to say that the range of materials and variety of structures amenable to the approach outlined in this paper will increase and that the resulting repertoire of novel applications will expand. In addition to incorporating new materials into our fibers, novel structures and geometries may be considered that are not necessarily cylindrically or longitudinally symmetric. The interplay between material properties, structure integration, and fabric-array construction that our group has pioneered is just beginning and promises to be an exciting field for fundamental and applied research besides many current and future applications. The further development of transistors and fiber-integrated logic devices would bring even more exciting functionalities and the prospect of truly intelligent fabrics.

5 References 1 Abouraddy, A. F.; Bayindir, M.; Benoit, G.; Hart, S. D.; Kuriki, K.; Orf, N.; Shapira, O.; Sorin, F.; Temelkuran, B.; Fink, Y. Nat. Mater. 2007, 6, Temelkuran, B.; Hart, S. D. ; Benoit, G.; Joannopoulos, J. D.; Fink Y.; Nature, 2002, 420, Kuriki, K.; Shapira, O.; Hart, S. D. ; Benoit, G.;Kuriki, Y.; Viens, J.; Bayindir, M.; Joannopoulos, J. D.; Fink, Y. Optics Express 2004, 12, Hart, S. D. ; Maskaly, G. R.; Temelkuran, B.; Prideaux P. H.; Joannopoulos, J. D.; Fink, Y. Science 2002, 282, Shapira, O.; Kuriki K.; Orf N.; Abouraddy A. F.; Benoit G.; Viens J.; Rodriguez A.; Ibanescu M.; Joannopoulos J. D.; Fink Y. Optics Express 2006, 14, Bayindir, M.; Sorin, F.; Abouraddy, A. F.; Viens, J.; Hart, S. D.; Joannopoulos, J. D.; Fink, Y. Nature 2004, 431, Sorin, F.; Abouraddy, A. F.; Orf, N.; Shapira, O.; Viens, J.; Arnold, J.; Joannopoulos, J. D.; Fink, Y. Adv. Mater. 2007, 19, F. Sorin et al., accepted in NanoLetters (2009) 9 Abouraddy, A. F.; Shapira, O.; Bayindir, M.; Arnold, J.; Sorin, F.; Hinczewski, D. S.; Joannopoulos, J. D.; Fink, Y. Nat. Mater. 2006, 5, Bayindir, M.; Abouraddy, A. F.; Joannopoulos, J. D.; Fink, Y. Advanced Materials 2005, 18, S. Danto et al., manuscript in preparation 12 N. Orf et al., submitted to Nature Materials