New Functionality in Glass
- PDF / 3,222,605 Bytes
- 4 Pages / 576 x 777.6 pts Page_size
- 92 Downloads / 174 Views
LLETIN/NOVEMBER 1998
original co-discoverers of secondharmonic generation in fibers, gives a broad overview of the phenomenon— associated defect species—and technological applications of these new glasses. In another serendipitous discovery, permanent refractive-index changes were observed forming spontaneously in telecommunications fibers illuminated with intense blue light. The initial discovery led to a new technique of photowriting Bragg gratings in the fiber core using ultraviolet-light holography. The spectral response of the gratings can be engineered to give extremely narrowband reflection, or when chirped, to have the effect of temporally compressing pulses on reflection. Fiber Bragg gratings have proved extremely useful in wavelength demultiplexing and adddrop filters in fiber-communications links, as distributed feedback for wavelength stabilization in lasers, and for optical pulse compression. Their spectral response can also be altered by stress or thermal expansion, so they are also useful in sensors such as those for "smart structures" in bridges and skyscrapers. This rapidly growing technology and the associated materials issues are surveyed in the article by J. Albert in this issue, in "Permanent Photoinduced RefractiveIndex Changes for Bragg Gratings in Silicate Glass Waveguides and Fibers." Glass can also be made to join with living human tissue. Bioactive glass granules are now used to restore lost bone mass. When the granules are implanted into damaged tissue, they form a Ca-Prich surface layer that stimulates adsorption of fibronectin (the "glue" that connects cell membranes to an extracellular matrix) and new bone growth. The body removes any remaining silica gel; only newly formed tissue remains. Bioactive glass is used to restore bony tissue in sinus cavities, and to repair compression injuries in joints and pockets of bone loss in the jaw that result from periodon-
tal disease. "Stimulation of Biological Function With Bioactive Glass" focuses on the role of the glass compositions in stimulating tissue regrowth and in promotion of long-term bone strength. Applications ranging from the development of new and durable solid electrolytes for batteries to the development of sensors are one of the primary reasons for much activity in the area of dynamics of ionically conducting glasses. The realization that incorporation of certain halide components into ion-conducting glasses can result in an increase in the ionic conductivity by orders of magnitude has provided much of the impetus of considerable activity in this area. The contribution on dynamics of mobile ions in glasses provides an assessment of the level of progress in understanding the dynamics of ions in ionically conducting glasses and discusses outstanding challenges that remain. Glasses are important laser hosts and optical-amplifier media. They are becoming increasingly important for fiber and waveguide lasers and up-conversion sources. Fluoride glasses exhibit very low optical losses over a broad spectrum, good solubility of rare-ear
Data Loading...
