Page 17 - Chalcogenide Glasses for Infrared Optics
P. 17

xvi   Intro duction


                                Wavelength
           1  2   3  4  5   6  7  8   9  10111213141516

                                                              Water
                                                              vapor




                                                              Carbon
          Relative absorption                                 Ozone
                                                              dioxide







              Window                    Window

                                                              Primary
                                                              atmospheric
                                                              constituents


            H 2 O  H 2 O  CO 2  H 2 O  O 3  CO 2       H 2 O, CO 2
                CO 2

        FIGURE I.1  Infrared absorption bands of primary atmospheric constituents for average
        conditions at sea level.

                 Over the years, materials used in infrared systems have included
              alkali halides, alkaline earth halides, melt formed semiconductors, vapor
              grown fine-grain polycrystalline semiconductors, and chalcogenide
              glasses. Each of the crystal materials has some advantages and some
              disadvantages that will be discussed toward the end of this book.
              However, this book will concentrate chiefly on chalcogenide glasses.
              After 17 years at Texas Instruments (TI), the author left in 1977 to found
              Amorphous Materials (AMI), a small company dedicated to producing
              infrared transmitting glasses for use in infrared optical systems. The
              company is still active in developing new glass compositions for new
              applications.
                 Some crystalline materials were produced at AMI. The production
              of vacuum float zoned silicon, gallium arsenide, and cadmium
              telluride, all useful in infrared technology, will be described. Most of
              the early glass work reported here was carried out at TI in government-
              sponsored programs as indicated in the references. Discussions of
              glasses developed at AMI and their applications will be given. Some
              results of infrared techniques applied to semiconductors at TI will be
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