caa a22 4500 388075910 CHVBK 20180307125200.0 cr unu---uuuuu 161130e199909 xx s 000 0 eng 10.1557/S0883769400053069 doi S0883769400053069 pii (NATIONALLICENCE)cambridge-10.1557/S0883769400053069 Spectral Data Storage Using Rare-Earth-Doped Crystals [Elektronische Daten] Conventional optical data-storage techniques, such as magneto-optic disks and CD-ROMs, record a single bit of information at each particular substrate location. In order to produce the gigabyte-class storage substrates demanded by today's computers using such conventional technologies, access to tens of billions of individual material locations is required. This brute-force approach to optical data storage has produced impressive results. However, there is increasing interest in methods for more efficiently accessing storage materials. One approach is to record multiple bits at a single storage-material location. This can be accomplished by multiplexing the bits spectrally, using differing optical frequencies to record data bits. It has been realized for over 20 years that when certain materials are cooled to appropriate temperatures, typically below 20 K, the possibility of spectrally multiplexing large numbers of bits in a single material location arises. Although this approach, known as spectral hole-burning, has been proposed as a data-storage mechanism, to date it has primarily been used as a tool to study material properties. Rare-earth-doped crystals have been demonstrated to have properties that lend themselves to a variety of different spectral hole-burning-based data-storage applications. In this article, we will review the principles of spectral hole-burning, discuss some specific material systems in which spectral hole-burning is of particular interest, and describe methods for producing high-capacity, high-data-rate spectral memories. Spectral hole-burning, and spectral memories based on spectral hole-burning, depend on a material property referred to as inhomogeneous absorption line broadening. Materials exhibiting this property contain active atoms or molecules that individually respond to (absorb) very specific frequencies of light, but the collective response of all of the material's active atoms or molecules covers a spectral region that is broad compared with the response of a particular active atom or molecule. Inhomogeneous absorption line broadening is caused by local variations in the structure of the host, which in turn lead to variations in the electronic levels of the active atoms or molecules. The absorption linewidth of an individual absorber is referred to as the homogeneous linewidth Γh, and the absorption width of a collection of inhomogeneously broadened absorption centers is referred to as the inhomogeneous linewidth Γi. Application of monochromatic light to such a material has the effect of exciting only a very small subset of active absorbing atoms—those residing in the illuminated spatial volume within a homogeneous width of the exciting light's specific frequency. If the frequency of the imposed light is shifted, a different subset of active absorbing atoms in the illuminated volume responds. Copyright © Materials Research Society 1999 Maniloff Eric S. Johnson Alan E. Mossberg Thomas W. MRS Bulletin Cambridge University Press 24/9(1999-09), 46-50 0883-7694 24:9<46 1999 24 MRS https://doi.org/10.1557/S0883769400053069 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1557/S0883769400053069 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Maniloff Eric S. NATIONALLICENCE 700 1- Johnson Alan E. NATIONALLICENCE 700 1- Mossberg Thomas W. NATIONALLICENCE 773 0- MRS Bulletin Cambridge University Press 24/9(1999-09), 46-50 0883-7694 24:9<46 1999 24 MRS CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge