Temperature-dependent broadband near-infrared luminescence in silicate glass ceramics containing Li 2 MgSiO 4 : Cr 4+ na
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ransparent glass ceramics containing Li2MgSiO4: Cr4þ nanocrystallites were prepared. Intense broadband near-infrared emission with full width at half-maximum larger than 200 nm and long fluorescence lifetime (t > 100 ms) were observed. The temperaturedependent optical characteristics of the glass ceramics containing Li2MgSiO4: Cr4þ crystallites were compared to those of Li2MgSiO4: Cr4þ single crystals. The reason for extra-long near-infrared fluorescence lifetime was illuminated by the mixed effect between 3T2 and 1E levels. The crystal-filed-induced particular energy-level scheme makes the fluorescence lifetime of the glass ceramics containing Li2MgSiO4: Cr4þ crystallites one order longer than those of other Cr4þ-doped glass ceramics. I. INTRODUCTION
The rare-earth (RE) ions-doped fiber amplifiers and subsequently developed wavelength division multiplexing technique have brought revolution into the field of optical telecommunication.1,2 The restriction on the transmission rate and distance due to intense signal attenuation has been removed, and a super high-speed, super mass-storage, and super long-range telecommunication network has been achieved. However, the bandwidth of telecommunication transmission is limited by the narrow emission band of RE ions. Novel fiber amplifiers, which cover the broad near-infrared (NIR) region from 1.1 to 1.7 mm, are expected to be fabricated in transition metal (TM)-doped materials.3,4 Many Cr4þ-activated materials show interesting optical properties for potential application in the telecommunication transmission system. Optical amplification and laser action have been observed in many Cr4þ-doped single crystals, such as Mg2SiO4, Y3Al5O12, and Y2SiO5.5–7 Some research focused on Cr4þ-doped Li2MgSiO4 and Li2ZnSiO4 crystals found extraordinary optical properties, especially extra-long NIR fluorescence lifetime in this group of Cr4þ-doped orthosilicates.8–10 Transparent glass ceramics containing nanocrystallites can interestingly be used as hosts for optical activators because they can potentially combine the advantages of both glass (such as easy fabrication) and doped crystals (such as optical activity). Broadband NIR luminescence has been found in several transparent glass ceramics containing Cr4þ-doped crystallites.11,12 Recently, we a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0243 J. Mater. Res., Vol. 25, No. 9, Sep 2010
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demonstrated broadband optical amplification in glass ceramics containing Li2ZnSiO4: Cr4þ at room temperature (RT).13 From the viewpoint of application, it is important to investigate the NIR luminescent properties of Cr4þ-activated glass ceramics at various temperatures. However, there have been few reports on the temperature-dependent broadband NIR emission of these glass ceramics. In this work, we study the broadband NIR luminescence in glass ceramics containing Li2MgSiO4: Cr4þ crystallites as a function of temperature. II. EXPERIMENTAL
Glass with composit
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