Text this

Number:

Provider:

CAPTCHA:

 ______      ___    __    __   __   __    _  _   
|      \\   / _ \\  \ \\ / //  \ \\/ //  | \| || 
|  --  //  | / \ ||  \ \/ //    \ ` //   |  ' || 
|  --  \\  | \_/ ||   \  //      | ||    | .  || 
|______//   \___//     \//       |_||    |_|\_|| 
`------`    `---`       `        `-`'    `-` -`

Please enter what you see:

Text this: Influence of Er<sup>3+</sup>ion concentration on optical and photoluminescence properties of Er<sup>3+</sup>-doped gadolinium-calcium silica borate glasses