Area in WordPress Attribute Inflicting Issues

I am attempting to write down my first caption plugin and having some difficulties.

I am establishing a shortcode like so:

operate Shortcode_Caption( $atts, $content material=null ){

   // DEFAULT ARGUMENTS ARRAY       
   $args=shortcode_atts( array(
    'caption' => 'Caption',
    'hyperlink' => 'http://www.hyperlink.com'
   ), $atts);

   // ENCLOSED SHORTCODES
   if($content material){
      return '<div class="Container-Caption" 
        alt="'. $args['caption'] .'" 
        rel="'. $args['link'] .'">
          '.$content material.'</div>';
   };
};  

add_shortcode( 'Caption', 'Shortcode_Caption' );

Some JS picks it up from there. So then when the shortcode is used:

[Caption caption="This is the Text" link="http://www.go_here.com"]some content material[/Caption]

The above does not work, due to the areas within the “caption” attribute. Nevertheless, eradicating the areas works 100%:

[Caption caption="Text" link="http://www.go_here.com"]some content material[/Caption]

I am unsure what I am doing fallacious with this?
Thanks!