caption featured image

Hello everybody! Im traying to resolve this for two days, reading so much in the web but nothing can resolve it ??

I adapted my theme for show in the main page (content.php) excerpts with thumbnail of featured image (here is the code of my content.php)

<?php if ( is_search() ) : // Only display Excerpts for Search ?>
	<div class="entry-content">
	<a href="<?php the_permalink() ?>" title="<?php the_title() ?>">
<?php if ( has_post_thumbnail() ) { the_post_thumbnail(array(200,200), array("class" => "alignleft post_thumbnail")); } ?>
</a>
		<?php
   if (function_exists('has_excerpt') && has_excerpt()) the_excerpt();
   else the_content('Read on...');
?>
<?php
 if (function_exists('has_excerpt') && has_excerpt()) { ?>
<a href="<?php the_permalink() ?>" title="Continue Reading <?php the_title_attribute(); ?>..."><span class="button">Leer post completo ?</span></a>
<?php  } ?>
	</div><!-- .entry-summary -->
	<?php else : ?>
	<div class="entry-content">
		<a href="<?php the_permalink() ?>" title="<?php the_title() ?>">
<?php if ( has_post_thumbnail() ) { the_post_thumbnail(array(200,200), array("class" => "alignleft post_thumbnail")); } ?>
</a>
		<?php
   if (function_exists('has_excerpt') && has_excerpt()) the_excerpt();
   else the_content('Read on...');
?>
<?php
 if (function_exists('has_excerpt') && has_excerpt()) { ?>
<a href="<?php the_permalink() ?>" title="Continue Reading <?php the_title_attribute(); ?>..." class="button next">Leer post completo</a>
<?php  } ?>

Now I added a style for my thumbnails (like polaroid photo). But I can’t to add caption text in the polaroid’s white spice under the thumbnail. I get this working on in thumbnails into a post, but no in thumbnails of featured image of content.php

?Anybode could help me?
Thanks in advance