How can show the only child categories using shortcode

Hello,
I am facing issue while fetching all child categories in shortcode
i want to show only child categories in one box when we click on parent category which is located on another box.here is my code

function catchild_shortcode($taxonomy_name, $termId, $args = array()) { 
	$args = array(
		'orderby' => 'name',
		'order' => 'ASC',
		'parent' => 0
	  );
	  $categories = get_categories($args);
	  $output .= '<ul class="childcat_popup">';
	  foreach($categories as $category) { 
			  if ($category){
			  $output .= '<li><a href="' . get_category_link( $category->term_id ) . '" title="' . sprintf( __( "View all posts in %s" ), $category->name ) . '" ' . '>' . $category->name.'</a>';
			  }
	  } 
	
	  $output .= '</li>';
	  $output .= '</ul>';
	return $output;
	} 
	// register shortcode
add_shortcode('cat-child', 'catchild_shortcode'); 

If anyone having idea about it.please let me know.
thanks in advance!