Order of categories

// list subcategories...
function wpse_filter_child_cats( $query ) {

if ( $query->is_category ) {
    $queried_object = get_queried_object();
    $child_cats = (array) get_term_children( $queried_object->term_id, 'category' );

    if ( ! $query->is_admin )
        //exclude the posts in child categories
        $query->set( 'category__not_in', array_merge( $child_cats ) );
    }

    return $query;
}
add_filter( 'pre_get_posts', 'wpse_filter_child_cats' );

Hello,
I use the above code to list the subcategories on parent category pages. But it does not list the categories in alphabetical order. Can you change this code for me so that it can list the subcategories alphabetically?