Use this code in your functions.php
file or in a plugin-
function wpse_253580_prevent_author_access(){
if( current_user_can( 'author' ) && is_admin() ) {
// do something here. maybe redirect to homepage
wp_safe_redirect( get_bloginfo( 'url' ) );
}
}
add_action( 'admin_init', 'wpse_253580_prevent_author_access' );
This will check if current user is an author and he is trying to access wp-admin area. If true, then redirect him to homepage.