Module.php

    public function onBootstrap($e)
    {
        $sm = $e->getApplication()
                ->getServiceManager();

        $sm->get('view_manager')
            ->getHelperManager()
            ->setFactory('fb', function($sm) {

                return new View\Helper\Facebook($sm->get('facebook_service'));
            });

        var_dump($sm->get('view_manager')
                    ->getHelperManager()
                    ->create('fb'));
        exit;
    }