JQuery Validation - Submit checkbox selected options

I am working with the JQuery validate plugin. All my validation works fine, but I am having difficulties passing the selected values of checkbox's to my PHP file. At the moment I have

var validator = $("#my_form").validate({
    rules: {
        'checkbox[]': {
            atLeastOneChecked: true
        }
    },
    messages: {
        'checkbox[]': {
            atLeastOneChecked: jQuery.validator.format("Please select at least one type of switch")
        }
    },
    submitHandler: function (form) {
        $.ajax({
            type: "POST",
            url: "php/process.php",
            data: {
                'checkbox[]': $("#checkbox").val()
            },
            dataType: "json"
        }).done(function (response) {

        });
        return false;
    }
});

How can I pass the selected checkbox options in my submitHandler? I know I could just send a serialized form, but I have to submit data separately.

Thanks