Or you can also use Fragments which does not require you to define it in the view code:
namespace/BusyDialogLight.fragment.xml
<core:FragmentDefinition
xmlns="sap.m"
xmlns:core="sap.ui.core">
<BusyDialog />
</core:FragmentDefinition>
And load it like this:
var oDialog = sap.ui.xmlfragment("namespace.BusyDialogLight");
Regards,
Kimmo