Yes. The DataLocker drive is designed to work as a standard external storage device. Encryption on the DataLocker drive is hardware based, and works automatically through the device. There is no need to re-encrypt the drive again after the backup process has been completed.
Normally when you start the backup process, Windows Server will wipe the external drive first before proceeding to transfer the backup data. However, because the DataLocker encryption is done on the hardware level, DataLocker drives save time without the need for backup to be completed to begin encryption, as is required with software based encryption solutions.