How to deter a male coworker away professionally?

You need to talk to your HR department (and should have done so already) if his persistent interest and pursuit are making you uncomfortable. There are laws against this, but you have to start somewhere, and HR is it. You can also see the EEOC website for information on harment and how to file a claim if the company does not address the issue satisfactorily. See a href="http://www.eeoc.gov" rel="nofollow"http://www.eeoc.gov/a