Will it hurt my grad school chances if I don't mention/contact a particular proffessor-potential guide?
If it's a PhD program, very probably yes.
Most PhDs are earned by working closely with one professor.  In experimental physics, you work in their lab space.  If there is not a professor you can work with during your PhD, then you will not be successful.  Admissions committees want to see that you have identified a small number of faculty who would be suitable for you to work with.
Also, some professors may have funding.  If they want to use the funding to pay you, you will probably be admitted.
We cannot tell you who to approach.