Holey waveplates from Tower Optical available
Precision waveplates with user-specified holes in specific locations are intended to allow optical system designers to change the beam path by providing a return path that uses the same space as the transmit path. For waveplates, this happens by placing a hole for either the transmitted or returned beam, as required by the design.
Tower Optical
Boynton Beach, FL
www.toweroptical.com