Optical reference devices for calibrating or monitoring the performance of an optical measurement device, such as a fluorometer, are made from thermoplastics from the polyaryletherketone (PAEK) family of semi-crystalline thermoplastics, including polyether ether ketone (PEEK). The reference device may be made as a master reference device having a known emission output—as determined by a standard optical measurement device—that is used to calibrate other optical measurement devices against the standard. The reference device may be made in the shape of a receptacle vial so that the reference device can be placed in the receptacle holding structure of an instrument in which the optical measurement device is installed and used to calibrate or monitor the optical measurement device within the instrument. The reference device may be part of the probe of a pipettor or pick and place mechanism or it may be a cap that can be secured to the end of such a probe.