PHASE RETARDERS HIGHLY INSENSITIVE TO THE INPUT ANGLE

In the few exceptional cases of total internal reflection phase retard ers that are weakly sensitive to variations in the input angle of inci dence i, the devices are of increasingly larger size; deviate or trans late the emergent beam; are difficult to align in optical systems; or, in coated rhombs, have an impermanent stability of the retardance. Ba sed on new compensating effects, novel devices of high retardance stab ility and advantageous characteristics are presented. One device is st able to within 0.09 degrees of 90 degrees for i +/- 3 degrees. It is a two-reflection quarter-wave retarder that does not alter the path of the compact size light beam, is of compact size (one seventh the size occupied by the achromatic device AD-1 for equal aperture lengths), an d can be easily aligned in optical systems or used as a rotating eleme nt. The path length of the beam inside the device is less than one thi rd the corresponding length inside the achromatic device AD-1. (C) 199 8 Optical Society of America.