Abstract: A theoretical prediction controls, by a purely passive fiber-optic element, a seemingly uncontrollable linear polarization whose orientation is all but unpredictable. A transformation of an unpredictable polarization orientation into a definite pre-assigned polarization orientation is useful in coherent optical communication and other fiber-optic polarization-dependent systems. A method of making the device utilizes, in a nonconventional way, the presently available fiber-fabrication techniques. A preform of an on-drawing optical fiber of appropriate birefringence is twisted with a monotonously slow-decaying rotational speed. The device is attractive to all obvious advantages inherent to the all-passive nature of the fiber structure.

Abstract: A diffractive lens has a plurality of diffractive zones at least one of which has an optical step having an optical height equal to j.lambda. and at least one of which has an optical step having an optical height equal to k.lambda. where .lambda. is a design wavelength of the lens and j and k are unequal nonzero integers. Alternatively stated at least one of the optical steps induces a relative phase shift of 2j.pi. at the back conjugate point between two light rays emerging from a point source at the front conjugate point and striking the lens immediately on opposite sides of the step and at least one of the steps induces a relative phase shift of 2k.pi. at the back conjugate point between two light rays emerging from a point source at the front conjugate point and striking the lens immediately on opposite sides of that step.

Abstract: An optical beam splitter including a prescribed number of stacked transparent parallel plates whose thicknesses are uniform to a high degree of precision, the back surface of the transparent parallel plate which is the farthest from the side at which light beam that is to be split enters is coated with a totally reflective film, while the back surfaces of all of the remaining transparent parallel plates are coated with different semi-reflective film whose respective reflectivities gradually increase and the coating region of the totally reflective film and semi-reflective films are positioned in an oblique arrangement which is struck by the light beam traveling obliquely through the interiors of the transparent parallel plates.