Abstract

The usefulness of the phase-space concept is well recognized in understanding the propagation of electromagnetic radiation. Furthermore, the principle of phase density conservation in the form of Liouville’s theorem has been broadly discussed for solar energy concentration in systems having axial symmetry¹ as well as in the case of more general non-Cartesian systems.² The purpose of this paper is to extend the applications of the phase density conservation principle to the fiber-optics area in order to demonstrate the feasibility of fabricating new types of fiber optic coupler, connector, and beam expander. Based on Liouville’s invariant^1,2 in design, such systems can potentially circumvent the aberration losses of conventional imaging or nonimaging optics, thus attaining the highest brightness (radiance) or efficiency permissible under the second law of thermodynamics. In addition, the approach of globally optimizing Liouville’s invariant (which is equivalent to maximizing the system efficiency) for the optical channels involved is analyzed. The consequences of the phase density conservation principle for low or moderate values of Fresnel number, like those in fiber-optic systems, are also discussed.

© 1986 Optical Society of America