Optical fiber with fractional orbital angular momentum.

A design method for the creation of photons with fractional orbital angular momentum (FOAM) is reported through the use of a metal-wedge optical fiber. The main focus was on a limiting zero-degree metal wedge, the case of light beams carrying ±â„2 OAM per photon. We compared this ideal case with a one-degree metal wedge in hopes of encouraging experimentalists to fabricate this type of waveguide. Various intensity and the Poynting vector plots for different modes and varying wedge angles were obtained and analyzed. We found that the Poynting vectors in the transverse direction for the zero and one degree metal wedges were essentially identical. In addition, as the metal wedge angle was increased, the real propagation constant decreased. Furthermore, the metal wedge enables a new method to obtain a local field enhancement in the center of the core of this waveguide, thus providing a wide range of applications in other fields. Finally, we found discrete complex propagation constants leading to discrete leaky modes with potentially an infinite number of these modes.