A field-profile transformer utilizing a graded-index oval-core (GIO) fiber

A field-profile transformer utilizing a graded-index (GI) fiber having an o val core is proposed, Numerical investigation has demonstrated that the new fiber is capable of performing the profile transformation from elliptical fields that have high aspect ratios of up to 9, to circular fields, and vic e versa, Experimental verification is also performed at a wavelength of 155 0 nm, by making use of plastic GI fibers, demonstrating that a circular mod al field of a standard single-mode fiber can be transformed into an ellipti cal field with an aspect ratio of 4.1. The transformer shows promise for lo w-loss coupling between fibers and functional devices that have elliptical fields, such as planar waveguides, semiconductor optical amplifiers, and la ser diodes.