Abstract

We clearify the conditions for a complete suppression of fundamental-mode backreflection in mode-converting short-period gratings from the viewpoint of full two-mode coupling theory. The self-reflection coefficients for both the fundamental mode and the higher converted mode must be zero. Experimental reflection spectra of various previous schemes with different efficiencies are interpreted. We propose a new annular photosensitivity profile for UV-writing of fiber gratings which convert the core-guided LP₀₁ and LP₁₁ modes and efficiently suppress backreflections into the fundamental mode.

© 2001 Optical Society of America