Design of a phase-shifted long-period grating using the partial-etching technique

In this paper, a newly designed reconfigurable phase-shifted long period grating using the partial etching technique is presented. In the locally etched long-period grating, there are discontinuities in the effective refractive index of the cladding modes. The phase shift in the long-period grating is generated due to the effective-refractive-index change of the cladding modes in the locally etched long-period grating. The phase shift is proportional to the partial etching depth and etching length. Thus, by controlling the etching depth and the etching area, we can tune the transmission spectrum of a long period grating after it has been written and create an arbitrary spectral response of the grating. Using this characteristic, we design a reconfigurable phase-shifted long-period grating. The phase-shifted long-period grating introduced in this paper will be used in a reconfigurable gain-flattening filter for optical amplifiers, such as the erbium-doped fiber amplifier (EDFA). We believe that this post-processing partial-etching technique can eliminate the complicated fabrication process in order to make a complex grating mask for a gain-flattening filter, thus simplifying the fabrication process and reducing manufacturing cost.