To fix hold time violations, timing analysis is initially performed on a circuit design for each set of timing constraints to determine a setup slack and a hold slack for each signal path for that set of timing constraints. In one embodiment, the write gap structure comprises at least one layer of inert material is disposed proximate to the P2 pole of a magnetic recording head. The second substrate is provided with a grating coupler and an optical waveguide on the third surface, the optical waveguide having light incident on the grating coupler propagating therethrough. In one embodiment, the energy source is channeled through a polarity-reversing module.