Modelling and compensation for laser induced transients to improve HAMR writing quality

A model including NFT slow and fast protrusions and heat transient in HAMR writing is given. The effects of transients on different types of writing are discussed. Based on the model, a pole placement method is proposed to design the parameters for overshoot circuit to handle fast protrusion and heat transient. The alternative method is a discrete solution using deconvolution to generate a table for add-on laser current. The effectiveness for both methods is demonstrated in simulation results. Slow protrusion can be compensated by the fly height delta produced by heater control. The heater current is obtained by deconvolution method to achieve a constant fly height for all writing samples.