Design of an Integrated Gradient-Index Light Condenser for the Light Delivery in a Heat-Assisted Magnetic Recording Head

In this paper, the authors have designed a light condenser device based on the integrated gradient-index (GRIN) lens for the light delivery in a heat-assisted magnetic recording head. The function of the GRIN light condenser is to solve the mode size mismatch and to realize a smooth and efficient light condensation between an external laser diode and a nano-waveguide. Two realizable approaches based on the alloying and two-material film stack to actualize the equivalent index profile have been discussed. From the numerical examples, optimized coupling efficiencies of 93.2% and 86.0% can be achieved for the case of transverse electric and transverse magnetic polarized light, respectively.