Efficiency Analysis of Near Field Optical Transducer Used in Heat-Assisted Magnetic Recording

For heat-assisted magnetic recording system, the efficiency of the optical energy delivery system is important for its application. It affects not only the requirement to laser source output power, but also the heat-assisted magnetic recording (HAMR) head performance and reliability. In this paper, the key factor caused the low efficiency of the near field optical transducer is studied. The results show that the main reason is the longitudinal polarization of the transducer radiation. Large permittivity difference between recording layer and air gap makes large electric field intensity difference within recording layer and air gap. Due to small electric field coupling from air to recording layer, large percentage of the incident power is reflected, absorbed or scattered by other components. The investigation results for power dissipation distributions show that the largest portion of power dissipation is reflection. Reusing the reflected power will be an effective way to improve whole optical system efficiency. Simulation results show that more than 30% increase of the efficiency can be obtained by reusing the reflected power.