Effects of Waveguide Refractive Index on Near-Field Transducer Efficiency in Heat-Assisted Magnetic Recording

In a heat-assisted magnetic recording (HAMR) system, optical power is delivered by the waveguide to interact with the near-field transducer. The influence of optical properties of waveguide core on transducer efficiency has been investigated by using finitedifference time domain simulations. It is observed that the waveguide core of large refractive index can improve transducer efficiency due to more effective exploitation of light power by the transducer. In addition, smaller power is absorbed by the transducer in a HAMR system of larger waveguide core refractive index during operation, which can result in better transducer thermal stability. With the knowledge of effects of large waveguide core refractive index, employing silicon (Si) waveguide in a HAMR system working at near-infrared wavelengths has been proposed to enhance transducer efficiency. Effects of Si waveguide core geometry on transducer performance have been analyzed. A high transducer efficiency of 9.2% at 1200 nm can be achieved in a HAMR system with a Si waveguide of optimized core size.