Near-field evanescent wave enhancement with nanometer-sized metal grating and microlens array in parallel optical recording head

To increase the data capacity and data transfer rate in optical data storage, a parallel near-field optical array head has been designed and prepared using the finite-difference time-domain (FDTD) simulation and nanofabrication process. Since the vertical cavity surface emitting laser (VCSEL) microprobe array head reported in our previous paper does not satisfy the required recording power for conventional phase change optical media, we have studied a new array head structure designed to enhance the optical throughput using the surface plasmon resonance effect between the incident light and the metal grating. The theoretical analysis and fabrication of a new integrated optical head were discussed with emphasis on the FDTD simulation for the metal grating structure. An approximately 500 times increase in the resonant power enhancement of evanescent waves was observed when a grating periodicity of 118 nm was maintained with the half-wavelength of the incident light inside the GaP substrate. Grating width and depth also affect the evanescent light enhancement between the incident light and metal grating; such result can be used as a guideline for future applications of near-field optical data storage.