Integration and evaluation of nanophotonic device using optical near field

Abstract

Progress in DRAM technology requires improved lithography. It is estimated that the technology nodes should be down to 16nm by the year 2019 [1]. Recent improvement of the immersion lithography using excimer laser (wavelength of 193 and 157 nm) has realized the technology node as small as 90 nm. Further decrease in the node is expected using extreme ultraviolet (EUV) light source with a wavelength of 13.5 nm. However, their resolution of the linewidth is limited by the diffraction limit of light. Furthermore, continued innovation for transistor scaling is required to manage power density and heat dissipation. To overcome these difficulties, we have proposed nanometer-scale photonic integrated circuits (i.e., nanophotonic ICs) [2]. These devices consist of nanometer-scale dots, and an optical near field is used as the signal carrier. Since an optical near field is free from the diffraction of light due to its sizedependent localization and size-dependent resonance features, nanophotonics enables the fabrication, operation, and integration of nanometric devices. As a representative device, a nanophotonic switch can be realized by controlling the dipole-forbidden optical energy transfer among resonant energy states in nanometer-scale quantum dots via an optical near field [3]. To realize room-temperature operation of nanophotonic switch, ZnO nanocrystallites are promising material, owing to their large exciton binding energy [4-6]. By considering the amount of the energy shift of the ground state of the exciton in the ZnO nanocrystallites due to the quantum confinement effect at room temperature, it is estimated that the size accuracy in ZnO nanocrystallites deposition must be as low as ±10% in order to realize efficient near-field energy transfer among the resonant energy state in nanophotonic switch composed of 5-, 7-, and 10-nm-dots [3]. In this chapter, we review the optical near-field phenomena and their applications to realize the nanophotonic device. To realize the nanometerscale controllability in size and position, we demonstrate the feasibility of nanometer-scale chemical vapor deposition using optical near-field techniques (see Sect. 2). In which, the probe-less fabrication method for mass-production are also demonstrated. To confirm the promising optical properties of individual ZnO for realizing nanophotonic devices, we performed the near-field evaluation of the ZnO quantum structure (see Sect. 3). To drive the nanophotonic device with external conventional diffraction-limited photonic device, the far/near-field conversion device is required. Section 4 reviews nanometerscale waveguide to be used as such a conversion device of the nanophotonic ICs.