I studied for efficient coupling between nanometer-scale metallic cavities and optical fibers. In this work, I especially more focused on finding a new fabrication method for efficient and accurate integration between a sub-5-nm-gap metallic Diabolo optical cavity and a single-mode optical fiber. By employing the transfer printing method using epoxy adhesives, I successfully integrated the sub-5-nm-gap Diabolo metallic cavity on the right surface of the core in the optical fiber. The printed Diabolo metallic cavity shows the extremely strong field confinement (mode volume ~ 10-6 λ3) and enhancement (intensity enhancement > 105) at the interface of the air/cavity and the direct light coupling to the single-mode fiber with a high efficiency. I believe the proposed movable and efficient fiber-coupled nanoscale metallic cavities are highly applicable to the high-precision optical tweezers, the super-resolution near-field optical microscopes, and the single molecular bio-sensors. Over the decades, optical devices has been developed by reducing their sizes with improvement of energy efficiency, operating speed and integration density. However, the dielectric optical devices are inevitably faced with the limitation of reducing sizes to the sub-wavelength scales due to the diffraction limit. Such a limitation has been overcome by utilizing the surface plasmon polaritons (SPPs) operated at the interface between a metal and dielectric layers. Since the SPPs has no theoretical cutoff in size, one can confine and focus the field into the extremely small space (i.e. a sub-5-nm space) by carefully designing the metallic structures. The metallic Diabolo nano-cavity can
three-dimensionally focus and confine photons into the sub-5-nm gap space. Its mode volume is calculated to be less than 10-6 λ3. However, their extremely small sizes make the coupling with conventional optics very difficult. In this work, I studied for the efficient and accurate integration between a sub-5-nm-gap metallic Diabolo optical cavity and a single-mode optical fiber.
본고에서는 나노 크기의 금속 공진기를 광 섬유 끝에 형성 시키고 그 특성에 대하여 연구 하였다. 특히 5 nm의 사이 간격을 갖는 금속 Diabolo 공진기를 제작하여 transfer printing 방법으로 광 섬유 끝에 형성시켰다. 광 섬유 끝에 형성시킨 금속 나노 공진기는 큰 field confinement (mode volume ~ 10^-6 λ^3)와 enhancement (intensity enhancement > 10^5) 를 갖고 광섬유의 core에 정확히 결합되어있다. 이렇게 제작 된 광섬유 끝에 형성시킨 금속 나노공진기는 3차원 manipulation이 용이하며, 큰 field enhancement 효과를 이용하여, optical tweezer, optical sensing, high resolution imaging등 여러 application에 용이 할 것이다.
