Study of dielectric and metallic cavities with small mode volume

Abstract

Optical resonators, which can focus light into a small volume, are still powerful tools for studying the light-matter interaction and have led the remarkable development of various photonics fields such as laser and quantum optics. Especially, the photonic crystal resonator or metallic resonator, which has a wavelength or smaller than the wavelength, has been successfully developed, ranging from a low threshold laser to a single photon source due to its small size. However, there are difficulties that arise from the small size, and the limitations arising from the small size still deserve to be studied. First, we propose and demonstrate a hybrid integration of a small one-dimensional photonic crystal laser onto a silicon waveguide. An optimally designed asymmetric photonic crystal laser is integrated on silicon waveguide by employing high-precision transfer printing techniques. Over 80 % of coupling efficiency can be achieved through the 3.2 $\mu$m long compact vertical coupler. In addition, a study on the strong Purcell effect of erbium using a metal resonator has been demonstrated. Compared to the photonic crystal, a point cavity having a very small mode volume (~10 nm × 10 nm × 10 nm) and an erbium atom having a slow decay time (~10 ms) were introduced to obtain a Purcell effect of 10000 or more. Erbium-doped silica with no background signal was fabricated for detecting only the light emitted from the erbium. However, no direct observation of the Purcell effect above 10000 was possible due to the gold photoluminescence from the small point cavity. Nevertheless, due to the large difference in gold and erbium emission decay time, a fast erbium decay time of ~ 23 $\mu$s was obtained, and over 1000 strong Purcell effect was obtained at erbium located at the mode maximum.