Luminescence enhancement from Si-based materials by introducing a photonic crystal double-heterostructure slot waveguide microcavity

Abstract

CWe demonstrate a novel SOI-based photonic crystal (PC) double-heterostructure slot waveguide microcavity constructed by cascading three PC slot waveguides with different slot widths, and simulate the luminescence enhancement of sol-gel Erdoped SiO 2 filled in the microcavity by finite-difference time-domain (FDTD) method. The calculated results indicate that a unique sharp resonant peak dominates in the spectrum at the expected telecommunication wavelength of 1.5509 m, with very high normalized peak intensity of ~10 8 . The electromagnetic field of the resonant mode exhibits the strongest in the microcavity, and decays rapidly to zero along both sides, which means that the resonant mode field is well confined in the microcavity. The simulation results fully verify the enhancement of luminescence by PC double-heterostructure slot waveguide microcavity theoretically, which is a promising way to realize the high-efficiency luminescence of Si-based materials.The realization of Si-based laser is the core in the whole Sibased optoelectronics field. But Si is a poor light emitter due to its indirect band-gap, and the high-efficiency luminescence from Si has become one of the most challenges in group IV photonics. Doping SiO 2 with erbium (Er) ions is a possible way to obtain a radiative transition. Nevertheless, the light emission from current Er-doped SiO 2 materials is too weak for practical applications. There are many methods proposed to fabricate Er-doped SiO 2 materials, among which the sol-gel [1] technology has attracted much attention, which has the advantages of low operating temperature, accurate control of doping, high concentration and uniformity of doping, etc.Photonic crystals (PCs) [2][3][4] have been shown to be an excellent means of controlling the interaction between light and matter. By introducing some point defects in perfect PC structures to form microcavity, the enhancement of luminescence at the resonant frequency can be realized by the mode confinement effect of microcavity [5][6][7][8][9] . Additionally, the spontaneous radiation also can be enhanced by PC band-edge slow-light effect [10,11] , which can raise photon state concentration. The slot waveguide structures [12] consisting of bilateral high-refractive-index media and central low-refractiveindex slot have strong field confinement effect, which can strengthen the interaction between light and media filled in the slot. If the microcavity can concentrate the properties of PC mode confinement effect, slow-light effect and slot strong field confinement effect, the interaction between light and Sibased luminance materials filled in the microcavity can be strengthened substantially, and the light emission efficiency can be enhanced dramatically.In this paper, we analyze the dispersion of two-dimensional SOI-based planar PC slot waveguides (SPCWs) with different slot widths by the two-dimensional plane-wave expansion (2D-PWE) method. According to the calculated results, we propose a novel PC double-heterostructure slot waveguide microcavity c...