Abstract:We demonstrate that linear absorption coefficient (LAC)of a graphene-silicon hybrid waveguide (GSHW) is determined by the optical transmission spectra of a graphene coated symmetrically coupled add-drop silicon microring resonator (SC-ADSMR), of which the value is around 0.23 dB/µm. In contrast to the traditional cut-back method, the measured results aren't dependent on the coupling efficiency of the fiber tip and the waveguide. Moreover, precision evaluation of graphene coated silicon microring resonator (SMR) is crucial for the optoelectronic devices targeting for compact footprint and low power consumption.Graphene is a two-dimensional material [1][2][3], which exhibits remarkable optoelectronic characteristics, such as ultrahigh carrier mobility at room temperature [4,5], ultra-broadband absorption [6,7], controllable band-gap transition [8], and giant Kerr coefficient [9,10]. Graphene has been integrated on photonic integrated circuits (PICs) in which the hexagonal carbon sheet is evanescently coupled to the waveguide, leading to unprecedented optical performances [11][12][13][14][15][16].Recently, grapheme resting on silicon-on-insulator (SOI) platform offers great potential for optoelectronic devices. Broadband optical modulator [17,18], mode locked laser [19], broadband photodetectors [20,21], and enhanced parametric frequency conversion [22] have all been demonstrated utilizing graphene-silicon hybrid waveguides (GSHWs). Owing to its intrinsic physical properties, the linear absorption coefficients (LACs) of GSHWs range from 0.04dB/µm to 0.33 dB/µm [23,24],which are much larger than those of silicon waveguides [25]. The LACs of GSHWs are dependent on the quality of the transferred graphene and the waveguide configurations [26], thus are required to be optimized for practical applications. For instance, Strong LAC is preferred in electro-absorption modulator (EAM) [27] to obtain a large modulation depth, while in the nonlinear optical application [28], the LAC should be as small as possible to avoid linear absorption. Therefore, it is of great importance to precisely evaluate the optical absorption loss induced by grapheme [29].Previously, the LACs of graphene-comprising waveguides were obtained by a cut-back method [14][15][16] in which the light-graphene interaction lengths were varied. And this method is subject to the following limitations:1. In order to measure the LACs induced by graphene, multiple stripe waveguides should be patterned with different lengths of graphene [14][15][16], of which the processes are burden some, time consuming and even expensive.2. The coupling efficiencies between the fiber tips and the waveguides as well as waveguide end facets maintain non-uniformity. Moreover, such fiber-to-waveguide coupling losses are often comparable to or even much higher than the propagation losses in the waveguides [27], leading to high uncertainties in loss measurements, as stated in [30].3. Because of the imperfect coverage of grapheme with cracks, the measured losses in these stripe...