Embedded ring resonators for microphotonic applications

Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
Optics Letters (Impact Factor: 3.29). 10/2008; 33(17):1978-80. DOI: 10.1364/OL.33.001978
Source: PubMed


We propose a new type of optical resonator that consists of embedded ring resonators (ERRs). The resonators exhibit unique amplitude and phase characteristics and allow designing compact filters, modulators, and delay elements. A basic configuration of the ERRs with two rings coupled in a point-to-point manner is discussed under two operating conditions. An ERR-based microring modulator shows a high operation speed up to 30 GHz. ERRs with distributed coupling are briefly described as well. (C) 2008 Optical Society of America.

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    • "The mode numbers, m 1 and m 2 , are set to be approximately 900 and 681, respectively, corresponding to a radius of ∼57 μm of Ring 2. Coupled mode theory [42] is used to analyze the transfer characteristics of the embedded rings (see [27] for more details). If m 1 and m 2 are both integers, the resonant wavelengths of Ring 1 and Ring 2 are aligned, and EIT-like responses or mode splitting are seen [25], [27]. When the resonant wavelengths of Ring 1 and Ring 2 are offset, we observe asymmetric Fano lineshapes, as shown in Fig. 2. The Fano effect in the embedded rings results from the interference between the optical fields in Ring 1 and Ring 2, where the resonance of Ring 1 serves as the continuum and the resonance of Ring 2 is analogous to a discrete state [29], [30]. "
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    • "The outer ring is coupled with parallel waveguides, and the amplitude coupling coefficients in the four coupling regions are labeled t 1 , t 2 , t 3 , and t 4 , as shown in Fig. 1(b). The embedded rings work at a resonant wavelength of 1.55 μm, and mode numbers are set to be m 1 = 101 and m 2 = 70 to enable the EIT-like effect [6]. Transfer function is calculated at the " out " port using coupled mode theory [7]. "
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    • "This requires less memory and computation time than the method in [29]. However, in some other cases [18], [28], [45], the optical fields at different parts of the rings have to be solved to examine the optical waves' interference and evolution. One need to use either the model in [29] or a modified version of the model in [42] by combining it with the steady-state coupledmode theory in [46], both of which require a time step less than one cavity round-trip time. "
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