Proposal and demonstration of a controllable Q factor in directly coupled microring resonators for optical buffering applications
Ying Zhang, Qiang Liu, Chenyang Mei, Desheng Zeng, Qingzhong Huang, Xinliang Zhang
Abstract
Optical resonators with controllable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> factors are key components in many areas of optical physics and engineering. We propose and investigate a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> -factor controllable system composed of two directly coupled microring resonators, one of which is tunable and coupled to dual waveguides. By shifting the resonance of the controllable microring, the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> factor of the system as well as the other microring changes significantly. We have demonstrated wide-range controllable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> factors based on this structure in silicon-on-insulator, for example. The influences of spectral detuning and coupling strength between two resonators on the variation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m5"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> factors are studied in detail experimentally. Then, we explore its applications in optical buffering. Tunable fast-to-slow/slow-to-fast light has been carried out by switching the system between the high- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m6"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> state and low- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m7"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> state. Moreover, optical pulse capture and release are also achievable using this structure with dynamic tuning, and the photon storage properties are investigated. The proposed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m8"> <mml:mrow> <mml:mi>Q</mml:mi> </mml:mrow> </mml:math> -factor tunable system is simple, flexible, and realizable in various integrated photonic platforms, allowing for potential applications in on-chip optical communications and quantum information processing.