Efficiently tunable and fabrication tolerant double-slot microring resonators incorporating nematic liquid crystal as claddings

Silicon-organic hybrid photonics: Overview of recent advances, electro-optical effects and CMOS-integration concepts

“…However, a slot waveguide ring resonator modulator having a 6 dB bandwidth of 1 GHz, a device tunability of 12.7 pm V −1 , and a Q-factor of 5000 was demonstrated in 2011 [88]. Furthermore, a double-slot waveguide ring resonator covered by liquid crystal was proposed and theoretically analyzed to have a device tunability of 81.4 pm V −1 , but was never realized in practice [91]. In 2016, Weiwei et al [92,93] demonstrated that it is possible to improve the Q-factor from 3000 to 30 600 by optimizing the coupling conditions.…”

Compact and low-loss liquid crystal loaded Mach-Zehnder optical switch based on Si wire waveguide

“…Liquid crystal (LC) is a promising integration material which exhibits wide-range and low-power-consumption phase shift while allowing for small device size [9,10,11,12,13,14,15,16,17]. This is because LC molecules generally have a large birefringence of more than 0.1, and their direction can be controlled with external electric fields.…”

“…Several LC loaded Si photonic devices have already been reported, such as a Si-ridge-waveguide-base Mach-Zehnder (MZ) optical switch and add-drop multiplexer incorporating a ferroelectric LC [9,10] and a Si-slot-waveguide-base phase shifter which achieved effective concentration of both the optical and electric fields within the waveguide slit filled with LC [11,12,15].…”

“…In IPS mode, the LC cladding that surrounds the Si waveguide is sandwiched between two in-plane electrodes, and by applying an electric field, the LC molecules initially aligned along the waveguides change their direction to in-plane. Thus, in this mode, a large phase shift can be expected in the transverse electric (TE)-like polarization mode mainly used in Si photonics [11,12,14,15]. However, while this previous device shows favorable switching operation, it is subject to a relatively large device footprint and increased device loss because the introduced loop-back-waveguide-base phase shifter means that both electrodes are located outside the island-like area in the MZ interferometer (MZI).…”