Tuning silicon-on-insulator ring resonators with in-plane switching liquid crystals

Abstract

We show that the resonance wavelength of Silicon-On-Insulator ring resonators can be tuned when a top cladding of liquid crystal is present. In-plane strip electrodes are used to generate an electric field that reorients the liquid crystal director in the plane parallel to the chip surface. This causes the resonance wavelength to shift towards longer wavelengths. The magnitude of this shift is about 1 nm, which is twice as large as previously reported shifts. The experimental results are verified extensively with our simulation tools, where a calculation of the director orientation is combined with a fully anisotropic mode solver. From this we get a clear view of the mechanism behind the tuning.

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.…”

“…LC devices based on Si-wire-waveguide phase shifters have also been developed [13,14]. Si wire waveguides can allow such devices to be miniaturized owing to the strong optical confinement in the Si core.…”

“…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).…”

Silicon-organic hybrid devices

“…By combining specialized cladding materials with silicon waveguides, it is possible to take advantage of the strong optical confinement and of the inexpensive silicon fabrication technology, while high optical nonlinearities, small TPA coefficients, voltage-dependent birefringence and optical emission come from tailored organic cladding materials. And indeed, high-speed modulators [2,3], wavelength converters [4], low-power phase shifters [5,6] and even lasers have been successfully demonstrated on the versatile silicon-organic hybrid (SOH) platform [7]. In this paper we review our recent advances in SOH high-speed modulators, showing the first silicon device having a 3 dB bandwidth higher than 90 GHz and demonstrating high-speed data transmission with an IQ modulator.…”

Silicon-on-Insulator polarization rotating micro-ring resonator

“…However, depending on the application and exact platform dimensions, the fundamental quasi-TM polarized mode can be preferred to resonate in the micro-ring. The lower confinement of the quasi-TM mode can be for example beneficial for a-thermal devices [2], sensors based on a cladding refractive index variation, high-Q rings due to a lower backscattering from the vertical sidewalls [3] and for large wavelength range tuning using liquid crystals [4]. Most of these applications, however, exhibit waveguides which are vertically asymmetrical.…”