Multifunctional sensors based on liquid crystals scaffolded in nematic polymer networks

A team based around the University of Wollongong in Australia has woven a flexible graphene supercapacitor for energy storage by processing the material from the nematic phase of graphene oxide [1,...

Liquid crystals: applications and industry

We consider the operation principles of the sensor of an external electric field on the bases of microring resonators that consist of bent-strip waveguides with vertical or horizontal slots filled with nematic liquid crystal. The mode-field distribution and dispersion parameters of the bent-slot waveguides are calculated by using the algorithm based on the method of lines. The influence of the waveguide and microresonator structure (slot width, position and orientation, microresonator radius, etc.) on the sensor sensitivity is analyzed.

Electric field sensing with liquid-crystal-filled slot waveguide microring resonators.

The operational principles of an optical sensor of an external electromagnetic field based on ring microresonators are considered. The microresonators are based on stripline waveguides with vertical and horizontal slots filled with a liquid-crystal material. The mode field propagation and dispersion constants of the waveguides are calculated by the method of lines. The influence of the width and position of the slots in the waveguides and the radius of the microresonators on the sensitivity of the sensor are analyzed.

Measurement of the Strength of Electric Fields by Means of Ring Resonators Based on Slot Waveguides with Liquid-Crystal Filling

The wide use of automated control and actuation systems, the adoption of new technological processes, and conversion to flexible manufacturing systems have stimulated the development of sensing and measurement devices. Sensors are also important elements of fire-alarm and disaster-protection systems. As well as high metrological (measurement) performance, sensors must offer reliability, durability, stability, light weight, compact size, low power consumption, and compatibility with microelectronic information processing devices. Fiber and integrated optical devices are those best able to fulfill all these requirements.1 Waveguide devices, in particular, have the capability to measure small changes in refractive index, and hence the physical quantities that cause those changes. An interesting design for sensing purposes is the slot waveguide, which consists of two strips of a high-refractive-index material separated by a subwavelength-scale region of lowrefractive-index material (the slot). The electric field discontinuity that arises at the interface between high-index-contrast materials results in high optical intensity concentration in the low-index slot region.2 This ability of a slot waveguide to strongly confine light, combined with the properties of a microring resonator (an optical waveguide in a closed loop having micron-scale radius), has shown great potential for optical sensing applications. As an improvement on this design, waveguides with a double-slot arrangement have also been proposed in recent years. Micro-ring resonators based on such double-slot waveguides have been shown to tolerate larger fabrication errors than their single-slot counterparts.3 Moreover, sensitivity can be enhanced by filling the waveguide slot with a substance whose refractive index is responsive to the parameter being measured. In the case of temperature sensing, we have found liquid crystal (LC) to be a useful and interesting filling material Figure 1. Structure of a double-slot waveguide micro-ring resonator showing the waveguide mode transverse electric field distribution (black curve). Liquid crystal (LC) fills the ring waveguide slots.

Enhanced temperature sensing with liquid-crystal filling

Methods of constructing and the operating principles of a high-speed optical sensor for highly accurate measurements of small temperature variations are considered. The sensor is based on micron-size ring resonators consisting of waveguides with one or several slots with a liquid crystal filling.

I. A. Goncharenko

Papers

A Temperature sensor based on a slot waveguide with a liquid crystal filling

Measurement of the Strength of Electric Fields by Means of Ring Resonators Based on Slot Waveguides with Liquid-Crystal Filling