Contemporary area of liquid crystals research is spreading its focus from display to non-display applications, such as electrically tunable photonic devices. One main drive of such spread in research interest is that liquid crystal displays (LCD) have become the most mature flat-panel technology and the hard-earned know-how on LC alignment can be readily leveraged for non-display LC devices, in which LC alignment is an equally important factor....[ Read more ]

Contemporary area of liquid crystals research is spreading its focus from display to non-display applications, such as electrically tunable photonic devices. One main drive of such spread in research interest is that liquid crystal displays (LCD) have become the most mature flat-panel technology and the hard-earned know-how on LC alignment can be readily leveraged for non-display LC devices, in which LC alignment is an equally important factor.

We see two ways on how LC can be applied for non-display photonic devices. Firstly, one can insert a tapered optical fiber with the guided mode evanescent field exposed in a LC cell, or an un-tapered optical fiber with the fiber end exposed in a LC cell . The use of LC cell does not impose any problems regarding LC alignment, but the alignment on the fiber itself is critical for achieving the desired performance. On this front, a FBG-based multipoint voltage sensor was proposed and demonstrated in this thesis, with the capability of a distributed high voltage sensor for power transmission lines applications.

Secondly, one can apply LC as a cladding layer on integrated waveguides on chips . However, LC alignment can be complicated on a non-planar surface profile, where the well-established polyimide (PI) rubbing technique is likely to fail due to poor rubbing quality at sharp edges and nearly vertical sidewalls. Moreover, the mechanical treatment imposed by the rubbing technique can cause damage to the integrated waveguide structures. Thus, for integrated photonics applications, non-contact photoalignment can be a preferred approach. On this front, the LC alignment on complex waveguide geometry surface is carefully studied. With the help of photoalignment, an effective tuning of a SiN microresanator-based filter integrated with a HAN LC cell was demonstrated.