Liangyu Shi

A fast response variable optical attenuator based on blue phase liquid crystal

Blue phase liquid crystals (BPLCs) are promising candidates for next generation display thanks to their fast response and quasi-isotropic optical properties. By taking these advantages, we propose to introduce the material into fiber-optic applications. As an example, a BPLC based variable optical attenuator (VOA) is demonstrated with a polarization independent design. The device shows normally-off feature when no field is applied. Response time down to submillisecond scale is achieved in switching between two arbitrary attenuation states. The attenuation range is also measured from 1480 to 1550 nm, which cover the whole telecomm S-band and part of the C-band. The overall performances reach the requirements for practical use; while still have room for further improvement. Through this example, the applicability of BPLC in fiber-optic devices is presented, which may impel the development of many other photonic applications from infrared to even microwave regions.

Fork gratings based on ferroelectric liquid crystals.

In this article, we disclose a fork grating (FG) based on the photo-aligned ferroelectric liquid crystal (FLC). The Digital Micro-mirror Device based system is used as a dynamic photomask to generated different holograms. Because of controlled anchoring energy, the photo alignment process offers optimal conditions for the multi-domain FLC alignment. Two different electro-optical modes namely DIFF/TRANS and DIFF/OFF switchable modes have been proposed where the diffraction can be switched either to no diffraction or to a completely black state, respectively. The FLC FG shows high diffraction efficiency and fast response time of 50µs that is relatively faster than existing technologies. Thus, the FLC FG may pave a good foundation toward optical vertices generation and manipulation that could find applications in a variety of devices.

Ultrashort helix pitch antiferroelectric liquid crystals based on chiral esters of terphenyldicarboxylic acid

Antiferroelectric liquid crystals (AFLCs) with a nanoscale helix pitch (<100 nm) were revealed in a composition containing achiral smectic-C biphenylpyrimidines and two non-mesogenic chiral dopants: p-terphenyldicarboxylates of chiral (2S)-1,1,1-trifluorooctane-2-ol and (S,S)-1,1,1-trifluorooctan-2-yl 2-hydroxypropanoate. The prepared multicomponent AFLCs exhibit two electro-optical effects, which are interrelated with the chemical structures of the mixture’s components. The first effect is hysteresis free under special voltage waveform U-shaped switching, which exhibits an electro-optical response similar to that of nematic liquid crystals (NLCs) but around 1–2 orders of magnitude faster. Secondly, the deformed helix antiferroelectric liquid crystal (DHAFLC) effect has been investigated. The observed temperature independence of the electro-optical parameters, in a certain temperature range, combined with a fast U-shape response or with DHAFLC, adds a great value for applications.

Large birefringence smectic-A liquid crystals for high contrast bistable displays

We developed two kinds of bistable smectic-A liquid crystal mixtures. Compared with traditional cyanobiphenyl and cyanoterphenyl derivatives, several changes have been made in molecular design: Isothiocyanato is used as a substitute for cyano to increase the optical anisotropy; fluoro groups are added on 3 and 5 positions of the isothiocyanato substituent terminal phenyl ring to increase both the dielectric anisotropy and eutectic property of the smectic mixture; derivatives of (4-isothiocyanatophenyl) pyridine are introduced to produce a wide smectic range. Thanks to above designs, the final smectic-A mixtures exhibit highly improved properties, such as higher contrast, lower operation voltages and wider temperature range. Based on the developed liquid crystals, electronic tags were also demonstrated, which exhibit reliable performance. This work reveals new insights for tailing liquid crystal molecules with bistability, which is extremely meaningful for the design and fabrication of green display devices.

2D–3D switchable display based on a passive polymeric lenticular lens array and electrically suppressed ferroelectric liquid crystal

We reveal a 2D-3D switchable lens unit that is based on a polarization-sensitive microlens array and a polarization selector unit made of an electrically suppressed helix ferroelectric liquid crystal (ESHFLC) cell. The ESHFLCs offer a high contrast ratio (∼10k∶1) between the crossed polarizers at a low applied electric field (∼1.7  V/μm) with a small switching time (<50  μs). A special driving scheme, to switch between a 2D and 3D mode, has been developed to avoid unwanted issues related to DC accumulation in the ferroelectric liquid crystal without affecting its optical quality. The proposed lens unit is characterized by low power consumption, ultrafast response, and 3D crosstalk <5%, and can therefore find application in TVs, cell phones, etc.

Restricted polymer-stabilised electrically suppressed helix ferroelectric liquid crystals

ABSTRACT The electrically suppressed helix ferroelectric liquid crystal (ESHFLC) electro-optical mode is characterised by the high contrast and fast response time at low driving voltage. However, the ESHFLC demands several constraints on the alignment layer and the cell gap. However, due to the fundamental characteristics of the ferroelectric liquid crystals, the cone angle decreases at higher temperatures, which is the biggest hurdle for this electro-optical mode to find the real application. In this article, we disclose a restricted polymer stabilisation (with very small polymer concentration in the mixture) for the ESHFLC without pushing other vital parameters out of the range of the constraints for ESHFLCs. The restricted polymer-stabilised ESHFLC shows large temperature range with stable high contrast, fast response time and low driving voltage, thus, it could find application in a range of the modern display and photonic devices. GRAPHICAL ABSTRACT