Achromatic ferroelectric liquid crystal polarization rotator

In this paper we propose a new approach to fiber optic voltage sensors via voltage-controlled Liquid Crystals (LC), which would allow direct measurement of up to 400 kV/m electric fields at multiple points. In addition, the electro-optical behavior of deformed helix ferroelectric (DHF) liquid crystal in reflective mode is described and tested. The electrically controlled reflectance has been measured at sub-kilohertz driving voltage frequency for different polarizations of the incident light. Full Text: PDF References Y.V. Izdebskaya, V.G. Shvedov, A.S. Desyatnikov, W. Krolikowski and Y.S. Kivshar, "Soliton bending and routing induced by interaction with curved surfaces in nematic liquid crystals", Opt. Lett. 35, 1692-1694 (2010). CrossRef Z. Ge, S. Gauza, M. Jiao, H. Xianyu and S.T. Wu, "Electro-optics of polymer-stabilized blue phase liquid crystal displays", Appl. Phys. Lett. 94, 101104 (2009). CrossRef Z. Brodzeli, F. Ladouceur, L. Silvestri, A. Michie, V. Chigrinov, G. Q. Guo, E. P. Pozhidaev and A. D. Kiselev, "Liquid crystal-based hydrophone arrays", APOS (2012). CrossRef T. Tanigawa, Y. Sakakibara, S. Fang, T. Sekikawa and M. Yamashita, "Spatial light modulator of 648 pixels with liquid crystal transparent from ultraviolet to near-infrared and its chirp compensation application", Opt. Lett. 34, 1696-1698 (2009). CrossRef K. H. Yang and T. C. Chieu, "Transport Properties of Ions in Ferroelectric Liquid Crystal Cells", Jpn. J. Appl. Phys. 28, 2240-2246 (1989) CrossRef I.C. Khoo and S.T. Wu, "Optics and Nonlinear Optics of Liquid Crystals", World Scientific, Singapore (1993). V.G. Chigrinov, "Liquid Crystal Devices: Physics and Applications", Artech House, Boston: London, (1999). A.D. Kiselev, E.P. Pozhidaev, V.G. Chigrinov and H.S. Kwok, "Polarization-gratings approach to deformed-helix ferroelectric liquid crystals with subwavelength pitch", Phys. Rev. E 83, 31703 (2011). CrossRef N. A. Clark and S. T. Lagerwall, "Submicrosecond bistable electro-optic switching in liquid crystals", Appl. Phys. Lett. 36, 899-901 (1980). CrossRef L.A. Beresnev, V.G. Chigrinov, D.I. Dergachev, E.P. Pozhidaev, J. Funfshilling and M. Schadt, "Deformed helix ferroelectric liquid crystal display: A new electrooptic mode in ferroelectric chiral smectic C liquid crystals", Liq. Cryst. 5, 1171-1177 (1989). CrossRef Z. Brodzeli, H.K. Bal, V.G. Chigrinov, A. Murauski, and F. Ladouceur, "Electrical energy harvesting device for current/voltage fibre-based sensors", Optical Fibre Technology (ACOFT), 2010 35th Australian Conference on Fibre Technology, 1-2, (2010). DirectLink X. Zhao, F. Boussaid, A. Bermak and V.G. Chigrinov, "High-resolution thin ?guest-host? micropolarizer arrays for visible imaging polarimetry", Opt. Exp. 19, 5565-5573 (2011). CrossRef X.H. Li, A. Murauski, A. Muravsky, P.Z. Xu, H.L. Cheung, and V. Chigrinov, "Grayscale Generation and Stabilization in Ferroelectric Liquid Crystal Display," J. Display Technol. 3, 273-279 (2007). CrossRef E.P. Pozhidaev, S. Torgova, M. Minchenko, C. Yednak, A. Strigazzi and E. Miraldi, "Phase modulation and ellipticity of the light transmitted through a smectic C* layer with short helix pitch", Liq. Cryst. 37, 1067-1081, (2010). CrossRef E.P. Pozhidaev and V.G. Chigrinov, "Bistable and multistable states in ferroelectric liquid crystals", Crystallography Reports. 51, 1030-1040 (2006). CrossRef Q. Guo, F. Fan, T. Du, and V.G. Chigrinov, "Electrooptic Response of FLC: Effect of Alignment Materials", SID'11 Conference, P-144, Los Angeles, USA, May, (2011). CrossRef G. Hegde, P. Xu, E.P. Pozhidaev, V.G. Chigrinov, and H.S. Kwok, "Electrically controlled birefringence colours in deformed helix ferroelectric liquid crystals", Liq. Cryst. 35, 1137-1144 (2008). CrossRef

Circularly polarized light plays a key role in many applications, including spectroscopy, microscopy, and control of atomic systems. Particularly in the latter, high polarization purity is often required. Integrated technologies for atomic control are progressing rapidly, but while integrated photonics can generate fields with pure linear polarization, integrated generation of highly pure circular polarization states has not been addressed. Here, we show that waveguide microring resonators, perturbed with azimuthal gratings and thereby emitting beams carrying optical orbital angular momentum, can generate radiated fields of high circular polarization purity. We achieve this in a passive device by taking advantage of symmetries of the structure and radiated modes, and directly utilizing both transverse and longitudinal field components of the guided modes. On the axis of emission and at the maximum intensity, we measure an average polarization impurity of 1.0×10−3 in relative intensity across the resonance FWHM and observe impurities below 10−4 in this range. This constitutes a significant improvement over the ∼10−2 impurity demonstrated in previous works on integrated devices. Photonic structures that allow high circular polarization purity may assist in realizing high-fidelity control and measurement in atomic quantum systems.

In this study, we report the improved response time of a thick nematic liquid crystal (LC) device by using an electrospun nanofiber (NF). We investigated the influence of NF characteristics including polymer material, NF volume ratio, and diameter, on the electrical characteristic of the NF/LC composite. A conventional LC device and a polymer-stabilized liquid crystal (PSLC) device were fabricated to compare their electrical characteristics with those of the NF/LC composite. The rise time, decay time, and threshold voltage of these LC devices are determined by measuring the dielectric permittivity. In comparison with the conventional LC device, the decay time of the NF/LC device is significantly improved. Compared with the PSLC device with the same thickness, the NF/LC device shows a lower threshold voltage while exhibiting the same decay time. Finally, we demonstrated the markedly improved response time of a THz phase shifter by using an NF/LC composite.

Photo-alignment technology is important for liquid crystal (LC) device applications where both high resistance to incident optical energy and spatially distributed alignment states over the device clear aperture are required. Coumarin-based photo-alignment materials developed at the Laboratory for Laser Energetics (LLE) possess near-IR laser damage resistance approaching that of fused silica and have been employed in the development and fabrication of a wide variety of LC high-peak-power laser optics. One example is a photo-patterned LC beam shaper, developed for use in LLE’s four-beam, petawatt-peak-power OMEGA EP laser, that has demonstrated 1054-nm, 1 ns laser-damage thresholds approaching those of dielectric thin-film Brewster’s angle polarizers (30 to 40 J/cm2). Achieving similar performance levels in LC devices for near-UV applications is challenging due to a scarcity of both UV-transparent LC materials and polymer alignment layers that can withstand repeated exposure to intense pulsed- or CW UV irradiation without degradation. Previously-employed alignment materials for UV-LC devices such as buffed polyvinyl alcohol (PVA) or Nylon 6/6 have limited usefulness; buffing embeds particulates and scratches into the alignment layer that reduce its UV damage thresholds to only a few J/cm2 and is incapable of producing highly resolved and spatially-distributed LC alignment states. In recent experiments, we have found that coumarin photoalignment materials are remarkably more resistant to damage from both incident 351 nm, 1 ns high-energy laser pulses [~11.42 J/cm2 (1-on-1) and ~15.70 J/cm2.(N-on-1)] and broad-band, continuous wave (CW) UV-visible light than would be expected due to their highly conjugated aromatic electronic structures. This finding opens a new chapter in the development of LC devices for UV applications in high-peak-power lasers (e.g. wave plates, polarization rotators, radial polarization converters, photo-patterned beam shapers) and other areas of optics and photonics where UV stability is important (e.g., space-based applications).

Liquid crystal (LC) devices are described, which modulate the orientation of incoming linearly polarized light. The reorientation is due to the twisted nematic effect and is therefore achromatic. In contrast to practically all other LC devices, the elements described here use alignment layers with modulated orientations [1]. Two new classes of LC devices will be considered. First, LC devices with macroscopic modulations leading to polarization converter devices will be examined. They are capable of generating linearly polarized light with axial symmetry, the beam propagation axis representing the symmetry axis [2]. When such polarization converters are illuminated with circularly polarized light they behave as achromatic spiral phaseplates [3] of integer order.

The polarization bistable characteristics of 980 nm vertical-cavity surface-emitting lasers (VCSELs) with a mesa structure were experimentally studied. To achieve this, a distributed Bragg reflector mirror was processed into a rectangular mesa structure waveguide using inductively coupled plasma reactive ion etching and was buried with a polyimide layer. The VCSELs oscillated with single frequency and the lowest order transverse mode under CW operation at room temperature. Additionally, the VCSELs with a nearly-square mesa structure oscillated in either of the two orthogonal linear polarization states. Bidirectional polarization switching was demonstrated by two injection lights for the orthogonal linear polarization states. These results, together with the former results of polarization bistablity, which were observed in another type of VCSEL [Kawaguchi et al.: Electron. Lett. 31 (1995) 109], suggest that polarization bistability is a basic characteristic of square-shaped waveguide VCSELs.

Light wave propagation in liquid crystal displays by the 2-D finite-difference time-domain method

Microwave Kinetic Inductance Detectors (MKIDs) provide a technological path towards the high-yield, large-format detector arrays needed for the next generation of experiments. The intrinsically integrated readout components of MKIDs generally give rise to high multiplexing factors, simplified assembly, and streamlined experimental integration. We describe the first MKID arrays fabricated and tested on monolithic 150 mm diameter silicon substrates – a crucial scaling in fabrication capacity that is necessary for future large-scale experiments aiming to incorporate hundreds of thousands of detectors in the coming years. The arrays described here are being developed for the TolTEC millimeter-wave imaging polarimeter being constructed for the 50-meter Large Millimeter Telescope (LMT), with observations planned to begin in early 2019. TolTEC uses dichroic filters to define three physically independent focal planes for operation in observational bands centered at 1.1, 1.4, and 2.0 mm. Each focal plane observes in just one wavelength band, allowing the use of simple to produce, direct-absorption pixel designs with each pixel comprising two detectors that are sensitive to orthogonal states of linear polarization. TolTEC comprises approximately 7,000 polarization sensitive MKIDs designed to operate at a base temperature of 100 mK. The primary working material used for these devices are TiN/Ti/TiN multilayer films, which have several advantageous qualities including: low two-level system noise at the TiN-silicon interface; linear responsivity; uniformity in deposition; and tunable transition temperature, sheet resistance and sheet inductance. We describe the detailed pixel and array layout designs, including focal plane integration and optical coupling via spline-profiled, silicon-platelet, feedhorn-coupled waveguide. We present measurements of full arrays and/or prototype small arrays of devices operating in each of the three observation bands and compare the observed noise and optical performance to that predicted from models and simulations. We also describe the fabrication methods used to produce these large-format arrays with high yield and uniformity.

A side-chain liquid crystal (LC) block copolymer with a ferroelectric smectic C* LC block has been shown to exhibit bistable switching behavior in electric fields. Ferroelectric switching was demonstrated for block copolymers with volume fractions of 0.58 and 0.52 liquid crystal block. SAXS and TEM showed that the bulk morphologies of these two materials were hexagonally packed minority amorphous polystyrene (PS) cylinders and alternating lamellar amorphous PS layers, respectively. Cross-sectional TEM of a 10 μm thick film of the 0.58 volume fraction liquid crystal material used for the optical switching studies showed the cylinders to be well aligned along the shear direction and orthogonal to the applied electric field direction. It is believed that switching is possible due to an unwinding of the pitch of the smectic C* phase due to the presence of the intermaterial dividing surface of the microphase-separated cylindrical domains of the block copolymer which spatially confine the mesophase. This interaction realizes the concept of a microphase-stabilized ferroelectric liquid crystal (MSFLC) device.

Computer simulations have been performed to investigate the behaviour of monolayers of ferroelectric liquid crystals (FELCs) in contact with polymer substrates. The aim of the work is to develop an understanding of the interactions between polymers and FELC molecules, with a view to predicting the size of the optical cone angle, which is an important parameter in determining the performance of FELC displays. We have examined systems consisting of the liquid crystal MBF, which forms a ferroelectric smectic C* phase when suitably doped, and the non-ferroelectric liquid crystal SCB, in combination with polyethylene and r. Ion 6 substrates. Molecular dynamics simulations have been performed, initially on isolated liquid crystal molecules and subsequently on small clusters. Although the systems were too small to observe large scale behaviour, such as phase transitions, it has been possible to observe alignment interactions between the liquid crystal molecules and the substrate, allowing estimates of the cone angle to be made. In the systems examined, we have found that the alignment is dominated by interactions between the flexible tails of the liquid crystal and the polymer.

Photo-embossing has been developed as a convenient and economical method for creating complex surface relief structures in polymer films. The pursuit for large aspect ratios of the photo-embossed structures has never stopped. Here, we demonstrate a simple strategy to obtain improved aspect ratios by adding a quick solvent developing step into the photo-embossing process. A good solvent for the monomer is used to remove unreacted monomers from the unexposed region, resulting in deepened valleys of the surface reliefs. In a polymer film as thin as 2.5 µm, the height of the surface reliefs can be increased by a factor of three to around 1.0 µm. This strategy is also shown to be compatible with other methods used to improve the aspect ratios of the photo-embossed structures. Lastly, we employ these surface relief structures in the fabrication of liquid crystal (LC) devices and investigate their performances for visible light regulation.

Variation in extremely-weak photon counts with changing gate time was investigated using a Mach–Zehnder interferometer and a liquid crystal (LC) device. The number of photon counts per unit time of measurement was miniaturized, and changes in the discrete counts were observed by changing the gate time. In addition, changing the voltage applied to the LC device confirmed that the average photon count in the extremely weak light state can be treated statistically and changes according to the Poisson distribution. This indicates that the photons flew independently. This phenomenon is considered a promising simple variable photon light source for Boson sampling.

We have developed a numerical simulation method on the basis of the ray tracing technique to evaluate a liquid-crystal (LC) spherical aberration compensation device for next-generation high-capacity optical memory devices. We numerically evaluated the performance and the tolerance of the LC device and showed its adequate capability to compensate the spherical aberration due to the nonuniformity of the disc cover layer thickness. Using the simulation method, we numerically examined the possibility of using LC devices to compensate the large spherical aberration due to the layer jump of the dual-layer optical disc and determined that the gradation-type LC device can be used for dual-layer optical recording.

This paper shows a millimeter wave (MMW) antenna based on low temperature co-fired ceramic (LTCC) technology with high polarization purity. By using the LTCC technology with multilayer parasitic patches in vertical direction, a wide bandwidth and high polarization purity can be obtained for the designed antenna. The V type patch is designed based on LTCC multi-layer technology, which is shaped by changing the distance of patch between different layers. By building this multi-layer structure, the polarization purity and bandwidth of antenna can be improved significantly. The simulation results show that the reflection coefficient of the antenna is smaller than −10 dB from 24.28 GHz to 27.84 GHz with a relative bandwidth of about 13.6%, and the cross-polarization isolation is higher than 50 dB within the operation band. The simulated results verify that the proposed antenna can be a promising candidate for 5G communication systems.

A basic experiment on 2-bit quantum calculations related to the Deutsch–Jozsa algorithm on a linear optical quantum computer using a liquid crystal (LC) device as a linear optical element was investigated. By controlling the phase of each of the two split laser beams and checking the number of photons at the output, it is possible to determine if the input bits are “not equal” or “not uniform.” The phase of the laser light was controlled using an LC device and a half-wave plate, and changes in the interference state of the output light and the number of photons were observed. The voltage application to the LC device is set at the input bit. As a result, the interference state changed according to the input bit, and changes in the number of photons were observed.