A new light-driven chiral molecular switch doped in a stable blue phase (BP) liquid crystal allows wide optical tunability of three-dimensional cubic nanostructures with a selective reflection wavelength that is reversibly tuned through the visible region. Moreover, unprecedented reversible light-directed red, green, and blue reflections of the self-organized three-dimensional cubic nanostructure in a single film are demonstrated for the first time. Additionally, unusual isothermal photo-stimulated less ordered BP II to more ordered BP I phase transition was observed in the system.

We demonstrated a highly efficient, polarization-independent and electrically tunable Fresnel lens based on dye-doped liquid crystal using double-side photoalignment technique. The maximum diffraction efficiency reaches 37%, which approaches the theoretical limit ~41%. Such a lens functions as a half-wave plate, and this feature could be well preserved under the applied voltage. In addition, the device is simple to fabricate, and has fast switching responses between focusing and defocusing state.

This work examines a planar cholesteric liquid crystal ͑CLC͒ cell with a negative dielectric anisotropy, doped with laser dye, as an electrically tunable one-dimensional photonic crystal laser device. The lasing wavelength is demonstrated to be tunable by applying a voltage. Additionally, lasing can be switched on and off changing the frequency of the applied voltage. Wavelength tuning caused by the shift of the reflection band of CLC is attributed to the electrohydrodynamical effect in the negative dielectric cell.

Highly tunable 3D liquid photonic crystals are demonstrated using low-dc-field-driven polymer-stabilized blue-phase liquid crystals. The central wavelength of the photonic band gap can be reversibly shifted to more than 200 nm away from the original position. Besides, by controlling the polymerization-induced morphology variations, the band gap can also be expanded from a bandwidth of around 30 nm to at least 310 nm, the first time a “white” blue phase is observed. Both types of band-gap modulation, namely, shifting and expansion, can be independently manipulated in any crystal axis without affecting the lattice spacings in the other dimensions. We envision polymer-stabilized blue-phase liquid crystals as a fascinating platform for photonic applications, such as 3D lasers, nonlinear optics, and photonic integrated circuits.

166 wileyonlinelibrary.com COMMUNICATION external stimuli, such as electric fi eld and light. A cholesteric grating with a fi eld-controlled period has been demonstrated. [ 8 ] The diffraction angle can be shifted 15° by varying the applied voltage. A reversible optically switchable beam steering device based on an azobenzene-doped CLC grating has been reported recently, [ 9 ] and it was observed that the grating structure can remain more uniform by the optical tuning than that by electrical tuning. However, the optical tuning range was limit to ≈6° only, because the infl uence of the doped azobenzene upon the pitch was fairly fi nite. It is of paramount importance to develop CLC gratings with reversible wide range beam steering capabilities for optical device applications.In conventional spectrometers, a prism or a diffraction grating spatially separates spectral components of light utilizing wavelength dispersion, which can be detected by an array of photodetectors. [ 13 ] Such spectrometers possess the advantages of easy fabrication and operational simplicity. However, for particular biological and medical analyses, e.g., hyperspectral imaging, [ 14 ] the entire spectrum needs to be recorded at every pixel. Thus, it is diffi cult to be achieved by using spatially dispersive elements. Alternatively, diffraction gratings can be implemented in a frequency sequential scanning system by detecting the incidence angle with mechanically scanning to separate a single spectral component on a single detector. However, the system is bulky and needs high mechanical accuracy. Many methods have been proposed to miniaturize grating dispersive spectrometers. [15][16][17][18] The advantage of a wavelength tunable LC spectrometer is that the entire spectrum can be recreated at single pixel. Nonmechanical tuning can also be realized with an applied external stimulus (light, temperature, electric fi eld) which can further improve the minimized system.In this communication, we report an optically tunable beam steering grating based on a high helical twisting power (HTP) light-driven axially chiral molecular switch-doped CLC fi ngerprint texture. The signifi cant differences of their HTPs resulting from confi gurational changes of the chiral molecular switch upon photoisomerization varies the pitch of CLC, [ 19 ] and consequently shifts the diffraction angle of the CLC grating. Based on this property, the beam steering and spectrum scanning technique have been studied and demonstrated. To the best of our knowledge, this is the LC grating with widest reversible beam steering range reported so far. As a consequence, herein its spectrum scanning capability with potential application in spectrometers as a dispersive element has been demonstrated.In this experiment, the commercially available achiral nematic LC E48 (Merck) with a positive dielectric anisotropy Δ ε Liquid crystals (LCs) are unique functional soft materials with remarkable multistimuli responsive attributes. The LCs formed by rod-shaped molecules have become ubiquitous in ...