Multichannel photonic devices based on tristable polymer-stabilized cholesteric textures

Abstract

We demonstrate in this paper an electrically tunable photonic device based on one-dimensional photonic crystal (PC) infiltrated with polymer-stabilized cholesteric texture (PSCT) as a central defect layer. With the hybrid PC/PSCT structure, not only is the wavelength of each defect mode switchable among three major stable states by various appropriate frequency-modulated voltage pulses, but also the intensity can be electrically tuned in multi-metastable states. As a result, an electrically controllable multichannel photonic device with several alluring features is proposed. It is wavelength-switchable, intensity-tunable, and polarizer-free and possesses optical tristability in the defect modes to reduce power consumption.

Chiral Optical Tamm States: Temporal Coupled-Mode Theory

“…This layer produces a set of localized states with nontrivial polarization properties [38,39]. Various combinations involving two mirrors have been extensively studied and proposed for practical applications [36,40], including less-than-one-pitch chiral layer [41][42][43][44][45][46]. The closer to the mirror, the higher the energy density of the states may become, but still the states are not localized at surface but within the bulk of the extra layer.…”

Electrically Rotatable Polarizer Using One-Dimensional Photonic Crystal with a Nematic Liquid Crystal Defect Layer

“…Furthermore, the modulation of defect mode lasing [25] and the high speed electrooptic switching [26,27] upon applying a low voltage have been demonstrated by using a 1D PC containing an NLC defect layer. Recently, some interesting concepts have been reported using various LC defects in a 1D PC [29][30][31][32]. In this paper, we investigate polarization characteristics of defect mode peaks in a 1D PC with an NLC defect.…”

Dynamic Tuning and Memory Switching of Defect Modes in a Hybrid Photonic Structure

“…Among them, the 1D PC/LC hybrid structures with dynamic-mode LCs allow the wavelength tunability of defect modes in accordance with the electrically controlled birefringence [13][14][15][16][17][18] or polarization-rotation effect [19]. Along the line of the rapidly emerging concept for green products, several memory-mode LCs as defect layers in PCs have been considered towards the design of energy-efficient devices in that the optical characteristics in the memory state of PC/LC cells persist without the need of any sustaining bias voltage [20][21][22][23][24].…”

“…In comparison with previously reported hybrid PC devices with various chiral-agent-doped LCs, it has been shown in the PC/twisted-nematic-LC cell that the spectral properties of defect modes are dominated primarily by the adiabatic following effect when the phase retardation is larger than the Gooch-Tarry first minimum condition [19]. Moreover, using cholesteric LC with a helical pitch much shorter than the cell gap as the defect layer, each resultant defect mode in the spectrum of the PC/cholesteric-LC cell exhibits a single peak for the unpolarized light in that the effective refractive index becomes (n e + n o )/2 for all polarization directions of light [22,23]. To verify the observed results from the experimental spectra, sophisticated simulations, which take the optical extinction and dispersion into account, were carried out using MATLAB as comparatively shown in the bottom panel of Figure 3.…”

“…Because the 180 • -twisted state is known to be the transient state during the textural transition from the bend to the splay state, this can reasonably be explained by the smaller voltage-induced phase changes in the sT-to-bB transition. Note that other 1D PC hybrid cells containing memory-mode LCs have been reported to possess wavelength tunability, too, when bistable chiral homeotropic nematic (BHN) [20] and dual-frequency cholesteric liquid crystal (DFCLC) [22,23] are infiltrated as the central defect layers. However, since the tunability is realized by electrical switching from the tilted-twist to homeotropic state in PC/BHN and from scattering focal-conic to planar or homeotropic state in PC/DFCLC, the tunable range in wavelength of these two hybrids is limited due to the limited variation in n eff .…”