Temperature‐Tunable Heliconical and Ferroelectric Nematics for White Lasing

Abstract

Nematic Liquid Crystals (LCs), noted for their simple molecular alignment and broad use in optoelectronics, remain unmodified for over a century. However, in 2017, a unique polar phase, the ferroelectric nematic (N_F), is confirmed. Subsequently, in 2024, the revolutionary spontaneous mirror symmetry breaking of ferroelectric twist‐bend nematic chiral structures (N_TBF phase) is demonstrated. Nematic LCs are commonly used as optically active matrices for luminescent dyes, allowing the fine‐tuning of emission properties through external fields. In this manuscript, the pioneering temperature‐tunable lasing studies utilizing commercial dyes doped into a mixture that displays the N_TBF phase within an exceptionally low‐temperature range of 34–43.3 °C are shown. The subsequent experiments explore how lasing characteristics within N_TBF and N_F phases can be employed in a single, compact device to produce multicolor and white lasers. Furthermore, there are introduced spontaneously formed emissive fibers from the N_TBF phase. As perspectives, the voltage‐dependent increase of lasing intensity in N_F is demonstrated, showing the exceptional result in two differently arranged LC cells. The findings highlight that simple molecules, like those in nature and living organisms, can shape intricate systems with significant implications for the accelerated progress of laser and display technologies, along with Li‐Fi concepts.

The discovery of the ferroelectric nematic (N_F) phase in 2017 and the spontaneous symmetry‐breaking of the ferroelectric twist‐bend nematic (N_TBF)phase in 2024 have made major breakthroughs in the context of self‐assembly materials. This study presents pioneering temperature and voltage‐tunable lasing in both phases, demonstrating multicolor and in‐demand white lasers. Additionally, spontaneously formed emissive fibers are shown, with promising applications for displays and Light Fidelity (Li‐Fi) technologies.

1. Introduction

Nematics, the simplest forms of LC thermotropic mesophases, play a pivotal role in various high‐tech applications. They are extensively used in optoelectronics for LC displays (LCDs),^{[ 1 ]} tunable optical devices,^{[ 2} , ³ , ^{4 ]} and in communication for optical switching.^{[ 3 ]} Additionally, nematic LCs are employed in sensing for environmental or chemical detection^{[ 5 ]} and in medical diagnostics for advanced imaging.^{[ 6 ]} For over a century, the field of nematics has seen minimal advancement in discovering new LC phase variants. However, more than a century ago, Max Born introduced a model of polar fluids, proposing that strong dipole‐dipole interactions could stabilize the head‐to‐tail polar alignment of rod‐shaped molecules commonly observed in LCs.^{[ 7 ]} This led to the prediction of a ferroelectric nematic phase, a concept that remained theoretical until 2017 when Mandle and Nishikawa et al.^{[ 8} , ⁹ , ^{10 ]} reported the existence of polar nematic materials with high fluidity. Subsequent research by Clark et al.^{[ 11 ]} confirmed the ferroelectric nature of this mesophase, now widely recognized as ferroelectric nematic (N_F).^{[ 12 ]} This established the exceptionally strong polar order previously thought impossible, bringing substantial novelty to the topic of nematics and leading to the development of subsequent polar LC mesophases.

In a pioneering discovery, Karcz et al.^{[ 13 ]} disclosed the ferroelectric twist‐bend nematic (N_TBF) phase, demonstrated by the formation of a heliconical molecular structure. The noted occurrence of spontaneous mirror symmetry breaking, coupled with the pronounced polarity of these materials, signifies a new chapter in the comprehensively studied field of nematics. Presently, there is a growing demand for applied studies to lay the groundwork for their technological deployment. The demonstration of new LC phases paves the way for exciting advancements in optics, mechanics, and electro‐optics.

At this point, it is vital to discuss future technologies concerning self‐assembly materials and lasers. LC lasers, given their proven potential^{[ 14} , ¹⁵ , ^{16 ]}, can bring significant innovations in terms of efficiency and high‐power coherent light sources. Emerging applications include novel laser‐based displays and projectors.^{[ 17} , ¹⁸ , ¹⁹ , ²⁰ , ^{21 ]} Laser televisions have recently entered the market, resulting in considerable demand for systems capable of producing white lasing (WL) and tunability of polychromatic light.^{[ 22} , ²³ , ²⁴ , ²⁵ , ^{26 ]} The increasing volume of literature in this area highlights its emerging importance and novelty. When combined with new polar nematics, this progress could provide significant advancements in the field. The emergence of macroscopic polar order in ferroelectric nematics enables a new regime of light‐matter interaction, supporting more stable and efficient lasing through various mechanisms, including band‐edge,^{[ 27 ]} Random Lasing (RL),^{[ 28} , ^{29 ]} and distributed feedback cavities.^{[ 30 ]} Such molecular ordering can significantly reduce lasing thresholds or minimize losses in stimulated emission. Enhanced lasing efficiency, combined with voltage‐tunable coherent output, is set to drive a new era of laser‐based displays featuring simplified, solid‐state architectures with no moving parts.

Another innovation is the emergence of Light Fidelity (Li‐Fi)Mater technology, which requires efficient WL sources to achieve data transmission speeds up to 100 times faster than traditional Wi‐Fi.^{[ 31} , ³² , ³³ , ^{34 ]} This underlines the crucial importance of reassessing LCs about stimulated emission effects, as this pairing could be integral to the future of high‐speed data transmission. Furthermore, the intrinsic polarity of these phases allows for rapid, reversible, voltage‐controlled modulation of white, multicolor, and single‐color laser emission, including intensity tuning – an essential feature for future Li‐Fi systems that demand broadband, stable data transmission.^{[ 33 ]}

Research on achieving laser action using novel LCs is ongoing, with a recent article discussing lasers obtained in the N_F phase with a chiral dopant.^{[ 35 ]} Yet, there are no application‐focused or lasing‐centric articles discussing the N_TBF. Furthermore, no studies compare the lasing performance in N_F and N_TBF, an entirely new field for exploring these polar phases’ properties. Additionally, there is a lack of publications addressing these aspects in the much sought‐after area of multicolor and WL.

In this study, we demonstrate for the first time the pioneering spectroscopic experiments and findings of host‐guest systems using a novel mixture, MUT_N_TBF1, containing two recently identified LC polar mesophases: N_F and N_TBF. First, we show structural investigations using Atomic Force Microscopy (AFM) and laser light diffraction techniques to confirm the presence of the novel heliconidal LC phase, gain insights into the helix pitch of N_TBF, and examine the sequence of mesophase transitions in MUT_N_TBF1. Then, we explore the emission and light amplification of the mixture in different temperature regimes. Initial experiments start from a crystalline (Cr) state at room temperature (RT); heating then facilitates a smooth transition through polar LC mesophases, such as N_TBF (noted for the first time within a close to RT range of 34–43.3 °C), culminating in the N_F phase. Through systematic investigations, we assessed the lasing performance of red (R) and green (G) emitting dyes in both N_TBF and N_F phases. We developed a compatible LCC that incorporates two Red‐Green dyes in MUT_N_TBF1 along with a separate hydrophilic blue (B) chromophore, allowing for RGB multicolor performance. This design generates White Fluorescence (WFluo) in its Cr form. Subsequent lasing tests lead to outstanding multicolor tuning, ranging from blue‐violet emission (in Cr) to the White Light (WL) region (matching the illuminant D75 standard) in N_TBF (further referred to as N_TBFWL) and extending to red in the N_F phase.

Then, we present the first evidence of spontaneously forming reusable fibers stemming from the N_TBF phase, separately doped with R and G dyes, thus forming highly useful emissive structures for advanced applications. Transient fiber‐like structures have been previously reported in polar phases.^{[ 13 ]} While N_F‐derived fibers required external electric fields for temporary stabilization, we demonstrate their spontaneous and permanent formation in the newly discovered N_TBF phase.^{[ 36} , ^{37 ]} Remarkably, the simple incorporation of organic dyes not only locks the fiber morphology but also induces emissive functionality. This dual effect originates from the intrinsic polarity of the N_TBF phase, which promotes directional molecular alignment and stabilizing dipolar interactions, while simultaneously supporting anisotropic dopant orientation. The result is a self‐assembled, light‐emitting microarchitecture with potential for rewritable optics, flexible photonics, and soft lasing elements.

Finally, in the context of future perspectives, beyond the influence of heat on optical effects in MUT_N_TBF1, we explored the effect of a DC electric field on molecular orientation in the N_F phase. Surprisingly, we experimentally confirmed that the N_F phase disregards the molecular orientation imposed by the cell's alignment layers, with its electrostatic interactions proving to be stronger than the cell's anchoring. This finding is groundbreaking given that both homogenic/planar (HG) and homeotropic (HT) cells exhibit enhanced light amplification under the influence of a DC electric field. It reflects the dominant role of polar intermolecular interactions in the N_F phase. This allows molecular reconfiguration that is decoupled from surface alignment, enabling highly tunable and geometry‐independent photonic responses. This universal electric‐field‐induced enhancement in lasing intensity paves the way for more flexible photonic device designs. It allows for tunable lasers, optical amplifiers, and integrated circuits that are less constrained by dielectric anisotropy, enabling both HG and HT configurations to achieve enhanced efficiency and broader operational ranges.

2. Results

2.1. Structural Characteristics of New Ferroelectric Mesophases

The textural properties of the recently discovered N_F and N_TBF phases play a crucial role in determining their optical and emission characteristics. We conducted structural exploration using AFM and laser light diffraction techniques (See Methods section). Studied mixture exhibits on cooling from isotropic liquid (Iso) a sequence of four nematic phases, and the lowest temperature LC phase is a liquid‐like smectic phase. The full sequence of phases on cooling is: Iso 200 N 132 N_x 127 N_F 43 N_TBF 34 SmC_F. N is a regular, nonpolar nematic phase, N_X is an antiferroelectric nematic phase, N_F is a previously mentioned ferroelectric nematic phase, while both N_TBF and SmC_F phases have a periodic structure due to heliconical modulation of long molecular axis orientation^{[ 13 ]} with the periodicity (pitch) comparable to the wavelength of visible light. Periodic structure has been directly observed with Atomic Force Microscopy (AFM), and recorded images allowed us to determine periodicity to be ≈1.4 µm and ≈450 nm in SmC_F and N_TBF, respectively (Figure 1a,b).

Figure 1.

AFM images (height sensor signal) recorded in helical a) SmC_F and b) N_TBF phases. The periodicity of the strips is 1.4 µm a) and 450 nm b); the stripe periodicity reflects the helical pitch.

No considerable temperature dependence of the helical pitch on approaching the N‐SmC_F transition was observed. Periodicity of the heliconical structure in N_TBF phase has also been confirmed by laser light diffraction experiments; however, observation of diffraction signal was possible only close to the transition to N_F phase, where the pitch critically unwinds on heating, being 550, 600, and 910 nm at 43.0, 43.1, and 43.2 °C, respectively. The further steps involve the examination of emissive and lasing properties of the unique polar mesophases, confirmed via AFM and diffraction experiments.

2.2. Host‐Guest Systems – Emission Properties

The research began with the creation of three simple host‐guest systems. As mentioned in the Methods, the study utilized a mixture in which the newly discovered polar mesophases, N_F and N_TBF, sequentially appear with increasing temperature. Figure 2a illustrates the molecular ordering typical of these LCs.

Figure 2.

Fundamental properties of the Host‐Guest System with N_F and N_TBF mesophases. a) Schematic representation of hosting polar LCs in MUT_N_TBF1: N_F and N_TBF molecular arrangements. b) Chemical structures of selected guest organic RGB dyes: SB420, CM540, and DCM. c) Fluorescence spectra of dyes, doped to MUT_N_TBF1, measured in RT. d) Fluorescence microscopic image showing blue emission from SB420 doped into the PVA/water solution. e) Green emission from CM540 in MUT_N_TBF1, heated to N_TBF temperature (40 °C). f) Orange fluorescence from DCM doped into MUT_N_TBF1, measured at 40 °C (N_TBF). Scale bars are 200 µm. g) CIE XYZ chromaticity triangle demonstrating the fluorescence from all measured dyes and the multicolor tunability range. All measurements were performed in a 20 µm Liquid Crystalline Cell (LCCs).

In the N_F phase, molecules align their long axes parallel to each other, resulting in uniform director and ferroelectric properties due to an inherent polarization vector. In contrast, the N_TBF phase features periodic twists and bend deformations along the helical axis, which adds complexity to its polar molecular alignment. This combines features of both the twist‐bend nematic^{[ 38} , ^{39 ]} and the N_F phases. Figure 2b presents the selected guest dyes and their chemical structures. The aim was to choose three well‐known, commercially available chromophores emitting in the RGB regions: R (DCM), G (CM540), and B (SB420). CM540 and DCM were separately incorporated into MUT_N_TBF1 for further lasing performance analyses via temperature increase, and each loaded into identical LCCs. SB420 was added to a hydrophilic solution of poly(vinyl) alcohol (PVA) and also introduced into a third LCC.

Figure 2c presents the fluorescence spectra: SB420 in PVA (ranging from 400 to 600 nm with a local maximum at 442 nm), CM540 in MUT_N_TBF1 (emitting from 460 to 650 nm with a λ_max at 497 nm), and DCM in MUT_N_TBF1 (fluorescing from ≈500 to 700 nm, with a distinct peak at 570 nm). Micrographs collected at 40 °C (Figure 2d–f) visibly show the color of the emitted light as blue, green, and orange, respectively. Moreover, in Figure 2d, we observe irregularities in the form of dye aggregation caused by the intentional addition of a large amount of SB420 dye into the PVA/water matrix (See Methods). Notably, the observed domain‐specific textures in Figure 2e,f are characteristic of the N_TBF phase and originate from its spontaneous polar ordering. This alignment not only promotes anisotropic organization of dye molecules but also facilitates directional energy transfer and localized field enhancement, both of which are essential for efficient light amplification. Furthermore, the inherent polar architecture of the N_TBF matrix naturally accommodates orientationally biased dye incorporation, leading to self‐assembled photonic‐like structures capable of Random Lasing (RL).^{[ 29} , ^{40 ]} As illustrated schematically, the formation of scattering centers ‐whether via dye aggregation, polar domains, or topological defects ‐supports internal optical feedback mechanisms.^{[ 41} , ⁴² , ⁴³ , ⁴⁴ , ^{45 ]} These effects are supposed to be further amplified by the intrinsic polar interactions within the N_TBF matrix, which support localized optical feedback and enable mirrorless lasing architectures.

Furthermore, Figure 2g displays the CIE XYZ chromaticity diagram, illustrating the tunable fluorescence range achievable with this laser dye set.

2.3. Single‐Dye LCCs: Temperature‐Tunable Lasing Performance in MUT_N_TBF1

After confirming the basic spectroscopic properties of all three dyes in their respective matrices, we initiated lasing experiments. The LCC with CM540 in MUT_N_TBF1 was pumped (λ_exc = 405 nm) and heated according to the procedure outlined in the Methods section to determine the temperature at which lasing occurs (Figure 3a).

Figure 3.

Fluorescence and lasing performance, driven by temperature changes in MUT_N_TBF1. a) Set of collected spectra – evolution from fluorescence to lasing with fixed fluence = 7.5 mJ cm⁻² and increasing temperature in CM540/MUT_N_TBF1. b) The lasing threshold in N_TBF for CM540/MUT_N_TBF1, as well as the maximum intensity and full width at half maximum (FWHM) changes observed with heating. c) Sequence of microscopic images taken under crossed polarizers for CM540/MUT_N_TBF1, showing the Cr structure at RT (23 °C), selective reflection characteristic of the N_TBF phase at 34, 36, and 40 °C, and the optical texture of the N_F phase. d) Acquired spectra demonstrating the evolution from fluorescence to lasing (for 7.5 mJ cm⁻²) with increasing temperature in DCM/MUT_N_TBF1. e) The lasing threshold in N_TBF for CM540/MUT_N_TBF1, as well as the maximum intensity and FWHM changes observed in heating. f) Sequence of microscopic images taken under crossed polarizers with increasing temperature for DCM/MUT_N_TBF1, showing the Cr structure at RT (23 °C), selective reflection characteristic of the N_TBF phase at 34, 36, and 40 °C, and the optical texture of the N_F phase. The scale bars are 200 µm.

The measurements were conducted at a fixed high fluence of 7.5 mJ cm⁻², enough to pump CM540, as this energy is significantly above the threshold observed in other LC‐based systems.^{[ 46} , ^{47 ]} Between RT and 34 °C, only broad fluorescence was observed (3b). At ≈34 °C, a drastic narrowing of the full width at half maximum (FWHM) is noticed in the nematic twist‐bend phase (N_TBF), from ≈65 to 18 nm, and further to below 10 nm at 40 °C. Two methods, FWHM and Light‐In‐Light‐Out (Li‐Lo), were employed to ensure that these observed changes are reliable and not incidental (See Methods). Above the N_TBF phase, upon entering the temperature range for the N_F occurrence, there is a progressive enhancement of the lasing effect. Although the line width does not narrow further, the lasing intensity significantly increases.

Detailed crossed‐polarizer microscopy studies of the MUT_N_TBF1 phase with CM540 during heating (3c) reveal a distinct Cr structure at the RT (23 °C), transitioning into characteristic selective reflection in the N_TBF ^{[ 13 ]} (see ESI, Figure S1, Supporting Information) when the temperature reaches 34 °C. The micrograph in ESI, Figure S2 (Supporting Information), depicts the molecular orientation typical of this mesophase. As demonstrated, the N_TBF phase often exhibits characteristic stripes or agglomerates, which arise from the heliconical arrangement of molecules within the layers. These patterns may display periodic interruptions, reflecting the unique cone angle and periodicity of the heliconical structure. Above 43.3 °C, the N_F becomes apparent, distinguished by a ferroelectric domain wall molecular pattern that remains stable concerning temperature adjustments (ESI, Figure S3, Supporting Information). Comparable experiments with a system involving DCM as a guest indicated similar trends to those of CM540 (3d). The narrowing of the FWHM to roughly 20–30 nm, along with a significant intensity increase, pinpoints the occurrence of lasing in the N_TBF phase (3e). A slightly broader lasing spectral linewidth is typically associated with DCM, as supported by existing literature.^{[ 48} , ^{49 ]} Figure 3f presents a series of microscopy images. DCM, a dye with an intense red‐orange color, shows less pronounced selective reflection compared to CM540. Nevertheless, N_TBF domains were still observable under these conditions (ESI, Figure S4, Supporting Information). In both N_TBF and N_F mesophases, which display varying LC domain types, the stimulated emission effect observed was categorized as RL^{[ 28} , ^{50 ]} (ESI, Figure S5, Supporting Information). Non‐averaged spectra featuring characteristic comb‐like shapes, along with a discussion on RL, are provided in ESI, Figure S5 (Supporting Information). The third system, SB420 in PVA, is intended for stable lasing behavior irrespective of temperature fluctuation. A study similar in scope was conducted over the same temperature range as the previous two LCCs and is substantiated in ESI, Figure S6 (Supporting Information).

2.4. Lasing Thresholds in N_TBF

Following the observation of lasing in the dye‐N_TBF system, the next step was to determine the RL thresholds in the function of pumping fluence. Figure 4a depicts the spectral progression from fluorescence to lasing for CM540/MUT_N_TBF1.

Figure 4.

Single dye‐doped systems – the lasing thresholds in N_TBF. a) RL spectra obtained with different excitation fluences (from 0.2 to 4.3 mJ cm⁻²) in CM540/MUT_N_TBF1, measured at 40 °C (N_TBF). b) RL threshold (in mJ cm⁻²) in N_TBF for CM540/MUT_N_TBF1, designated with the Li‐Lo and FHWM methods. c) RL spectra obtained with different excitation fluences (from 0.2 to 7.5 mJ cm⁻²) in DCM/MUT_N_TBF1, measured at 40 °C (N_TBF). d) RL threshold (in mJ cm⁻²) in N_TBF for DCM/MUT_N_TBF1, assigned with both methods.

The analyzed lasing spectra (3a) of CM540, measured in N_TBF, indicate a threshold ≈0.5 mJ cm⁻², with Li‐Lo and FWHM remaining consistent (4b). Comparing this value to other LC systems, we note that in N_TBF, the threshold is lower than in the commercially available nematic mixture E7^{[ 48 ]} and similar to values found in ionic liquids.^{[ 51 ]} For DCM (4c), the convergence of both methods is satisfactory, as it is close to 2.0 mJ cm⁻² (4d). DCM in E7 also showed a higher threshold.^{[ 48 ]} A similar analysis was conducted for the N_F phase (80 °C) (see ESI, Figure S7, Supporting Information). Interestingly, in N_F, the thresholds are approximately twice as high as those in N_TBF, roughly aligning with commercial nematic LC‐dye systems previously mentioned. On the other hand, we found that the lasing intensity in N_F is higher than in N_TBF. These findings are not coincidental, as the trend remains consistent for both dyes. As these materials are relatively new and have not been extensively studied in the context of RL, we can propose several hypotheses. While RL phenomena have been reported in various LC systems, including polar phases, our study uniquely compares two distinct polar nematic phases – N_F and N_TBF – with fundamentally different molecular organizations and polarization textures. Both phases exhibit intrinsic polarity; however, their disparate molecular architectures yield markedly different lasing behaviors. This contrast cannot be simply attributed to random orientational disorder or the presence of defects alone. As both phases are polar and exhibit RL, yet their polar order manifests differently, directly modulating the optical gain mechanisms. In the N_F phase, molecules align parallel to each other, resembling nematic orientation, which may cause less photon dispersion and lower energy losses during the emission, leading to high RL intensity. Conversely, the complex helical structure of the N_TBF phase creates various domains (visible in microscopic images) that form specific molecular regions. These areas may offer local light enhancements and population inversion, often leading to a decreased lasing threshold. Consequently, polarity is not merely a structural feature but plays a direct role in controlling the photonic feedback mechanisms essential for RL. This insight advances the understanding of polar LC phases in photonic applications and highlights the unique functional properties of N_TBF compared to other polar nematic materials. To further explore the role of polarity and distinguish its effects from those caused by random disorder alone, we conducted analogous experiments on RL thresholds and microscopy imaging of dye/LC systems in nonpolar mesophase E7, as detailed in the ESI file, Figure S8 (Supporting Information). These systems were identically prepared to the polar N_TBF and N_F phases. As shown in Figure S8 (Supporting Information), both the emission morphology and domain structures differ drastically across the mesophases. RL occurs in all three systems despite some degree of orientational disorder in each; however, the lasing thresholds vary significantly. Under identical experimental conditions, the lowest lasing threshold for CM540 was recorded in the N_TBF phase, followed by N_F, while the highest threshold‐up to 13.7 mJ cm⁻² for CM540 and 14.8 mJ cm⁻² for DCM, was observed in the nonpolar E7 phase. These findings underscore that the enhanced RL performance cannot be solely attributed to structural randomness, but rather arises from distinct polarization textures and molecular organizations inherent to polar mesophases. In Figure S7 (Supporting Information), we also discuss the lasing thresholds for SB420 in PVA as determined by both methods.

2.5. Multicolor and White Emission Performance in N_F and N_TBF

In the subsequent phase of analyzing RL performance, we examined multicolor systems. The LCC cell, containing both SB420 in PVA (blue region – captured with fluorescence microscopy, λ_exc = 375 nm) and MUT_N_TBF1 hosting a mixture of DCM and CM540 (orange region), is schematically depicted in Figure 5a.

Figure 5.

Temperature‐Tunable Multicolor and WL in MUT_N_TBF1. a), Schematic demonstration of LCC device hosting SB420 in PVA, and CM540+DCM mixture in MUT_N_TBF1. The image was captured using the fluorescence microscope with λ_exc of 375 nm (scale bar = 200 µm). b) The WFluo spectrum was recorded in a three‐dye‐doped doped‐LCC in Cr (RT). c) CIE XYZ chromaticity triangle demonstrating the WFluo point. d) Acquired spectra showing the temperature‐tunable multicolor performance for Cr, N_F, and the N_TBFWL (all measured for a fixed fluence of 7.5 mJ cm⁻²). e) Maximum intensities of different bands, and their ratio for N_TBFWL. f) CIE XYZ diagram with all collected points for the three‐dye LCC, and the range created by the single dyes’ lasing in N_TBF and N_F mesophases. g) Spectral evolution from fluorescence to lasing with increasing fluence (from 0.2 to 7.5 mJ cm⁻² in N_TBFWL)_. An N_TBFWL threshold, h), is designated by Li‐Lo (4.7 mJ cm⁻²). The inset demonstrates the bright‐field image of the LCC device. Similar micrographs were made in the cross‐polarized mode for Cr i), N_TBF j), and N_F k). The scale bar is 200 µm.

The aim was to design a compact, small LCC device without moving parts that could be carefully controlled and adjusted for optical output. The LCC houses a temperature‐sensitive material (CM540+DCM/MUT_N_TBF1) and a substance that remains unaffected by heat (SB420/PVA). Moreover, these two phases spontaneously separate. The investigation started with basic spectroscopic characterization. RT fluorescence studies (5b) of the device reveal that, in the Cr state, WFluo can be achieved, with x and y coordinates aligning perfectly with the widely accepted D65 standard (Figure 5c, ESI, Figure S9, Supporting Information). The following step involved comparing the RL performances within the framework of multicolored output at various temperatures (fluence kept constant at 7.5 mJ cm⁻²). Figure 5d presents the acquired spectra. In the Cr state, the dominant band originates from SB420, accompanied by a weak and broad fluorescence from the mix of CM540 and DCM. As the temperature escalates to N_TBF (40 °C), lasing occurs from both the SB420 band and the combination of CM540‐DCM, with the latter peaking at 565 nm. At N_F (80 °C), the mix of CM540‐DCM prevails (λ_max = 580 nm), indicating a minor redshift. In our previous publications, we demonstrated that in compact systems, where different dyes are used nearby, Förster Energy Transfer (FRET) can occur if certain conditions are met. Specifically, FRET requires donor and acceptor fluorophores to be within 1–10 nm, and there must be an overlap between donor emission and acceptor absorption. Regarding the second condition, we studied the same set of dyes in^{[ 48 ]} where their absorption and emission spectra are presented (this information is also included in the Methods section of this manuscript), clearly showing the overlap between the spectra of CM540 and DCM. As demonstrated by Adamow et al.^{[ 48 ]} FRET occurs even in scenarios where DCM and CM540 do not mix within the same volume, as the phenomenon arises at the interface between these two dyes despite their spatial separation. This process was also studied under conditions of perfect mixing of the dyes within the same volume of an LC matrix.^{[ 47 ]} For this reason, we posit that FRET is even more possible to occur in the system we present here, especially at elevated temperatures where dye blending is more effective and where most of the energy from CM540 is likely transferred to DCM. Figure 5e contrasts the bands’ intensities and their ratios in the N_TBFWL (frame with dashed lines).

Interestingly, this device enables temperature‐controlled modulation of both intensity and emission color. As demonstrated in Figure 5f, a single LCC can emit light ranging from blue‐violet (Cr) to the highly desirable white (N_TBFWL) and then to orange‐red (N_F). A comparison of N_TBFWL to the D75 standard is covered in Figure S10 (Supporting Information). Additionally, the CIE XYZ diagram highlights the RGB range between individual dyes in N_F (solid line) and N_TBF (dashed line). The N_F phase offers a broader tuning range with more intense and monochromatic lasing compared to N_TBF, where the fluorescence background remains pronounced. The utility of the achieved RGB range to industry standards such as sRGB, AdobeRGB, DCI‐P3, and Rec. 2020 is discussed in ESI, Figures S11 and S12 (Supporting Information).

Figure 5g presents the evolution of spectra from fluorescence to RL in N_TBFWL depending on fluence, which varies between 0.2 and 7.5 mJ cm⁻². The activation threshold (5h) for collective emission in N_TBFWL's white region is comparatively low (4.7 mJ cm⁻²) in relation to values found in the relevant literature.^{[ 48} , ^{52 ]} Li‐Lo and FWHM are used for a detailed analysis of individual bands provided in ESI, Figure S13 (Supporting Information). The inset of 5h provides a bright‐field microscopic image of the LCC, underlining the boundary between the hydrophilic SB420 in PVA and the hydrophobic MUT_N_TBF1 combined with CM540 and DCM. The following micrographs (Figure 5i,j, k) showcase the Cr phase under crossed polarizers, along with the N_TBF and N_F.

2.6. Applications – Emissive Fibers from N_TBF Mesophase

Karcz et al.^{[ 13 ]} demonstrated that in N_TBF and N_F, cylindrical fibers form, stabilized by a polar order. These fibers break when their aspect ratio (AR, length/diameter) approaches 70, a value significantly larger than that predicted by the Rayleigh‐Plateau theory for the isotropic phase. Today, we provide evidence that these fibers can be preserved and stabilized by maintaining their structure, even when they contain fluorescent dyes. These dyes, namely CM540 and DCM, were selected for the experiments (Figure 6a,b).

Figure 6.

Emissive fibers, spontaneously created from N_TBF. a) The micrographs captured in the fluorescence mode (λ_exc = 375 nm). Fiber obtained with CM540 doping, scale bar is 100 µm, and b) with DCM addition. Scale bar is 100 µm. c) The fluorescence spectrum of CM540‐doped fiber, and d) DCM‐doped fiber. The insets demonstrate the macrographs of fibers, captured under UV illumination. Scale bar is 0.5cm.

During extraction from elevated N_TBF temperatures, the fibers undergo rapid cooling, which stabilizes their structures. As a result, significantly long fibers, in the range of 3–4 cm, are obtained and maintain their shape at RT. They remain solid and stable, without any breakage or alteration to their structure. The CM540 dye fiber (Figure 6a has an average diameter of 72.4 µm and appears quite uniform in diameter (± 4 µm), indicating controlled growth conditions. Its length was measured to be ≈3 cm, resulting in an outstanding AR parameter of ≈414. The surface demonstrates a textured appearance, potentially due to the intrinsic molecular arrangement and possible influence from the CM540 doping. The preservation of fiber morphology during rapid cooling from elevated N_TBF temperatures can be attributed to the strong polar alignment and associated elastic forces within the mesophase, which effectively “lock in” molecular order and prevent surface tension‐driven instabilities. The fluorescent micrograph presents another elongated DCM fiber (6b) exhibiting a relatively uniform diameter (Avg. D = 91.7 µm, AR≈435), though it shows slight surface irregularities. Notably, both fibers emit in the green (Figure 6c) and red (Figure 6d) regions. In the insets of 5c,d, photos demonstrate the fibers under a UV lamp (λ_exc = 405 nm). Additionally, these structures are reusable; they can be reheated and re‐extracted from the N_TBF or N_F phase. Thus, polarity in the dye‐doped N_TBF phase not only controls the mechanical stability of the fibers but also enables their function as emissive microstructures with potential for advanced optoelectronic applications.

2.7. Perspectives – Lasing in N_F Mesophase versus DC Voltage

N_F is second of the newest LC mesophase, and extensive research is currently underway, focusing both on theoretical modeling and experimental investigations. As previously mentioned, in this phase, the dipole moments of the molecules are aligned in a single direction, resulting in the summation of dipoles on a macroscopic scale and the formation of a macroscopic electric field. This molecular ordering grants the material strong polarity and an exceptionally high dielectric constant.^{[ 53 ]} To date, we have studied the effect of DC voltage on the reorientation of LC molecules in the simplest nematic systems as hosts, which also influenced the dyes and ultimately modulated the intensity of laser light.^{[ 54} , ^{55 ]} In these earlier studies, we used LCs with negative dielectric anisotropy in HT cells, a configuration that facilitated an increase in lasing intensity with low voltage values. Achieving a similar electro‐deformation effect in nematics with positive dielectric anisotropy would, however, require using homogenous/planar (HG)‐oriented LCCs. Building on these previous works, we expanded our study to investigate the response of an N_F‐based system doped with the guest dye CM540 to a DC electric field within the range of 0–10 V. For comparison, we employed both HT and HG cell orientations. The results are presented below in Figure 7a–d and provide interesting insights.

Figure 7.

Comparable DC modulation results of CM540/MUT_N_TBF1 in N_F mesophase in HT and HG LCCs. a) The maximum peak intensity versus applied DC Voltage with the marked Freedericksz threshold. The inset shows the texture of the investigated HT LCC; the scale bar is 200 µm. b) The comparison of spectra for the 0 and 7 V applications. c) The maximum peak intensity versus applied DC Voltage with the marked Freedericksz threshold, with the inset showing the texture of the investigated HG LCC (the scale bar is 200 µm). d) The comparison of spectra collected for the 0 and 6 V applications.

One of the most valuable findings is that, regardless of whether there has been used HT or HG LCCs have been used, there is demonstrated a significant increase in lasing intensity, with a maximum enhancement occurring at 7 V for HT (Figure 7a) and 6 V (Figure 7b) for HG cells. The rise in intensity relative to 0 V was 3.1 times higher for the HT (Figure 7c) and 1.7 times higher for the HG LCCs (Figure 7d). These results suggest that the N_F phase exhibits a remarkable response to an external electric field, even in the presence of different alignment configurations. The findings align with the theoretical predictions and microscopic observations of N_F textures by Brown et al.^{[ 56 ]}, who demonstrated that even with HT surface treatment, the N_F phase adopts a planar orientation. Interestingly, while the HT alignment should theoretically favor a perpendicular orientation relative to the glass electrodes, there are no significant differences in the molecular textures between the two LCC configurations, both of which exhibited a planar structure (see Insets in Figure 7a,c). This suggests that the electrostatic interactions within the N_F phase are strong enough to override the surface‐induced alignment, promoting a dominant planar orientation in both cases. This is due to the very high dielectric permittivity (reports mention values ranging from 10 000 to 30 000).^{[ 10} , ^{53 ]} Such a structure facilitates the material's easy response to an external electric field. In the literature,^{[ 56 ]} the importance of ions and polarization at the LC/electrode interface is also emphasized. A high concentration of ions in the N_F sample could lead to local field disturbances, which contribute to the increase in intensity in both configurations. Parameters such as LCC thickness and surface boundary conditions (for example, anchoring strength) are also important factors. Why the emission intensity decreases after some time is currently a matter of speculation. Electrohydrodynamic effects may be responsible for this. Higher voltage values could induce the movement of ions in the sample, leading to the destabilization of the molecular orientation and loss of emission coherence. According to the work,^{[ 57 ]} the decrease in intensity may result from nonlinear responses of the material as a consequence of high polarity. Authors also suggest that in the N_F phase, the higher electric field values dampen the molecular fluctuations (phason mode), which reduces their ability to interact with radiation. Consequently, we observe the lasing emission decrease after some threshold of applied voltage.

These findings confirm that the pronounced electro‐optical response of the N_F mesophase is directly tied to its macroscopic polarity. The alignment of dipoles across the entire volume leads to extremely high dielectric permittivity and internal electrostatic coherence, which in turn enhances the field‐induced molecular reorientation and the lasing emission. The increase in emission intensity at moderate voltages can thus be interpreted as a polarity‐assisted modulation of optical gain through improved molecular alignment. At the same time, the subsequent decline in intensity at higher voltages may stem from polarity‐driven nonlinear effects – such as ion migration, interface polarization, or suppression of molecular fluctuations (phason damping) – all of which are fundamentally related to the collective polar order. This electro‐responsive behavior, significantly more pronounced than in nonpolar nematic systems, highlights the functional relevance of polarity in emergent LC photonics and opens pathways for tunable laser devices based on polar mesophases.

3. Discussion

The recent discovery of polar phases N_F and N_TBF has made a significant impact on the fields of material physics and chemistry, especially with regard to LC design and application. This study represents the first exploration of the N_TBF phase, appearing in the novel MUT_N_TBF1 mixture close to RT. We carried out a systematic investigation into the unique properties and applications of N_TBF, demonstrating its influence on lasing performance.

Initially, we compared the RL of single‐dye‐doped MUT_N_TBF1 in LCCs by modulating the temperature. Our findings revealed significant variations in intensity and optical output as we transitioned from the Cr state through the newly identified N_TBF phase to N_F. This research highlighted the smooth phase transitions and diverse lasing characteristics enabled by these polar phases. Considering the lasing mechanism, our study suggests that, prospectively, band‐edge lasing in the N_TBF phase – indicated by the presence of a helix pitch of ≈450 nm, as evidenced by AFM and optical diffraction studies – might be achievable. However, this phenomenon is not observed in our case, for which the anticipated reflection band lies outside the spectral ranges of both the pump and the dye's absorption/emission. However, this requires further studies, and band‐edge lasing thus remains an intriguing avenue for future research, particularly with specifically tailored dyes. In contrast, our work demonstrates that the N_TBF and N_F matrices provide an excellent platform for lasing via an alternative mechanism, namely, RL. This underscores the substantial versatility of the N_TBF and N_F mesophase, suggesting that novel mesophases can accommodate a wide range of organic dyes, either commercial or newly synthesized, and even other additives. It is not confined solely to band‐edge lasing mechanisms, which are typically associated with cholesteric structures, thereby opening new ways for multifunctional photonic applications. In the case of RL, specific domains and local refractive index fluctuations facilitate constructive multiple scattering. Notably, our findings reveal that the N_TBF phase exhibits lasing thresholds approximately two times lower than those in the N_F phase, while the N_F phase yields higher emission intensity. Moreover, AFM and optical diffraction studies have demonstrated an interesting dependency: during the N_TBF‐N_F transition (upon heating), the helix rapidly unwinds from 550 to 910 nm in the temperature range of 0.2 °C. Such a drastic transition leads to a more homogeneous, N_F‐type molecular alignment, probably supporting higher intensity lasing. Conversely, the polar heliconical structure of the N_TBF phase may form microdomains that selectively concentrate light intensity, lowering lasing thresholds through enhanced optical feedback. However, increased scattering from local structural complexity may reduce overall emission intensity. This interplay suggests that polar order and its modulation of local molecular arrangements critically influence lasing performance. All observations show that subtle differences in molecular organization between the N_F and N_TBF phases strongly influence their RL‐based photonic performance, offering potential avenues for optimizing lasing characteristics through controlled manipulation of the helix pitch.

Building on these insights, we extend our investigation to complex multi‐dye systems. A single LCC integrating three RGB dyes – R and G in MUT_N_TBF1, and B in PVA (which retains stability during temperature variations) – exemplifies the system's simplicity and tunability. This setup not only facilitates the modulation of lasing intensity but also empowers dynamic color changes, exploiting the unique characteristics of the Cr, N_TBF, and N_F phases. Traditionally, energy transfer in multicolor and WL applications is avoided. Despite our study incorporating R and G dyes in MUT_N_TBF1, promoting energy transfer, it offers an added advantage: it permits the utilization of temperature effects on their combined emission. Impressively, we achieve RL in the white region, correlating with the D75 standard, a significant feat in FRET situations. Future research ought to concentrate on doping all three dyes into various matrices and individually tuning their emission properties through LC modifications (using factors like temperature/electric, or magnetic fields). Additionally, our findings highlight the importance of the Cr phase, which, despite its decreased utility in RL applications, delivers substantial WFluo at RT – a benefit for optoelectronic devices.

Emissive fibers hold a lot of value in optoelectronics, serving crucial roles in areas such as optical, biomedical sensing and detection, diagnostics, quantum communication, and light‐guiding illumination.^{[ 58} , ⁵⁹ , ⁶⁰ , ^{61 ]} Usually, more complex techniques like electrospinning^{[ 62} , ^{63 ]} are employed in their production. While a substantial body of literature exists on polymer fibers, those drawn from innovative LC phases represent a novel area that merits further study.

The formation and retention of emissive microfibers in the N_TBF phase are closely tied to the intrinsic polarity of the host matrix. The long‐range polar order stabilizes the head‐to‐tail molecular alignment, which is further reinforced upon dye incorporation due to dipole‐dipole compatibility between the guest and the host. This results in robust supramolecular structures that preserve their geometry even after cooling or removal of external stimuli. Unlike nonpolar mesophases, polar phases such as N_TBF exhibit local internal fields and cohesive interactions that suppress molecular rearrangement, thereby locking the fibers in place. This unique self‐stabilization mechanism is a direct consequence of the ferroelectric and polar nature of the N_TBF matrix.

The stabilization of these fibers at RT using luminescent dopants offers significant advantages in terms of cost‐efficiency, ease of fabrication, and the construction of multicolored structures for both fundamental research and practical applications.

Finally, our findings highlight the unique advantages of the N_F over other LC phases, such as the ability to modulate laser emission intensity at relatively low applied DC voltages. Although Okada et al.^{[ 64 ]} recently demonstrated interesting electric‐field‐induced lasing with a low threshold in a dye‐doped polar nematic fluid, their mechanism relies on interference modulation within a microcavity. Despite the differences observed between HT and HG cells, the N_F mesophase demonstrates remarkable resilience to external alignment and electrostatic perturbations, leading to enhanced emission characteristics in both arrangements. It arises directly from macroscopic polarity and is observed regardless of alignment geometry, pointing to a more intrinsic and general photonic function of polar order. These findings open up new possibilities for the development of advanced materials based on the N_F phase, including efficient light sources, tunable laser devices, and electro‐optic components. Additionally, the N_F phase holds promise for applications in optoelectronics where precise control over light emission is crucial, such as in displays, sensors, and integrated photonic circuits. However, these are preliminary results, and further studies are needed to fully understand the underlying mechanisms. In particular, future experiments with alternating current and further theoretical modeling will be crucial in understanding the dynamics of the N_F phase. Moreover, the ongoing research will continue to investigate the N_TBF phase, though reliable experiments for this phase are still in progress. As the understanding of N_TBF materials grows, we anticipate that future studies will show further insights into their unique optical properties and potential applications in laser and electro‐optic technologies.

4. Experimental Section

Materials and Device Preparation—MUT_N_TBF1

The eutectic composition of the multicomponent mixture from the MUT_JK10n and nJK series^{[ 65 ]} was calculated based on Le Chatelier‐Schröder‐van Laar equations. The mixture was prepared by combining components in a laminar flow chamber situated within a quartz vial. This vial was heated to a temperature between 140 and 150 °C for 15 min, with vigorous mixing. A thermopolarizing microscope was used to determine the following phase sequence: RT Sm_CF 34 N_TBF 43.3 N_F 142 N_x 146 N 200 Iso. Upon cooling, the N_TBF phase was supercooled to RT and maintained stability for a period dependent on the sample geometry.

Materials and Device Preparation—Other Compounds

The laser dyes were procured from Exciton, Photonic Solutions. The chosen chromophores emitted three different colors and included Stilbene 420 (SB420), Coumarin 540 (CM540), and DCM. Stilbene 420 (2,2′’‐([1,1′‐biphenyl]‐4,4′‐diyldi‐2,1‐ethenediyl)bis‐benzenesulfonic acid disodium salt) served as the blue‐emitting dye. Coumarin 540 (3‐(2‐benzothiazolyl)‐7‐(diethylamino)‐2H‐1‐benzopyran‐2‐one) was employed as the green‐emitting compound. DCM ([2‐[2‐[4‐(dimethylamino)phenyl]ethenyl]‐6‐methyl‐4H‐pyran‐4‐ylidene]propanedinitrile) was used for orange‐red emission. Polyvinyl Alcohol (PVA) was sourced from Sigma–Aldrich ®.

Materials and Device Preparation ‐ Preparation of Single‐Dye Systems in MUT_N_{TBF 1}

In experiments involving single dyes, the host material MUT_N_TBF1 was doped with a 1% (w/w) dye concentration. Since MUT_N_TBF1 was available in a crystalline form at RT, appropriate amounts of MUT_N_TBF1 and dye were weighed and combined. This mixture was heated on a stage until the dye completely dissolved. The resulting fluid‐like state was introduced into homeotropic (HT) LCCs through an opening on the side. The cells were allowed to cool to RT and left overnight. The LCCs, fabricated at the Military University of Technology, had a thickness of 20 µm, a commonly used dimension in light amplification studies.^{[ 15} , ^{66 ]}

Materials and Device Preparation—Preparation of Stilbene 420 (SB420) Solution

A 1% (w/v) PVA solution was prepared using deionized water. To this solution, 10 mg of SB420 was added to 1 mL, establishing the desired dye concentration for RL action. This ratio yielded a heterogeneous solution, necessary for RL, given the need for scattering centers.^{[ 52 ]} The solution was combined using a vortex mixer and introduced into an HT cell with a thickness of 20 µm. Side openings were sealed with tape to prevent water evaporation.

Materials and Device Preparation—Preparation of Multi‐Dye LCC

A 1:1 mixture of CM540 and DCM was prepared and added to MUT_NTBF1, upholding a 1% guest‐to‐host ratio. This mixture was dissolved at a high temperature and capillary‐introduced into a 20µm LCC from one side. From the other side of the cell, the previously prepared 1% PVA solution with SB420 was incorporated. A distinct phase separation, forming an automatic boundary, was observed at the interface between the two mixtures. This occurred because MUT__NTBF1, CM540, and DCM were hydrophobic, while SB420 doped into a water‐based matrix was hydrophilic. The cell was monitored over several days for potential mixing of the two substances, but no changes were detected, even after extended periods, and it remained stable at high temperatures (up to 80 °C).

Experimental Set‐Ups—Fluorescence Measurement

The fluorescence emission spectra were collected using a Fluoromax‐4 Horiba spectrofluorometer with a step size of 1.0 nm.

Experimental Set‐Ups—Random Lasing

For the lasing studies, a triple‐frequency Nd: YAG pulsed laser (Surelite II) with a pulse duration of 6 ns and a repetition rate of 10 Hz was used. This system was combined with a Continuum Horizon Optical Parametric Oscillator, acclaimed for its high efficiency in the mid‐band wavelength range. An excitation wavelength of 405 nm was selected to efficiently coincide with the absorbance of all employed dyes.^{[ 48 ]} The laser beam was molded into a 6.5 × 1.4 mm stripe using a slit and a converging cylindrical lens, and this patterned beam was then aimed at the sample. This configuration enables the spontaneous emission to be effectively amplified along the stripe's length, facilitating a more efficient and directional process.^{[ 67 ]} The power of the incoming light was measured using a calibrated Coherent Field Max II laser energy meter fitted with a J‐10MB‐HE sensor.

Two spectrometers were used for the measurements: a high‐resolution Shamrock SR‐500i‐B1‐R (0.1 nm) to verify RL in single‐dye LCCs, and a broadband Qmini (AFBR‐S20M2WV) for multi‐dye LCCs. The Qmini was chosen for its ability to capture a wide spectral range from 225 to 1000 nm, with optimal spectral sensitivity at 500 nm. Broadband detection was crucial for simultaneously recording the emission spectra of SB420 (blue range) and CM540/DCM (extending into the red region). This approach facilitated comprehensive data collection and analysis. The resulting signals were then analyzed using a computer.

A DC power supply (NDN DF1750SL3A) was used to apply an electric field across the LCCs, with the field directed through Indium Tin Oxide electrodes. The experimental LC mixture MUT__NTBF1 was capillary introduced inside the LCC and heated to the N_F phase temperature of 80°C. Measurements were conducted comparatively for two types of cells, HT and HG, both with an identical thickness of 20 µm. The pump energy density was consistently maintained at 7.5 mJ cm⁻², ensuring a uniform excitation. This setup allowed for precise control of the electric field within the range of 0 to 10 V.

Experimental Set‐Ups—Structural and Helix Pitch Studies

Atomic Force microscopy (AFM) measurements were performed using a Bruker Dimension Icon Microscope working in scan‐assist mode, and cantilevers with 0.4 N m⁻¹ force constant were applied.

Laser diffraction studies were performed by illuminating the samples with green (520 nm) laser light. The diffraction pattern was observed on the half‐sphere screen placed above the sample, and the angular position of the diffraction signal allowed for the calculation of the helical pitch length.

Experimental Set‐Ups—Microscopic Studies

The patterns of the investigated LC mesophases were examined using photoluminescence and crossed‐polarization imaging, which were performed through an Olympus BX60 microscope with a UplanFL 10× objective and an excitation wavelength (λ_exc) of 375 nm. These studies were conducted at RT and involved heating the same LCCs used for spectroscopic investigations (fluorescence, RL). Microscopic analyses in ESI, Figure S8 (Supporting Information), were performed using a Nikon ECLIPSE Ti2‐E inverted microscope equipped with epifluorescence, motorized focus, and software‐controlled LED illumination (transmitted and reflected light). Imaging was conducted using Nikon CFI60 objectives: Plan Fluor 10× (N.A. 0.30, W.D. 16 mm) and Super Plan Fluor LWD 20× C (N.A. 0.70, W.D. 2.3–1.3 mm). A monochrome Nikon Qi2 camera (16.25 MP) was used for detection. Fluorescence excitation was provided by a multichannel LED source (DAPI‐Cy7 range, used λ_exc of 475 nm), with a BrightLine quad‐band filter set (DAPI/FITC/TRITC/Cy5, ZERO Pixel Shift). Image processing included AI‐based correction algorithms for background suppression and denoising. The system was operated via a high‐performance HP/Dell workstation with a 32″ 4K display. A temperature‐controlled Linkam LTS120 stage was utilized to heat the devices. In the case of LCCs with multiple dyes, the excitation area was clearly marked during lasing studies to ensure the provision of reliable morphological information.

There were used the heated stage ((MS‐H‐Pro+; measurement accuracy ± 0.2 °C, heating control accuracy: ± 1 °C (<100 °C) ±1% (>100 °C)) and a pyrometer Benetech GM 900 (measurement range: −50–950 °C, accuracy: 0 to 950 °C ± 1.5 °C / −50 to 0 °C ± 3 °C, resolution: 0.1 °C (°F), emissivity range: 0.10 to 1.00).

Methods

The measurements of the fabricated devices started from the Cr phase. To maintain a consistent thermal regime, the LCCs were progressively heated during the measurements, avoiding cycles of heating and cooling. A heated stage was utilized to sustain consistent thermal conditions. The LCC was positioned directly on the temperature‐maintaining holder to ensure homogeneous heating. Before conducting measurements, it was confirmed that the LCCs had reached a stable temperature, suitable for the desired mesophase. A pyrometer was used to precisely supervise and control the thermal conditions. Measurements were only undertaken once temperature stability was confirmed, ensuring the generated data accurately represented the sample's properties. Moreover, the N_TBF phase showcases a unique structure characterized by selective reflection visible to the naked eye. This distinct pattern surfaces only between 34 and 43.3 °C. Multiple visual checks were performed throughout the measurements to verify that the sample remained within the targeted mesophase.

Two methods were utilized to assess the lasing thresholds: FWHM and the Li‐Lo method. The FWHM measures the width of the emission band at half of its peak intensity. Through the examination of this parameter, the threshold where the linewidth significantly tapers, signifying the shift from fluorescence to RL, was pinpointed. On the other hand, the Li‐Lo method evaluates the maximal intensity or the amalgamated intensity of the emission spectrum in comparison to the input light. This technique necessitates fitting a linear trend into both the pre‐lasing and post‐lasing regions of the spectrum and pinpointing the inflection point where lasing's onset transpires.

ImageJ software was used to analyze the fiber diameters. The CIE XYZ color space was employed to discern fluorescence and RL colors. Developed by the International Commission on Illumination (CIE), the CIE XYZ 1931 color model provides color representation that mirrors human visual perception. It designates three color‐matching functions – X, Y, and Z – corresponding to the primary colors of human vision. These functions serve to convert color data into a standard format, thus allowing accurate color comparison and characterization across various devices and conditions. In this study, the CIE XYZ coordinates were computed to evaluate and contrast the color output of the fluorescent and RL emissions.^{[ 68 ]}

Conflict of Interest

The authors declare no conflict of interest.

Supporting information

Supporting Information

Szukalska A. B., Karcz J., Herman J., et al. “Temperature‐Tunable Heliconical and Ferroelectric Nematics for White Lasing.” Adv. Mater. 38, no. 1 (2026): e11648. 10.1002/adma.202511648

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.