This study presents a systematic investigation of the optical and mechanical responses of nonporous and porous cholesteric liquid crystal elastomers (CLCEs) under uniaxial tensile and compressive strain. The CLCE devices were fabricated using a UV-curing process, and porous structures were obtained by removing non-reactive liquid crystal components. The optical characteristics were analyzed using a wavelength-swept laser (WSL), enabling both spectral- and temporal-domain measurements through a one-to-one correspondence between wavelength and time. Under uniaxial tensile strain, the transmission band of the CLCEs exhibited a clear blue shift due to a reduction in the cholesteric pitch. The porous CLCE showed a higher Poisson’s ratio (~0.44) compared to the nonporous CLCE (~0.39), resulting in enhanced wavelength sensitivity. The tensile wavelength sensitivities were −4.31 nm/% and −5.11 nm/% for the nonporous and porous CLCEs, respectively. Under compressive strain, the reflection spectra also shifted toward shorter wavelengths, with good agreement between spectral- and temporal-domain measurements. The compressive wavelength sensitivities were measured to be −15.21 nm/% and −12.78 nm/% for nonporous and porous CLCEs, respectively. The reported sensitivity and effective Poisson's ratio values correspond to representative devices and may vary depending on the precursor composition and the resulting porous structure. The results demonstrate that structural modification of CLCEs significantly influences their mechanical and optical responses.

OBJECTIVE:To investigate whether point-of-care ultrasound of the external jugular vein (EJV) can predict fluid responsiveness (FR) in healthy, anesthetized, mechanically ventilated dogs. DESIGN:Prospective, nonrandomized experimental study. SETTING:University-based small animal research facility. ANIMALS:Six healthy Beagle dogs. INTERVENTIONS:Dogs were investigated at six time points (TPs): baseline (TP1); 20 mL/kg of circulating blood was collected over 10 min (TP2); half of the collected blood was autotransfused for 10 min (TP3); remaining collected blood was autotransfused for 10 min (TP4); 0.9% normal saline (10 mL/kg for 10 min) was administered (TP5); and an additional dose of 0.9% normal saline (10 mL/kg for 10 min) was administered (TP6). Hemodynamic variables, Doppler images of the left ventricular outflow tract (LVOT), and M-mode images of the EJV were obtained at each TP. FR was evaluated during TP3-6. FR was defined as an increase of >15% in the LVOT velocity time integral following fluid challenge, while other results were defined as fluid nonresponsiveness (FNR). The external jugular vein distensibility index (EJVDI) was calculated as follows: [(maximal EJV diameter - minimal EJV diameter)/minimal EJV diameter] × 100%. The maximal EJV diameter was measured during inspiration, and the minimal EJV diameter was measured during expiration. In addition, gray zones indicating the range of diagnostic uncertainty were proposed in various indices for predicting FR. MEASUREMENTS AND MAIN RESULTS:Among the 24 fluid challenges performed between TP3 and TP6, 11 FR and 13 FNR were identified. The area under the receiver operating characteristic curve for the EJVDI in predicting FR was 0.92, with a cut-ff value of 22.7%, and the gray zone was identified as 22.6%-27.3%. CONCLUSIONS:The EJVDI could be used to predict FR in healthy, anesthetized, mechanically ventilated dogs. Further studies are required before point-of-care ultrasound of the EJV can be applied in various clinical settings.

In this study, we present an all-fiber sensor based on porous cholesteric liquid crystal film (CLCF) coated on the cross-section of an optical fiber ferrule for real-time monitoring of flammable vapors in industrial environments. Reflection band shifts according to the concentration of gases were measured using a broadband wavelength-swept laser, and the sensitivity were 3.19 pm/ppm, 4.88 pm/ppm, and 6.61 pm/ppm were obtained for acetone, toluene, and benzene vapors, respectively, with benzene vapor showing the highest sensitivity. Compared to nonporous CLCFs, the porous CLCF showed six times higher sensitivity. This sensor, which operates passively without a battery, is immune to electromagnetic interference, suggesting its potential as a reliable sensor.

Real-time detection of flammable volatile organic compounds (VOCs) vapors is essential for ensuring safety in various industrial environments. This paper presents a compact, all-fiber sensor designed for real-time monitoring of high concentration of flammable VOC vapors. The sensor is fabricated by coating a porous cholesteric liquid crystal film (CLCF) onto the cross-section of an optical fiber ferrule. An ultra-wideband, high-speed wavelength-swept laser (WSL) is employed to monitor shifts in the reflection band of the CLCF in response to varying concentrations of benzene, toluene, and acetone vapors. Sensitivities of 6.11 pm/ppm, 4.48 pm/ppm, and 3.19 pm/ppm were achieved for benzene, toluene, and acetone vapors, respectively, with the highest sensitivity observed for benzene. By leveraging the one-to-one correspondence between spectral and temporal domains, the sensor enables real-time vapor concentration measurements. The device demonstrated excellent repeatability, with a standard deviation of 0.228 nm in the reflection band center wavelength after five exposures to 25 % of the lower explosive limit of benzene vapor. Additionally, the porous CLCF exhibited approximately six times greater sensitivity than its nonporous counterpart. The sensor also features low dependence on temperature and humidity, operates without a battery, and is immune to electromagnetic interference. These results underscore the potential of the proposed sensor as a reliable and practical solution for flammable VOC vapor detection. Furthermore, an analysis of the porous CLCF's vapor sensing mechanism reveals that the high sensitivity to benzene is attributed to its porous structure and benzene's high refractive index.

Broadband wavelength-swept lasers (WSLs) have many advantages in multi-point sensing and dynamic sensing in fiber optic sensors. In this paper, we report the implementation of an ultra-wideband WSL source with a 440 nm scanning range. It is composed of a polygonal scanning mirror-based wavelength tunable filter (PSM-TF) and four semiconductor optical amplifiers (SOAs). It consists of two independent gain media and PSM-TF, each gain media is configured in a MachZehnder interferometer, and the central wavelengths are approximately 1250 nm and 1450 nm, respectively. The WSL achieved a 10-dB spectral bandwidth of 440.8 nm in the spectral domain and a temporal output duration of 323.8 mu s at a scanning frequency of 2.338 kHz. The conversion ratio between the spectral and time domains over the scanning range was determined to be 1.361 nm/mu s. The duty cycle was measured to be 75.7% from the oscilloscope trace, and the free spectral range in the spectral domain was calculated to be approximately 582.3 nm.

In this study, we propose a lossy mode resonance (LMR)-based optical fiber humidity sensor developed by depositing M13 bacteriophage onto a D-shaped optical fiber (DSF) coated with an 80 nm-thick indium tin oxide (ITO) layer. A broadband wavelength-swept laser (WSL) was used as the light source to analyze the LMR dip shift under varying humidity conditions. As the humidity applied to the fabricated device increased, the LMR dip shifted to shorter wavelengths, with a measured humidity sensitivity of −1.01 nm/% R.H. In addition, the response time of the device was approximately 30 s for a 4% R.H. change, verifying its real-time detection capability. The response of the device to acetone gas exposure was also examined, revealing a minor shift in the LMR dip, indicating potential gas sensing applications. The proposed LMR-based fiber optic sensor, using M13 bacteriophage, has potential for use in environmental monitoring and biosensing applications.

This study presents a lossy mode resonance-based fiber-optic humidity sensor utilizing M13 bacteriophage deposited on an indium tin oxide coated D-shaped fiber. The sensitivity of the sensor was measured to be -1.01 nm/% R.H.

The recent progress in semiconductor processing technology has served as a major driving force behind the rapid development of nanophotonics research.Among the emerging applications,metasurfaces have attracted signifi-cant attention as saturable absorbers(SAs)for mode-locked laser systems that generate short pulses.In this study,we present the comprehensive design,fabrication,and experimental demonstration of a metasurface-based SA operating in the 1 μm wavelength range,leveraging both the localized surface plasmon resonance(LSPR)phe-nomenon and the epsilon-near-zero(ENZ)effect of indium tin oxide.The proposed metasurface SA significantly enhances the nonlinear optical response by combining the effects of LSPR and ENZ phenomena.The design was optimized using finite-difference time-domain simulations,which enabled both structural optimization and com-prehensive characterization of optical properties.Based on the simulation results,the metasurface SA was fab-ricated via a commercial electron-beam lithography process.Linear transmission measurements of the fabricated SA confirmed the presence of LSPR around 1050 nm.Nonlinear transmission measurements revealed a modu-lation depth of 10.9％and a saturation intensity of 10.98 MW/cm2.The metasurface SA was successfully in-tegrated into a mode-locked Yb-doped fiber laser,achieving stable Q-switched mode-locking operation at a central wavelength of 1058 nm.The resulting laser exhibited a spectral bandwidth of 11.7 nm,a repetition rate of 16.15 MHz,and a pulse envelope duration of approximately 2.6 μs.These results validate the reliability and effectiveness of the metasurface-based approach.The experimental findings highlight the strong potential of metasurface SAs incorporating ENZ materials as a versatile platform for next-generation high-performance ultra-fast fiber lasers.The integration of plasmonic metasurfaces with ENZ effects offers a promising pathway toward compact,efficient,and tunable ultrafast laser sources for applications in communications,spectroscopy,and pre-cision measurement.

This study details the implementation of an ultrawideband wavelength-swept laser (WSL) employing a polygonal scanning mirror-based wavelength tunable filter (PSM-TF) and four semiconductor optical amplifiers (SOAs). The system incorporates two independent gain media with center wavelengths of 1250 and 1450 nm, each configured in a Mach-Zehnder interferometer, with the PSM-TF shared between the two SOAs. Precise angular alignment between the optical axes of the two wavelength bands incident on the PSM-TF is critical for achieving ultrawideband WSL. The theoretically calculated angle was 33.725 degrees, whereas the experimentally measured angle was 33.788 degrees, yielding a relative error of approximately 0.19%, a value considered negligible in relation to the full-scanning wavelength range. The WSL achieved a 10-dB bandwidth of 442.8 nm in the spectral domain (1130.8-1573.6 nm) and a temporal output duration of 329.4 mu s at a scanning frequency of 2.338 kHz. The conversion ratio between the spectral and temporal domains across the scanning range was determined to be 1.344 nm/mu s, closely aligning with the ratios observed in the two resonators. The duty cycle in the temporal domain was 77.0%, and the free spectral range in the spectral domain was 575.0 nm. In addition, the ultrawideband WSL demonstrated excellent wavelength repeatability and stability in both short-term and long-term measurements. This system exhibits significant potential for real-time multipoint dynamic fiber-optic sensing applications and offers promising enhancements for image resolution in biophotonics.

In this study, single-walled carbon nanotube (SWCNT)/Cu nanocomposites were systematically synthesized from oxidized SWCNTs and Cu formate via photothermal heating.

The scanning speed stability of a wavelength-swept laser (WSL) with a polygon-scanner-based wavelength filter (PSWF) is affected by the speed of the brushless direct current (BLDC) motor driving a polygonal scanner mirror (PSM). In particular, the PSM running at low speeds experiences fluctuations in rotational speed, causing the output of the WSL to fluctuate in the temporal domain. The speed variation of the WSL causes critical measurement errors in the fiber Bragg grating (FBG) interrogator sensors. In this study, we successfully corrected the output error of the FBG array sensor caused by the PSM rotational speed fluctuations in a WSL running at a low scanning rate. The FBG array used five FBGs, and the time intervals of the FBGs were corrected according to the PSM rotation speed variation based on the periodic interval of the array signal. A WSL with a scanning rate of 1.0 kHz suggested a 97% improvement after compensating for rotational speed variations of the PSM.

The conventional carbonization process for synthesizing hard carbons (HCs) requires high-temperature furnace operations exceeding 1000 degrees C, leading to excessive energy consumption and lengthy processing times, which necessitates the exploration of more efficient synthesis methods. This study demonstrates the rapid preparation of HC anodes using intense pulsed light (IPL)-assisted photothermal carbonization without the prolonged and complex operations typical of traditional carbonization methods. A composite film of microcrystalline cellulose (MCC) and single-walled carbon nanotubes (SWCNTs) is carbonized at high temperatures in less than 1 min. The SWCNTs efficiently absorbed light energy, enabling ultrafast heating and eliminating the need for prolonged, high-energy furnace-based processes. The IPL-assisted HC anodes exhibited excellent electrochemical performance, with an initial desodiation capacity of 260.4 mAh g(-)(1)anode and 97.5% capacity retention after 200 cycles. These results are comparable to those achieved using traditional furnace-based carbonization processes, such as carbonizing HC anodes at 1200 degrees C, validating the effectiveness of IPL-assisted processes. Additionally, surface and structural analyses revealed the development of pseudo-graphitic domains, crucial for enhanced sodium-ion storage. This research highlights IPL-assisted photothermal carbonization as a viable, time-efficient, and energy-saving alternative to conventional methods, offering a sustainable pathway for the large-scale production of HC anodes for future sodium-ion battery technologies.

Measuring temperature and strain using fiber Bragg grating (FBG) simultaneously has been a difficult task in recent years. Creating a dataset to differentiate temperature and strain via machine learning (ML) techniques necessitates collecting voluminous data rapidly. This study proposes a method to simultaneously measure the temperature and strain of a single FBG using ML while employing a wavelength-stabilized wavelength-swept laser (WSL). We analyzed peak intensities and sidelobe positions in the temporal domain under different temperatures (0degree celsius-55degree celsius) and strains (0-300 mu epsilon) of FBG, amassing approximately 46000 datasets comprising six variables. ML was performed using Python's Scikit-learn, with the dataset split into training (75%) and testing (25%) subsets. Temperature and strain could be measured simultaneously with approximately 95% accuracy, suggesting the potential of ML in accurately predicting temperature and strain using FBG responses.

We present a cholesteric liquid crystal (CLC)-based optical fiber temperature sensor using a 1250 nm band wavelength-swept laser (WSL). The WSL is implemented using two semiconductor optical amplifiers (SOAs) with different center wavelengths connected in parallel in the form of a Mach-Zehnder interferometer in a laser resonator. At 3.6 kHz scanning frequency, the 10 dB bandwidth was about 223 nm from 1129 nm to 1352 nm. As the temperature of the CLC cell increased, the long-wavelength edge of the reflection band shifted to shorter wavelengths. The relationship between the temperature change and the central wavelength change of the reflection band was obtained to be almost linear.

Cholesteric liquid crystals (CLCs) can be applied to various physical and chemical sensors because their alignment structures are changed by external stimuli. Here, we propose a CLC device fabricated by vertically forming the helical axis of the CLC between the cross-sections of two optical fiber ferrules. An optical fiber temperature sensor was successfully implemented using the proposed optical fiber ferrule-based CLC device. A wideband wavelength-swept laser with a center wavelength of 1073 nm and scanning range of 220 nm was used as a light source to measure the variations in the reflection spectrum band according to the temperature change in the CLC cell. The wavelength variation of the reflection spectrum band according to the temperature applied to the CLC cell was reversible and changed linearly with a change in the temperature, and the long-wavelength edge variation rate according to the temperature change was −5.0 nm/°C. Additionally, as the temperature applied to the CLC cell increased, the reflection spectrum bandwidth gradually decreased; the reflection spectrum bandwidth varied at a rate of −1.89 nm/°C. The variations in the refractive indices with temperature were calculated from the band wavelengths of the reflection spectrum. The pitch at each temperature was calculated based on the refractive indices and it gradually decreased as the temperature increased.

We report 1.45 µm band wavelength-swept laser using two semiconductor optical amplifiers (SOAs) and a polygonal mirror scanning wavelength filter. We have achieved 220 nm scanning bandwidth from 1348 nm to 1568 nm.

Broadband wavelength-swept lasers (WSLs) are widely used as light sources in biophotonics and optical fiber sensors. Herein, we present a polygonal mirror scanning wavelength filter (PMSWF)-based broadband WSL using two semiconductor optical amplifiers (SOAs) with different center wavelengths as the gain medium. The 10-dB bandwidth of the wavelength scanning range with 3.6 kHz scanning frequency was approximately 223 nm, from 1129 nm to 1352 nm. When the scanning frequency of the WSL was increased, the intensity and bandwidth decreased. The main reason for this is that the laser oscillation time becomes insufficient as the scanning frequency increases. We analyzed the intensity and bandwidth decrease according to the increase in the scanning frequency in the WSL through the concept of saturation limit frequency. In addition, optical alignment is important for realizing broadband WSLs. The optimal condition can be determined by analyzing the beam alignment according to the position of the diffraction grating and the lenses in the PMSWF. This broadband WSL is specially expected to be used as a light source in broadband distributed dynamic FBG fiber-optic sensors.