A highly sensitive, reversible, and linear sensor, exhibiting excellent stability in response to temperature and humidity, has been successfully proposed and demonstrated for the first time. This sensor is achieved by wrapping a polyvinyl alcohol/graphene nanofiber film onto a chiral long-period fiber grating (CLPG), which is fabricated by periodically twisting single mode fiber. In the experiment, the CLPG sensor demonstrates a temperature sensitivity of 74 pm/°C, which is approximately twice as high as that of conventional fiber grating sensors. Note that, by wrapping the graphene nanofiber film on CLPG, the temperature sensitivity of the sensor is up to 115.23 pm/°C in the range of 30°C to 75°C. In addition, CLPG using for humidity sensing is first demonstrated. The humidity sensitivity measures −9.92 pm/%RH with linearity of 0.995 during a change from 40%RH to 80%RH. In comparison to other humidity sensors, the sensitivity of the CLPG is comparable, whereas its sensing linearity stands out notably above the rest. The results show that CLPG has the characteristics of simple fabrication, easy combination with materials, stable performance, and high sensitivity and holds significant development potential in optical fiber sensing application fields.
The optical binding force (BF) of stratified chiral particles induced by Bessel beam is computed by using the Generalized Lorenz Mie theory. The axial intensity profile of such non-diffracting beams can suppress the influence of the axial intensity which then depended on the interactions between inter-particles. The arbitrarily polarized high order Bessel beam (HOBB) is described in terms of beam shape coefficients (BSCs) within the framework of generalized Lorenz-Mie theories (GLMT). We discuss the influence of the beam half-conical angles and chirality parameter in detail. Different illuminating Bessel beams with arbitrary polarizations are considered, and the corresponding BFs are analyzed. It is shown that the optical BF of stratified chiral spheres can be significantly depending on the incident beam polarizations and the interacting chiral particles handedness. In binding stratified chiral spheres, the out-layered chirality of the stratified chiral spheres should be chosen in accordance with the incident polarizations. This finding may give a recipe to understand the physical mechanism of interactions between multiple chiral stratified particles by using the analytical approach, which plays an important role in manipulating complex multi-layered chiral structures self-arrangement.
The THz absorption spectrum of barbituric acid has been investigated utilizing terahertz time-domain spectroscopy (THz-TDS). The vibrational spectra of barbituric acid and its dihydrate have been studied in the framework of density functional theory using Perdew-Burke-Ernzerhof functional. In addition, the comparison of THz patters between barbituric acid and its anhydrate were also performed. It is found that four distinct THz spectral peaks and two shoulder peaks are exhibited in barbituric acid measurement. Peak assignment implies that all measured features come from the intermolecular forces. For barbituric acid dihydrate, three absorption peaks are predicted, which comes from the interactions of barbituric acid and barbituric acid molecules, barbituric acid and water molecules in solid-state. Finally, these different spectral patters indicate the ability of THz spectra to identify hydrate from anhydrate in practice.
In this paper, for the first time, we propose a large-broadband orbital angular momentum (OAM) mode converter based on helical long period fiber grating (HLPG) working at turning point (TP). Owing to the combination of dual-resonance peaks at TP, an OAM mode converter with 3-dB bandwidth of ~287 nm is readily obtained, and a high coupling efficiency of ~100% is achieved. We believe that this OAM mode converter will play a key role in fiber communication and other fields.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.