We present the fabrication and characterization of fiber Bragg gratings (FBGs) in an endlessly single-mode microstructured polymer optical fiber (mPOF) made of humidity-insensitive high-Tg TOPAS cyclic olefin copolymer. The mPOF is the first made from grade 5013 TOPAS with a glass transition temperature of Tg = 135°C and we experimentally demonstrate high strain operation (2.5%) of the FBG at 98°C and stable operation up to a record high temperature of 110°C. The Bragg wavelengths of the FBGs are around 860 nm, where the propagation loss is 5.1 dB/m, close to the fiber loss minimum of 3.67 dB/m at 787 nm.

/pdf/high-tg-topas-microstructured-polymer-optical-fiber-for-39nxat58fu.pdf

High-Tg TOPAS microstructured polymer optical fiber for fiber Bragg grating strain sensing at 110 degrees

Ethanol is widely used in chemical industrial processes as well as in the food and beverage industry. Therefore, methods of detecting alcohol must be accurate, precise, and reliable. In this content, a novel Zeonex-based photonic crystal fiber (PCF) has been modeled and analyzed for ethanol detection in terahertz frequency range. A finite-element-method-based simulation of the PCF sensor shows a high relative sensitivity of 68.87% with negligible confinement loss of 7.79×10−12 cm−1 at 1 THz frequency and x-polarization mode. Moreover, the core power fraction, birefringence, effective material loss, dispersion, and numerical aperture are also determined in the terahertz frequency range. Owing to the simple fiber structure, existing fabrication methods are feasible. With the outstanding waveguiding properties, the proposed sensor can potentially be used in ethanol detection, as well as polarization-preserving applications of terahertz waves.

Terahertz detection of alcohol using a photonic crystal fiber sensor.

Over the past decades, signicant attention has been paid to biomedical applications of terahertz (THz) technology. Nowadays, THz spectroscopy and imaging allow for solving numerous demanding problems in biological, medical, food, plant and pharmaceutical sciences. Among all biomedical applications, a label-free diagnosis of malignant and benign neoplasms represents one of the most attractive branches of THz technology. Despite the attractiveness, the methods of THz diagnosis are still far from medical practice. In this review, we consider the modern research results in THz diagnosis of malignant and benign neoplasms, along with the topical research and engineering problems, which restrain the THz technology translation to clinics. We start from analysis of the common models of THz-wave { tissue interactions and the eects of tissue exposure to THz waves. Then, we discuss existing modalities of THz spectroscopic and imaging systems, which either have been already applied in medical imaging, or hold strong potential. We summarize the earlier-reported and the original results of THz measurements of neoplasms with dierent nosology and localization. We pay attention to the origin of contrast between healthy and pathological tissues in the THz spectra and images and discuss the prospective of THz technology in non-invasive, minimally-invasive and intraoperative diagnosis, as well as in aiding histology. Finally, we review the challenging problems of THz diagnosis, as well as attempts to solve them, which should bring the THz technology much closer to the medical practice. This review allows one to objectively uncover benets and weaknesses of the THz technology in diagnosis of malignant and benign neoplasms.

https://iopscience.iop.org/article/10.1088/2040-8986/ab4dc3/pdf

The progress and perspectives of terahertz technology for diagnosis of neoplasms: a review

We have developed a fluorescence-based fiber-optical biosensor, which can selectively detect different antibodies in serial at preselected positions inside a single piece of fiber. The fiber is a microstructured polymer optical fiber fabricated from TOPAS cyclic olefin copolymer, which allows for UV activation of localized sensor layers inside the holes of the fiber. Serial fluorescence-based selective sensing of Cy3-labelled α-streptavidin and Cy5-labelled α-CRP antibodies is demonstrated.

/pdf/selective-serial-multi-antibody-biosensing-with-topas-c266wcugkd.pdf

Selective Serial Multi-Antibody Biosensing with TOPAS Microstructured Polymer Optical Fibers

Extremely low material loss and dispersion flattened TOPAS based circular porous fiber for long distance terahertz wave transmission

We present a numerical and experimental investigation of a low-loss porous-core honeycomb fiber for terahertz wave guiding. The introduction of a porous core with hole size of the same dimension as the holes in the surrounding honeycomb cladding results in a fiber that can be drawn with much higher precision and reproducibility than a corresponding air-core fiber. The high-precision hole structure provides very clear bandgap guidance and the location of the two measured bandgaps agree well with simulations based on finite-element modeling. Fiber loss measurements reveal the frequency-dependent coupling loss and propagation loss, and we find that the fiber propagation loss is much lower than the bulk material loss within the first band gap between 0.75 and 1.05 THz.

/pdf/fabrication-and-characterization-of-porous-core-honeycomb-2u8e2yx1aq.pdf

Fabrication and characterization of porous-core honeycomb bandgap THz fibers.

Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

/pdf/dielectric-tube-waveguides-with-absorptive-cladding-for-1yv7a7rv04.pdf

We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down-doped with a triangular array of air holes. A figure of merit taking both the 3-dB bandwidth and loss of the coupler into account, is used for optimization of the structure parameters, given by the diameter and pitch of the cladding (d and Λ) and of the core (d(c) and Λc) air-hole structure. The coupler with Λ = 498.7 µm, d = 324.2 µm, Λc = 74.8 µm, and d(c) = 32.5 µm is found to have the best performance at a center frequency of 1THz, with a bandwidth of 0.25 THz and a total device loss of 9.2 dB. The robustness of the optimum coupler to structural changes is investigated.

Design and optimization of mechanically down-doped terahertz fiber directional couplers

/pdf/fabrication-and-characterization-of-porous-core-honeycomb-1fm3rr51c5.pdf

Fabrication and characterization of porous-core honeycomb bandgap THz fibers

/pdf/terahertz-fibres-and-functional-fibrei-based-devices-xbekgy1or1.pdf

Hualong Bao

Papers

Fabrication and characterization of porous-core honeycomb bandgap THz fibers.

Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

Design and optimization of mechanically down-doped terahertz fiber directional couplers

Fabrication and characterization of porous-core honeycomb bandgap THz fibers

Terahertz Fibres and Functional FibreI-Based Devices