This paper proposes a low-power, wide demodulation range solution for Fiber Bragg Gratings (FBG) based on voltage and current dual-wavelength tuning of VCSEL lasers. The paper first explains the principle of the demodulation system and then discusses the impact of driving voltage, current, and temperature on the emission wavelength of the laser. By investigating the wavelength scanning overlap range of the laser at different temperatures, the wavelength range of the FBG sensor is determined to be 4.5nm. The experimental results show that the demodulation system exhibits good wavelength repeatability, with the wavelength repeatability of all three channels within ±3pm. Furthermore, the overall power consumption of the system is only around 189mW, indicating that the demodulation system possesses the low power consumption characteristic and can be powered by portable power sources.
A switching multifunctional metasurface with wideband absorption, cross-polarization conversion, and wideband line-to-circle in the terahertz frequency band is designed based on the phase transition characteristic of vanadium dioxide (VO2). The simulation results show that when the VO2 is in the metallic state, the structure has the function of broadband absorption; the absorption rate reaches more than 90% in the range of 3.32 to 8.04 THz, and it has the characteristics of wide-angle incidence and polarization insensitivity. When the VO2 is in the insulated state, the designed metasurface can realize cross-polarization conversion and broadband line to circular polarization conversion. The linear polarization of 1.85 to 2.76 THz is transformed into cross-polarization, the polarization conversion efficiency is >90 % , and the ellipticity is >90 % for 1.61 to 1.75 THz and 3.06 to 8.37 THz ranges, which can convert line polarization to circular polarization and maintain good efficiency in the polarization conversion function within acceptable incidence and polarization angles. The proposed optical metasurface has great potential in terahertz fields, such as stealth technology, polarization conversion, and radar communication.
KEYWORDS: Education and training, Super resolution, Image processing, Biomedical optics, Data modeling, Image restoration, Image quality, Performance modeling, Angiography, Image enhancement, Medical image processing, Super resolution microscopy, Deep learning, Medical image reconstruction
Deep learning-based super-resolution models have the potential to revolutionize biomedical imaging and diagnoses by effectively tackling various challenges associated with early detection, personalized medicine, and clinical automation. However, the requirement of an extensive collection of high-resolution images presents limitations for widespread adoption in clinical practice. In our experiment, we proposed an approach to effectively train the deep learning-based super-resolution models using only one real image by leveraging self-generated high resolution images. We employed a mixed metric of image screening to automatically select images with a distribution similar to ground truth, creating an incrementally curated training data set that encourages the model to generate improved images over time. After five training iterations, the proposed deep learning-based super-resolution model experienced a 7.5% and 5.49% improvement in structural similarity and peak-signal-to-noise ratio, respectively. Significantly, the model consistently produces visually enhanced results for training, improving its performance while preserving the characteristics of original biomedical images. These findings indicate a potential way to train a deep neural network in a self-revolution manner independent of real-world human data.
An ultrawideband metamaterial perfect absorber based on vanadium dioxide is proposed. It achieves >95 % absorption of vertically incident electromagnetic waves in the range of 3.50 to 10 THz. The absorption intensity can be dynamically adjusted in the range of 0.2% to 99.98% by varying the conductivity of VO2. The mechanism of ultrawideband perfect absorption is interpreted using electric field distribution analysis and impedance-matching theory. The absorption rate related to the structural parameters of the absorber is investigated by numerical simulation. Finally, its polarization angle-insensitive and incidence angle-insensitive properties are demonstrated. This proposed absorber has potential applications in optical switching, electromagnetic stealth, and sensing applications.
In our work, the temperature sensing properties and intrinsic mechanism based on a bismuth–erbium co-doped optical fiber (BEDF) were explored. Through temperature sensing experiments, we found that when the 980-nm pump laser was used, the fluorescence intensity ratio (FIR) at 1560 and 1435 nm showed a good linear relationship at different temperatures and its sensitivity reached 0.1151 dB/°C, the accuracy was 0.2°C, and the R2 of the FIR curve is about 0.9923. At the same time, we also proposed a detection algorithm to judge the working state of the sensor. By changing the BEDF coating material while the fiber is being fabricated, the temperature measurement range can be further improved. The optical fiber temperature sensor will have a broader range of applications.
We propose a fiber optical cell catapult that is bird beak-shaped fiber cone optical tweezers that trap cells, then push them to the fiber tip via the evanescent fields on the side surface of the fiber cone, and finally eject them in a particular direction. The intensity distribution of the light field and the optical force of the fiber catapult are calculated by the finite element method. Moreover, an experimental study of the fiber catapult is given using yeast cells.
This article proposes and demonstrates a kind of all fiber vector magnetic field sensor based on side-polished hollow-core fiber (SPHCF) coated with magnetic fluid. The magnetic field sensor is composed of a single mode fiber- SPHCF - single mode fiber structure coated with the magnetic fluid. Our designed sensor has good identification of magnetic field orientation. In the experiments, the maximum orientation sensitivity and the intensity sensitivity are 0.19dB/° and -769.05 pm/mT, respectively. Additionally, we found that the changes of the concentration of the magnetic fluid and the sidepolished depth will lead to the change of the higher-order modes involved in the interference as well as the sensitivity of the magnetic field sensor. The proposed vector magnetic field sensor has the advantages of all fiber, simple structure, cost-effective and easy to manufacture, and etc.
In this study, we propose a dual-band wide-range tunable terahertz absorber based on graphene and bulk Dirac semimetal (BDS), which consists of a patterned BDS array, dielectric material, continuous graphene layer, and gold mirror. Simulation results show that the absorption at 3.97 and 7.94 THz achieve almost 100%. By changing the Fermi energy of graphene and BDS, the resonance frequency can be tuned between 3.97 and 9.28 THz. In addition, we found that when the background refractive index changes, the absorption is almost the same. This feature will broaden its applications. Finally, the influence of structural parameters and incident angles on device performance is discussed. The proposed absorber may have potential applications in photoelectric sensors and other optoelectronic devices.
A low cost and easily fabricated plastic optical fiber (POF) displacement sensor is presented. The sensor is based on the macrobending POF with a V-groove structure fabricated by a simple die-press-print method, which is easy to implement and effectively reduces the complexity of the fabrication process. The intensity modulation method is adopted for displacement sensing, which lowers the sensor system’s cost and complexity. Experiments are carried out to investigate the influence of the structural parameters on the displacement sensing performance and the proposed POF probe is optimized by changing the structure parameters. Results showed that when the V-groove structure depth is 200 μm, the length is 22 mm, the angle is 60 deg, the pitch is 2 mm, and the macrobending radius of the POF probe is 15 mm, the highest sensitivity could reach to 3.19 × 10 − 2 / mm with the measurement range of 18 mm.
The plastic optical fiber (POF) with a multi-notched structure was used for liquid level measurement. The multi-notched structure was fabricated on the POFs by a die-press-print method. When the notched structure was immerged by the liquid, the transmitted light power of the POF probe could be changed. So, this can be used as a liquid level sensor. The influence of the structure parameters on the sensor performances was investigated experimentally. Experimental results show that the sensitivity can reach to 0.0457/mm with a resolution of 1 mm, and the sensor resolution is flexible. The sensor is simple structure and easy fabrication, and it is a low cost solution for the liquid level measurement.
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