RESUMEN
Stimulated Brillouin scattering (SBS) is effective for realizing a laser with an ultra-narrow linewidth. Although photonic crystal fiber (PCF) is considered an excellent medium to achieve SBS, it does not meet the requirements of low loss, large birefringence, and ease of fabrication. We propose a polarization-maintaining PCF (PM-PCF) structure and theoretically analyze the effects of the geometric structural parameters of the PM-PCF on various optical properties. Our theoretical analysis and experimental results contribute to the advancement of the field of ultra-narrow linewidth fiber lasers, distributed fiber sensing, and fiber-optic gyroscopes related to SBS.
RESUMEN
Hollow-core nested anti-resonant nodeless fibers (HC-NANFs) exhibit great performance in low loss and large bandwidth. Large core sizes are usually used to reduce confinement losses, but meanwhile, bring side effects such as high bending and coupling losses. This study proposes a small-core HC-NANF with a relatively low confinement loss. Semi-circular tubes (SCTs) are added to constitute the core boundary and reduce the fiber-core radius (R). Double NANFs tubes and single-ring tubes are added inside the SCTs to reduce loss. Simulation results show that the optimized structure with R of 5 µm has confinement loss and total loss of 0.687 dB/km and 4.27 dB/km at 1.55 µm, respectively. The bending loss is less than 10 dB/km at 1.4 â¼ 1.6 µm with a bending radius of 10 mm. The direct coupling loss with standard single mode fiber is greatly reduced to â¼ 0.125 dB compared to other HC-NANFs. The modified structure of HC-NANFs also shows a large bandwidth, effective single-mode operation, potentially high birefringence performance, and remarkable robustness of the optimized structure parameters, making it suitable for short-haul applications in laser-based gas sensing, miniaturized fiber sensing, etc.
RESUMEN
A hybrid photonic bandgap effect in twisted hollow-core photonic bandgap fibers (HC-PBFs) is theoretically investigated for the first time, to the best of our knowledge. Due to the topological effect, twisting of the fibers changes the effective refractive index and lifts the degeneracy of the photonic bandgap ranges of the cladding layers. This twist-induced hybrid photonic bandgap effect shifts up the center wavelength and narrows the bandwidth of the transmission spectrum. A quasi-single-mode low-loss transmission is achieved in the twisted 7-cell HC-PBFs with a twisting rate α = 7-8â rad/mm, which has a loss < 30â dB/km and higher-order mode extinction ratio > 15â dB. The twisted HC-PBFs could be suitable for applications such as spectral and mode filters.
RESUMEN
In this study, a low-noise Fabry-Perot interference-based method is promoted to measure the longitudinal uniformity of the distance between six pairs of opposite silica-air interfaces within the core of a seven-cell hollow-core photonic bandgap fiber. The experimental results demonstrate that the precision of the method is improved to the subnanometer scale. Based on the test results, a model is established to study the effect of the longitudinal uniformity of the core structure on the fiber loss, and the simulation results indicate that the fiber loss could reach â¼22.73 dB/km, which is consistent with the practical loss value.
RESUMEN
A novel single-polarization single-mode hollow-core photonic bandgap fiber with thin slab waveguide (TSW) was designed and simulated. Single-polarization guidance is achieved by the high loss of a polarized fundamental mode (FM) induced by mode coupling with a higher-order TE/TM mode of TSW and low loss of another polarized FM. We achieve a polarization loss ratio â¼ 46.9 dB, birefringence Δn â¼ 2.4 × 10-4, loss â¼ 35.9 dB/km and minimum higher-order mode extinction ratio > 15 dB. Moreover, the performance could be maintained when the guidance wavelength λ = 1.44 â¼ 1.56 µm and bending radius rc > 9 mm. The proposed model will be suitable for application as resonator sensing paths of miniaturized resonator fiber optic gyroscopes, high-performance interferometers, fiber lasers, frequency metrology, quantum communications, and laser-based gas sensing, etc.
RESUMEN
We present a modified fiber model based on the nested hollow core anti-resonant fiber that enables the stable transmission of the orbital-angular-momentum mode HE21. By replacing a pair of nested anti-resonant tubes in the horizontal axis with resonant tubes, the coupling between core mode and cladding mode has been increased. Therefore, the relative strength of fundamental mode HE11 and the first higher mode HE21 has been modified. The numerical simulation results indicate that the loss ratio of the lowest loss HE11 to HE21 can be optimized to more than 187, while the HE21 still maintains a low confinement loss as 0.0027 dB/m. Our research has brought about a solution of low loss hollow core mode propagation in optical fiber. Those properties will make this fiber an ideal medium for blue-detuned atomic guidance.
RESUMEN
The polarization extinction ratio (PER) of the multifunction integrated optic circuit (MIOC) is significant in maintaining polarization reciprocity in the fiber-optic gyroscope (FOG), and a high PER value is required, particularly in high-precision FOGs. Practically, the value of the PER decreases owing to the recoupling of the TM mode to the output port, thereby degrading the performance of the FOG. To improve the PER, the propagation of the leaking TM mode in the substrate is analyzed first. The variation of the PER with the chip structure is simulated based on the overlap integral algorithm of the optical mode. According to the analysis results, a structure of double absorption trenches at the bottom of the MIOC is proposed to block the TM mode from reflecting to the output port. In comparison with the traditional design, the optimized MIOC exhibits a higher PER that increases by approximately 25 dB and the average value of the PER reaches 75 dB. The MIOC design proposed in this study has good potential for application in high-precision FOGs.
RESUMEN
A novel high-precision photonic crystal fiber-based pressure sensor with low-temperature sensitivity is proposed. The sensor is fabricated by fusion splicing a photonic crystal fiber with a hollow core fiber immersed in polydimethylsiloxane. Owing to the special structure of the photonic crystal fiber, the temperature cross-coupling effect can be minimized and the membrane shape can be controlled. Experimental results indicate that the pressure sensitivity of the FP pressure sensor is 2.47 nm/kPa, 5.37 times the temperature sensitivity of 0.46 nm/°C. The proposed FP pressure sensor has broad application prospects in chemical and biological detection for monitoring pressure in real time.
RESUMEN
A hollow-core antiresonant fiber (HC-ARF) with nested supporting rings (NSRs) is designed and simulated. The HC-ARF with NSRs has advantages and benefits of low loss, large bandwidth, simple structure and a well bending characteristic, in which confinement loss (CL) is â¼ 0.15 dB/km @ 1.55 µm and the bandwidth is â¼ 220 nm @ CL < 1 dB/km. The bending loss (BL) is lower than â¼ 1 dB/km @ bend radius rc > 24â mm at 1.55 µm. Therefore, the HC-ARF with NSRs has potential applications of data transmission, sensing, high power delivery and so on.
RESUMEN
In this Letter, we propose a simple and nondestructive method for the determination of the core size of a hollow-core photonic bandgap fiber (HC-PBF) and its axial uniformity based on a Fabry-Perot cavity induced by a pair of opposite silica-air interfaces within the hollow core. The experimental results indicate that the core size test of the HC-PBF has a nanometer-level precision, and its axial uniformity test has an ultimate spatial resolution of tens of microns. The method provides an effective and precise tool for the investigation of the hollow-core size and its longitudinal evolution.
RESUMEN
Air-core photonic bandgap fiber (PBF) is a good choice for fiber-optic gyroscopes (FOGs) owing to the fact that it can be adapted to a wide variety of environments. However, its multimode properties are disadvantageous for the application to FOGs. An interference-based method is proposed to precisely determine the secondary waves caused by the high-order modes and their coupling. Based on the method, two groups of secondary waves have been found, having optical path differences (OPDs) of ~1.859 m and ~0.85 m, respectively, relative to the primary waves in a PBFOG that consists of a 7-cell PBF coil, approximately 180 m in length. Multi-turn bends of the PBF at both ends of the PBF coil after the fusion splicing points are shown to suppress the intensity of these secondary waves by approximately 10 dB.
RESUMEN
Osteoarthritis (OA), one of the most common joint disorders, is one of the leading causes of disability among the elderly. Proinflammatory cytokines, such as interleukin (IL)-1ß, which is synthesized locally by synovial cells and chondrocytes, have been shown to play a critical role in sustaining cartilage damage in arthritis by creating an imbalance between cartilage degradation and the repair process. Alpha-lipoic acid (α-LA), which is synthesized in animal and plant tissues, has demonstrated its protective effects in a variety of diseases. However, whether or not LA has a protective effect in OA is still unknown. In this study, we found that α-LA inhibits the IL-1ß-induced increase in matrix metallopeptidase 3 (MMP-3) and matrix metallopeptidase 13 (MMP-13) expression and activity. Our data also demonstrate that interferon regulatory factor 1 (IRF-1) participates in the induction of MMP-3 and MMP-13. However, α-LA treatment did not change IRF-1 levels. Importantly, we found that α-LA increases SUMOylation of IRF-1, which attenuates IRF-1's transcriptional activity. Finally, we found that α-LA treatment leads to an increase in SUMO-1, but not in SUMO-2 or SUMO-3. Taken together, this study shows that α-LA exerts anti-inflammatory effects in an IL-1ß-stimulated chondrocyte model, thereby suggesting a potential protective effect of α-LA in OA.
