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Linear Transformation of Polarization Modes in Coiled Optical Spun Fibers. III. Approximate Analytic Presentation
摘要： We have obtained approximate analytical dependences of the integrated values of effective elliptic birefringence of eigenpolarization modes on the length of coiled spun optical fibers by using approximations of numerical simulation. The dependence of the integrated elliptic birefringence of the polarization eigenmodes on the length of these optical fibers very quickly reaches its limiting value. This dependence also has a complex periodic structure including two substantially different spatial periods. The shape of the considered dependences is determined by the lengths of the polarization beats of the initial linear birefringence of the spun fiber, unperturbed by coiling, and circular birefringence due to torsion of the spun fiber.
关键词： polarization eigenmodes,elliptical birefringence,spun optical fibers
更新于2025-09-23 15:21:01
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A new type of structure of optical fiber pressure sensor based on polarization modulation
摘要： In this study, a new type of structure of optical fiber pressure sensor (OFPS) based on polarization modulation is proposed, which selects a high-birefringence fiber (HBF) as the sensing unit to measure the pressure in the fluid medium. The PM-1550-01 fiber produced by NTK Photonics Inc. is evaluated as the sample in our subject. Firstly, the regularities of birefringence variation on the PM-1550-01 followed by the external pressure load and the ambient temperature are analyzed by the finite element method (FEM). The results show that the pressure sensitivity is 2.05 × 10 ? 6 RIU/MPa in the pressure range of 0–100 MPa, and the temperature sensitivity is 7.27 × 10 ? 10 RIU/°C in the temperature range of 0–100 °C. Thus, the pressure-temperature cross-sensitivity is only 0.355 kPa/°C in theory. Secondly, the expression of the output light intensity of the introduced OFPS is deduced based on the principles of polarization interference and phase modulation. Combined with simulation results, the measurement ranges of the sensor can be set and adjusted by the length of the sensing unit. Finally, the proposed OFPS is fabricated and external pressure tests within the range of 0–50 MPa are completed. The results show that the pressure sensitivity is approximately 0.145 dB/MPa in the pressure range of 0–44 MPa. There is a fine consistency between the experimental data and simulation results. In addition, the proposed OFPS has many other advantages, such as small size, simple fabrication process and large measurement range, which make it appropriate to be applied in high-pressure measurement in hostile conditions, e.g., downhole and ocean-bottom.
关键词： Low temperature cross-sensitivity,Polarization modulation,High-birefringence fiber,Optical fiber pressure sensor
更新于2025-09-23 15:21:01
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Birefringence measurement of biological tissue based on polarization-sensitive digital holographic microscopy
摘要： We present a polarization-sensitive digital holography to measure the birefringence of biological tissues with complex structures. The birefringence measurement system is established by incorporating the modified Mach–Zehnder interferometer and lab-developed software. Normal and cancerous bladder tissue samples are measured by using the proposed experimental system. The polarization-dependent phase-shifted holograms are recorded by rotating the polarizer. Moreover, the hybrid reconstruction and least-square unwrapping algorithms are used to extract phase information of biological tissues at different polarization states. The birefringence of tissue is obtained from the above-phase distributions. The results show that polarization sensitivity exists in the normal bladder tissue and cancerous bladder tissue, and the median birefringence value of the cancerous tissue is significantly higher than that of the normal tissue. These results will provide reference for pathological research and clinic diagnoses.
关键词： Mach–Zehnder interferometer,birefringence,polarization-sensitive digital holography,biological tissue,phase distribution
更新于2025-09-23 15:21:01
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Ultra high birefringence and lower beat length for square shape PCF: Analysis effect on rotation angle and eccentricity
摘要： In this article, a circular air hole organized in a square manner cladding with porous core using elliptical holes index-guiding photonic crystal fiber (IG-PCF) has been proposed and numerically examined. The numerical study is obtained by using finite element method (FEM) inclusion with an electromagnetic absorption boundary perfectly matched layer (PML). Investigation process runs over a broader wavelength range near IR region from 1.20 mm to 1.80 mm for evaluating modal properties of proposed square shaped PCF. S-PCF expresses higher birefringence (2.2 (cid:1) 10(cid:3)3), high nonlinearity (23.46 W(cid:3)1 km(cid:3)1) along with lower beat length (553.86 mm) at the pumping wavelength k = 1.20 mm. Core holes angle orientation and eccentricity are tuned for gaining higher birefringence. Furthermore, beat length, Veff, spot size, beam divergence are inquired in details. Finally, this research is focused on birefringence and nonlinearity behaviors are highly affected by angle effect and eccentricity.
关键词： Beat length,Birefringence,Nonlinearity,Single mode PCF,Eccentricity,Spot size
更新于2025-09-23 15:21:01
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Mosaics of topological defects in micropatterned liquid crystal textures
摘要： Topological defects in the orientational order that appear in thin slabs of a nematic liquid crystal, as seen in the standard schlieren texture, behave as a random quasi–two-dimensional system with strong optical birefringence. We present an approach to creating and controlling the defects using air pillars, trapped by micropatterned holes in the silicon substrate. The defects are stabilized and positioned by the arrayed air pillars into regular two-dimensional lattices. We explore the effects of hole shape, lattice symmetry, and surface treatment on the resulting lattices of defects and explain their arrangements by application of topological rules. Last, we show the formation of detailed kaleidoscopic textures after the system is cooled down across the nematic–smectic A phase transition, frustrating the defects and surrounding structures with the equal-layer spacing condition of the smectic phase.
关键词： smectic A,nematic,birefringence,micropatterned,topological defects,liquid crystal
更新于2025-09-23 15:21:01
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Design of quad core photonic crystal fibers with flattened zero dispersion
摘要： Two photonic crystal fiber structures with quad-core have been investigated in this paper. Both the structures are geometrically similar but have different background materials. Both PCF structures exhibit very high birefringence. However, structure with silica background material reports birefringence of the order 10-2. It is to be noted that, this PCF structure has also shown zero dispersion behavior over a wide range of telecommunication wavelength. Moreover, the other structure with lead silicate as background material has also reported very low dispersion. Thus both the PCF structures simulated show ability to mitigate the effect of polarized mode dispersion. Besides this, other propagation characteristics like confinement loss, normalized frequency and non linear coefficient have been reported.
关键词： confinement loss,dispersion,birefringence,nonlinearity,Photonic crystal fibers
更新于2025-09-23 15:21:01
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Orthogonally polarized dual-wavelength laser based totally on intrinsic birefringence of the gain crystal
摘要： Based totally on the intrinsic difference of polarizing emission spectra and birefringence of the a-cut Nd:YAP gain crystal, an orthogonally polarized 1079.5 and 1099 nm dual-wavelength laser is demonstrated. A specially designed dielectric Fabry–Perot filter is exploited as output coupler and gain balancer of the laser cavity. The maximum output power and slope conversion efficiency of the dual-wavelength laser is 976 mW and 7%, respectively. The experimental results show that the intrinsic birefringence of the laser gain material is the principle source for the generation of the orthogonal polarized laser. The competition between the two lasing wavelengths is analyzed and attributed to the stark energy levels involved. The method presented can be used to other biaxial laser gain crystals for the generation of orthogonal polarized dual-wavelength lasers.
关键词： intrinsic birefringence,orthogonally polarized,dual-wavelength laser
更新于2025-09-23 15:19:57
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Enhancement of magneto-optical properties in magnetic photonic crystal slab waveguide based on yttrium iron garnet
摘要： In this work, a polarization-independent waveguide based on magnetic photonic crystal (MPC) with a triangular lattice of air holes in Yttrium Iron Garnet (YIG) slab grown on alumina (Al2O3) substrate is proposed, where both TE-like and TM-like periodic band gaps overlap. YIG is well known for its attracting magneto-optical (MO) properties and used to produce a coupling between the TE and TM modes. Thus, a nonreciprocal effect can be obtained by applying an external magnetic field parallel to the direction of propagation. At 1550 nm, the complete photonic band gap is simulated and optimized using the three dimensional plane-wave expansion method. The aim of this study is to enhance Faraday rotation (FR) while maintaining a low modal birefringence. A numerical analysis in function of magnetic gyration (g) has been reported, using the BeamProp software. The results reveal a proportional relation between FR, ?n and g, such for g = 0.5, a large FR of 26.11×104 °/cm with ?n = 7×10–6. The results show a real improvement of this MPC structure based on YIG with larger FR, lower modal birefringence and minimal losses. The notable enhancement in the MO behaviour could improve the performance of optical isolators, and makes it suitable for nonreciprocal devices.
关键词： modal birefringence,magneto-optical properties,Yttrium Iron Garnet,Faraday rotation,magnetic photonic crystal
更新于2025-09-23 15:19:57
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Rays via Single-Shot Laser-Electron Interaction
摘要： Generation of circularly polarized (CP) and linearly polarized (LP) γ rays via the single-shot interaction of an ultraintense laser pulse with a spin-polarized counterpropagating ultrarelativistic electron beam has been investigated in nonlinear Compton scattering in the quantum radiation-dominated regime. For the process simulation, a Monte Carlo method is developed which employs the electron-spin-resolved probabilities for polarized photon emissions. We show efficient ways for the transfer of the electron polarization to the high-energy photon polarization. In particular, multi-GeV CP (LP) γ rays with polarization of up to about 95% can be generated by a longitudinally (transversely) spin-polarized electron beam, with a photon flux meeting the requirements of recent proposals for the vacuum birefringence measurement in ultrastrong laser fields. Such high-energy, high-brilliance, high-polarization γ rays are also beneficial for other applications in high-energy physics, and laboratory astrophysics.
关键词： nonlinear Compton scattering,electron-spin-resolved probabilities,high-energy physics,Monte Carlo method,circularly polarized γ rays,vacuum birefringence,quantum radiation-dominated regime,laboratory astrophysics,linearly polarized γ rays
更新于2025-09-23 15:19:57
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Bias current and temperature dependence of polarization dynamics in spin-lasers with electrically tunable birefringence
摘要： We investigate and compare the intensity and polarization dynamics in a vertical-cavity surface-emitting laser (VCSEL) with a monolithically integrated, electrically controlled birefringence tuning mechanism. The influence of the bias current on the polarization dynamics is investigated over a large range of birefringence values. Bias current tuning toward low values and simultaneous maximization of the resonance frequency is an important strategy to optimize the spin-VCSEL toward energy-efficient operation. A polarization dynamics resonance tuning range from a few GHz up to the maximum frequency of 36 GHz was achieved, and polarization dynamics at maximum frequency are demonstrated at minimum bias current and at high temperatures of approximately 70 ○C. We propose a strategy for data communication with low energy consumption and low cooling effort.
关键词： energy-efficient operation,spin-lasers,birefringence,VCSEL,polarization dynamics
更新于2025-09-23 15:19:57