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- 实验方案
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Laser-stimulated birefringence of Ga2O3-La2S2.95Se0.05 glasses for optical recording of information
摘要： We show an opportunity to change the birefringence of Ga2O3 – La2S2.95Se0.05 glasses doped by Er3+ and La3+ ions at λ = 1150 nm wavelength of cw He-Ne laser under illumination of the femtosecond laser. The variation of the refractive indices was found during illumination by 180 fs laser with frequency about 65 MHz (at wavelength λ = 1045 nm). The laser-stimulated birefringence has been explored versus temperature. The observed laser induced and temperature dependences of the birefringence con?rm a huge contribution of anharmonic phonon subsystems which is typical for chalcogenide glasses. Due to an occurrence of local space charge density asymmetry, the e?ciency of birefringence is enhanced. The anisotropy e?ect exists only during the illumination and is diminished during 10…12 s after switching o? of the photo-inducing laser treatment. There is observed also a correlation between the occurred grating patterns and the values of the birefringence.
关键词： Chalcogenide glasses,Optoelectronic materials,Laser-induced e?ects,Birefringence,Electronic and electrical engineering
更新于2025-09-19 17:13:59
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Design and Electro-optic investigations of de Vries smectics for exhibiting broad temperature ranges of SmA* and SmC* phases and fast electro-optic switching
摘要： In this paper we report on the design, synthesis and characterisation of two new ferroelectric liquid crystalline compounds based on using cores of (i) 5-phenyl-pyrimidine benzene and (ii) 5-phenyl-pyrimidine benzoate terminated by achiral trisiloxane chain, and chiral (S) alkyl chain on the opposite ends of their respective mesogens. These compounds exhibit broad temperature ranges of SmA* and SmC* phases, whereas the latter exists at room temperature down to 11 oC. This is one of the desirable features of the compounds for perspective applications in devices. In both compounds, the differential scanning calorimetry shows a weak first order SmA*-SmC* transition. This observation is supported by determining the critical exponent of the power law as ~0.2 that describes the dependence of the tilt angle and the spontaneous polarization on temperature. The two compounds show excellent de Vries characteristics in terms of the layer shrinkage in SmC*, the maximum shrinkage in both cases is ~ 1.5%. Furthermore (i) the birefringence decreases with a reduction in temperature instead of increasing in SmA*, and (ii) a large field-induced birefringence is observed in SmA* close to the SmA*-SmC* transition temperature, (iii) the maximum birefringence measured is much lower than of a typical FLC material. The characteristics of these compounds when compared to a conventional/typical ferroelectric liquid crystalline mixture show that these materials surpass in performance in terms of having a (i) wider temperature range of both SmA* and SmC* phases and (ii) higher switching speed. The layer thickness in SmA* and SmC* is measured using the techniques of (a) small-angle X ray diffraction, and the (b) optical interferometry of free standing smectic films. A comparison of the results is used to determine an exceptionally useful result of the apparent tilt angle as a function of temperature in SmA* without the need of applying the electric field across the cell.
关键词： de Vries characteristics,electro-optic switching,SmA* and SmC* phases,ferroelectric liquid crystalline compounds,birefringence
更新于2025-09-19 17:13:59
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Powerful transversally diode-pumped Nd:YAG laser with low depolarization losses
摘要： The optical losses introduced into the cavity of transversally diode pumped Nd:YAG lasers operating in the linearly polarized Q-switched mode by the induced birefringence were evaluated. The relationship between the loss values and the state of the side surface of laser active elements was established. It has been shown that the active elements with adhesive light-scattering layers on their side surfaces make it possible to create the laser sources not only with a high degree of uniformity of the distribution of radiation within the output beam cross-section, but also with a low level of the optical depolarization losses.
关键词： Solid-state laser,Transversal diode pumping,Depolarization optical losses,Induced birefringence
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Highly-Birefringent Solid-Core Bragg Fiber with a High-Index-Contrast Cladding
摘要： We propose a highly-birefringent solid-core Bragg fiber (SC-BF) with a high-index-contrast cladding by symmetrically introducing two air holes into the solid core. The birefringence properties of such a SC-BF and their influencing factors are numerically investigated by using the finite element method. The numerical results show that the modal birefringence can be effectively improved by optimizing the refractive index, size and position of the air holes. We numerically demonstrate a highly-birefringent SC-BF with the 2.43 10?× modal birefringence of at 1550 nm.
关键词： high-index-contrast cladding,high birefringence,Solid-core Bragg fiber
更新于2025-09-16 10:30:52
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Dual-wavelength Yb:YAP laser
摘要： Dual-wavelength operation of Yb:YAP laser with an intracavity birefringent filter (BRF) was demonstrated. By using a 1 mm-thick BRF, DW pairs with wavelength separation ranging from 1.8 nm up to 11.3 nm could be generated based on gain balancing provided by a single transmission peak of the filter. In this way, the wavelength separation was not limited by the available free spectral range of the filter.
关键词： Diode-pumped lasers,Birefringence,ytterbium lasers
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Enhanced Magneto-Optical Effects in Magnetic Photonic Crystal Fiber Based on Yttrium Iron Garnet
摘要： In this paper, a kind of magnetic photonic crystal fiber of Yttrium iron garnet (YIG) is presented. The influence of gyrotropy on TE-TM mode conversion is analysed, which depends on Faraday rotation. The structure parameters are simulated and optimized. The optimum efficiency of 93.57% is obtained. Faraday rotation and modal birefringence have been calculated by varying gyrotropy from 0.01 to 0.04. The numerical results reveal an increased Faraday rotation and a reduced modal birefringence of 10-5. The enhanced properties of the structure could improve photonic devices performance, which make it suitable for magneto-optical isolators.
关键词： Modal birefringence,Faraday rotation,YIG,Magnetic photonic crystal fiber,Mode conversion
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - N-Matrix Jones Analysis of a Fiber-Optic Current Sensor
摘要： Fiber-optic current sensors (FOCS) based on Faraday effect could potentially be exploited in several high voltage applications where the electromagnetic immunity is a mandatory requirement. Nevertheless their actual in-field exploitation has always been limited due to critical issues such as fiber residual birefringence that degrades the current measurement accuracy. To this purpose special low-birefringence fibers and spun fibers featuring minimal residual birefringence have been developed. Yet these solutions do not prevent the birefringence contribution induced by the curvature arising during the realization of the current sensing coil. In the present work a novel numerical simulator based on the N-matrix Jones formalism [1] has been developed to analyse the detrimental effect of the birefringence on the Faraday-induced rotation of the state of polarization (SOP) of the light inside a FOCS due to the presence of an electrical current. In particular, the simulator takes into account both the intrinsic fiber birefringence and the bending-induced birefringence [2], combined with the circular birefringence caused by the Faraday effect. Simulation results have evidenced interesting behaviors related to the dependence of the effective Verdet constant Veff on both the number N of turns of the sensing fiber coil and the coil curvature radius r. Indeed Veff represents the FOCS effectiveness in inducing a polarization rotation theta, which is directly proportional to the electrical current I according to: ? = 2Veff (N ,r) ? N ? I . (1) In particular, simulations have shown that increasing N the values of Veff reduce due to the presence of intrinsic and bending-induced birefringence. This implies that the FOCS effectiveness does not grow linearly with N. A same trend also occurs when the coil radius r is progressively reduced. The simulation results have also been experimentally validated with the polarimetric setup shown in Fig. 1(a). The FOCS has been realized by wrapping a standard single-mode ?bre around an electrical cable supplied with an AC current up to a rms value of 35 A at the frequency of 50 Hz. A linearly polarized laser at 1.55 μm is coupled to the fiber coil through a circulator and reflected back to the receiver by a Faraday rotator mirror (FRM). This FRM cancels out all the reciprocal birefringence effect in the retracing path, while maintaining the Faraday rotation to be measured [3,4]. At the receiver side the orthogonal components of the SOP of the light are analyzed by means of a polarizing-beam splitter (PBS) together with a pair of photodiodes (PD1, PD2) and the Faraday-induced rotation is recovered.
关键词： Fiber-optic current sensors,Faraday effect,N-matrix Jones formalism,Verdet constant,birefringence
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Vector magnetic field sensor based on polarization-maintaining fiber long-period grating with magnetic fluid
摘要： We present a vector magnetic field sensor based on long-period thin-cladding polarization-maintaining fiber and immersed the grating in magnetic fluid. The proposed sensor can measure both magnetic intensity and orientation simultaneously.
关键词： birefringence,long-period grating,magnetic field,polarization-maintaining fiber
更新于2025-09-16 10:30:52
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Impact of H <sub/>2</sub> gas on disruptive birefringence optical fibers with embedded Palladium particles for developing robust sensors
摘要： Optical fiber sensors of hydrogen gas (H2) are conventionally based on the reaction of a sensitive material deposited on the surface of a fiber. Long-term applications of H2 monitoring require more robust configurations, less sensitive to the degradations of the sensitive layer. To overcome this issue, we develop disruptive polarisation-maintaining optical fibers composed of a sensitive material (Palladium, Pd) integrated into the silica cladding. We present the development of two Panda-type optical fibers with or without embedded Pd particles. These fibers have been fabricated for evaluating, through the measurement of the birefringence, the contribution of Pd particles on the detection of H2 gas. We have specially developed a gas chamber for measuring on-line the detection of H2 during its diffusion into the fiber. Dynamic comparisons between both fibers demonstrate the contribution of Pd particles resulting in a faster response time (of about 20 h for our experimental conditions). These results pave the way to the realization of robust optical fibers with enhanced sensitivity to H2 gas for developing sensing systems compatible with long-term hydrogen monitoring applications in extreme and harsh environments, such as radioactive waste repositories.
关键词： birefringence,hydrogen,optical fiber sensor
更新于2025-09-16 10:30:52
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[Institution of Engineering and Technology 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Lecce, Italy (23-25 May 2018)] 20th Italian National Conference on Photonic Technologies (Fotonica 2018) - Polarization digital holography for birefringence characterization of sperm cells
摘要： Birefringence in sperm heads depends on a very compact and organized structural normality. Additionally, when the acrosome reaction happens, due to a reorganization of the proteins, the birefringence occurs only in the post-acrosomal region. Thus, the polarization state of the semen is an interesting method to characterize their healthy state and to select reacted sperm cells. In this paper, a characterization of the birefringence pattern of sperm head by polarized digital holography microscopy is presented as a label free technique.
关键词： Digital holography,Sperm selection,Digital morphology,Sperm texture,Birefringence
更新于2025-09-16 10:30:52