- 标题
- 摘要
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- 实验方案
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Performances of Microwave Photonic Notch Filter Based on Microring Resonator with Dual-drive Modulator
摘要： A tunable microwave photonic notch ?lter with ultrahigh radio frequency (RF) rejection ratio is achieved by using a dual-drive Mach–Zender modulator and a microring resonator. In addition, we dedicated to clarify the mechanisms of the microwave photonic notch ?lters based on a microring resonator under both overcoupled and undercoupled states and the performance differences between these two situations are investigated in detail. Furthermore, the experimental results show that the cancellation microwave photonic notch ?lter with ultrahigh RF rejection ratio can be achieved with both undercoupled and overcoupled microring resonators. Besides, an RF rejection ratio exceeding 50 dB was achieved for a microring resonator with an optical extinction ratio of only 4 dB, where a 46-dB enhancement from optical to RF response is obtained. Also, the bandwidth of the microwave photonic ?lter can tuned from 0.65 to 2.2 GHz by adjusting the coupling ratio of the ring resonator. Meanwhile, by tuning the wavelength of the optical carrier, the ?ltering frequency can be tuned and a tuning range of about 25 GHz was achieved. The implementation is much simpler and more economical compared with previous reports and has great potential in monolithic integration of microwave photonic ?lters on chip.
关键词： Optical ?lter,Microwave photonics,Microring resonator,Integrated optics devices
更新于2025-09-23 15:23:52
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Limitations of graphene nanocoated optical tapers for high-power nonlinear applications
摘要： In this letter, we investigate the limitations of graphene as a saturable absorber for high-power nonlinear optical applications. The response of graphene nanocoated optical tapers against the average optical power injected is tested. We point out that the power handled by such components is limited and their nonlinear properties are strongly and permanently modified when exposed to high optical power. The origin of the degradation of the components is discussed.
关键词： nonlinear optics,mode-locking,fiber laser,Graphene,optical tapers
更新于2025-09-23 15:23:52
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Photon bunching and N-photon interference in thermal light
摘要： We investigate the contribution of four-photon bunching term in fourth-order double-slit interference intensity correlation based on two different detection schemes with a pseudo-thermal light source. It is clearly demonstrated that the resolution of intensity correlation is significantly enhanced by using of double-slit in both fourth-order and third-order intensity correlation. Meanwhile, the visibility of fourth-order correlation can be dramatically improved in contrast to the third-order due to the four-photon bunching term by contributing in the visibility of fourth-order correlation. The position and full width at half maximum of interference peaks of fourth-order intensity correlation are same as third-order. We also use two different scanning approaches to change the resolution and visibility of interference intensity correlation. In the first detection scheme, we scan three reference detectors along the same orientation and speed. In second detection scheme we scan two of three reference detectors in the same orientation, and speed of one reference detector is twice that of the other, and simultaneously moving the other two reference detectors with opposite orientation but identical speed. Those investigations can also be promoted to high order intensity correlation of thermal light.
关键词： Correlation,Photon bunching,Photon interference,Fourier optics
更新于2025-09-23 15:23:52
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Magneto-optical imaging characteristics of weld defects under alternating and rotating magnetic field excitation
摘要： This paper mainly examines the characteristics of magneto-optical (MO) images of weld defects under alternating and rotating magnetic field excitation. Weld defects including surface and subsurface defects were subjected to magneto-optical imaging (MOI) nondestructive testing (NDT) experiments. The MO images of different weld defects under alternating magnetic field excitation and rotating magnetic field excitation have been compared to determine the best effect of nondestructive testing, and a cruciform welding seam was used to verify the detection effect of rotating magnetic field. Besides, the values of standard deviation and maximum difference have been determined to analyze the difference in the effects of two magnetic fields, and image processing methods were applied to extract defect information, such as histogram equalization. Experimental results show that the optimal excitation voltage and lift-off value of rotating magnetic field are 120 V and 20 mm, respectively; image histogram equalization can significantly improve the contrast of MO images, and there is a distinct difference in the detection effect of two magnetic fields. Under the same excitation conditions, the detection effect of rotating magnetic fields is always better than the effect of alternating magnetic fields, and rotating magnetic field excitation has obvious advantages in detecting multidirection and subsurface defects in that the detection depth can reach about 8 mm.
关键词： Magneto-optical imaging,Electromagnetic optics,Nondestructive testing,Rotating magnetic field
更新于2025-09-23 15:23:52
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - A High Dynamic Range in Situ Flow Sensor
摘要： High dynamic range and high accuracy flow sensor is a highly desirable device in quantifying mixing in the atmosphere and the ocean, which is critical in our understanding of energy dissipation and flux studies. We discuss a design that utilizes only a single point sensor in different angles, based on our novel oriented temperature Fabry-Perot using interferometry approach. We report the sensitivity of a high-dynamic range sensor head orientation in such configuration. We discuss initial configuration, data collection, processing, analysis and calibration including sensor orientation for future deployment.
关键词： Fabry-Perot interferometer,flow meter,turbulence,kinetic energy dissipation,fiber optics
更新于2025-09-23 15:23:52
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Light in power
摘要： We present in this paper a generic and parameter-free algorithm to efficiently build a wide variety of optical components, such as mirrors or lenses, that satisfy some light energy constraints. In all of our problems, one is given a collimated or point light source and a desired illumination after reflection or refraction and the goal is to design the geometry of a mirror or lens which transports exactly the light emitted by the source onto the target. We first propose a general framework and show that eight different optical component design problems amount to solving a light energy conservation equation that involves the computation of visibility diagrams. We then show that these diagrams all have the same structure and can be obtained by intersecting a 3D Power diagram with a planar or spherical domain. This allows us to propose an efficient and fully generic algorithm capable to solve these eight optical component design problems. The support of the prescribed target illumination can be a set of directions or a set of points located at a finite distance. Our solutions satisfy design constraints such as convexity or concavity. We show the effectiveness of our algorithm on simulated and fabricated examples.
关键词： Mirror design,Caustics,Lens design,Power diagram,Optimal Transport,Non-imaging Optics
更新于2025-09-23 15:23:52
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Acquiring spatially varying appearance of printed holographic surfaces
摘要： We present two novel and complimentary approaches to measure diffraction effects in commonly found planar spatially varying holographic surfaces. Such surfaces are increasingly found in various decorative materials such as gift bags, holographic papers, clothing and security holograms, and produce impressive visual effects that have not been previously acquired for realistic rendering. Such holographic surfaces are usually manufactured with one dimensional diffraction gratings that are varying in periodicity and orientation over an entire sample in order to produce a wide range of diffraction effects such as gradients and kinematic (rotational) effects. Our proposed methods estimate these two parameters and allow an accurate reproduction of these effects in real-time. The first method simply uses a point light source to recover both the grating periodicity and orientation in the case of regular and stochastic textures. Under the assumption that the sample is made of the same repeated diffractive tile, good results can be obtained using just one to five photographs on a wide range of samples. The second method is based on polarization imaging and enables an independent high resolution measurement of the grating orientation and relative periodicity at each surface point. The method requires a minimum of four photographs for accurate results, does not assume repetition of an exemplar tile, and can even reveal minor fabrication defects. We present point light source renderings with both approaches that qualitatively match photographs, as well as real-time renderings under complex environmental illumination.
关键词： Diffraction,real-time rendering,spectral,polarization,wave optics
更新于2025-09-23 15:23:52
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Cone–Photoreceptor Density in Adolescents With Type 1 Diabetes
摘要： Changes to retinal structure and function occur in individuals with diabetes before the onset of diabetic retinopathy. It is still unclear if these changes initially affect vascular or neural retina, or if particular retinal areas are more susceptible than others. This paper examines the distribution of cone photoreceptor density in the retina of adolescents with type 1 diabetes. This cross-sectional prospective study includes 29 adolescents and young adults with type 1 diabetes and no diabetic retinopathy and 44 control participants recruited at the Hospital for Sick Children. Adaptive-optics enhanced retinal imaging of the cone photoreceptor mosaic was performed in four quadrants at an eccentricity of ~78 from the fovea. After image registration and averaging, cone photoreceptors were counted and photoreceptor density was calculated. Analysis of variance with repeated measures was used to assess the differences in photoreceptor density between groups. Cone density was similar in both control participants and participants with diabetes. There was a small effect of retinal hemisphere; participants with diabetes did not show the expected radial asymmetry observed in control participants. Cone density in the parafoveal retina is not reduced in adolescents with type 1 diabetes.
关键词： adolescent,retina,type 1 diabetes,adaptive optics
更新于2025-09-23 15:23:52
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Averaged nonlinear equations for multimode fibers valid in all regimes of random linear coupling
摘要： We develop averaged equations to model nonlinear propagation in multimode fibers that are valid in all regimes of random, linear, intermodal coupling. The propagation equations apply to the three existing regimes of linear coupling – the two previously studied all-mode (strong) and mode-group (weak) couplings and the new intermediate coupling regime. The equations are therefore general and can describe nonlinear propagation for all types of intermodal linear coupling that can exist between modes in a fiber supporting multiple spatial modes. Numerical simulations are performed to validate the new averaged propagation equations in the nonlinear regime.
关键词： Space-division multiplexing,Nonlinear optics,Multimode fibers
更新于2025-09-23 15:23:52
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Performance Evaluation of Hybrid FSO-SACOCDMA System under Different Weather Conditions
摘要： Spectral amplitude coding optical code division multiple access (SACOCDMA) is a multiplexing technique, which provides faster speed, efficiency, security and unlimited bandwidth. It is widely preferred because of its ability to eliminate multiple access interference (MAI). Free space optics (FSO) provides a wireless link to transmit data securely at higher rates for last mile access. In this work, a 100 Gb/s hybrid FSO-SACOCDMA is designed using direct detection. The performance of FSO using SACOCDMA utilizing NZCC (New Zero Cross Correlation) code is evaluated under different weather conditions (clear weather, haze and fog) for ten users where each user carries 10 Gb/s. The results indicate that in clear weather FSO distance can be extended up to 13 km. Moreover, after using pre-amplifier in clear weather, FSO enhances the maximum distance to 35 km with acceptable signal to noise ratio and bit error rate. Using an amplifier in the link not only makes the quality of the signal better but it also increases the communication range.
关键词： spectral amplitude coding optical code division multiple access (SACOCDMA),free space optics (FSO),direct detection (DD),new zero cross correlation (NZCC)
更新于2025-09-23 15:23:52