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Customizing supercontinuum generation via on-chip adaptive temporal pulse-splitting
摘要： Modern optical systems increasingly rely on complex physical processes that require accessible control to meet target performance characteristics. In particular, advanced light sources, sought for, for example, imaging and metrology, are based on nonlinear optical dynamics whose output properties must often finely match application requirements. However, in these systems, the availability of control parameters (e.g., the optical field shape, as well as propagation medium properties) and the means to adjust them in a versatile manner are usually limited. Moreover, numerically finding the optimal parameter set for such complex dynamics is typically computationally intractable. Here, we use an actively controlled photonic chip to prepare and manipulate patterns of femtosecond optical pulses that give access to an enhanced parameter space in the framework of supercontinuum generation. Taking advantage of machine learning concepts, we exploit this tunable access and experimentally demonstrate the customization of nonlinear interactions for tailoring supercontinuum properties.
关键词： machine learning,optical pulse shaping,supercontinuum generation,photonic chip,nonlinear optics
更新于2025-09-23 15:21:01
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Structured-illumination Makyoh-topography: optimum grid position and its constraints
摘要： Complementing conventional Makyoh topography with structured illumination using a sparse square grid, the large-scale surface shape can be calculated with a deflectometry approach, while the sample’s morphology can still be imaged. However, the grid’s image must be sharp not to mask the Makyoh image of the sample morphology. In this paper, the instrumental conditions for the grid sharpness are established. The two main types of Makyoh set-ups (lens and mirror based) are analysed. It is shown that the lens-based set-ups allow the position of the grid to be sharp on the Makyoh image. However, for mirror-based set-ups this is not possible because of geometrical instrumental constraints. The calculations are corroborated with experiments.
关键词： Makyoh topography,surface defects,structured illumination,deflectometry,geometrical optics,flatness testing
更新于2025-09-23 15:21:01
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Panda type few-mode fiber capable of both mode profile and polarization maintenance
摘要： We report the design, fabrication and characterization of panda type few-mode fiber (panda-FMF) capable of both mode profile and polarization maintenance, due to the use of two applied stress rods into the conventional FMF. The panda-FMF can support six spatial modes including LP01, LP11a, LP11b, LP21a, LP21b and LP02, and each possesses two orthogonal linear polarization modes. According to the characterization results of panda-FMF, we theoretically identify that the effective refractive index (RI) difference between either two spatial or orthogonal linear polarization modes is more than 1×10-4 over the C-band. Moreover, the experimental results verify that, both mode profile and polarization of high-order radially asymmetric modes can be perfectly maintained even under severe twist rate of 1.57 rad/m.
关键词： polarization-maintaining,fiber optics,Fiber design and fabrication,fibers
更新于2025-09-23 15:21:01
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Active Maintenance of the Gradient of Refractive Index Is Required to Sustain the Optical Properties of the Lens
摘要： To determine whether the cellular physiology of the lens actively maintains the optical properties of the lens and whether inhibition of lens transport affects overall visual quality. One lens from a pair of bovine lenses was cultured in artificial aqueous humor (AAH), while the other was cultured in either AAH-High-K+ or AAH + 0.1 mM ouabain for 4 hours. Lens pairs or whole enucleated eyes were then imaged in 4.7 Tesla (T) high-field small animal magnet. Lens surface curvatures, T1 measurements of water content, and T2 measurements of water/protein ratios were extracted from cultured lenses, while the geometrical parameters that define the optical pathway were obtained from whole eyes. Gradients of refractive index (GRIN), calculated from T2 measurements, and the extracted geometric parameters were inputted into optical models of the isolated lens and the whole bovine eye. Inhibiting circulating fluxes by inhibiting the Na/K-ATPase with ouabain or depolarization of the lens potential by High K+ caused changes to lens water content, the water/protein ratio (GRIN) and surface geometry that manifested as an increase in optical power and a decrease in negative spherical aberration in cultured lenses. Changes to optical properties of the lens resulted in a myopic shift that impaired vision quality in the optical model of the bovine eye. The cellular physiology of the lens actively maintains its optical properties and inhibiting the Na/K/ATPase induces a myopic shift in vision similar to that observed clinically in patients who go on to develop cataract.
关键词： physiological optics,optical modeling,cataract,gradient of refractive index,lens physiology,magnetic resonance imaging
更新于2025-09-23 15:21:01
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Light sprinkler
摘要： Although high rotation rates have been achieved with optically driven micro-rotors, particularly in low-viscosity fluids or with small rotor sizes to minimize drag, the demonstrated torque efficiency is typically small in practice compared with theoretical maxima. Now, Silvio Bianchi and colleagues in Italy and Hungary have demonstrated that with precise rerouting of light in 3D structures fabricated by direct laser writing, optical micro-turbines can better harness light’s momentum and efficiently generate uniform and controllable torque.
关键词： light sprinkler,direct laser writing,torque efficiency,optical micro-turbines,micro-optics
更新于2025-09-23 15:21:01
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Light control through a nonlinear lensing effect in a colloid of biosynthesized gold nanoparticles
摘要： Biosynthesis of four samples of colloidal suspensions of gold nanoparticles is achieved using hydroalcoholic extract and three different separated compounds of the plant Bacopa procumbens. The nonlinear optical properties of each sample are characterized with the Z-scan technique. In all cases, the Z-scan curves indicate a negative or self-defocusing response, which is mainly attributed to thermal effects. Among the four samples, the hydroalcoholic extract was noted to have the highest nonlinear optical response and was selected to demonstrate the formation of self-collimated beams (SCBs). This kind of beams are obtained when a convergent CW laser, with only few tens of milliwatts of optical power, is introduced into the sample and induces a negative-lens effect that shifts the focal spot forward. As a result, the otherwise highly focused beam propagate with little divergence over lengths of up to 10 mm. Moreover, an SCB is capable of controlling and steering a weak probe beam of a different wavelength, since the probe experiences the lensing induced by the pump. Noteworthy, the response time of the material was found to be less than 0.07 s, which makes it a plausible candidate for photonic applications.
关键词： gold nanoparticles,Nonlinear optics,nonlinear optical materials,self-effects
更新于2025-09-23 15:21:01
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Tailoring coupling between light and spin waves with dual photonic-magnonic resonant layered structures
摘要： We report on judiciously designed stratified periodic structures of magnetic dielectric materials with a localized defect layer, which are able to concurrently confine light and spin waves in the same ultra-small defect region for a long time period, thus resulting in enhanced photon-magnon interaction and large dynamic optical frequency shift. Our results for a specific realization of such a one-dimensional, so-called photomagnonic, crystal magnetized at saturation perpendicular to the interfaces, obtained by means of rigorous calculations using scattering-matrix techniques, show that the inherently weak coupling between visible/near-infrared light and GHz-frequency spin waves can be greatly increased leading to strong modulation of the optical field through multi-magnon exchange mechanisms. Such novel multifunctional composite materials offer a promising platform for tailoring light–spin-wave coupling in view of fast and energy-efficient spin-optical information processing applications.
关键词： Inelastic Light Scattering,Photomagnonic Crystal,Magneto-optics,Spin Waves
更新于2025-09-23 15:21:01
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Characterization of a Time-Resolved Diffuse Optical Spectroscopy Prototype Using Low-Cost, Compact Single Photon Avalanche Detectors for Tissue Optics Applications
摘要： Time-resolved diffuse optical spectroscopy (TR-DOS) is an increasingly used method to determine the optical properties of diffusive media, particularly for medical applications including functional brain, breast and muscle measurements. For medical imaging applications, important features of new generation TR-DOS systems are low-cost, small size and efficient inverse modeling. To address the issues of low-cost, compact size and high integration capabilities, we have developed free-running (FR) single-photon avalanche diodes (SPADs) using 130 nm silicon complementary metal-oxide-semiconductor (CMOS) technology and used it in a TR-DOS prototype. This prototype was validated using assessments from two known protocols for evaluating TR-DOS systems for tissue optics applications. Following the basic instrumental performance protocol, our prototype had sub-nanosecond total instrument response function and low differential non-linearity of a few percent. Also, using light with optical power lower than the maximum permissible exposure for human skin, this prototype can acquire raw data in reflectance geometry for phantoms with optical properties similar to human tissues. Following the MEDPHOT protocol, the absolute values of the optical properties for several homogeneous phantoms were retrieved with good accuracy and linearity using a best-fitting model based on the Levenberg-Marquardt method. Overall, the results of this study show that our silicon CMOS-based SPAD detectors can be used to build a multichannel TR-DOS prototype. Also, real-time functional monitoring of human tissue such as muscles, breasts and newborn heads will be possible by integrating this detector with a time-to-digital converter (TDC).
关键词： diffuse optical spectroscopy,time-resolved spectroscopy,tissue optics,single-photon avalanche diode,silicon photodetectors,time-correlated single-photon counting
更新于2025-09-23 15:21:01
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[IEEE 2018 IEEE Photonics Conference (IPC) - Reston, VA, USA (2018.9.30-2018.10.4)] 2018 IEEE Photonics Conference (IPC) - Crack-Free Silicon-Nitride-on-Insulator Nonlinear Circuits for Continuum Generation in the C-Band
摘要： We report on the fabrication and testing of silicon-nitride-on-insulator nonlinear photonic circuits for complementary metal–oxide–semiconductor (CMOS) compatible monolithic co-integration with silicon-based optoelectronics. In particular, a process has been developed to fabricate low-loss crack-free Si3N4 730-nm-thick ?lms for Kerr-based nonlinear functions featuring full process compatibility with existing silicon photonics and front-end Si optoelectronics. Experimental evidence shows that 2.1-cm-long nanowires based on such crack-free silicon nitride ?lms are capable of generating a frequency continuum spanning 1515–1575 nm via self-phase modulation. This work paves the way to time-stable power-ef?cient Kerr-based broad-band sources featuring full process compatibility with Si photonic integrated circuits on CMOS lines.
关键词： frequency continuum,photonic integrated circuits (PICs),Complementary metal–oxide–semiconductor (CMOS),nonlinear optics,silicon-nitride-on-insulator (SiNOI)
更新于2025-09-23 15:21:01
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Transmission of Higher Order Solitons created by Optical Multiplexing
摘要： The nonlinear Fourier transform (NFT) is a promising tool to linearize the inherently nonlinear optical fiber channel. The NFT transforms a time domain signal into the continuous and the discrete spectrum. The discrete spectrum is composed of an arbitrary number of complex valued discrete eigenvalues and their associated amplitudes. These discrete eigenvalues relate to solitons, which maintain their shape or return to it in an oscillating manner, while passing through the optical channel. Higher order solitons consisting of multiple eigenvalues are complex pulses, which are created and demodulated by sophisticated digital signal processing (DSP) leading to demanding hardware requirements. This paper shows a way to work with higher order solitons in a WDM like fashion by using optical-electrical signal processing and presents boundaries of this method. Optical-electrical signal processing decreases the required electrical and electro-optical hardware specifications substantially and enables to use a simplified DSP. The proposed creation method is subsequently employed to transmit higher order solitons consisting of five QPSK modulated eigenvalues. Furthermore, the optical-electrical processing is benchmarked against the Darboux transformation, which creates higher order solitons purely numerically. The results show that for a 5th order soliton transmission the proposed method can significantly reduce the hardware requirements and DSP complexity.
关键词： solitons,nonlinear Fourier transform,optical signal processing,nonlinear optics,optical fiber communication,Darboux transform
更新于2025-09-23 15:21:01