- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Third-order nonlinear optical response of Yb:YAG ceramics under femtosecond laser irradiation
摘要： Transparent ceramic laser materials, as an important alternate of traditional laser gain medium materials, have aroused much attention for their excellent performance. Here, we investigated the third-order nonlinear susceptibility of high quality transparent Ytterbium-doped Yttrium Aluminium Garnet (Yb:YAG) ceramics. Under an ultrafast femtosecond laser irradiation, we experimentally demonstrated the nonlinear optical limiting and self-focusing behaviors of Yb:YAG ceramic by Z-scan method at 800 nm. It was found that Yb:YAG ceramics exhibit a relatively small nonlinear refractive index (~3.8 × 10?20 m2/W) which exerts little dependence on the Yb3+ doping concentration and laser intensity. This work could illustrate the application potential of transparent ceramic under high-power condition and can also provide useful design guidelines for high power ceramic laser system.
关键词： Third-order optical nonlinearity,Z-scan,Nonlinear refractive index,Yb:YAG ceramics
更新于2025-09-16 10:30:52
-
Evaluation of Nanoplasmonic Optical Fiber Sensors Based on D-Type and Suspended Core Fibers with Metallic Nanowires
摘要： The introduction of metallic nanostructures in optical fibers has revolutionized the field of plasmonic sensors since they produce sharper and fine-tuned resonances resulting in higher sensitivities and resolutions. This article evaluates the performance of three different plasmonic optical fiber sensors based on D-type and suspended core fibers with metallic nanowires. It addresses how their different materials, geometry of the components, and their relative position can influence the coupling between the localized plasmonic modes and the guided optical mode. It also evaluates how that affects the spatial distributions of optical power of the different modes and consequently their overlap and coupling, which ultimately impacts the sensor performance. In this work, we use numerical simulations based on finite element methods to validate the importance of tailoring the features of the guided optical mode to promote an enhanced coupling with the localized modes. The results in terms of sensitivity and resolution demonstrate the advantages of using suspended core fibers with metallic nanowires.
关键词： suspended core fiber,metallic nanowires,finite-element method,optical fiber sensors,D-type fiber,surface plasmon resonance,plasmonic refractive index sensor
更新于2025-09-16 10:30:52
-
Mode-crossing spectroscopy for photonic waveguide characterization
摘要： We report a novel spectroscopic technique to characterize photonic waveguides over more than an octave of wavelength. The technique, called mode-crossing spectroscopy, uses a broadband source and a spectrometer that are coupled to the input and output ends of a series of straight dielectric waveguides via single-mode optical fibers. Measurements of the wavelengths at which multiple modes are degenerate in a single waveguide enable the determination of the refractive index of the core, as well as the waveguide width variation. In addition, mode-dependent losses are reported from 700 nm to 1550 nm using waveguides of varying lengths. The core refractive indices are measured within an error of ±0.5%, waveguide width variation to an accuracy of less than 5 nm, and waveguide propagation losses within an error of ±0.5 dB/cm. Ultrabroadband in situ measurements of loss and index over an octave of bandwidth are crucial for the accurate characterization of photonic integrated circuits and devices, especially those based on precision broadband couplers, interferometers, and resonant cavities.
关键词： propagation losses,mode-crossing spectroscopy,photonic waveguides,waveguide width variation,refractive index
更新于2025-09-16 10:30:52
-
Solar Engineering of Thermal Processes, Photovoltaics and Wind || Radiation Transmission through Glazing
摘要： The transmission, reflection, and absorption of solar radiation by the various parts of a solar collector are important in determining collector performance. The transmittance, reflectance, and absorptance are functions of the incoming radiation, thickness, refractive index, and extinction coefficient of the material. Generally, the refractive index n and the extinction coefficient K of the cover material are functions of the wavelength of the radiation. However, in this chapter, all properties initially will be assumed to be independent of wavelength. This is an excellent assumption for glass, the most common solar collector cover material. Some cover materials have significant optical property variations with wavelength, and spectral dependence of properties is considered in Section 5.7. Incident solar radiation is unpolarized (or only slightly polarized). However, polarization considerations are important as radiation becomes partially polarized as it passes through collector covers.
关键词： absorptance,refractive index,solar radiation,transmittance,extinction coefficient,wavelength,reflectance,collector performance,polarization
更新于2025-09-16 10:30:52
-
[IEEE 2019 41st Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) - Berlin, Germany (2019.7.23-2019.7.27)] 2019 41st Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Ultrasonically Steerable Graded-Index Optical Waveguides for Deep Tissue Light Delivery: Theory and Applications
摘要： Graded-index (GRIN) fibers have been used as implantable optical waveguides to guide light and relay images through the depth of the tissue. We have recently shown that non-invasive ultrasound can generate refractive index gradients within the tissue that form virtual GRIN lenses for imaging and photostimulation deep into the tissue. Here we present the theory behind this idea by analyzing the coupled acoustic-photonic system that models the interaction of light with the ultrasonically modulated medium. We will discuss how changing the parameters of ultrasound will change the confinement and guiding of light within the modulated medium. We will also demonstrate that using a custom-designed cylindrical ultrasonic array, the pressure interference can be controlled to sculpt complex patterns of light in the medium, such as dipole and quadrupole shapes, suitable for multisite imaging. Finally, we will discuss experimental results corroborating the theoretical predictions to generate single and multisite in situ virtual lenses that can be used for fluorescent imaging of mouse brain tissue that expresses green fluorescent protein (GFP).
关键词： refractive index gradients,fluorescent imaging,Graded-index fibers,acousto-optic system,ultrasound,virtual GRIN lenses,photostimulation
更新于2025-09-12 10:27:22
-
Plasmonic Sensors Based onMetal-Insulator-Metal Waveguides for Refractive Index Sensing Applications: A Brief Review
摘要： Optical sensors are widely used for refractive index measurement in biomedical, chemical, and food processing industries and offer high sensitivity to ambient refractive index variations due to the specific field distribution of the resonances. The sensor’s sensitivity is greatly dependent on its material and structure. In this review, we focused on plasmonic refractive index sensors with no fluorescent labelling required. The latest developments on special types of plasmonic structures such as metal-insulator-metal waveguides and their application in refractive index sensors are presented. Moreover, numerous types of plasmonic waveguides, geometries, materials, fabrication processes, and losses related to plasmonic waveguides are explained to provide a better understanding of this topic. The highlight of this review is to discuss the spectral performance of recently reported refractive index sensors by emphasising their sensitivity and figure of merits.
关键词： Lorentzian line shape,Surface plasmon polaritons,Fano resonances,Metal-Insulator-Metal,Plasmonics,refractive index sensor
更新于2025-09-12 10:27:22
-
Mid-infrared sensing properties of a plasmonic metal-insulator-metal waveguide with a single stub including the defects
摘要： A highly sensitive surface plasmon polariton (SPP) based sensor with a simple structure that composes of a metal-insulator-metal waveguide with a single stub including several silver nanorod defects, is designed and numerically investigated using finite element method for the applications of refractive index sensors and temperature sensors. The simulation results show that the existence of silver nanorod defects in the single stub have a great influence on the sensitivity performance, which provides an additional degree to manipulate the system response in the nanometer scale. The refractive index sensitivity can be reached as high as 5140 nm/RIU (RIU is refractive index unit) and the temperature sensitivity is about 2.05 nm/0C, which can be further improved by varying the length of stub (h), radius of defect rod (r) and the number of defects (N) in the stub. The sensing characteristics of the proposed simple structure would pay the way for highly integrated optical circuits for designing nanoscale refractive index sensors and temperature sensors with the single stub including the defects.
关键词： integrated optical circuits,refractive index sensors,silver nanorod defects,metal-insulator-metal waveguide,temperature sensors,surface plasmon polariton,finite element method
更新于2025-09-12 10:27:22
-
[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) - THz Time-Domain Reflection Spectroscopy of KTiOPO <sub/>4</sub>
摘要： Terahertz (THz) radiation has been of increasing interest in the last decades, for security, manufacturing, quality control, medical and security imaging applications. The field requires more efficient and affordable sources and nonlinear upconversion schemes point in this direction. KTiOPO, (KTP) is a well-established material for nonlinear optical applications in the visible and near-IR region thanks to its large transparency, high nonlinear coefficient and damage threshold. Its reasonably low absorption [1, 2] and strong polariton resonances [1] show promise for efficient IR to THz upconversion and Wu et al. [2] recently demonstrated its superiority to LiNbO3 and LiTaO3 in a back to back experiment. However, the complex refractive index needs to be measured before further power scaling is realistic. Terahertz time-domain spectroscopy (TTDS) allows for direct extraction of both the phase and amplitude of the THz electric field and grants the possibility of extracting the optical parameters n and α. In this work, we report on THz time-domain reflection spectroscopy of flux grown KTP from 0.5 to 7 THz at room temperature. The THz-TDS setup used air-filament plasma for generation of the THz radiation and the Pockel's effect in 300um thick GaP for detection. The a and b-axis of a KTP crystal were probed using an HDPE polarizer and rotation of the sample. The geometry of the setup is based on the work of Pashkin et al. [3], where the THz was focused onto the GaP crystal after the 25x15x0.5mm3 sample. Fig.1 shows the refractive index and the absorption coefficient from left to right, respectively. Blue and red color depict the two axes of the KTP crystal. Errors are estimated to: ?n < ±0.025 and ?α <±5 cm?1 (0.5?3THz), ?n < ±0.05 and ?α < ±25 cm?1 (3?5THz), ?n < ±0.1 and ?α < ±50 cm?1 (5?6THz), ?n < ± 0.25 and ?α < ±150 cm?1 (6?7THz). The accuracy in frequency was ≈ 90 GHz or 2 cm?1, limited by the scan time of 11ps. To the best of our knowledge, the convoluted frequency dependent nature of the refractive index has not been measured by direct time-resolved THz measurement before. Earlier spectroscopic studies of KTP have either lacked the possibility of directly extracting the complex refractive index [4] or been limited by absorption of the transmitted signal due to the strong resonances of KTP, limiting the bandwidth to about 2.5 THz [5]. In the regions where the bandwidth of this and older studies overlap, the measurements are similar, giving credibility to both measurements over the whole bandwidth. Besides, the measured resonances in Fig.1 can be related to IR active phonon modes, as seen in, e.g. [6]. This study will be of utmost importance when constructing new devices for optical to THz conversion. We also report a possible new phonon mode at 1.4 THz.
关键词： absorption coefficient,KTiOPO4,refractive index,THz time-domain spectroscopy,Terahertz
更新于2025-09-12 10:27:22
-
Plasmonics-Integrated Ge PIN-Photodetectors
摘要： Refractive index sensors can be designed for high sensitivities at small device foot-print. Using a complementary metal-oxide-semiconductor compatible process for fabrication paves the way to cheap devices enabling integrated biosensors. We present results on combining vertical Ge PIN photodetectors with metallic nanostructures such as Al nanohole arrays placed directly on top of the diode. The interaction of plasmonic resonances and photonic modes such as waveguide modes or optical modes in nanostructured photodetectors can potentially be exploited to design refractive index sensors with very high sensitivities. We discuss how the interplay of material properties and device geometry can be tailored for applications in integrated biosensing.
关键词： CMOS,Plasmonics,Ge PIN-photodetectors,refractive index sensors,biosensors
更新于2025-09-12 10:27:22
-
Voltage-gated optics and plasmonics enabled by solid-state proton pumping
摘要： Devices with locally-addressable and dynamically tunable optical properties underpin emerging technologies such as high-resolution reflective displays and dynamic holography. The optical properties of metals such as Y and Mg can be reversibly switched by hydrogen loading, and hydrogen-switched mirrors and plasmonic devices have been realized, but challenges remain to achieve electrical, localized and reversible control. Here we report a nanoscale solid-state proton switch that allows for electrical control of optical properties through electrochemical hydrogen gating. We demonstrate the generality and versatility of this approach by realizing tunability of a range of device characteristics including transmittance, interference color, and plasmonic resonance. We further discover and exploit a giant modulation of the effective refractive index of the gate dielectric. The simple gate structure permits device thickness down to ~20 nanometers, which can enable device scaling into the deep subwavelength regime, and has potential applications in addressable plasmonic devices and reconfigurable metamaterials.
关键词： optical properties,solid-state proton pumping,refractive index modulation,hydrogen loading,electrochemical hydrogen gating,voltage-gated optics,plasmonics
更新于2025-09-12 10:27:22