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Holography with Photochromic Diarylethenes
摘要： Photochromic materials are attractive for the development of holograms for different reasons: they show a modulation of the complex refractive index, meaning they are suitable for both amplitude and phase holograms; they are self-developing materials, which do not require any chemical process after the light exposure to obtain the final hologram; the holograms are rewritable, making the system a convenient reconfigurable platform for these types of diffractive elements. In this paper, we will show the features of photochromic materials, in particular diarylethenes in terms of the modulation of a transparency and refractive index, which are mandatory for their use in holography. Moreover, we report on the strategies used to write binary and grayscale holograms and their achieved results. The outcomes are general, and they can be further applied to other classes of photochromic materials in order to optimize the system for achieving high efficiency and high fidelity holograms.
关键词： holography,refractive index,diarylethenes,photochromism,CGH
更新于2025-09-11 14:15:04
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Dewetting Metal Nanofilms—Effect of Substrate on Refractive Index Sensitivity of Nanoplasmonic Gold
摘要： The localized surface plasmon resonance (LSPR) sensitivity of metal nanostructures is strongly dependent on the interaction between the supporting substrate and the metal nanostructure, which may cause a change in the local refractive index of the metal nanostructure. Among various techniques used for the development of LSPR chip preparation, solid-state dewetting of nano?lms offers fast and cost effective methods to fabricate large areas of nanostructures on a given substrate. Most of the previous studies have focused on the effect of the size, shape, and inter-particle distance of the metal nanostructures on the LSPR sensitivity. In this work, we reveal that the silicon-based supporting substrate in?uences the LSPR associated refractive index sensitivity of gold (Au) nanostructures designed for sensing applications. Speci?cally, we develop Au nanostructures on four different silicon-based ceramic substrates (Si, SiO2, Si3N4, SiC) by thermal dewetting process and demonstrate that the dielectric properties of these ceramic substrates play a key role in the LSPR-based refractive index (RI) sensitivity of the Au nanostructures. Among these Si-supported Au plasmonic refractive index (RI) sensors, the Au nanostructures on the SiC substrates display the highest average RI sensitivity of 247.80 nm/RIU, for hemispherical Au nanostructures of similar shapes and sizes. Apart from the signi?cance of this work towards RI sensing applications, our results can be advantageous for a wide range of applications where sensitive plasmonic substrates need to be incorporated in silicon based optoelectronic devices.
关键词： refractive index sensitivity,metal nano?lm,localized surface plasmonic resonance,dewetting
更新于2025-09-11 14:15:04
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Analysis of the Processing‐Pressure Dependent Refractive Index of Polycarbonate by Transmission Measurements of Glass‐Filled Specimen
摘要： In this study, the influence of pressure during processing on the refractive index (RI) of polycarbonate (PC) was investigated by transmission measurements on glass-filled samples with a spectrometer. In order to isolate the pressure dependence of the RI from other influencing parameters such as cooling rate, orientation and stress states, the samples were prepared in a pressure-specific volume-Temperature (pvT) instrument under constant cooling rate and temperature history and without shear effects. Subsequently, the RI was determined at the intersection of the dispersion curves of the glass and the polymer by evaluating the wavelength of the maximal transmission of the samples. The mean RI over the entire cross section of the sample is determined by the transmission measurements without complex sample preparation. The investigations show that the RI of PC increases by 3.26 E-6 per bar with increasing pressure.
关键词： glass-filled specimen,processing-pressure,refractive index,polycarbonate,transmission measurements
更新于2025-09-11 14:15:04
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Single shot high bandwidth laser plasma probe
摘要： A novel scheme to probe a plasma’s ion acoustic resonances in single shot high-bandwidth pump-probe experiments is proposed. Our design utilizes concepts similar to smoothing by spectral dispersion; however, we propose a method of applying the bandwidth to the probe that avoids the effects of angular dispersion. Theoretical modeling and ?uid simulations of the interaction are presented and compared. The results show the possibility of recovering a plasma’s full complex index of refraction in a single shot pump-probe experiment. This wavelength dependent refractive index is directly related to the plasma’s particle distribution function and can be used to recover plasma parameters including electron and ion temperatures, electron density, and plasma ?ow velocity.
关键词： electron density,plasma,refractive index,high-bandwidth,plasma flow velocity,ion acoustic resonances,pump-probe experiments
更新于2025-09-11 14:15:04
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U-shaped photonic quasi-crystal fiber sensor with high sensitivity based on surface plasmon resonance
摘要： A U-shaped external photonic quasi-crystal fiber (PQF) sensor based on surface plasmon resonance is proposed for refractive index (RI) sensing. The advantages of sensing with metal/liquid surface plasmon polariton (SPP) mode are summarized. The gold/liquid SPP mode is excited and used for sensing in the U-shaped external PQF, which can detect a small variation of the analyte RI. The maximum sensitivity of the sensor is 33600 nm/RIU, and the average sensitivity is 21643.75 nm/RIU within the detection RI range of 1.420–1.436. The U-shaped PQF sensor will provide a new design idea for the RI sensor with high sensitivity.
关键词： U-shaped photonic quasi-crystal fiber,surface plasmon resonance,refractive index sensing,high sensitivity
更新于2025-09-11 14:15:04
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Design of Microdisk-Shaped Ge on Si Photodetector with Recess Structure for Refractive-Index Sensing
摘要： In this paper, we introduce a disk-shaped Ge-on-Si photodetector for refractive-index difference sensing at an operating wavelength of 1550 nm. For the implementation of a small-scale sensor, a Ge layer was formed on top of a Si layer to increase the absorption coefficient at the expense of the light-detection area. Additionally, the sensor had a ring waveguide structure along the edge of the disk formed by a recess into the inner part of the disk. This increased the interaction between the dominant optical mode traveling along the edge waveguide and the refractive index of the cladding material to be sensed, and conclusively increased detection sensitivity. The simulation results show that the proposed sensor exhibited a detection sensitivity of >50 nm/RIU (Refractive Index Unit), a quality factor of approximately 3000, and a minimum detectable refractive index change of 0.95 × 10?2 RIU with a small disk radius of 3 μm. This corresponds to 1.67 times the sensitivity without a recess (>30 nm/RIU).
关键词： refractive index sensor,disk resonator,silicon on insulator,germanium photodetector
更新于2025-09-11 14:15:04
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Dual-wavelength plasmonic perfect absorber suitable for refractive index sensing
摘要： In this paper, a plasmonic perfect absorber (PPA) based on metal-insulator-metal-insulator-metal (MIMIM) structure has been designed for refractive index sensing of glucose solutions (analyte) and then a new method has been proposed for fast, low-cost, and easy measurement of sensor’s sensitivity. Simulation results show that the absorption spectrum of the proposed sensor has two resonance peaks that with an increase in analyte refractive index, both of them are red-shifted. In our proposed measurement technique, two conventional single-wavelength lasers (with wavelengths of 1050 nm and 1750 nm) are used for vertical plane wave light illumination on the structure. Then, the absorbed powers at 1750 nm (A2) and 1050 nm (A1) wavelengths are calculated and variation of the absorption ratio (A2/A1) due to change of analyte refractive index would be introduced as the sensitivity of sensor (S = Δ(A2/A1)/Δn). Obtained results show that the increase of analyte refractive index from n = 1.312 to n = 1.384 will result in an increase of sensor’s sensitivity from 9.3/RIU to 33.475/RIU.
关键词： A new definition of sensitivity,Absorption ratio,Plasmonic perfect absorber,Refractive index sensor
更新于2025-09-11 14:15:04
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Label-free detection of ambient refractive index based on plasmonic Bragg gratings embedded resonator cavity sensor
摘要： In this work, we incorporated Bragg gratings in the standard ring resonator design in order to enhance the sensitivity of the refractive index sensor. The transmission spectrum and electric field distribution of the device are simulated using the finite element method (FEM). The numerical simulation results obtained from the transmission spectrum are used to examine the sensing characteristics of the structure. The size of the grating teeth has a significant effect on the intensification of surface plasmons which in turns enhances the interaction between the ambient medium and the light. Bragg grating embedded resonator cavity design has the best sensitivity, FOM and Q-factor of 1680 nm/RIU, 48 and 48.4, respectively which is much higher than several previously reported values.
关键词： metal-insulator-metal waveguide,Plasmonics,Bragg grating,Refractive index sensor,finite element method
更新于2025-09-11 14:15:04
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Packaged Negative Axicon Optical Fiber Probe and Bessel Beam Interferometry for Refractive Index Measurement of Hazardous Liquid Samples
摘要： In this work, we demonstrate the packaging of an optical fiber negative axicon probe generating Bessel beam and its application in the measurement of refractive index (RI) of hazardous liquids. The negative axicon probe is placed inside cascaded capillary tube capped with a glass coverslip of RI ~1.52 and thickness ~0.15 mm. The packaged probe, connected to a broadband source through an optical circulator, is dipped in different hazardous liquid samples. The reflected light from the air-glass as well as the glass-liquid interface couples to the negative axicon probe and interferes with the reference beam generated at the air-negative axicon interface. The interference spectra recorded in a spectrometer through the circulator are analyzed applying Fast Fourier Transform (FFT). The FFT helps to separate and measure powers reflected from the different interfaces which are used to solve the Fresnel equation for estimating the RI of hazardous liquid samples, such as HCl, H2SO4 solutions. The resolution achieved is 1*10-4 ± 0.0005. The probe can be useful to measure RI of liquid samples remotely and in hazardous environmental condition.
关键词： refractive index,Bessel beam,Negative Axicon,optical fiber,hazardous liquid
更新于2025-09-11 14:15:04
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Theoretical and Experimental Investigation of an All-Fiber Waveguide Coupled Surface Plasmon Resonance Sensor With Au–ZnO–Au Sandwich Structure
摘要： In this paper, we proposed an all-fiber waveguide coupled surface Plasmon resonance (SPR) sensor which was designed and fabricated with Au-ZnO-Au sandwich multi-layer structure. Based on the transfer matrix method (TMM), the theoretical modeling of the proposed sensor structure was investigated. The influence of the layer thickness on the transmission spectrum of the sensor was studied numerically, in order to optimize each layer thickness, leading to sensitivity enhancement in the infrared spectral range. Meanwhile, an experimental testbed for the refractive index measurement was implemented based on the proposed all-fiber waveguide coupled SPR sensor. Using this waveguide coupled SPR sensor, the refractive index sensing was realized with a sensitivity enhancement of 7%—131% compared with conventional SPR sensors.
关键词： refractive index sensing,optical fiber,Surface plasmon resonance,waveguide coupled,sensitivity
更新于2025-09-11 14:15:04