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Our research focuses on the development of a surface-plasmon sensor that uses a stationary surface plasmon, referred to as a "nonpropagating mode." This mode is observed when light is incident perpendicularly on a surface-plasmon sensor based on a metal diffraction grating. We performed a comprehensive analysis of the behavior of the surface-plasmon resonances within this nonpropagating mode, employing the rigorous coupled-wave analysis method. Using electron-beam lithography, sputtering, and a lift-off process, we fabricated such a surface-plasmon sensor and evaluated its optical properties rigorously. By combining simulations and experiments, we successfully utilized the nonpropagating mode to detect a liquid medium with a refractive index of 1.70. Simulations show that the nonpropagating mode arises due to a Fano resonance; i.e., to a resonant interaction between a localized surface plasmon generated at the edge of a metal grating strip during normal incidence and a propagating surface plasmon that occurs at the boundary between the metal diffraction grating and the measurement medium. The present results provide useful information for the advancement of surface-plasmon sensing technologies. [ABSTRACT FROM AUTHOR]

High-efficiency integrated photodetectors can assist in future high-speed communication devices for achieving high responsivity characteristics. In this paper, we designed and optimized a graphene/GaAs heterojunction photodetector based on ellipse wall grating-nanowire (EWG-NW) structure. We evaluated the optical and electrical performance of the photodetector between 400 and 800 nm by COMSOL. Compared with graphene/GaAs heterojunction photodetector based on plain structure, our device exhibits enhanced responsivity performance within the visible spectrum at 0 bias voltage. The maximum photocurrent responsivity of 514 mA/W (increased by 56%) and detectivity of 1.16 × 1011 Jones (increased by 41%) are achieved at 725 nm. The mechanism of improvement originates from surface plasmon resonance-enhanced electromagnetic field excited by elliptical wall gratings and metal nanowires in graphene/GaAs heterostructures, thus significantly enhancing carrier separation and transfer. We also analyzed the influence of structural parameter on the absorptivity. The result indicates that the performance of our photodetector can be significantly improved by our design of the plasma structure, which provides a potential scheme for the application of plasma structure optoelectronic devices. [ABSTRACT FROM AUTHOR]

We experimentally investigated the changes in the ethanol concentration of an ethanol--water solution using a polarization property of the (specularly) reflected light associated with surface plasmon resonance (SPR) occurring in an aluminum diffraction grating in a conical mounting. The polarization property, which is observed as a rapid change in the normalized Stokes parameter s3 of the reflected light, can be successfully applied to refractive index sensing: the zero-crossing point of s3 precisely and easily determines the resonance angle θsp at which SPR occurs; s3 in the vicinity of θsp varies largely in response to a small change in the refractive index of a sample. Using the features of the rapid change in s3, we examined the ethanol concentration changes over a wide range from 0 to 100 percent by weight (wt%) through the measurement of θsp. Furthermore, we detected a small amount of ethanol component in water through the measurement of s3 under the angle of incidence fixed at the resonance angle of pure water. [ABSTRACT FROM AUTHOR]

Nanostructured metal–semiconductor-metal photodetectors (MSM-PDs) can assist in future high-speed communication devices for achieving high responsivity characteristics. However, such devices suffer from low responsivity due to low absorption, and the large band gap limits its detection range. Herein, we propose a GaAs-based photodetector with enhanced photoresponse by plasmonic Au-GaAs grating structure. The design of a grating structure on the surface of n-GaAs can excite a plasmon mode to enhance the photoelectric performance of photodetectors. Consequently, under 795 nm incident light irradiation, the grating hybrid detector exhibits a nearly 4.2-fold increase in photocurrent compared to the bare GaAs device. The enhanced absorption can be up to 99% and a specific responsivity of 240 mA/W is realized. These results can thus provide a potential scheme to fabricate high-performance GaAs detector for numerous applications. [ABSTRACT FROM AUTHOR]

Optical biosensors based on grating-coupled surface plasmon resonance (GCSPR) technology are an important research topic in the field of bio-photonics. This paper presents a high-performance and high-sensitivity nanostructured bimetallic GCSPR sensor based on two-dimensional materials. When designing the sensor, the sensitivity, full width at half peak (FWHM) and dip strength of the absorption peak (DS) were considered comprehensively, and the comprehensive evaluation parameter FOM+ is defined by making improvements on the basis of figure of merit (FOM). The performance of the sensor can be judged more comprehensively. The performance of the sensor was further improved by optimizing the structure of the sensor. An ultra-thin gold layer was added on the surface of the silver-based GCSPR sensor, which solves the problem of the easy oxidation of silver metal. We tried to coat graphene oxide two-dimensional nanomaterials on the surface of the bimetallic sensor, and the sensitivity and FOM+ of the sensor reached 350 deg/RIU and 473.23, respectively. This is a great improvement compared with the GCSPR sensor in a previous study, and it can be improved at least 74.7%. This sensor can measure a variety of biological molecules and biological cells with high sensitivity and performance by detecting the change in the refractive index of the solution to be measured. [ABSTRACT FROM AUTHOR]

Although hot-carrier-based photodetection using plasmonic effects has been widely investigated, photodetectors of this type with an external quantum efficiency (EQE) >1% ${ >}1\%$ and an active area of

Multi-wavelength polarizers have many essential applications in optics, quantum communication, Q switch and relating research fields. However, polarizing waveband of the traditional polarizer is restricted in the structure of fibers, which results in finite polarizing wavelengths. In this work, a novel D-shaped microstructure fiber polarizer (DMFP) with metal grating was proposed. Utilizing the abundant harmonic vector characteristics on the surface of metal grating, the DMFP can realize the function of multi-band polarization filtering. Numerical results show that it can achieve three bands of polarization filtering in x-polarized mode from 350 nm to 1600 nm and the resonance wavelengths are periodically modulated by grating. In the meanwhile, by optimizing grating parameters, the number of bands of polarization filtering can be further increased, thus, it fulfills the effective adjustment of polarization filtering. It is promising that metal grating based DMFP has great potential values in the fields of optical filter, communication, and functional devices, etc.

Quantum dot infrared photodetector (QDIP) for detecting infrared rays emitted by the human body has attracted more and more attention from scientific researchers all over the world in the past decade. However, low absorption efficiency at the infrared band in the reported detectors as the major challenge still seriously limits their practical applications. In order to overcome the problem, the QDIP device with a new quantum dot structure together with a rectangular and hole metal grating structure was developed to enhance the light absorption performance through the localized surface plasmon resonance (LSPR). The QDIPs can effectively detect three typical infrared peaks emitted by a human body in the range of 20–53.6 THz with absorption rates of greater than 90%. COMSOL simulation results demonstrate that the optimized QDIP can have the maximum photon absorption rate of 94.1%, which is 2.53 times than that of conventional ones without the metal hole structure. The dramatic increase in absorbance can be attributed to the local coupled surface plasmon effect caused by the novel quantum dot structure and the metal grating structure. It is believed that the study could provide a certain theoretical support for developing high performance infrared detector in the field of human sensing application. [ABSTRACT FROM AUTHOR]

This paper presents the results of numerical analysis by the finite element method of metal circular wire gratings illuminated by plane electromagnetic waves with s-polarization at the microwave and terahertz frequencies. Numerical data made it possible to obtain a closed-form expression for an approximate calculation of the s-transmittance of such gratings in wide ranges of variations in their sizes. The validity and accuracy of this design equation have been tested analytically, numerically, and experimentally. A comparison of the electromagnetic properties of metal gratings with circular and rectangular wires shows some similarity in the behavior of the transmission spectra of both types of gratings depending on the sizes. An extra analytical expression was obtained for circular gratings with a high filling factor. The fabricated prototype of a metal grating with a period of 40 μm demonstrated an extinction ratio of about 120. The results of this study help to better understand the propagation and scattering of EM waves in such 1-D periodic structures at frequencies from 75 to 350 GHz. [ABSTRACT FROM AUTHOR]

Optical biosensors based on grating-coupled surface plasmon resonance (GCSPR) technology are an important research topic in the field of bio-photonics. This paper presents a high-performance and high-sensitivity nanostructured bimetallic GCSPR sensor based on two-dimensional materials. When designing the sensor, the sensitivity, full width at half peak (FWHM) and dip strength of the absorption peak (DS) were considered comprehensively, and the comprehensive evaluation parameter FOM+ is defined by making improvements on the basis of figure of merit (FOM). The performance of the sensor can be judged more comprehensively. The performance of the sensor was further improved by optimizing the structure of the sensor. An ultra-thin gold layer was added on the surface of the silver-based GCSPR sensor, which solves the problem of the easy oxidation of silver metal. We tried to coat graphene oxide two-dimensional nanomaterials on the surface of the bimetallic sensor, and the sensitivity and FOM+ of the sensor reached 350 deg/RIU and 473.23, respectively. This is a great improvement compared with the GCSPR sensor in a previous study, and it can be improved at least 74.7%. This sensor can measure a variety of biological molecules and biological cells with high sensitivity and performance by detecting the change in the refractive index of the solution to be measured.

A novel microfluidic metal grating integrated terahertz sensor has been designed, which is composed of a metal microstructure array-dielectric layer-metal layer, where the dielectric layer is the microfluidic channel carrying the analyte. By adjusting the structural parameters of the metal grating sensor, a highly confined electromagnetic field can be obtained in the microfluidic channel, thereby significantly enhancing the interaction between the analyte and the terahertz wave and improving the terahertz detection sensitivity. The metal grating described in this paper is composed of an array of square holes, which is manufactured using laser micromachining technology, so that the measurement method is simplified and improved. The results show that the addition of different concentrations of carbendazim solution resulted in a redshift of the overall spectrum, with the highest sensitivity reaching 8.773 GHz/mg L−1, which is about eight times more sensitive than the traditional terahertz transmission sensor. The relative error of using this method to determine carbendazim levels in orange juice samples was less than 5.3%. The terahertz time-domain spectroscopy technology combined with the metal grating integrated microfluidic sensor can improve the sensitivity of sample detection and realize the rapid detection and analysis of trace elements. [ABSTRACT FROM AUTHOR]

• Effects of coupling strength on lasing of quantum emitters on a plasmonic metal grating are elucidated. • Plasmonic lasing of the emitters on the metal gratings takes place only in the strong coupling condition. • Stimulated emission for lasing cannot be induced even as population inversion is achieved at high pumping levels. Plasmonic lasers have been actively studied for nearly two decades, but status of coupling between gain emitters and surface plasmon resonance (SPR) modes and its effect on lasing have not been elucidated. In this work, we have a numerical study on photoluminescence/lasing behaviors of emitters in weak and strong coupling with SPR modes on metal gratings based on a four-level two-electron model for the emitters. The strong coupling is achieved by incorporating high-density emitters in the gain medium on metal gratings. It is found that lasing of the emitters on the metal grating takes place only in the strong coupling condition; and the lasing spectral width can be far less than those of the emitters' intrinsic spontaneous emission and the SPR mode. In the weak coupling condition, there is only spontaneous emission; stimulated emission cannot be induced even when population inversion is achieved at high pumping levels. The results indicate important role of strong coupling in realization of plasmonic lasing. [ABSTRACT FROM AUTHOR]

Multi-wavelength polarizers have many essential applications in optics, quantum communication, Q switch and relating research fields. However, polarizing waveband of the traditional polarizer is restricted in the structure of fibers, which results in finite polarizing wavelengths. In this work, a novel D-shaped microstructure fiber polarizer (DMFP) with metal grating was proposed. Utilizing the abundant harmonic vector characteristics on the surface of metal grating, the DMFP can realize the function of multi-band polarization filtering. Numerical results show that it can achieve three bands of polarization filtering in x-polarized mode from 350 nm to 1600 nm and the resonance wavelengths are periodically modulated by grating. In the meanwhile, by optimizing grating parameters, the number of bands of polarization filtering can be further increased, thus, it fulfills the effective adjustment of polarization filtering. It is promising that metal grating based DMFP has great potential values in the fields of optical filter, communication, and functional devices, etc. [ABSTRACT FROM AUTHOR]

Owing to the high contrast of the refractive indices at the end facets of a nanowire, lasing emission can be achieved in an individual nanowire without external, reflected feedback. However, the reflection provided by the end facet is not high enough to lower the threshold gain, especially for nanowires with smaller diameters. This work proposes a novel structure of nanowire laser partially sandwiched in double Ag gratings. Compared to a nanowire with a single metal grating or without a grating, the parallel double metal gratings play the reflector role with higher reflectivity to enhance the round-trip feedback and reduce the threshold gain. The reflective properties are calculated using the finite elements method. Simulation results show that a high reflectivity of more than 90% can be achieved when the number of periods is more than 8. The reflectivity of double gratings is 2.4 times larger than that of the nanowire end facet for large nanowire diameters. When the nanowire has a small diameter of 150 nm, the reflectivity of double gratings is 17 times larger than that of the nanowire end facet. Compared to a single grating, the reflective performance of double gratings is much better. Owing to the highly reflective properties of the double gratings, nanowires partially sandwiched in the double gratings can realize lasing emission at a very low threshold gain, and the period of the grating can be very short to benefit on-chip interconnection systems. [ABSTRACT FROM AUTHOR]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, the wavelength selection characteristics of metal gratings on Si-based blocked-impurity-band (BIB) detectors in the terahertz band were studied by performing experiments and a finite difference time domain (FDTD) simulation. The transmission spectra of metal gratings with different periods on 130 μm intrinsic Si substrates were measured. When the metal grating period increased from 16 to 20 to 32 μm, the peak position of the spectrum moved from 21.71 to 24.50 to 36.59 μm, which is in good agreement with the FDTD simulation results. The structure with the period of 32 μm shows the best wavelength selective transmission characteristics. Then, the bare Si-based BIB devices and metal grating/Si-based BIB hybrid devices with different thicknesses of blocking layers of 2 and 5 μm were fabricated. By covering different periods of metal gratings for the devices with a thicker blocking layer of 2 μm, we obtained more effective wavelength selection characteristics and stronger response spectra enhancement ratios that were about 1.3, 2.4, or 1.9 times. This was mainly due to the localized optical field enhancement effect of the plasmons resonance in metal gratings, which decays exponentially in a vertical direction. Our results demonstrate a new approach for the Si-based BIB detector to realize multiband selective detection applications. [ABSTRACT FROM AUTHOR]

As a novel detection method of CuSO4, terahertz (THz) spectroscopy detection has great application prospects, but the terahertz detection with the tablet method has low sensitivity, and with the metamaterials has complicated manufacture. This work has proposed a high-sensitivity pesticide THz spectroscopic detection method with a novel metal grating. The metal grating was composed of a circular hole array. It was made by laser micromachining technology to provide a simplified but improved measurement and had a strong transmission peak at the 0.4–1.0 THz band. The results indicated that the addition of copper sulfate (CuSO4) solutions to different concentrations caused the transmission peak frequency to shift red. The detection limit was about 103 times higher than that of CuSO4 measured on the polyethylene (PE) film substrate, which reached 0.375 mg/L. The method was applied for detecting CuSO4 in apple and grape, and the relative error was less than 5.8%. The metal grating combined with Terahertz time-domain spectroscopy (THz-TDS) can improve the sensitivity of sample detection and realize the detection and analysis of trace elements. [ABSTRACT FROM AUTHOR]

Subject and purpose. The terahertz frequency range now attracts much attention of researchers and consumers in connection with the wide possibilities of using it for solving a number of problems in science, technology and medicine. Metal gratings with the period shorter than the wavelength are widely used in this range as partially transparent mirrors of lasers and in various quasi-optical devices. Determining the parameters of such gratings is an actual problem. Methods and methodology. The method of experimental determining of the parameters (transmittance and phase shift) of metal gratings consisting of parallel conductors is presented in the paper. A THz laser with a smooth adjustment of the output of laser radiation from the resonator was used as a measuring device. The investigated metal grating serves as the exit mirror of this laser. The dihedral 90° mirror is the second mirror of the laser resonator. Adjustment of feedback is performed by rotating the dihedral mirror around the resonator axis. Laser radiation acquires elliptical polarization as a result of this. The angle of rotation of the dihedral mirror, which ensures the equality of the powers of the E and H polarizations of the laser radiation, is an experimental value for calculating the transmission coefficient of the investigated grating. The polarization ellipse of radiation at this angle of rotation serves as the basis for calculating the phase shift introduced by the grating. Results. An experimental determination of the parameters of metal gratings made on a transparent substrate, having different structures was carried out as an approbation of the method. Comparison of the experimental data with theoretical calculations was carried out. Recommendations for increasing the reliability of measurements and further development of this method were developed during the tests. Сonclusions. The proposed method makes it possible to determine the parameters of one-dimensional metal gratings without using metrological instruments.

A terahertz absorber is designed by integrating the graphene dielectric stack (GDS) above and the metal grating below. The GDS is formed through arranging the graphene monolayer and dielectric film periodically. In the case of impedance matching, two near-unity absorption modes arise as the coupling result of Fabry-Pérot (FP) resonance and surface plasmon polaritons (SPP) resonance. Tuning the chemical potential or the period of GDS, both modes can be shifted. Changing the period or the duty cycle of metal grating, all of the locations and amplitudes of modes along with the peak-peak distance between modes are controllable. Altering the thickness of dielectric slab, these modes move towards the same direction linearly almost. Deviating the normal incidence, the number of absorption modes can be increased. The designed graphene absorber should be useful to multiple targets sensing, photoelectric detection and frequency conversion of nonlinear system. [ABSTRACT FROM AUTHOR]

In this work, the wavelength selection characteristics of metal gratings on Si-based blocked-impurity-band (BIB) detectors in the terahertz band were studied by performing experiments and a finite difference time domain (FDTD) simulation. The transmission spectra of metal gratings with different periods on 130 μm intrinsic Si substrates were measured. When the metal grating period increased from 16 to 20 to 32 μm, the peak position of the spectrum moved from 21.71 to 24.50 to 36.59 μm, which is in good agreement with the FDTD simulation results. The structure with the period of 32 μm shows the best wavelength selective transmission characteristics. Then, the bare Si-based BIB devices and metal grating/Si-based BIB hybrid devices with different thicknesses of blocking layers of 2 and 5 μm were fabricated. By covering different periods of metal gratings for the devices with a thicker blocking layer of 2 μm, we obtained more effective wavelength selection characteristics and stronger response spectra enhancement ratios that were about 1.3, 2.4, or 1.9 times. This was mainly due to the localized optical field enhancement effect of the plasmons resonance in metal gratings, which decays exponentially in a vertical direction. Our results demonstrate a new approach for the Si-based BIB detector to realize multiband selective detection applications.

Owing to the high contrast of the refractive indices at the end facets of a nanowire, lasing emission can be achieved in an individual nanowire without external, reflected feedback. However, the reflection provided by the end facet is not high enough to lower the threshold gain, especially for nanowires with smaller diameters. This work proposes a novel structure of nanowire laser partially sandwiched in double Ag gratings. Compared to a nanowire with a single metal grating or without a grating, the parallel double metal gratings play the reflector role with higher reflectivity to enhance the round-trip feedback and reduce the threshold gain. The reflective properties are calculated using the finite elements method. Simulation results show that a high reflectivity of more than 90% can be achieved when the number of periods is more than 8. The reflectivity of double gratings is 2.4 times larger than that of the nanowire end facet for large nanowire diameters. When the nanowire has a small diameter of 150 nm, the reflectivity of double gratings is 17 times larger than that of the nanowire end facet. Compared to a single grating, the reflective performance of double gratings is much better. Owing to the highly reflective properties of the double gratings, nanowires partially sandwiched in the double gratings can realize lasing emission at a very low threshold gain, and the period of the grating can be very short to benefit on-chip interconnection systems.

We propose a new polarizing color filter (CF) design based on one-dimensional subwavelength grating. The proposed CF only allows the transverse magnetic (TM)–polarized light transmission with the desired colors, and broad palettes can be acquired by only tuning the geometric parameter of period. Specifically, the transmittances of 74.7%, 87.9%, and 84.5% are obtained for the blue, green, and red polarizing filters. Furthermore, the corresponding full width at half-maximum is less than 58 nm for the designed tricolor filters. Theoretical analyses demonstrate that cavity modes and guide mode resonant contribute to the enhanced optical TM polarized light transmission. [ABSTRACT FROM AUTHOR]

Grating coupled surface plasmon resonance (GCSPR) sensors with wavelength modulation are widely used in many fields, but the low sensitivity holds their practical applications. Here we theoretically analyze the sensitivity limit of GCSPR sensors, provide design methods to reach the maximum sensitivity and the way to increase the sensitivity limit. The theoretical analysis shows that metal gratings with periods as large as possible should be used and the incident angle should be set close to 90∘ in order to maximize the sensitivity for a certain detecting wavelength, moreover the sensitivity limit increases as the detecting wavelength increases. Experimentally, we prepare three gratings with periods of 314 nm, 1470 nm and 6733 nm by stripping commercial optical discs or photolithography. The measured sensitivities of the sensors based on these gratings are 319.96 nm/RIU, 1477.74 nm/RIU and 2077.26 nm/RIU, respectively. The sensitivity achieved in this article is much higher than existing ones due to the use of design method following the theoretical analysis. This work paves the way for the optimal design of GCSPR sensors.

Subject and purpose. The terahertz frequency range currently attracts much attention due to the wide possibilities of its application for solving a number of problems in science, technology, and medicine. In this range, metal gratings with the period shorter than the wavelength are widely used as partially transparent mirrors of lasers and in various quasi-optical devices. The determination of the parameters of such gratings is an actual problem. Methods and methodology. The method of experimental comparison of the parameters (losses and transmittance) of metal gratings consisting of parallel conductors is presented in the paper. A THz laser with a smooth adjustment of the output of laser radiation from the resonator was used as a measuring device. The investigated metal grating serves as the exit mirror of this laser. The dihedral 90° mirror is the second mirror of the laser resonator. The adjustment of feedback is performed by rotation of the dihedral mirror around the resonator axis. The angle of rotation of the dihedral mirror, which provides the maximum power of laser radiation, characterizes the transmittance coefficient of the investigated grating. The value of the maximum power of laser radiation characterizes the magnitude of the losses in the investigated grating. This allows one to compare the grating parameters experimentally without the use of metrological instruments. Results. An experimental comparison of the parameters of metal gratings with different structures was carried out as an approbation of the method. Recommendations for the increase of the measurement reliability and further advancement of this method were developed. Conclusions. The proposed method is an effective tool for comparing the transmittance and loss factors in one-dimensional metal gratings for their control and culling. In addition, this method can serve as a measuring device, when reference gratings with known parameters are used for comparison.

We introduce a new two-step method to fabricate silver-silicon gratings that can excite surface plasmons efficiently. The grating structure was firstly created on a flat silicon substrate by single-pulse nanosecond laser interference lithography. Next, a silver layer of 50 nm was evaporated on the silicon substrate. With proper laser energy, a silver-silicon grating with a period of 1120 nm and depth of 18 nm was successfully fabricated. This grating can produce high-quality surface plasmon resonance (SPR) peaks at various incident angles. Moreover, a SPR sensor was experimentally demonstrated based on the silver-silicon grating, which had high sensitivity of 961.5 nm/RIU and figure of merit of 60. Our method is an efficient way to fabricate periodically nanostructured metals at high speed and low cost. [ABSTRACT FROM AUTHOR]

A D-shaped optical-fiber refractive index sensor based on surface plasmon resonance is reported. Rigorous coupled-wave analysis was used to simulate the numerical modeling. The influences of different metal grating parameters on the coupling efficiency were studied and an optimal phase match was obtained. The results show that wavelength sensitivity of the proposed optical fiber sensor is as high as 0.925 μm/RIU for refractive index values from 1.35 to 1.43 with a high linearity value of 0.997. The reported structure may promote the development of high-performance biochemical sensing devices. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • We simulated a 465 nm GaN-based Vertical-Cavity Surface-Emitting Laser (VCSEL) with Al rectangular grating. • A 30 percent increase in effective radiated power compared to conventional structure. • Investigation of the surface plasmon resonance effect of Au, Ag and Al on different wavelength bands. • Review of surface plasmon mode dependence on the structural parameters of grating such as period and depth. Abstract Based on the research of surface plasmon (SP) applied to Vertical-Cavity Surface-Emitting Lasers (VCSEL), we proposed a new 465 nm GaN-based VCSEL to enhance illumination by deposit Al rectangular grating onto p-i-n layer. Meanwhile, an increase in the effective radiated power was obtained by the control of a surface plasmon mode, which depends strongly on the structural parameters such as material, period, depth and dipole location. Compared to conventional structure, we have a 30% improvement in effective radiated power. Such advantages make surface Al-grating be an alternative low-cost and simple technique used in SP-coupled VCSEL for the blue range. [ABSTRACT FROM AUTHOR]

This work proposed a miniaturized nanowire laser with high end-facet reflection. The high end-facet reflection was realized by integrating an Ag grating between the nanowire and the substrate. Its propagation and reflection properties were calculated using the finite elements method. The simulation results show that the reflectivity can be as high as 77.6% for a nanowire diameter of 200 nm and a period of 20, which is nearly three times larger than that of the nanowire without a metal grating reflector. For an equal length of nanowire with/without the metal grating reflector, the corresponding threshold gain is approximately a quarter of that of the nanowire without the metal grating reflector. Owing to the high reflection, the length of the nanowire can be reduced to 0.9 μm for the period of 5, resulting in a genuine nanolaser, composed of nanowire, with three dimensions smaller than 1 μm (the diameter is 200 nm). The proposed nanowire laser with a lowered threshold and reduced dimensions would be of great significance in on-chip information systems and networks.

Although a metal grating structure is usually fabricated for momentum-matching a surface plasmon polariton (SPP) with photon, for surface plasmon (SP) coupling application in a light-emitting diode (LED), localized surface plasmon (LSP) on such a structure also plays an important role. We numerically study the LSP resonance behaviors, including the localized resonance behavior of counter-propagating SPP interference, of an Ag grating on GaN. It is found that the resonance behaviors of LSP are controlled not only by the geometry of a grating ridge, but also by grating period, particularly when the grating period is small. In a grating with sharp ridge, large ridge height or width, LSP features of dense charge distributions around the boundaries between ridges and connecting valleys exist. The spectral positions of such LSP features are weakly dependent on the ridge width. Among such features, those with their mode field oscillations across a ridge and hence distributions in an extended space around the ridge can more strongly couple with the quantum wells of an LED. Because of the short coverage range of SPP evanescent field, the localized resonance feature caused by counter-propagating SPP interference has a shorter coupling range. For LED application, an LSP mode with field oscillation across a ridge is preferred. [ABSTRACT FROM AUTHOR]

Graded grating has been commonly used to trap the plasmonic surface waves of different frequencies, called “trapped rainbow.” The physical origin is believed that the group velocity of the surface waves is decreased to zero at the trapping point because the surface wave vector can be increased to an infinite value by the graded grating. However, this theory needs to be further modified according to our results. We demonstrated the surface terahertz (THz) waves near the cutoff frequency of a grating could not be coupled into the propagated modes, but are reflected back, which means the surface THz wave vector cannot be increased to an infinite value. Hence, the trapped rainbow is actually only a kind of reflection. Furthermore, one single deeper groove is enough to reflect most of the surface THz waves, which could be an easier way to control the reflection and transmission of the surface THz waves and realize the compact integrated slowing waveguide, band-pass filter, surface THz wave switch, and reflector. [ABSTRACT FROM AUTHOR]

In this paper, we derive the analytical expression for the sensitivity of grating-based surface plasmon resonance (SPR) sensors working in wavelength interrogation. The theoretical analysis shows that the sensitivity increases with increasing wavelength and is saturated beyond a certain wavelength for Au and Ag gratings, while it is almost constant for Al gratings in the wavelength range of 500 to 1000 nm. More importantly, the grating period (P) and the diffraction order (m) dominate the value of sensitivity. Higher sensitivity is possible for SPR sensors with a larger grating period and lower diffraction order. At long wavelengths, a simple expression of P/|m| can be used to estimate the sensor sensitivity. Moreover, we perform experimental measurements of the sensitivity of an SPR sensor based on an Al grating to confirm the theoretical calculations.

A polarizing beam splitter (PBS) based on a two-layer metal grating operating in the near-infrared wavelength region is proposed. The PBS structure comprises a high refractive index dielectric layer and a subwavelength grating layer, which increases the transmittance and the extinction ratio of the grating. Using the rigorous coupled-wave analysis (RCWA) method, the parameters of the proposed polarizing beam splitter were simulated and optimized. The results show that transmission of more than 97% for the transverse-magnetic (TM) wave polarization and reflection of more than 98% for the transverse-electric (TE) wave polarization are achieved within the 1220–1690 nm wavelength range. The corresponding maximum extinction ratios for the transmittance and reflectance are 33 dB and 34 dB, respectively. When compared with a single-layer PBS grating, the proposed two-layer structure shows greater design flexibility. The proposed PBS shows potential for application to devices such as routers and switches. [ABSTRACT FROM AUTHOR]

A new high-performance plasmonic absorber based on the metal-insulator-metal grating nanostructure is proposed and numerically studied. The effect of geometric parameters of grating stripe and insulator layer on light absorption is investigated. Four main absorption bands with efficiencies nearly 100 % are obtained by modulating duty cycle of the metal grating, which show redshift with the increased stripe width. The physical mechanism responsible for the absorption is discussed based on distributions of the magnetic field and the Poynting vector and is found to be different for the four bands. It is also found that perfect absorption of the nanostructure can be achieved when the insulator layer thickness ranges from 20 to 70 nm; meanwhile, the resonant wavelength corresponding to perfect absorption can be tuned and it shifts towards red side with the increase of the grating thickness when the air slit is narrow. The proposed highly efficient light absorber exhibits a very simple geometrical structure and is easy to be fabricated, which has potential applications in photonic device, such as photodetectors, sensors, and so on. [ABSTRACT FROM AUTHOR]

• A simple broadband absorber consisting of 2D Au square grating on graphene-SiO 2 film and Au substrate is proposed. • The absorber achieve nearly perfect absorption with absorption of exceeding 90 % spanning a broad range from100 nm to 700 nm). • The absorber is polarization and angle insensitive for incident light even at large angle. • The absorption are well explained by Rayleigh anomaly, cavity resonance, surface plasmon polaritons and magnetic polaritons. A broadband metamaterial absorber (BMA) based on a thin metamaterial nanostructure consisting of 2D Au square grating on graphene-SiO 2 film and Au substrate is proposed and designed. The optimized structure can achieve nearly perfect absorption with absorption of exceeding 90 % spanning a broad range from deep UV light to visible light (100 nm−700 nm). The excitation of Rayleigh anomaly (RA), cavity resonance (CR), surface plasmon polaritons (SPPs) and magnetic polaritons (MPs) are responsible for nearly perfect broadband absorption, which have been analysed clearly by finite-difference time-domain (FDTD) method and the LC circuit model. Furthermore, the BMA is polarization and angle insensitive for incident light even at large angle. This proposed BMA not only has a simple geometry and ordinary metal-based material composition, but also shows a high performance in both bandwidth and absorptivity, suggesting that great potential in solar cell and photodetector applications. [ABSTRACT FROM AUTHOR]

Compact surface plasmon resonance (SPR) sensors are highly demanded due to their small size, low cost, and wide application scenarios compared with benchtop sensors. To realize high-precision spectral or angular analysis, most compact SPR sensors need spectrometers or rotation stages, which increase the cost of the device. We demonstrate a low-cost and compact SPR sensor by utilizing a single grating as a coupler and a disperser. The polychromatic light emitted from a light-emitting diode was coupled to surface plasmon modes by a grating made from a digital versatile disc-recordable disc. The light was dispersed by the same grating and collected by a linear charge-coupled device. The real-time detection of the SPR spectra and the resonant wavelengths was realized by homemade software based on the laboratory virtual instrument engineering workbench. By measuring different concentrations of glucose solution and sodium chloride solution, we obtain a high refractive index (RI) resolution of 5.52 × 10 − 5 RI unit. This compact SPR sensor can be applied in the areas of food safety, environmental monitoring, medical diagnosis, and so on. [ABSTRACT FROM AUTHOR]

A terahertz band-stop filter was proposed based on the transmission properties of parallel metal plates with corrugated grating grooves. The influence of distance w between two corrugated plates and mismatch length l of two plates were simulated and experimentally studied. The bandwidth of the stop-band increases with the decreasing of w. The filter can be optimized by adjusting l. The optimal filter can be achieved by adjusting l to half the period of grating grooves. [ABSTRACT FROM AUTHOR]

Detection of polarisation of microwave signals using infrared thermography is described in this paper. A metal grating consisting of parallel, equally spaced metallic strips is placed in between a microwave source (antenna) and a microwave absorption screen for permitting the determination of direction of electric field vector (polarisation). Very low frequency modulation of the microwave source is added to permit lock-in thermography which enhances thermal resolution. In case of linear polarisation when the metallic strips of the grating are parallel to the direction of electric field vector, the temperature rise on the screen as observed by an infrared camera, is minimum. On the other hand if the metallic strips are perpendicular to the electric field vector the temperature rise observed on the screen is maximum. The orientation of the grid is changed by rotating the grid about a central axis perpendicular to its plane. With each different orientation of the grid a change in temperature rise is observed on the screen. In case of circular polarisation the temperature rise on the absorption screen is almost independent of the grid orientation i.e. there is negligible change in temperature rise with each different orientation of the grid, as the electric field strength perpendicular to grid strips is almost constant for all grid orientations, corresponding to an axial ratio of unity. While in case of elliptical polarisation the temperature change is appreciable depending on the axial ratio. The proposed method is validated on linearly, circularly and elliptically polarised patch antennas radiating at 8 GHz. Simulation is carried out in CST MICROWAVE STUDIO (CST MWS2013) and a good agreement between simulated and experimental (thermographic) results is observed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Large-scale uniform plasmonic gratings were fabricated by laser processing. • The depth of the silicon grating can be controlled by the chemical etching time. • The gold–silicon grating can efficiently excite surface plasmon resonance. • The sensitivity and resolution of the SPR sensor are 707.4 nm/RIU and 0.00053 RIU. • The SPR sensor was applied to monitor BSA solutions in real time. Surface plasmon resonance (SPR) sensors based on nanostructures have received much attention in recent years for constructing portable devices. A main barrier for their widespread use is that traditional nanofabrication methods are expensive and time-consuming. Here, we demonstrate a mask-free, low-cost and high-production method to fabricate large-scale uniform plasmonic gratings with variable depths. Regular amorphous silicon strips were firstly triggered on the silicon surface via scanning by a cylindrically focused femtosecond laser. Subsequently, the laser processed silicon was etched by alkaline to form highly regular gratings, whose depth is flexible to be adjusted by controlling the etching time. After depositing a 53 nm gold film, the fabricated plasmonic gratings are able to efficiently generate SPR absorption dips as observed in the reflection spectra. Moreover, a SPR sensor was built based on the optimal grating, which has a sensitivity of 707.4 nm/RIU, a figure of merit of 13.37 RIU−1 and a refractive index resolution of 5.3 × 10 - 4 RIU. The combination process of bovine serum albumin and the gold grating was also studied. The fabrication method introduced here paves the way for mass-production of high-quality plasmonic gratings. The SPR sensor can be potentially used in applications like medical diagnoses, biotechnology, security and food safety. [ABSTRACT FROM AUTHOR]

Surface-plasmon-polariton (SPP) wave excitation in a composite structure obtained by depositing a columnar thin film (CTF) on a metal (silver) substrate decorated periodically by an array of rectangular grooves was analyzed using the rigorous coupled-wave approach. The SPP wave is excited as a Floquet harmonic of different orders by light incident from different directions, the incidence plane being the same as the grating plane. But, in some instances, the SPP wave appears to be excited as a doublet, i.e., a Floquet harmonic of the same order at two closely spaced angles of incidence, the excitation being less efficient for one angle of incidence than for the other. The characteristics of the SPP wave are affected by the vapor incidence angle chosen to deposit the CTF. [ABSTRACT FROM AUTHOR]

Whereas noble metal films deposited directly onto an undulated photosensitive polymer exhibit plasmon-mediated resonant transmission of free-space waves accompanied by excess losses of approximately 40 %, adequate hard baking of the photosensitive polymer, together with pre- and post-deposition of nanometer-thick ZnS or MgF dielectric interfacial layers, restores excellent propagation conditions for the long-range plasmon mode, reducing resonant transmission excess losses to 10 %, and creating the conditions for the experimental evidence of the long-sought plasmonic anomalous reflection phenomenon. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel surface plasmon resonance (SPR) fiber sensor with an axisymmetric sub-wavelength metal grating layer was proposed. [•] The sensitivity S and quality factor Q of the SPR dip are investigated. [•] The proposed sensor has a sensitivity of 13,000nm/RIU (refractive index unit) at refractive index range from 1.3 to 1.4. [Copyright &y& Elsevier]