Aluminum Grating Research Articles

Polarization Property Associated with Surface Plasmon Resonance in a Palladium Thin-Film Coated Aluminum Grating in a Conical Mounting and Its Application to Hydrogen Gas Detection.

We have investigated a polarization property of the (specularly) reflected light from an aluminum grating, coated with a palladium (Pd) thin-film on its surface. The polarization property, which is associated with surface plasmon resonance (SPR), and occurs in the Pd thin-film on the aluminum grating in a conical mounting, is observed as a rapid change in the normalized Stokes parameter s3, around the resonance angle, θsp, at which point, SPR occurs. The sensing technique used the rapid change in s3 to allow us to successfully detect a small change in the complex refractive index of the Pd thin-film layer upon exposure to hydrogen gas, with a concentration near the lower explosion level. Experimental results showed that the sensing technique provided a sensitive and stable response when the Pd thin-film layer was exposed to gas mixtures containing hydrogen at concentrations of 1 to 4% (by volume) in nitrogen.

Вплив тонких плівок Se на ефективність збудження поверхневих плазмон-поляритонів в срібних та алюмінієвих голографічних решітках

In this paper, we study the effect of thin selenium layers up to 3 nm thick on the efficiency of excitation of surface plasmon polaritons (SPPs). The Se layers were deposited by thermal evaporation in vacuum on the surface of silver and aluminum gratings. Gratings with a groove profile close to sinusoidal and a period equal to а = 694 nm were formed on chalcogenide photoresist films using interference lithography. Then they were coated with layers of the above metals with a thickness of 80–85 nm using thermal evaporation. Registration of SPP excitation on the gratings was carried out by measuring the angular dependences of the intensity of specularly reflected or diffracted p-polarized He-Ne laser radiation on a stand mounted on the basis of a G5M goniometer and a Fedorov table. An atomic force microscope was used to determine the shape of the groove profile and the depth of the grating relief. It has been found that for silver gratings with a relief modulation depth h/a less than the optimal value (which ensures maximum plasmon absorption, i.e., the maximum efficiency of SPP excitation), selenium deposition causes significant degradation of the plasmon resonance: a decrease in the depth of the minimum of the total reflection Rpt (i.e., a decrease in the efficiency of plasmon absorption), a shift of the Rpt minimum towards larger angles, and its widering. For silver gratings with h/a greater than the optimal value, a similar shift and widering of the plasmon resonance is also observed. However, at the same time, a significant deepening of the Rpt minimum is recorded, that is, an increase in the efficiency of SPP excitation. Such changes in the plasmon characteristics also appear on aluminum gratings, however, in this case the effect of the selenium layers is weaker by an order of magnitude. The obtained results allow us to propose a method of correcting the plasmonic characteristics of silver gratings in which the value of h/a is higher than optimal.

Investigation into Ethanol Concentration Changes of Ethanol–Water Solution Using Polarization Property Associated with Surface Plasmon Resonance in Aluminum Grating in Conical Mounting

Investigation into Ethanol Concentration Changes of Ethanol–Water Solution Using Polarization Property Associated with Surface Plasmon Resonance in Aluminum Grating in Conical Mounting

Tailoring nanowire lasing modes via coupling to metal gratings

Tailoring the emission of plasmonic nanowire-based lasers represents one of the major challenges in the field of nanoplasmonics, given the envisaged integration of such devices into on-chip all-optical circuits. In this study, we proposed a mode selection scheme based on distributed feedback, achieved via the external coupling of single zinc oxide nanowires to an aluminum grating, which enabled a quasi-single mode lasing action. The nano-manipulation of a single nanowire allowed for a reliable comparison of lasing emission characteristics in both planar (i.e., a nanowire on the metallic substrate) and on-grating configurations. We found that, by varying the orientation of the nanowire on the grating, only when the nano-cavity was perpendicular to the ridge direction, an additional peak emerged in the emission spectrum on the low-energy side of the gain envelope. As a consequence of the fulfillment of the Bragg condition, such a peak was attributed to a hybrid mode dominating the mode competition. Simulation results showed that the hybrid mode could be efficiently waveguided along the nanowire cavity and supported by localized plasmon polaritons building up at the raised features (“fences”) on top of metal grating ridges. Moreover, the hybrid mode was found to experience an extra reflectance of nearly 50% across the grating periods in addition to that provided by nanowire end facets.

Extraction of Attenuation Parameter in Periodic Shorted Reflectors of One-Port SAW Resonator Using Scattering Matrix Approach

In this work, the well-known scattering matrix approach to the design of one-port surface acoustic wave (SAW) resonators is adapted toward extraction of the coupling-of-modes (COM) attenuation parameter, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> for Rayleigh SAW propagation on a periodic shorted aluminum grating. The attenuation close to resonance inside the reflectors of the one-port SAW resonator is extracted by matching the measured conductance of the resonator to its version calculated from the experimentally measured interdigital transducer (IDT) scattering coefficients, intrinsic substrate parameters, and geometry of the resonator. Based on the extracted value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> , it was observed that the proposed method could predict the unloaded <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor of the resonator at a minor discrepancy of ~7.02%. At the same time, since the proposed method utilizes the measured IDT scattering coefficients to consider the effect of IDT losses on the measured conductance of the resonator, it offers a convenient scheme to directly extract the attenuation of SAW contributed by the reflectors of the device through numerical means while operating purely in the frequency domain. The proposed method could be applied to quantify the increase in attenuation caused by viscous damping of SAW inside sensing film-coated reflectors of one-port SAW resonator sensors, and thereby, aid to optimize the sensing film thickness to deploy these devices for high-resolution frequency-based sensing applications.

Opto-electrical and polarization performance of a mesa-structured InGaAs PIN detector integrated with subwavelength aluminum gratings.

Polarization detection in the short-wave infrared (SWIR) region presents broad applications in target-background contrast enhancement, underwater imaging, material classification, etc. A mesa structure can prevent electrical cross talk due to its intrinsic advantages, making it potentially suited to meet the need for manufacturing smaller-sized devices to save cost and shrink volume. In this Letter, mesa-structured InGaAs PIN detectors with a spectral response ranging from 900 nm to 1700 nm and a detectivity of 6.28 × 1011 cm·Hz1/2/W at 1550 nm and -0.1 V bias (room temperature) have been demonstrated. Furthermore, the devices with subwavelength gratings in four orientations show obvious polarization performance. Their extinction ratios (ERs) can reach 18:1 at 1550 nm and their transmittances are over 90%. Such a polarized device with a mesa structure could realize miniaturized SWIR polarization detection.

Electric Field Enhancement Effect of Aluminum Grating With Nanosecond Pulsed Laser Irradiation

Aluminum grating has wide applications in laser systems and photoelectric equipment. Research on the laser damage characteristics of aluminum grating has guiding significance and application value for improving the laser damage resistance. The aim of this study is to investigate the characteristics of damage induced by nanosecond pulsed lasers on the aluminum grating. To better understand the laser damage characteristics of aluminum grating, herein, Maxwell’s equations were numerically solved according to the finite difference time-domain method, and the electric field model of 1,064 nm Gaussian laser damage aluminum grating was established. The simulation results showed that the light field is modulated by the grating; furthermore, the maximum value of the electric field occurred at the ridge of the grating when the laser is irradiated vertically. Analysis suggested that the electric field distribution is in accordance with the laser energy distribution, and the distribution region of the maximum electric field is a vulnerable location. To further verify the local electric field enhancement effect, based on the 1-on-1 laser damage measurement method, an experimental study of the nanosecond laser (@1,064 nm, 6.5 ns) damage to the aluminum grating was carried out. Moreover, the damage morphology was analyzed using a scanning electron microscope (SEM), and the simulation results showed good agreement with the experimental results.

Fabrication and performance analysis of infrared InGaAs polarimetric detector with complete coverage of superpixel-structured grating

Polarization detection is widely used in various fields due to its unique advantages in increasing the dimensionality of information detected effectively. Here, we analyzed the effects of signal crosstalk among pixels and grating morphology on the polarization performance of SWIR InGaAs detector integrated with superpixel-structured subwavelength aluminum grating by test and FDTD simulation. Based on the analysis results, a superpixel-structured subwavelength aluminum grating was integrated on InGaAs FPA to realize the full coverage of grating on a 320 × 256 SWIR InGaAs detector. The detector has a responsivity non-uniformity of less than 6%. The pixel operability is better than 99.99% and peak detectivity reaches 5.99 × 1011 cm·Hz1/2/W at room temperature. An extinction ratio of up to 18:1 at 1064 nm is realized.

Anisotropy of DNA molecule detection and enhancement by GaN-based electronic sensor.

An electrical characterization approach with a newly, to the best of our knowledge, defined electrical anisotropy (η) was proposed to characterize and enhance the anisotropy signals of DNA molecules. This approach utilizes L-shaped aluminum gratings on a gallium nitride PiN electronic sensor system to adjust and improve the η signals. Using this approach, the η signals of DNA molecules can be adjusted more easily and efficiently by changing the electrical parameters of the sensor. For instance, the η modes of DNA were enhanced more than 22 times with the change of the incident power and the reverse bias voltage of the PiN structure.

Дослідження ефективності збудження поверхневих плазмон-поляритонів на алюмінієвих гратках з урахуванням дифрагованого випромінювання

Detailed studies of the efficiency of excitation of surface plasmon-polaritons (SPP) on aluminum gratings with a period a = 694 nm, which exceeds the incident wavelength of λ = 632,8 nm, have been carried out. The gratings relief depth (h) range was 6–135 nm. Research samples were formed on As40S30Se30 chalcogenide photoresist films using interference lithography and vacuum thermal deposition of an opaque aluminum layer about 80 nm thick. An atomic force microscope was used to determine the groove profile shape and the grating relief depth. The study of the SPP excitation features was carried out on a stand mounted on the basis of a G5M goniometer and an FS-5 Fedorov stage by measuring the angular dependences of the intensity of specularly reflected and diffracted p-polarized radiation of He-Ne laser. When determining the SPP excitation efficiency, the resonance values of both specular reflection and reflection in the -1st DO were taken into account. It was found that the dependence of the integral plasmon absorption on the grating modulation depth (h/a) is described by a somewhat asymmetric curve with a wide maximum, the position of which corresponds to an h/a value of about 0.07 and a half-width of about 0.123. This allows to excite SPP with an efficiency ≥ 80% of the maximum value on the gratings with the 0,05-0,105 h/a range. The half-width of the plasmon minimum of the reflection in the -1st DO is less than in the specular reflection, which can increase sensitivity of sensor devices when registering the shift of the minimum from angular measurements. The dependence of the half-width of the SPP reflection minima on the grating modulation depth is close to quadratic. In the investigated h/a range (from 0.009 to 0.194), the maximum dynamic range of the reflection coefficient is two orders of magnitude and is achieved in specular reflection for gratings with h/a ≈ 0.075.

Tunable and plasmon-enhanced four-wave mixing on an aluminum grating

We report on wavelength-tunable and plasmon-enhanced four-wave mixing (4WM) on an Al grating. When surface plasmons (SPs) are excited at the first and second pump wavelengths, the electromagnetic fields near the grating surface are dramatically enhanced and the corresponding 4WM signals are enhanced by factors of 177 and 42 compared with off resonant conditions. The maximum output power of the 4WM signal is as high as 25 nW. Moreover, by fixing the first pump beam to the SP excitation angle and tuning the second pump beam from 1200 to 1550 nm, we obtain a tunable and enhanced 4WM output from 539 to 600 nm. This setup can potentially be applied to frequency conversion, beam steering and dispersion control.

Semi-permeable resonant aluminum gratings for structural coloration in transmission.

The novel type of diffraction gratings consists of a semi-permeable corrugated aluminum film with periods supporting first-order diffraction in the visible wavelength range. These gratings exhibit coloring of the transmitted zeroth order due to excitation of surface plasmons. The hue depends on the angle of incidence and may be adjusted by varying the grating period. Manufactured samples with motifs containing grating arrays of different periods demonstrate a wide range of achievable colors. The fabrication process is suited for scale-up to large area production, since the replication on plastic foils can be implemented as a cost-effective roll-to-roll process. These gratings have practical applications as security features, since they are fully compatible to widely used rainbow holograms.

Nanoimprinting metal-containing nanoparticle-doped gratings to enhance the polarization of light-emitting chips by induced scattering

Polarized radiative luminous semiconductor chips have huge application potential in many highly value-added fields. The integration of a subwavelength grating is recognized to be the most promising method for the development of polarized chips, but still faces the challenge of low polarized radiative performance. This paper describes a proposal for, and the development of, a scattering-induced enhanced-polarization light-emitting diode chip by directly nanoimprinting a metal-containing nanoparticle-doped grating onto the top surface of a common flip chip. The rate at which quantum-well light emission is used by the developed polarized chip is improved by more than 30%. More attractively, the doped scattering nanoparticles function as a scattering-induced polarization state converter that is sandwiched in between the top aluminum grating and the bottom silver reflector of the chips. The originally non-radiated light, with an electric-field vector parallel to the grating lines, is reflected back and forth inside the sandwich until it changes to the perpendicular vibration mode and is radiated outside the chip. Therefore, the polarization extinction ratio is greatly improved, compared to undoped samples.

ЗАЛЕЖНІСТЬ ЕФЕКТИВНОСТІ ЗБУДЖЕННЯ ПОВЕРХНЕВИХ ПЛАЗМОН-ПОЛЯРИТОНІВ ВІД ГЛИБИНИ РЕЛЬЄФУ АЛЮМІНІЄВОЇ ГРАТКИ

An experimental study of the excitation of surface plasmonpolaritons (SPP) on aluminum diffraction gratings with a fixed period of 519 ± 0,5 nm and a variable modulation depth h/a(where h is the grating depth, and a – its period) was carried out. Gratings with a sine-like profile were formed on vacuum chalcogenide photoresists films by interference lithography and covered with an opaque aluminum film. A Dimension 3000 Scanning Probe Microscope was used to determine the grating groove profile. The characteristics of the SPP were determinedfor28 gratings with h/a ranged from 0,018 to 0,20, by measuring the dependences of specular reflection of p-polarized radiation of He-Ne laser on the angle of incidence, which was defined as the angle between the normal to the substrate plane and the laser beam. It was found that there is an optimal grating relief depth for a given excitation wavelength, which provides the maximum transfer of the incident electromagnetic wave energy to the surface plasmon-polariton mode.The dependence of the SPP excitation efficiency on the grating modulation depth has a maximum at a relatively small value of h/a ≈ 0.086. At such modulation depth the absorption of electromagnetic radiation of the incident laser beam is more than two orders of magnitude higher than the absorption of aluminum film with flat surface at the same angle of incidence. The position of the angle of resonant excitation of SPP practically does not change from h/a= 0,018 up to h/a ≈ 0,06. With further increase of h/a it begins to shift to the region of smaller incidence angles, with the rate of the shift accelerating gradually. With an increase of h/a, a decrease in the depth of the plasmon resonance and a significant increase in its half-width are also observed, and the dependence of the half-width of the SPP band on the modulation depth is close to quadratic. Using this grating-coupled SPP technique, the estimated thickness of air-formed oxide layer on the aluminum gratings surface (about 3.9 nm) is close to the value obtained in the literature with a set of complicated techniques.

Parallel Polarization Illumination with a Multifocal Axicon Metalens for Improved Polarization Imaging.

Polarization imaging is an important branch of the microscopy technique that can provide additional information and enhanced contrast. The illumination system of a polarization microscope enables many different polarizations but makes the setup bulky, complicated, and slow. Here, we design and fabricate an ultrathin planar axicon metalens that also enables parallel illumination with different polarizations. Our results reveal a diffraction-limited size and high degree of linear polarization. To verify our approach, we accurately map the polarization angle of an aluminum grating, which is used as a polarizer. Furthermore, we demonstrate that elliptical polarization can be generated without additional design. A single metalens has the same capabilities as a conventional illumination module containing a polarizer, compensator, and rotation-stage/optical modulator. In addition, our device has the potential to enable rapid super-resolution polarization imaging. The new method could be useful in many applications and areas, including, e.g., materials research and biomedicine.

Electrically tunable polarization‐independent visible transmission guided‐mode resonance filter based on polymer‐dispersed liquid crystals

AbstractA tunable polarization‐independent narrowband guided‐mode resonance filter (GMRF), consisting of a 2D subwavelength aluminum grating and a polymer‐dispersed liquid crystal (PDLC) layer is demonstrated. By taking advantage of 2D structural phase matching, the guided mode resonance occurs under both transverse electric and magnetic guided modes, we obtained polarization‐independent bandpass filtering without loss of polarization, as verified via finite‐difference time‐domain simulations. Meanwhile, we use PDLC as a property adjustable material, when the orientation of the PDLC was controlled with an applied voltage, the transform mode of the incident light changed, which enabled easy refractive index tunability. A finite element method was used to design and characterize a tunable GMRF with a transmission resonance wavelength that can be shifted from 492.31 to 505.94 nm, based on the PDLC refraction. The relationship between resonance wavelength and the PDLC refractive index exhibits a linear curve, the shape and peak of the resonance transmission curve is stable during adjustments. With the design of this structure parameter, the GMRF transmission efficiency was over 82% in the visible band.

Spectral emissivity design using aluminum-based hybrid gratings.

We propose a strategy to design infrared emitters with predefined spectral response using aluminum gratings as building blocks. We begin by identifying 3 target spectra with resonances in the 7-15 µm wavelength range. Next, we use FDTD simulations and interpolation to create a reference library of gratings relating their structural parameters to attributes of their infrared spectra. By using a search algorithm based on minimization of errors in spectral attributes, we identify gratings from this library corresponding to peaks in the target spectra. Finally, we discuss an approach for designing hybrid structures from these gratings to generate each of the 3 target spectra. This strategy can be extended to design structures with complex spectral responses.

Experimental Demonstration of the Effect of Magnetic Polaritons on the Radiative Properties of Deep Aluminum Gratings

Despite the abundant theoretical studies of magnetic polaritons (MPs) in tailoring the radiative properties of nanostructures, experimental investigation of MPs in deep metal gratings is still lacking. This work experimentally demonstrates the excitation of MP from several microfabricated aluminum gratings in the mid-infrared region by measuring the specular reflectance (zeroth-order diffraction) of the specimen using a Fourier-transform infrared (FTIR) spectrometer. The rigorous coupled-wave analysis (RCWA) and an LC-circuit model are employed to elucidate the mechanism of various resonant modes and their coupling effect. The influence of incidence angle, plane of incidence, polarization, and the trench depth on the spectral reflectance is also discussed. Moreover, the MP dispersion for off-plane layout has been investigated and demonstrated for the first time. The insight gained from this work may facilitate future design and applications of subwavelength periodic structures with desired radiative properties.

Research on polarization performance of InGaAs focal plane array integrated with superpixel-structured subwavelength grating.

Polarization imaging has become a widely-applied detection technique, due to the capabilities of enhanced image contrast and object recognition. Here, we demonstrate 320 × 256 InGaAs focal plane array (FPA) integrated with superpixel-structured subwavelength aluminum grating. An extinction ratio of up to 19:1 at 1310 nm is realized, which indicates a good capability of near-infrared polarization detection. Theoretical simulation shows a fairly high extinction ratio for such superpixel structure. This difference between the actual extinction ratio and the theoretical extinction ratio is further discussed by analyzing the effects of the alignment deviation and structural parameter deviations induced during the actual process. Moreover, the imaging results show that the fabricated polarimetric InGaAs FPA presents a more obvious profile for artificial objects, compared to the conventional detector. Such FPAs integrated with superpixel-structured grating are very promising for high performance polarization imaging in the short wavelength infrared band.

Polarization-Independent Narrowband Near-Perfect Absorption Based on One-Dimension Embedded Aluminum Grating

In the past, the polarization-insensitive absorption is realized mainly employing the two-dimensional periodic structure of fourfold rotational symmetry, which greatly increases the manufacturing complexity and cost. Here, we present the numerical design of a polarization-independent near-perfect absorber incorporating one-dimensional embedded aluminum grating. The absorption peaks near 99% at 520-nm wavelength for different polarization angles are achieved. The underlying mechanism associated with the resonance is attributed to the magnetic polariton resonance and the cavity-mode resonance for TM and TE polarization, respectively, and further explained by the inductor-capacitor circuit model and the eigen equation of cavity mode. Furthermore, the effects of geometrical parameters of the nano-cavity on the absorption performance are discussed. The proposed structure may provide a new way to achieve polarization-independent absorption with one-dimensional meta-surface, which has broad applications in plasmonic sensors, photo-detectors, and so on.