Absorptive Mode Research Articles

Dual-band and spectrally selective infrared absorbers based on hybrid gold-graphene metasurfaces

In this paper, we propose a dual-band and spectrally selective infrared (IR) absorber based on a hybrid structure comprising a patterned graphene monolayer and cross-shaped gold resonators within a metasurface. Rooted in full-wave numerical simulations, our study shows that the fundamental absorption mode of the gold metasurface hybridizes with the graphene pattern, leading to a second absorptive mode whose properties depend on graphene’s electrical properties and physical geometry. Specifically, the central operation band of the absorber is defined by the gold resonators whereas the relative absorption level and spectral separation between the two modes can be controlled by graphene’s chemical potential and its pattern, respectively. We analyze this platform using coupled-mode theory to understand the coupling mechanism between these modes and to elucidate the emergence and tuning of the dual band response. The proposed dual-band device can operate at different bands across the IR spectrum and may open new possibilities for tailored sensing applications in spectroscopy, thermal imaging, and environmental monitoring.

Hercules, Vampires, and the Opera of Attractions

ABSTRACT Opera’s specter has long haunted film and more recently, film haunts opera productions seeking to entice new audiences. Patrick Morganelli’s opera Hercules vs. Vampires (2010) harnesses the tension between live and recorded media. In this production, singers deliver their lines in loose synchronization with the film’s characters, dubbing over the original’s visuals with operatic voices. By encouraging an attentive rather than absorptive mode of consumption, Hercules vs. Vampires restores to both opera and film a joy and effervescence made possible through the pungent postmodern incongruencies of the high art of opera and the popular Italian sword and sandal film.

Single-band Series Absorptive Common-mode Noise Filter

A Single-band Series Absorptive Common Mode Noise Filter (ACMF) is proposed. The ACMF is embedded in a four-layer printed circuit board (PCB) and consists of three parts: a Reflective Common Mode Noise Filter (RCMF), a matching circuit, and an absorber. The RCMF is designed using mushroom-type resonators. The matching circuit is designed using meander lines to reduce the size of the filter dimensions. The absorber of the Common Mode noise (CM) is a series resistor. The designed operating frequency is 2.45 GHz. The simulation results are as follows: the insertion loss of CM (Scc21) is -22.49 dB at the frequency of 2.61 GHz, the return loss of CM (Scc21) is -18.62 dB at the frequency of 2.5 GHz, while the integrity of the Differential Mode signals (DM) can be maintained with a very small insertion loss (Sdd21) of -1 dB at the frequency range of 0-8 GHz, and the achieved Absorption Efficiency (AE) is 93% at the frequency of 2.54 GHz. The proposed ACMF dimension is 10.3 x4.6 mm. The fractional bandwidth is 19%. The measurement results of the fabricated ACMF do not deviate significantly the simulation results. They are as follows: Scc21 is -17.87 dB at the frequency of 2.31 GHz, Scc11 is -20.87 dB at the frequency of 2.38 GHz, Sdd21 is -2.8 dB at the frequency range of 0–8 GHz, the Absorption Efficiency is 97% at the frequency of 2.32 GHz, and the fractional bandwidth is 17%. Therefore, the results of the ACMF design carried out by simulation can be implemented into a fabricated ACMF with measurement results similar to the calculation results in the design.

Michael Fried’s theatricality and the practice of painting

ABSTRACT This article is the posthumous publication of a lecture given by the artist and academic Beth Harland (1964–2019). It was originally presented at a conference on Theatricality, at Lancaster University in 2017. This paper begins by working through the arguments of Michael Fried, to situate the key terms of theatricality and absorption, before then turning to contemporary painting practice (with notable reference to the work of Tomma Abts) to advance her reading of ‘an absorptive mode of address within contemporary painting’. This article also situates Harland's own art practice.

A Dual-Beam Wideband Filtering Patch Antenna With Absorptive Band-Edge Radiation Nulls

A dual-beam filtering patch antenna with two absorptive band-edge radiation nulls and four reflective stopband radiation nulls is proposed. By loading a pair of T-shaped metallic strip underneath the radiating patch, a modified TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sub> mode with TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> -like radiation pattern is obtained, which combines with the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode of the radiating patch, generating a wide operating band with symmetrical dual-beam radiation pattern. Two reflective radiation nulls are generated in both upper and lower stopbands for suppressing the out-of-band radiation. Through embedding two pairs of shorted small patch in the radiating patch, one absorptive radiation null combining with one absorptive resonant mode is produced at each band edge to absorb the band-edge incident energy, leading to a reduced reflection and sharp roll-off at both band edges, and therefore, the transceiver can be protected. With a total height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.038~\lambda _{0}$ </tex-math></inline-formula> , a prototype is designed, fabricated, and measured, showing a −10 dB impedance bandwidth from 4.63 to 6.10 GHz with sharp band-edge roll-off, two radiation beams directed at ±40° with an in-band gain of 6.0 dBi, and high out-of-band suppression of over 15 dB.

Tunable dual-wavelength absorption switch with graphene based on an asymmetric guided-mode resonance structure.

We propose a tunable dual-wavelength absorption (TDWA) switch based on an asymmetric guided mode resonance (AGMR) structure. A TDWA switch consists of a graphene layer and an AGMR structure sandwiched by cap and slab layers on a buffer/silicon substrate. The AGMR structure adds a smaller grating unit cell next to a larger one, exciting a second resonance close to but distinct from the first resonance. For switching, the TDWA between an absorptive or reflective mode with each on-/off-state, the chemical potential of graphene is tuned from 0.0 eV to 0.6 eV. For the absorptive mode, two absorption peaks of ≥ 96.2% are separated by 23 nm, both having an on-off ratio of ∼15.52. For the reflective mode, two reflectance peaks of ≥ 93.8% are separated by 23 nm, having on-off ratios of 15.56 dB and 18.95 dB. The maximum on-off ratios of 39.98 dB and 34.55 dB are achieved near the reflectance peaks. Both the period of the AGMR and the cap thickness alters the two peak wavelengths linearly, while the grating width of the AGMR varies nonlinearly from 17 nm to 28 nm. The buffer excites a weak Fabry-Perot resonance, which interacts with the TDWA structure, the result of which is the two absorption peaks are varied. Finally, as the incidence angle of light increases up to 5.3°, the distance of the two peak wavelengths is tuned from ∼22 nm to ∼77 nm with ≥ 96% absorption or ≥ 93% reflectance in each mode.

Reconfigurable Filter for Bandpass-to-Absorptive Bandstop Responses

A frequency tunable filter with a bandpass-to-absorptive bandstop reconfigurable characteristic is studied, designed and validated theoretically and experimentally. To control the filter bandwidth and impedance matching performance, variable capacitors are used in each external and internal coupling structure, and, by using equivalent circuits, the required frequency responses of two different modes are obtained. Two single-pole double-throw switches embedded in the transmission lines running from the source to the load accommodate external coupling structures to control the operational mode of the proposed filter. All commercially available electronics such as switches and varactor diodes are placed on the microstrip line layer, and the frequency-tunable substrate integrated waveguide (SIW) resonators are coupled to the transmission line through coupling slots. In the absorptive bandstop mode, the stopband is tuned from 1.83 GHz to 2.49 GHz, while the passband can be tuned from 1.86 GHz to 3.3 GHz in the bandpass mode. In both modes, more than 10 dB in return loss over the frequency tuning range of interest has been achieved. Theoretical, simulated, and measured results are in good agreement, which validate the proposed filter structure.

SEMESTER

This article proposes an analysis of Billy Mullaney’s performance SEMESTER, through the dual perspective of theatricality and attention. For SEMESTER, Mullaney is memorizing a semester’s worth of quantum mechanics lectures and then performing them. Although he does not know quantum mechanics, he has managed to memorize it in a very disciplined way, which he calls ‘a choreographic way of learning’. Questions about spectatorship, attendance and the value of theatre are generated in SEMESTER, this article argues. More specifically, it shows how theatricality, understood as the theatrics, exaggerations and basic mechanisms of theatre, is what keeps audiences on their seats watching and Mullaney delivering the lecture. Theatricality is considered here bound to how SEMESTER simultaneously and excessively demands as well as sabotages an absorptive mode of attention, which results in a process of noticing and displacing practices of attention that are habitual to lecture and theatre settings. Theatricality is thus examined through the perspectives of attention and absorption, finally proposed as a form of labour that signals a critical reconsideration of the value of theatre and of attendance as such.

DQF J-RES NMR: Suppressing the singlet signals for improving the J-RES spectra from complex mixtures.

Two-dimensional J-RESolved spectroscopy (J-RES) finds routine use in metabolomics for reducing signal overlap as it separates chemical shift and multiplet information along two frequency axes. However, only magnitude mode of the experiment is practical which prevents exploitation of its full resolving power. Tailing from high-intensity metabolite peaks often obscure nearby low-intensity metabolite peaks which leads to ambiguity in assignment of metabolites. Absorptive mode J-RES spectroscopy offers better-resolving power but comes at the cost of either sensitivity or complicated post-processing. Quite often for certain complex mixtures such as bio-fluids some components of the mixture display intense singlet signals which dominate the whole spectrum resulting in less reliable detection of weaker metabolite signals. Multi-frequency presaturation could suppress these intense singlets but will also remove the useful weaker multiplet peaks which are either totally eclipsed with the intense singlets or very close in frequency. We show that by using a double quantum filter (DQF) in magnitude mode J-RES technique, the intensity of the strong singlet metabolite peaks can be reduced relative to the intensity of the sparsely present multiplet metabolite signals. This approach leads to the identification of many weak intensity multiplet peaks which are otherwise undetected due to their overlap with intense singlet peaks in regular J-RES as well as 1D 1H spectra. Although the improved intensity of most of the weaker peaks relative to the strong singlet peaks is observed, some multiplets can disappear due to the delay-dependent modulation of the signals by the DQF. A few DQF J-RES spectra recorded with different DQF delays, therefore, produce better assignment when analyzed together. The technique is demonstrated on a mixture of eight compounds, human urine, and plant extract samples.

Field enhancement and spectral features of hexagonal necklaces of silver nanoparticles for enhanced nonlinear optical processes.

The nonlinear properties of hybrid metallic-dielectric systems are attracting great interest due to their potential for the enhancement of frequency conversion processes at nanoscale dimensions. In this work, we theoretically and experimentally address the correlation between the near field distribution of hexagonal plasmonic necklaces of silver nanoparticles formed on the surface of a LiNbO3 crystal and the second harmonic generation (SHG) produced by this nonlinear crystal in the vicinities of the necklaces. The spectral response of the hexagonal necklaces does not depend on the polarization direction and is characterized by two main modes, the absorptive high-energy mode located in the UV spectral region and the lower energy mode, which is strongly radiant and extends from the visible to the near infrared region. We show that the spatial distribution of the enhanced SHG is consistent with the local field related to the low energy plasmon mode, which spectrally overlaps the fundamental beam. The results are in agreement with the low absorption losses of this mode and the two-photon character of the nonlinear process and provide deeper insight in the connection between the linear and nonlinear optical properties of the hybrid plasmonic-ferroelectric system. The study also highlights the potential of hexagonal necklaces as useful plasmonic platforms for enhanced optical processes at the nanoscale.

On-Chip Integration of Photodetector and Sensor: A Multimodal Photonic Device for Sensing Applications

In this paper, we present the design and development of a novel miniaturized multimodal photonic sensor, which can be configured dually as a photodetector in the absorptive mode and as a pyro-detector in the photonic sensor mode. In this paper, we have fabricated a polyvinyl alcohol (PVA) photoactive layer-based MEMS structure and analysed the effect of effective inter-electrode separation on the photoactive area of the photoactive film using the four quadrant metal-semiconductor polymer-metal (MSM) design on the photoresponsivity of this device in terms of photoconductive and the pyroelectric responses. Our analysis reveals that the interdigitated electrode configuration is best suited for photoconductive response while the cross-electrode configuration with large effective inter-electrode spacing is advantageous for pyroelectric measurement in the infrared region. Here, the unique design of this device offers the choice of electrode configurations that enables the utility of this device in various regions of the electromagnetic spectrum. In this regard, we demonstrate the optical detection of localized surface plasmon resonance of immobilized gold nanoparticle monolayer in the visible region, employing the absorptive mode and the detection of the spectroscopic signature of RDX and TNT molecules ( $134~\mu \text{g}$ /cm $^{2})$ in the midinfrared region using photonic sensor mode. This paper paves a way for designing a low-cost PVA-based miniaturized sensor architectures with huge potential for on-chip real-time detections in various fields of scientific and commercial applications.

Biologically Active Secondary Metabolites from the Fungi.

Many Fungi have a well-developed secondary metabolism. The diversity of fungal species and the diversification of biosynthetic gene clusters underscores a nearly limitless potential for metabolic variation and an untapped resource for drug discovery and synthetic biology. Much of the ecological success of the filamentous fungi in colonizing the planet is owed to their ability to deploy their secondary metabolites in concert with their penetrative and absorptive mode of life. Fungal secondary metabolites exhibit biological activities that have been developed into life-saving medicines and agrochemicals. Toxic metabolites, known as mycotoxins, contaminate human and livestock food and indoor environments. Secondary metabolites are determinants of fungal diseases of humans, animals, and plants. Secondary metabolites exhibit a staggering variation in chemical structures and biological activities, yet their biosynthetic pathways share a number of key characteristics. The genes encoding cooperative steps of a biosynthetic pathway tend to be located contiguously on the chromosome in coregulated gene clusters. Advances in genome sequencing, computational tools, and analytical chemistry are enabling the rapid connection of gene clusters with their metabolic products. At least three fungal drug precursors, penicillin K and V, mycophenolic acid, and pleuromutilin, have been produced by synthetic reconstruction and expression of respective gene clusters in heterologous hosts. This review summarizes general aspects of fungal secondary metabolism and recent developments in our understanding of how and why fungi make secondary metabolites, how these molecules are produced, and how their biosynthetic genes are distributed across the Fungi. The breadth of fungal secondary metabolite diversity is highlighted by recent information on the biosynthesis of important fungus-derived metabolites that have contributed to human health and agriculture and that have negatively impacted crops, food distribution, and human environments.

Objective and perceptual evaluation of distance-dependent scattered sound effects in a small variable-acoustics hall.

Performance spaces are characterized by a complex sound field, due to the presence of absorptive and diffusive surfaces. In situ evaluations of the acoustic effects that these surfaces have on the objective acoustic parameters and on sound perception have not yet been fully understood. To this aim, acoustic measurements have been performed in a variable-acoustic concert hall, the Espace de Projection, at the Institut de Recherche et Coordination Acoustique/Musique. These measurements have allowed the effects of one single wall to be determined. A diffusive and a reflective condition of one of the long lateral walls of the shoebox-like hall have been considered, while the other surfaces have been fixed in absorptive mode. Measurements have been carried out at different distances from the test wall, using an artificial head and an array of omnidirectional microphones. Objective acoustic parameters, such as early decay time, reverberation time (T30), clarity (C80), definition (D50), and interaural cross correlation, have been compared between both conditions. In addition to the objective indexes, a perceptual evaluation has been performed using listening tests that had the purpose of determining the maximum distance from a diffusive surface at which acoustic scattering effects are still audible.

Absorptive lasing mode suppression in ZnO nano- and microcavities

We conclusively explain the different lasing mode energies in ZnO nano- and microcavities observed by us and reported in literature. The limited penetration depth of usually used excitation lasers results in an inhomogeneous spatial gain region depending on the structure size and geometry. Hence, weakly or even nonexcited areas remain present after excitation, where modes are instantaneously suppressed by excitonic absorption. We compare the effects for ZnO microwires, nanowires, and tetrapod-like structures at room temperature and demonstrate that the corresponding mode selective effect is most pronounced for whispering-gallery modes in microwires with a hexagonal cross section. Furthermore, the absorptive lasing mode suppression will be demonstrated by correlating the spot size of the excitation laser and the lasing mode characteristic of a single ZnO nanowire.

Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience

“Pure shift” NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording.

Resonant intersubband plasmon induced current in InGaAs quantum wells on GaAs

We present measurements of the current enhancement due to the coupling of two intersubband plasmons in In0.05Ga0.95As quantum wells. With changing bias, an emissive and an absorptive intersubband plasmon mode cross attractively and trapped electrons in the ground state gain enough energy from the plasma wave to be lifted up to the second subband, where they can contribute to the current. This effect can be directly observed as an increase of 33% in the current. A magnetic field applied parallel to the growth direction allows a control of the strength of the intersubband plasmon coupling up to a quenching.

The switch of intestinal Slc26 exchangers from anion absorptive to HCO3− secretory mode is dependent on CFTR anion channel function

CFTR has been recognized to function as both an anion channel and a key regulator of Slc26 anion transporters in heterologous expression systems. Whether this regulatory relationship between CFTR and Slc26 transporters is seen in native intestine, and whether this effect is coupled to CFTR transport function or other features of this protein, has not been studied. The duodena of anesthetized CFTR-, NHE3-, Slc26a6-, and Scl26a3-deficient mice and wild-type (WT) littermates were perfused, and duodenal bicarbonate (HCO(3)(-)) secretion (DBS) and fluid absorptive or secretory rates were measured. The selective NHE3 inhibitor S1611 or genetic ablation of NHE3 significantly reduced fluid absorptive rates and increased DBS. Slc26a6 (PAT1) or Slc26a3 (DRA) ablation reduced the S1611-induced DBS increase and reduced fluid absorptive rates, suggesting that the effect of S1611 or NHE3 ablation on HCO(3)(-) secretion may be an unmasking of Slc26a6- and Slc26a3-mediated Cl(-)/HCO(3)(-) exchange activity. In the absence of CFTR expression or after application of the CFTR(inh)-172, fluid absorptive rates were similar to those of WT, but S1611 induced virtually no increase in DBS, demonstrating that CFTR transport activity, and not just its presence, is required for Slc26-mediated duodenal HCO(3)(-) secretion. A functionally active CFTR is an absolute requirement for Slc26-mediated duodenal HCO(3)(-) secretion, but not for Slc26-mediated fluid absorption, in which these transporters operate in conjunction with the Na(+)/H(+) exchanger NHE3. This suggests that Slc26a6 and Slc26a3 need proton recycling via NHE3 to operate in the Cl(-) absorptive mode and Cl(-) exit via CFTR to operate in the HCO(3)(-) secretory mode.

Long-period fiber-grating-based bandpass filter using self-aligned absorptive core mode blocker

We present an all-fiber bandpass operation by using an absorptive core mode blocker self-aligned between two long-period fiber gratings (LPFGs). The first LPFG converts the core mode into the cladding modes at resonant wavelengths, and the second LPFG operates in reverse direction. The core mode blocker attenuates the nonresonant core mode from the first LPFG but passes the resonant cladding modes to the second LPFG. This bandpass filter exhibits a passband of 20-nm bandwidth at a center wavelength of 1542 nm with nonresonant light suppression greater than 15 dB. Thermal tuning coefficient is found to be −0.51 nm/°C for the temperature range from 10 to 70 °C.

Optical fiber temperature sensor using a pair of nonidentical long-period fiber gratings for intensity-based sensing

We propose and demonstrate a new technique for intensity-based fiber temperature sensing based on long-period fiber grating pairs having different temperature coefficients and an absorptive core mode blocker placed between the two gratings. The constructed fiber sensor exhibits a bandpass filter response that varies with the temperature. A light-emitting diode is used as the input light source to convert the wavelength shift into an optical intensity change. A photodetector is used to measure the output intensity as a temperature-encoded signal.

Cleavage of phosphate diesters mediated by Zn(II) complex in Gemini surfactant micelles

The cleavage of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) catalyzed by the Zn(II)–biap (biap: N , N -bis(2-ethyl-5-methylimidazole-4-ylmethyl)aminopropane) complex has been investigated spectrophotometrically in a micellar solution of cationic Gemini surfactant 16-2-16 [bis(hexadecyldimethylammonium)ethane bromide] and CTAB (hexadecyltrimethylammonium bromide) at 25 ± 0.1 ° C . The experimental results reveal that a higher rate of acceleration (about 2016-fold) of HPNP cleavage promoted by the Zn(II)–biap complex has been observed in the 16-2-16 micellar solution in comparison with the background rate ( k 0 ) of HPNP spontaneous cleavage at 25 °C. Reaction rates of HPNP cleavage in CTAB micellar solutions are only about 40% of that in Gemini 16-2-16 micelles under comparable conditions. In addition, the cleavage rates of HPNP in Gemini micelles and in CTAB micelles are respectively 29.5 times and 12 times faster than that in aqueous buffer. Especially, a “sandwich absorptive mode” has been proposed to explain the acceleration of HPNP cleavage in a cationic micellar solution.