Μm Light Research Articles

Cerium-Modulated Zinc Oxide for enhanced Photoelectrochemical Non-Enzymatic biosensing of Cholesterol: An experimental and First Principle Analysis

Herein, we synthesized CexZn1-xO (x = 0.00, 0.01, 0.02, and 0.03) using the wet chemical method. The investigation explores photoelectrochemical (PEC) biosensors for enzyme-free detection of cholesterol, employing Ce0.03Zn0.97O (CZO3)/Nickel Foam (NF) as the active material. The investigation revealed notable enhancements in sensitivity for cholesterol detection, with a recorded activity of 2.812 mA.mM−1.cm−2, marking a twofold increase in comparison to dark mode (1.37 mA.mM−1.cm−2). The Limit of Detection (LOD) was determined to be 17 µM (light) and 28 µM (dark), while the Limit of Quantification (LOQ) was measured at 54 µM (light) and 98 µM (dark) in 0.1 M KOH solution. These findings demonstrate a linear detection range spanning from 80 µM to 2 mM. Ab-initio calculations based on Density Functional Theory (DFT) were carried out on 101 surfaces of both pristine ZnO and CZO3 to understand how the doping affected the pristine ZnO band gap. The findings indicate that CZO3 exhibits superior activity compared to pristine ZnO, underscoring its enhanced performance and potential for sensing application. The CZO3/NF photoelectrochemical (PEC) biosensor displayed notable cyclic stability, retaining 97 % of its performance over a 60-day period. This underscores its potential for reliable and enduring operation in biosensing applications. Additionally, CZO3/NF exhibited robust sensing capabilities when utilized with human serum samples, showcasing consistent performance in both dark and illuminated conditions.

Using 3.4 μm Variability toward White Dwarfs as a Signpost of Remnant Planetary Systems

Roughly 2% of white dwarfs harbor planetary debris disks detectable via infrared excesses, but only a few percent of these disks show a gaseous component, distinguished by their double-peaked emission at the near-infrared calcium triplet. Previous studies found that most debris disks around white dwarfs are variable at 3.4 and 4.5 μm, but they analyzed only a few of the now 21 published disks showing calcium emission. To test if most published calcium emission disks exhibit large-amplitude stochastic variability in the near-infrared, we use light curves generated from the unWISE images at 3.4 μm that are corrected for proper motion to characterize the near-infrared variability of these disks against samples of disks without calcium emission, highly variable cataclysmic variables, and 3215 isolated white dwarfs. We find that most calcium emission disks are extremely variable: 6/11 with sufficient signal-to-noise show high-amplitude variability in their 3.4 μm light curves. These results lend further credence to the notion that disks showing gaseous debris in emission are the most collisionally active. Under the assumption that 3.4 μm variability is characteristic of white dwarfs with dusty debris disks, we generate a catalog of 104 high-confidence near-infrared variable white dwarfs, 84 of which are published as variable for the first time. We do near-infrared spectroscopic follow-up of seven new candidate 3.4 μm variables, confirming at least one new remnant planetary system, and posit that empirical near-infrared variability can be a discovery engine for debris disks showing gaseous emission.

Mid-infrared dielectric laser acceleration in a silicon dual pillar structure.

Dielectric laser accelerators use near-infrared laser pulses to accelerate electrons at dielectric structures. Driving these devices with mid-infrared light should result in relaxed requirements on the electron beam, easier fabrication, higher damage threshold, and thus higher acceleration gradients. In this paper, we demonstrate dielectric laser acceleration of electrons driven with 10 μm light in a silicon dual pillar structure. We observe the acceleration of 27 keV electrons by 1.4 keV, corresponding to a 93 MeV/m acceleration gradient. The damage threshold of the structures of 3.3 ± 0.6 GV/m peak field is significantly higher than for near-infrared accelerators. The dual pillar acceleration structure itself even survived 5.2 ± 0.9 GV/m, the highest field strength we could achieve with the current system. This together with the larger structure acceptance bodes well for future dielectric laser accelerators driven with mid-infrared light.

Blue-green emitting ZnS0.75O0.25:Ce3+,x%Tb3+ phosphor with tunable fluorescence lifetime

A series of ZnS0.75O0.25:0.1%Ce3+,x%Tb3+ phosphors were prepared by high temperature solid state reaction method. These phosphors exhibited two mixed phases consisting of hexagonal phase ZnS and hexagonal phase ZnO with the average particle size of 13.83 μm and emitted blue-green light. The luminescence mechanism consisted of Zn vacancy defects, the 5d1 → 2F5/2 radiative transitions of Ce3+, the 5D4 → 7F5 and 5D4 → 7F6 radiative transition of Tb3+ induced by the energy transfer of Ce3+ → Tb3+. An equation for the variation of the fluorescence lifetime of ZnS0.75O0.25:0.1%Ce3+,x%Tb3+ phosphors with concentration of Tb3+ fraction was obtained by exponential fitting. The short fluorescence lifetime could be tuned within the range of 113 μs to 550 μs with the increase of Tb3+ concentration, and the color was tunable from blue to blue-green, which is of important application in the field of high-energy particle detection.

Frequency characteristics of collimated blue light generated by four-wave mixing in cesium vapor.

The frequency evaluation of collimated blue light (CBL) generated by parametric four-wave mixing (FWM) in hot atomic vapor is presented. The cesium (133Cs) atoms are excited from the 6S1/2 ground state to 8S1/2 excited state with the 852 and 795 nm pump lasers, producing an optical field at 4.2 µm through an amplified spontaneous emission via population inversion on the 8S1/2 → 7P3/2 transition and the 456 nm CBL via FWM on the 7P3/2 → 6S1/2 transition. The frequency shift of 456 nm CBL has been measured by velocity-selective optical pumping spectral technique when the frequency of any one of two pumping lasers is tuned. The ratio of the frequency shift of 456 nm CBL to the two-photon frequency detuning of two pumping lasers is 0.8912, implying that the generated 4.2 µm light frequency is also correspondingly shifted.

Influence of Aberration-Free, Narrowband Light on the Choroidal Thickness and Eye Length.

To determine whether light chromaticity without defocus induced by longitudinal chromatic aberration (LCA) is sufficient to regulate eye growth. An interferometric setup based on a spatial light modulator was used to illuminate the dominant eyes of 23 participants for 30minutes with three aberration-free stimulation conditions: (1) short wavelength (450nm), (2) long wavelength (638nm), and (3) broadband light (450-700nm), covering a retinal area of 12°. The non-dominant eye was occluded and remained as the control eye. Axial length and choroidal thickness were measured before and after the illumination period. Axial length increased significantly from baseline for short-wavelength (P < 0.01, 7.4 ± 2.2 µm) and long-wavelength (P = 0.01, 4.8 ± 1.7 µm) light. The broadband condition also showed an increase in axial length with no significance (P = 0.08, 5.1 ± 3.5 µm). The choroidal thickness significantly decreased in the case of long-wavelength light (P < 0.01, -5.7 ± 2.2 µm), but there was no significant change after short-wavelength and broadband illumination. The axial length and choroidal thickness did not differ significantly between the test and control eyes or between the illumination conditions (all P > 0.05). Also, the illuminated versus non-illuminated choroidal zone did not show a significant difference (all P > 0.05). All stimulation conditions with short- and long-wavelength light and broadband light led to axial elongation and choroidal thinning. Therefore, light chromaticity without defocus induced by LCA is suggested to be insufficient to regulate eye growth. This study helps in understanding if light chromaticity alone is a sufficient regulator of eye growth.

The Infrared Variability of V1647 Ori over 26 yr with Spitzer, (NEO)WISE, and ISO

Outbursts from young Class 0 protostars are now being detected using 3–5 μm light curves assembled from Spitzer and WISE/NEOWISE photometry. For comparison, we present a 4–8 μm light curve of the erupting, more evolved protostar V1647 Ori (HOPS 388), assembled from photometry obtained with the ISOCAM camera on ISO, the IRAC camera on Spitzer, and from WISE and NEOWISE. Covering 26 yr, this light curve spans the longest available time interval from infrared space-based telescopes capable of separating individual young stellar objects in nearby molecular clouds. This curve does not include a two year interval where the visible-light photometry shows a large drop in brightness. In the case of V1647 Ori, we find that the increase in brightness (3.1 mag) and duration (16 yr) are similar to infrared (3–5 μm) outbursts found toward Class 0 protostars in Orion.

Oxygen Availability on the Application of Antimicrobial Photodynamic Therapy against Multi-Species Biofilms.

Methylene blue (MB)- or Curcumin (Cur)-based photodynamic therapy (PDT) has been used as an adjunctive treatment for periodontitis. Its actual clinical efficacy is still in question because the lack of oxygen in a deep periodontal pocket might reduce the PDT efficacy. We aim to investigate the effect of oxygen on PDT efficacy and to examine if the addition of hydrogen peroxide (HP) could improve PDT performance anaerobically. To this end, we cultured 48 h saliva-derived multi-species biofilms and treated the biofilms with 25 µM MB or 40 µM Cur, HP (0.001%, 0.01% and 0.1%), light (L-450 nm or L-660 nm), or combinations thereof under ambient air or strictly anaerobic conditions. MB- and Cur-PDTs significantly reduced biofilm viability in air but not under anaerobic conditions. HP at 0.1% significantly enhanced the killing efficacies of both MB- and Cur-PDTs anaerobically. The killing efficacy of Cur-PDT combined with 0.1% HP was higher anaerobically than in air. However, this was not the case for MB-PDT combined with 0.1% HP. In conclusion, this study demonstrated that the biofilm killing efficacies of MB- and Cur-PDTs diminished when there was no oxygen. HP at 0.1% can enhance the efficacy of PDT performed anaerobically, but the level of enhancement is photosensitizer-dependent.

Improved Companion Mass Limits for Sirius A with Thermal Infrared Coronagraphy Using a Vector-apodizing Phase Plate and Time-domain Starlight-subtraction Techniques

We use observations with the infrared-optimized Magellan Adaptive Optics (MagAO) system and Clio camera in 3.9 μm light to place stringent mass constraints on possible undetected companions to Sirius A. We suppress the light from Sirius A by imaging it through a grating vector-apodizing phase plate coronagraph with a 180° dark region (gvAPP-180). To remove residual starlight in postprocessing, we apply a time-domain principal-components-analysis-based algorithm we call PCA-Temporal, which uses eigen time series rather than eigenimages to subtract starlight. By casting the problem in terms of eigen time series, we reduce the computational cost of postprocessing the data, enabling the use of the fully sampled data set for improved contrast at small separations. We also discuss the impact of retaining fine temporal sampling of the data on final contrast limits. We achieve postprocessed contrast limits of 1.5 × 10−6–9.8 × 10−6 outside of 0.″75, which correspond to planet masses of 2.6–8.0 M J. These are combined with values from the recent literature of high-contrast imaging observations of Sirius to synthesize an overall completeness fraction as a function of mass and separation. After synthesizing these recent studies and our results, the final completeness analysis rules out 99% of ≥9 M J planets from 2.5 to 7 au.

Sulfur-Passivated InSb Nanowires for Infrared Photodetectors

Sulfur-passivated InSb nanowires (S-InSb NWs) with a single-crystalline structure were synthesized via a chemical vapor deposition process, where S plays the role of a growth catalyst as well as a surface passivator. Studies revealed that the prepared S-InSb NWs displayed typical n-type semiconductor behavior with a maximum field-effect mobility of 823.62 cm2 V–1 s–1 at room temperature. The S-InSb NW-based photodetector was characterized as possessing stable negative photoresponse properties toward incident infrared light, and the corresponding responsivity and external quantum efficiency were calculated to be 123.46 A/W and 14,400%, respectively, for 1.06 μm light and 120.99 A/W and 9680%, respectively, for 1.55 μm light. These values are higher than those for other reported photodetectors based on InSb nanosheets. Through the analysis of excited electron states in the band structure during light irradiation, the negative photoresponse was identified as stemming from the photogating effect of the Sb–S layer on the S-InSb NW surface. These outstanding transport and optoelectronic performances empower S-InSb NWs with technological potential to be used in next-generation infrared quantum devices.

Effects and mechanisms of Celastrol on the formation of neutrophil extracellular traps (NETs).

To investigate the effect and mechanism of Celastrol on the formation of neutrophil extracellular traps (NETs), and to provide a theoretical basis for the clinical application of Tripterygium wilfordii. First, we isolated neutrophils from the peripheral blood of healthy volunteers, and then observed the effect of Celastrol on Phorbol Myristate Acetate (PMA)-induced neutrophil release of NETs. The level of NETs was detected by using the membrane-impermeable nucleic acid dye, SytoxGreens. In addition, the levels of reactive oxygen species (ROS) were also examined to determine whether Celastrol affects ROS production during PMA-induced NETs. Celastrol produced significant cytotoxicity at a concentration of 5 µM (213.2±75.07), and the effect of stimulant PMA (25 nM) treatment was not statistically different (197.3±25.15) (P=0.9167). Celastrol (1.25, 0.625, and 0.3125 µM) did not exhibit cytotoxicity when treating neutrophils. Compared with the PMA (25 nM) + Celastrol (1.25, 0.625, and 0.3125 µM) group and the PMA (25 nM) monotherapy group, SytoxGreen showed a statistically significant reduction in fluorescence at 528 µM under 485 µM light excitation. Also, under the co-localization marker of Hochest and SytoxGreen double staining, we observed that the release of NETs in the PMA-treated group was higher than that in the control group. The PMA-induced neutrophil release of NETs was markedly reduced compared to the PMA-treated group. The NET release was substantially decreased under double staining with the Hochest and SytoxGreen co-localization markers. The fluorescence intensity of the Celastrol plus PMA group was significantly lower than that of the PMA treatment group alone, indicating a decrease in the level of intracellular ROS. Interestingly, the level of ROS in the treatment group who received Celastrol alone was lower than that in the control group, indicating that Tripterygium wilfordii could inhibit the spontaneous production of ROS by neutrophils in the absence of stimulation. The molecular mechanism of Celastrol involves inhibition of PMA-stimulated neutrophil NETs formation in vitro, which is possibly related to the reduction of ROS levels. This indicates that Celastrol, the main component in Tripterygium wilfordii, can inhibit the formation of NETs, which provides a theoretical basis for the study of NETs-related diseases.

Laser Heating Nanoelectrospray Emitters for Fast Protein Melting Measurements with Mass Spectrometry.

Temperature-controlled nanoelectrospray ionization has been used to measure heat-induced conformational changes of biomolecules by mass spectrometry, but long thermal equilibration times associated with heating or cooling an entire emitter limit how fast these data can be acquired. Here, the tip of a borosilicate electrospray emitter is heated using 10.6 μm light from an unfocused CO2 laser. At 1.2 W, the solution inside the emitter tip can be heated from room temperature to a steady-state temperature of 78.2 ± 2.5 °C in less than 0.5 s and cools from 82.6 ± 0.6 °C back to room temperature within 4 s. The time required to establish a steady-state temperature is more than 100-fold faster than that required for a resistively heated emitter due to the low thermal mass. Protein unfolding curves measured as a function of laser power can be acquired in ∼40 s compared to a resistively heated apparatus that required ∼21 min to acquire similar data. Laser power is calibrated to temperature by comparisons of the average charge state of the protein cytochrome c measured with laser heating and with resistive heating. This laser heating method is applied to a three-component protein mixture to demonstrate the ability to rapidly acquire melting temperatures of proteins in mixtures. The ability to rapidly assess the thermal stabilities of multiple proteins simultaneously shows significant promise for coupling temperature-controlled electrospray ionization (ESI) to separation techniques, providing a high-throughput method for determining the effects of solution composition, drug binding, or sequence mutations on protein thermal stability.

Additive manufactured of pure copper by blue diode laser induced selective laser melting

The authors developed a galvano selective laser melting (SLM) system equipped with a blue diode laser and clarified that the volume of the fabricated pure copper part has an influence on the relative density. SLM is a 3D printing technology. Blue diode laser is anticipated to effectively form pure copper parts because the absorptance of 450 nm light on pure copper is higher than that of conventional 1 μm light. In our previous study, the authors reported a newly developed blue diode laser whose wavelength was 450 nm. Laser power and fiber core diameter were 200 W and 100 μm, respectively. In this study, the height and width of the copper part were changed, and their influence on the density of the parts was investigated. As a result, it was found that the larger the volume of the fabricated copper part, the lower the density. In addition, the diluted layer of pure copper and the stainless steel baseplate in the copper part were measured. By controlling the amount of laser heat input between the diluted layer and the undiluted layer, it was possible to form a pure copper part with a high density of 99.6%.

GOALS-JWST: Hidden Star Formation and Extended PAH Emission in the Luminous Infrared Galaxy VV 114

James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) images of the luminous infrared (IR) galaxy VV 114 are presented. This redshift ∼0.020 merger has a western component (VV 114W) rich in optical star clusters and an eastern component (VV 114E) hosting a luminous mid-IR nucleus hidden at UV and optical wavelengths by dust lanes. With MIRI, the VV 114E nucleus resolves primarily into bright NE and SW cores separated by 630 pc. This nucleus comprises 45% of the 15 μm light of VV 114, with the NE and SW cores having IR luminosities, L IR(8 − 1000 μm) ∼ 8 ± 0.8 × 1010 L ⊙ and ∼ 5 ± 0.5 × 1010 L ⊙, respectively, and IR densities, ΣIR ≳ 2 ± 0.2 × 1013 L ⊙ kpc−2 and ≳ 7 ± 0.7 × 1012 L ⊙ kpc−2, respectively—in the range of ΣIR for the Orion star-forming core and the nuclei of Arp 220. The NE core, previously speculated to have an active galactic nucleus (AGN), has starburst-like mid-IR colors. In contrast, the VV 114E SW core has AGN-like colors. Approximately 40 star-forming knots with L IR ∼ 0.02–5 × 1010 L ⊙ are identified, 28% of which have no optical counterpart. Finally, diffuse emission accounts for 40%–60% of the mid-IR emission. Mostly notably, filamentary polycyclic aromatic hydrocarbon (PAH) emission stochastically excited by UV and optical photons accounts for half of the 7.7 μm light of VV 114. This study illustrates the ability of JWST to detect obscured compact activity and distributed PAH emission in the most extreme starburst galaxies in the local universe.

Dust reverberation mapping and light-curve modelling of Zw229-015

ABSTRACT Multiwavelength variability studies of active galactic nuclei can be used to probe their inner regions that are not directly resolvable. Dust reverberation mapping (DRM) estimates the size of the dust emitting region by measuring the delays between the infrared (IR) response to variability in the optical light curves. We measure DRM lags of Zw229-015 between optical ground-based and Kepler light curves and concurrent IR Spitzer 3.6 and 4.5 µm light curves from 2010 to 2015, finding an overall mean rest-frame lag of 18.3 ± 4.5 d. Each combination of optical and IR light curve returns lags that are consistent with each other within 1σ, which implies that the different wavelengths are dominated by the same hot dust emission. The lags measured for Zw229-015 are found to be consistently smaller than predictions using the lag–luminosity relationship. Also, the overall IR response to the optical emission actually depends on the geometry and structure of the dust emitting region as well, so we use Markov chain Monte Carlo modelling to simulate the dust distribution to further estimate these structural and geometrical properties. We find that a large increase in flux between the 2011–2012 observation seasons, which is more dramatic in the IR light curve, is not well simulated by a single dust component. When excluding this increase in flux, the modelling consistently suggests that the dust is distributed in an extended flat disc, and finds a mean inclination angle of 49$^{+3}_{-13}$ deg.

Ultrahigh Photogain Short-Wave Infrared Detectors Enabled by Integrating Graphene and Hyperdoped Silicon.

Highly sensitive short-wave infrared (SWIR) detectors, compatible with the silicon-based complementary metal oxide semiconductor (CMOS) process, are regarded as the key enabling components in the miniaturized system for weak signal detection. To date, the high photogain devices are greatly limited by a large bias voltage, low-temperature refrigeration, narrow response band, and complex fabrication processes. Here, we demonstrate high photogain detectors working in the SWIR region at room temperature, which use graphene for charge transport and Te-hyperdoped silicon (Te-Si) for infrared absorption. The prolonged lifetime of carriers, combined with the built-in potential generated at the interface between the graphene and the Te-Si, leads to an ultrahigh photogain of 109 at room temperature (300 K) for 1.55 μm light. The gain can be improved to 1012, accompanied by a noise equivalent power (NEP) of 0.08 pW Hz-1/2 at 80 K. Moreover, the proposed device exhibits a NEP of 4.36 pW Hz-1/2 at 300 K at the wavelength of 2.7 μm, which is exceeding the working region of InGaAs detectors. This research shows that graphene can be used as an efficient platform for silicon-based SWIR detection and provides a strategy for the low-power, uncooled, high-gain infrared detectors compatible with the CMOS process.

Fully Additive Electrohydrodynamic Inkjet‐Printed TiO2 Mid‐Infrared Meta‐Optics

AbstractAdditive manufacturing at the micron and sub‐micron scale is a rapidly expanding field with electrohydrodynamic inkjet (EHDIJ) printing proving to be a critical fabrication technique that will enable continued advancement. Increasing the range of materials that can be used with EHDIJ printing to create micron and sub‐micron scale features is critical for increasing the variety of devices that can be fabricated with this method. Ceramic, semiconducting, and hybrid organic–inorganic materials are essential for meta‐optics and micro‐electromechanical systems devices, yet these materials are vastly underexplored for applications in EHDIJ printing. A novel printing solution is presented containing a titania alkoxide precursor that is compatible with EHDIJ printing and capable of producing final printed features of 1 µm and below; the highest resolution features ever reported for this family of materials and this method. This solution is used to fabricate the first EHDIJ printed and functioning mid‐infrared meta‐optics lens, capable of focusing 5 µm light.

Near-Infrared Polarimetric Image Sensors Based on Ordered Sulfur-Passivation GaSb Nanowire Arrays.

The near-infrared polarimetric image sensor has a wide range of applications in the military and civilian fields, thus developing into a research hotspot in recent years. Because of their distinguishing 1D structure features, the ordered GaSb nanowire (NW) arrays possess potential applications for near-infrared polarization photodetection. In this work, single-crystalline GaSb NWs are synthesized through a sulfur-catalyzed chemical vapor deposition process. A sulfur-passivation thin layer is formed on the NW surface, which prevents the GaSb NW core from being oxidized. The photodetector based on sulfur-passivation GaSb (S-GaSb) NWs has a lower dark current and higher responsivity than that built with pure GaSb NWs. The photodetector exhibits a large responsivity of 9.39 × 102 A/W and an ultrahigh detectivity of 1.10 × 1011 Jones for 1.55 μm incident light. Furthermore, the dichroic ratio of the device is measured to reach 2.65 for polarized 1.55 μm light. Through a COMSOL simulation, it is elucidated that the origin of the polarized photoresponse is the attenuation of a light electric field inside the NW when the angle of incident polarization light rotates. Moreover, a flexible polarimetric image sensor with 5 × 5 pixels is successfully constructed on the ordered S-GaSb NW arrays, and it exhibits a good imaging ability for incident near-infrared polarization light. These good photoresponse properties and polarized imaging abilities can empower ordered S-GaSb NW arrays with technological potentials in next-generation large-scale near-infrared polarimetric imaging sensors.

Modulation transfer function measurements of HgCdTe long wavelength infrared arrays for the Near-Earth Object Surveyor

The modulation transfer function (MTF) is a useful measure in image quality analysis and performance budget determination. Sensitive long wavelength infrared (LWIR) detectors for astronomical space telescopes require slight modifications to the existing MTF measurement methods due to the increased prevalence of high dark current pixels. Presented here are the specifics of a modified slanted edge method to determine the MTF in λc > 10 μm HgCdTe detectors to be used with the planned Near-Earth Object Surveyor Mission. The measured MTF at Nyquist using 6 μm light is 0.22 ± 0.02 and is 0.25 ± 0.02 using 10 μm light for both 250 and 350 mV of applied reverse bias. These measurements are from edge spread functions with median signal values around 50% of the well depth, as the MTF is expected to change with signal value due to two brighter-fatter type effects. The expected trends caused by the influences of these two effects and the expected trends with wavelength of absorbed photons are all observed.

Hybrid polymer-titania waveguides for highly integrated circuits

We present an innovative waveguide based on the hybridization of a titanium dioxide nano-waveguide within a polymer strip. Through simulations and design we demonstrate that the waveguide sustains principally the quasi-TM fundamental mode and that even in tight bends (radius smaller than 2 μm) light remains confined in the titania layer. Such a waveguide, in addition of enabling low loss propagation is a way towards efficient evanescent sensing in highly integrated scheme, i.e., small footprint. We also show that the fabrication, here based on electron beam lithography and atomic layer deposition, can be extended easily to large scale manufacturing using nanoimprinting technology.