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Airborne particulate matter has become an emerging issue globally due to environmental degradation and the health risk it causes. Volatilization of weakly adsorbed particles onto quartz filter paper (QFP) limits its performance. The adsorption of particulate matter ( P M 10 ) onto QFP coated with different concentrations of graphene oxide (GO) was investigated to enhance the adsorption potential. Hummer’s method was adopted to synthesize GO. QFPs were coated with different concentrations of GO using a spin coating technique to optimize the result. The morphology and microstructure of GO-QFP were characterized by various experimental techniques, like XRD, FTIR, EDX, and SEM. GO showed considerable affinity to aerosol particles for GO-QFP weighing 5 mg/ml, whereas adsorption of the coated samples before and after was significantly reduced. The high affinity to aerosol particles was due to dominated π - π interactions and the grooved regions formed on the GO layer. It was considered that the high surface to volume ratio of GO-QFP improves the adsorptive property of the QF and consequently enhances the performance of the filter paper.

We have demonstrated an efficient speckle reduction method for laser illumination using a micro-vibrated paper screen along the projection direction. Using this method, a micro-vibrated amplitude of 0.532 μm, or a 2π phase change is sufficient to de-correlate the generated speckle pattern for a static SHG green laser beam image. When the measured speckle contrast is lowered to about 5.0%, and comparable with an LED source, a speckle-free image can be achieved. This technique will be suitable for compact and portable laser illumination equipment, image display, signal sensing devices, and so forth. Wearable and near-to-eye laser display applications are also included.

I propose a model for predicting the total reflectance of color halftones printed on paper incorporating fluorescent brighteners. The total reflectance is modeled as the additive superposition of the relative fluorescent emission and the pure reflectance of the color print. The fluorescent emission prediction mod- el accounts for both the attenuation of light by the halftone within the excitation wavelength range and for the attenuation of the fluorescent emission by the same halftone within the emission wavelength range. The model’s calibration relies on reflectance measurements of the optically brightened paper and of the solid colorant patches with two illuminants, one including and one excluding the UV components. The part of the model predicting the pure reflectance relies on an ink-spreading extended Clapper–Yule model. On uniformly distributed surface coverages of cyan, magenta, and yellow halftone patches, the proposed model predicts the relative fluorescent emission with a high accuracy (mean ΔE94 1⁄4 0:42 under a D65 standard illuminant). For optically brightened paper exhibiting a moderate fluorescence, the total reflectance prediction improves the spectral reflectance prediction mainly for high- light color halftones, comprising a proportion of paper white above 12%. Applications include the creation of improved printer characterization tables for color management purposes and the prediction of color gamuts for new combinations of optically brightened papers and inks. © 2008 Optical Society of America

In situ ablation of thin metal films on fused silica substrates by picosecond class lasers was investigated as a method of characterizing the beam at the sample plane. The technique involved plotting the areas enclosed by constant fluence contours identified in optical microscope images of the ablation sites versus the logs of the pulse energies. Inconel films on commercially available neutral density filters as well as magnetron sputtered gold films were used. It was also shown that this technique could be used to calibrate real-time beam profile diagnostics against the beam at the sample plane. The contours were shown to correspond to the boundary where part or all of the film was ablated.

The far-infrared properties of spruce wood are examined with a terahertz time-domain spectrometer. The solid wood is shown to exhibit both birefringence and diattenuation. The birefringence properties are sufficient for construction of a quarter-wave plate operating at 0.36 THz, and a half-wave plate operating at 0.71 THz. The origin of the birefringence is attributed to preferential fiber orientation within the wood. Similar birefringence is observed in lens paper in which the fibers are preferentially oriented in one direction.

Color characteristics of an RGBW (red, green, blue, white) electrophoretic display (EPD) prototype developed by Samsung Electronics are analyzed. EPD shows strong crosstalk between subpixels because of both the fringe field between subpixels and the scattering phenomena at the display surface. An RGB-to-RGBW color-decomposition algorithm optimized to EPD characteristics is developed that compensates for color deterioration due to the fringe field and scattering phenomena. For the four-color-decomposition algorithm, white is added to the primary colors to enhance the reflectance of the vivid colors while minimizing chroma loss. The psychophysical experimental result shows that images rendered with the algorithms developed in this study are preferred more than 90% of the time over those rendered with algorithms from previous studies. This research proves that, in spite of the limited physical property of EPD, the color quality can be improved dramatically through the use of well-designed color-rendering algorithms.

We have corrected typing errors related to the characterization of the dynamic range of the acrylamide photopolymer described in an earlier study [Appl. Opt. 42, 7008 (2003)]. The M number is expressed as M/# instead of M# as appears in the text. The value calculated from the experimental results that are included in the article is M/# = 3.8 instead of 38 as appears in the text.

The measurement of the bonded area of pulp fibers has been an unsolved issue in paper science for more than 40 years. By the use of an established pulp fiber model, and a 4 × 4 transfer matrix formalism we simulated the optical behavior of pulp fibers in a modified imaging ellipsometer, and we demonstrate that there are rather strong symmetries in the ellipsometric angles Ψ and Δ when comparing single fibers, unbonded fiber crossings, and fiber-fiber bonds. Based on these symmetries we propose and test an algorithm that allows to distinguish the three cases (single fibers, unbonded fiber crossings, and fiber-fiber bonds) in the analysis of ellipsometric data.

A critical factor that affects the appearance of printed paper surfaces is gloss uniformity, which is usually assessed visually. To relate gloss uniformity to nonvisual quantities, we first visually identified areas of either high or low gloss on the same sample for two different types of paper. We then measured the roughness and the reflectance of these areas. Microroughness was measured with an atomic-force microscope, and roughness was measured over a larger area with a confocal laser scanning microscope. The local reflectance of the high-gloss and the low-gloss areas was obtained from images taken with a gloss-imaging instrument and compared with the roughness of each area. This correlation is nonlinear, and roughness is insufficient to predict the local reflectance. Light-scattering measurements were made in the specular direction to map the gloss uniformity over larger areas than was possible with the gloss-imaging instrument. These maps were used to show the possibility of using both the spatial frequency and the fan filters, which together form a set of cortex filters, to analyze the variation of the gloss about the mean value and its spatial distribution on the surface in terms of spatial frequency and azimuthal orientation.

A simplified stochastic model for the fiber structure of paper is introduced. The packing density and optical thickness of the fiber network are derived analytically, and their dependence on fiber characteristics can be seen. We undertake a Monte Carlo simulation of light scattering that is based on geometrical optics, using a realization of the model, which gives packing densities and optical thicknesses well in accordance with those given by the stochastic model and the scattering quantities as functions of three angles.

Writing tests were made on commercial Electrofax paper using an all glass thin window cathode ray tube. Developed line widths from 5 mil to 15 mil could be obtained by varying beam current. Writing speeds of up to 790,000 in./sec were achieved. Electron beam current appeared to vary linearly with writing speed.

We report on the advanced implementation of the biprimary color system in applications where subtractive color is performed inside a single pixel to alter the magnitude and color of reflection (electronic paper displays) or the optical transmission and color temperature (smart windows). A novel device structure can switch between four states: clear, black, either of two complementary colors from RGB and CMY sets, and also mixed states between one of these four states. The device structure utilizes an electrokinetic pixel structure, which combines the spectral performance of in-plane electrophoretic devices with the improved switching speeds of vertical electrophoresis. The electrophoretic dispersions are dual-particle dual-colored and are controlled using two traditional planar electrokinetic electrodes on the front and back substrates, along with a third electrode conveniently located at the perimeter of each unit cell. Demonstrated performance includes contrast ratios reaching ~10∶1, reflectance of ~62%, and transparency of ~75%. For electronic paper displays, these results provide a pathway to double the reflective performance compared to the traditional RGBW color-filter approach. For smart windows, the technology provides not only control of shade (transmission) but also provides complete control over color temperature. Furthermore, this three-electrode device can be roll-to-roll fabricated without need for any alignment steps, requiring only a single micro-replication step followed by self-aligned contact printing of the third electrode.

High detector efficiency has broad appeal and includes such diverse fields as quantum optics and solar energy. An optical resonator can improve detector efficiency by employing multiple re-reflections to the detector. This short paper uses geometric ray tracing to examine-for a given entry port size-the probability that a photon will escape from an ideal perfectly reflective two-dimensional cavity.

In this paper, the performance of solar cells with graphene transparent electrodes is compared with cells using conventional indium tin oxide (ITO) electrodes, and it is demonstrated the optical absorption of solar cells with bare graphene structure is worse than that of bare ITO structure because of the higher refractive index of graphene. To enhance the light trapping of graphene-based thin-film solar cells, a simple two-layer SiO(2)/SiC structure is proposed as antireflection coatings deposited on top of graphene transparent electrodes, and the thickness of each layer is optimized by differential evolution in order to enhance the optical absorption of a-Si:H thin-film solar cells to the greatest degree. The optimization results demonstrate the optimal SiO(2)/SiC/graphene structure can obtain 37.30% enhancement with respect to bare ITO structure, which has obviously exceeded the light-trapping enhancement of 34.15% for the optimal SiO(2)/SiC/ITO structure. Therefore, with the aid of the light-trapping structure, the graphene films are a very promising indium-free transparent electrode substitute for the conventional ITO electrode for use in cost-efficient thin-film silicon solar cells.

The specific points raised here augment the full paper on this same subject by Measures [Appl. Opt. 13, 1121 (1974)]. In support of the feasibility of such a laser, an electrochemiluminescent system with ø(ecl) ~0.2 is cited from the literature (vs ø(ecl) ~1.4 x 10(-2)); and in relation to the feasibility calculations, the incompleteness of the Feldberg model is noted. Various other topics are also discussed.

Dennis Gabor’s seminal idea of a simple all-optical setup aimed at reconstructing the object wavefront stored on a photographic plate gave birth a little over seven decades ago to the field of holography. In 1971 Gabor obtained the Nobel Prize in Physics for this invention. Still, the road in the early days after his two first papers on the subject was one full of obstacles, so his scientific and engineering contemporaries put his idea to rest for more than 10 years, until the invention of the laser. This fact made his holographic concept take off to new and unsuspected applications. This invited review paper is a homage to Dennis Gabor’s 50th anniversary of his Nobel Prize accolade. For this purpose, the review departs from the typical common route, i.e., those written following a timeline fashion, and instead is written with the intent to cover only a few of the holography applications in optics while scanning the electromagnetic spectrum. In doing this, the authors are aware that other invited papers for this special issue will tackle other subjects not dealt with in this review non-timeline paper.

Chalcogenide phase-change materials (PCMs) offer a unique feature that can be used to dynamically control the response of the photonic devices and achieve fast, nonvolatile, reversible, multilevel, and specific optical modulation. The phase-change material G e 2 S b 2 S e 4 T e 1 (GSST) has recently received a lot of attention due to the large index contrast between its amorphous and crystalline states with significantly low optical loss in the optical to near-IR spectrum. In this paper, we propose a tunable and reconfigurable hybrid PCM plasmonic nanostructure composed of a spacer layer of GSST sandwiched between a Ag back reflector and a 1D Ag Fabry–Perot grating structure. We use the finite element method (FEM) to numerically calculate the light absorption, absorption contrast, and figure of merit of the plasmonic nanostructure for both the amorphous and crystalline state of the GSST. Our calculations show that with constant structural variation the observed multimode absorption is drastically modified when the GSST undergoes a phase change from the amorphous to the crystalline state. The absorption contrast spectrum, which is defined as the absorption difference between the amorphous and crystalline state of GSST, shows four extrema modes between 70% and 89%. The figure of merit spectrum shows two large values of 44.39 and 37.78 at the 1502 nm and 2063 nm wavelengths, respectively. We also address the observed modes in the absorption contrast spectrum through spatial representation of the enhanced electric field distribution at their corresponding wavelengths. We show how the phase change in the GSST spacer can control the coupling between the optical cavity modes and the Ag surface plasmon resonance modes in the cavities and GSST spacer strip boundaries. The findings in this paper may open new avenues toward the design of next-generation photonic systems such as thermal emission controllers, sensors, ranging holograms, modulators and optical detection devices.

Traditional micro-Raman spectroscopy technology has the disadvantages of a weak signal and low signal-to-noise ratio. To fix these issues, a cost-effective and rigorous design method is proposed in this paper, whereby a confocal micro-Raman spectroscopy system is designed and built, and a low-cost reflector and high-pass filter are introduced into the Raman signal-receiving module. The Raman light incident is fully perpendicular to the coupling lens by adjusting the reflection angle of the mirror, making the focus of the coupling lens highly conjugate with the focus of the microscope objective, to enhance the intensity of the Raman signal and improve the signal-to-noise ratio. In order to better apply this technology to the detection and study of microplastics in offshore sediments, a reflective illumination light path is used to avoid the visual interference caused by the capillary structure and opacity of the glass cellulose filter membrane. The detection and analysis of the microplastics on the glass cellulose filter membrane have been carried out by the confocal micro-Raman system designed, which is low cost and capable of obtaining good detection results and meeting the requirements of microplastics detection. The system designed in this paper is expected to be applied to the research and development of Raman detection equipment for microplastics in marine sediments, which is beneficial to promote the development of marine microplastic monitoring technology in the world.

In low-Earth orbit, the already existing population of small and medium debris (between 1 cm and several dozens of cm) is a concrete threat to operational satellites. A space-based laser space debris removal (SLDR) system that can remove hazardous debris around selected space assets appears to be a flexible and effective project. To achieve high-precision tracking and emitting, the optical system of the SLDR mission includes a target-detection telescope and emitting telescope, adopting a common light path structure. The optical design results, system performance, tolerance budget, and detailed stray light control design are presented in this paper. The large-aperture off-axis two-mirror beam-narrowing system characteristics are also discussed in terms of stray light control. This paper will present the lateral-displacement (LD) setting, two-stage fore baffle design, black baffle surface selection, and opening direction of the telescope door. The results showed that the stray light elimination reaches a 10 − 9 order, meeting design requirements.

The sidelobe phenomenon of acousto-optic tunable filter (AOTF)-based hyperspectral imaging is the result of the phase mismatching condition, which will reduce the quality of hyperspectral imaging data. This phenomenon can be observed in two specified scenes, namely, high brightness panchromatic target imaging and high brightness monochromatic target imaging. In this paper, the acousto-optic interaction in these two scenes is discussed using the phase matching condition. As a follow-up work of the previous related research, this paper studies laser interference in AOTF imaging, which is a typical example of the second case. A method to remove laser sidelobes in AOTF-based hyperspectral imaging is proposed, which combines a series of procedures including laser point extraction, reverse imaging before AOTF, ray tracing in AOTF, forward imaging process after AOTF, and laser elimination. Experimental results have verified the effectiveness of the proposed method.

In this paper, we present a method of solving the chromatic aberration problem of large spectral bandwidth optical systems encountered during the internal focusing process. Rational selection of the focal length of each lens group and the distance between them retained the achromatic characteristic of the optical system when the inner focus lens group was mobilized. The proposed design was experimentally validated. This paper can be useful to research on internal focusing in wide-band systems.

Lane detection is crucial for driver assistance systems. However, road scenes are severely degraded in dense fog, which leads to the loss of robustness of many lane detection methods. For this problem, an end-to-end method combining polarimetric dehazing and lane detection is proposed in this paper. From images with dense fog captured by a vehicle-mounted monochrome polarization camera, the darkest and brightest images are synthesized. Then, the airlight degree of polarization is estimated from angle of polarization, and the airlight is optimized by guided filtering to facilitate lane detection. After dehazing, the lane detection is carried out by a Canny operator and Hough transform. Having helped achieve good lane detection results in dense fog, the proposed dehazing method is also adaptive and computationally efficient. In general, this paper provides a valuable reference for driving safety in dense fog.

Failure prediction of any electrical/optical component is crucial for estimating its operating life. Using high temperature operating life (HTOL) tests, it is possible to model the failure mechanisms for integrated circuits. Conventional HTOL standards are not suitable for operating life prediction of photonic components owing to their functional dependence on thermo-optic effect. This work presents an IR-assisted thermal vulnerability detection technique suitable for photonic as well as electronic components. By accurately mapping the thermal profile of an integrated circuit under a stress condition, it is possible to precisely locate the heat center for predicting the long-term operational failures within the device under test. For the first time, the reliability testing is extended to a fully functional microwave photonic system using conventional IR thermography. By applying image fusion using affine transformation on multimodal acquisition, it was demonstrated that by comparing the IR profile and GDSII layout, it is possible to accurately locate the heat centers along with spatial information on the type of component. Multiple IR profiles of optical as well as electrical components/circuits were acquired and mapped onto the layout files. In order to ascertain the degree of effectiveness of the proposed technique, IR profiles of CMOS RF and digital circuits were also analyzed. The presented technique offers a reliable automated identification of heat spots within a circuit/system., Comment: 2020 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited

The low efficiency of coupling a hollow Gaussian beam into single-mode fiber terribly decreases the transmission efficiency of an optical communication system. In this paper, a coupling system containing a shaping lens and a coupling lens is designed based on the vector theory of refraction. The simulation results show that our coupling system can improve coupling efficiency to 81.45%, and the efficiency can still reach 74.73% even though chamfering and other factors are considered. This paper may not only provide engineers with a more efficient coupling system but also provide designers with ideas of hollow–solid (or solid–hollow) beam shaping systems.

In this paper, we propose a terahertz dual-channel modulator by combining a high electron mobility transistor (HEMT) with a metamaterials structure, in which the HEMT is embedded in the opening of the structure metamaterial. The modulator consists of a metamaterial structure, silicon carbide (SiC), HEMT active device, and feeder. The concentration of the two-dimensional electron gas (2DEG) in the HEMT can be controlled by gate voltages, and the change of the concentration can realize the modulation of the intensity and phase of the terahertz wave. The simulation results indicate that when a single channel works, the modulation depth is 90.7% at 0.22 THz and 94.0% at 0.34 THz. When both channels work, the modulation depth is 88.9% at 0.22 THz and 93.3% at 0.34 THz. The terahertz modulator designed in this paper can work in two frequency bands and can be controlled independently, which efficiently uses the spectrum resources and has broad application prospects in the field of terahertz communication.

Precision glass molding (PGM) technology has recently emerged as a promising fabrication method for mass-fabricating optical glass lenses with complex surfaces. However, lens fracture as a common problem has not been analyzed in detail. In this paper, the divergent cone cracks in the molded lens were analyzed using the finite element method, because crack propagation cannot be seen in the molding process. A three-dimensional model was established in MSC Marc software for analyzing the temperature, stress components, and principal stress of the glass in different molding stages. The crack paths were analyzed using the simulation results and the fracture basis. Based on the analysis, PGM experiments with different processing parameters were carried out. The appearance of the molded lenses demonstrated the rationality and correctness of the analysis. Thus, analyses of other types of lens fractures can use the analysis method proposed in this paper rather than relying on trial and error.

Taking the influence of alloying elements into consideration, a hardness prediction model based on a newly proposed parameter named actual carbon diffusion time (ACDT), which was calculated by combining temperature history with carbon diffusivity, is developed in this paper. The hardness distribution was directly derived from a 3D thermal model, which was constructed to simulate the laser surface hardening of AISI 1045, and from which the temperature history was also obtained. Using this 3D thermal model, the geometric characteristics after laser hardening (e.g., the width of the hardened layer, the depth of the phase change layer) were determined according to the martensitic transformation. The influences of the scanning speed and the laser power on the geometric characteristics were investigated, and the relations among the geometric characteristics after laser hardening were further determined. The laser hardening experiments with various parameters were conducted, and it was found that the hardness can be accurately predicted using the developed hardness prediction model (R-squared, 97.0%). The proposed parameter ACDT, as the core of the hardness prediction model in this paper, broadens the way for hardness prediction in laser hardening with the alloying effect involved.

The Southern Spectroscopic Survey Telescope (SSST) is a planned multi-wavelength space survey telescope by China located in Chile. In this paper, we present a feasible optic system design based on wide-field Cassegrain corrector configuration for the SSST of China. Our recommended design has a large field of view (FOV) of 2.4 ∘ × 2.4 ∘ with its image spot size less than 0.3 arcsec in diameter for its full FOV in 80% encircled energy. The atmospheric dispersion effect and actual science requirements are taken into consideration. In addition, a trade-off study is presented. This paper can also provide a reference to the next generation of spectroscopic survey telescopes.

Due to the limited processing accuracy of the platform and unevenness of the glass substrate itself, a holographic lithography system is prone to out-of-focus imaging problems; therefore, the real-time focusing components are critical for holographic lithography systems. In this paper, a real-time focus monitoring and adjusting system using an electrically tunable lens (ETL) for large-area lithography is introduced. Combined with the ETL, the limited depth of field of the microscopic objective has been effectively expanded, and the automatic focusing evaluation and adjustment are achieved. The development, including simulation using Zemax, optics system design and implementation, experiments, and evaluation are demonstrated in this paper. The results show that the out-of-focus problem in our large-area holographic lithography system has been significantly alleviated.

This paper presents research work about the design and fabrication of a 44-layer optical reflective notch filter. The performance of the fabricated notch filter was studied at normal (0°) and oblique (45°) incidence angle. In addition, the paper also discusses a three-layer broadband antireflective coating on both sides of the multilayer stack to suppress the ripples in the passband region. The thickness-modulated reflective stack of the filter was designed by using the materials A l 2 O 3 (1.63) and S i O 2 (1.46). Optimization of the multilayer stack was carried out by using the damped least-squares algorithm. The theoretical and experimental results from the ion-assisted e-beam deposited samples for single notch reflective filters are presented. Good agreement in the design and experimental results was observed when the deposition process was controlled by time of evaporation. Further, the filter was characterized for the optical properties by using a UV-VIS-NIR spectrophotometer, surface morphology and protective properties using field emission scanning electron microscopy, a coherence correlation interferometer, and water contact angle.

This paper presents the results of application of the laser speckle correlation (LSC) technique for studying the combustion process of aluminum-based nanopowders. For assessing the results, a combined experimental scheme is proposed with simultaneous application of LSC analyses and another feasible method of nanopowder combustion study, i.e., laser monitoring. In this paper, we present the principle of using the LSC technique to characterize the surface changes of nanopowder during combustion. Calculating the correlation coefficient of image sequencing, it is possible to estimate the time parameters of combustion of aluminum nanopowder and an aluminum mixture with iron nanopowder. Comparing the results obtained with the LSC method and laser monitoring, we conclude that LSC is quite acceptable for investigating the combustion process of metal nanopowders. In contrast with laser monitoring, the LSC method allows us to determine the preheating period preceding the first combustion wave. In practice, the LSC method application for nanopowder combustion control is prospective because of the simple hardware implementation.

Detection accuracy is an important performance indicator of ground-based telescopes and is affected mainly by pointing error, geometric distortion of the optical system, and parameter errors caused by machining error and installation error. To improve detection accuracy, a modified algorithm based on a simulated annealing algorithm is proposed in this paper; this algorithm is able to correct pointing, derive a geometric distortion solution, and re-estimate some parameters of telescopes simultaneously. The efficiency of the proposed method is verified by using the observation data of the telescope, whose aperture is 600 mm under two distortion models (the physical model and polynomial fitting model). The results show that the method presented in this paper can effectively solve the problem of nonconvergence of the distortion solution with a pointing error. The final angle error under the polynomial fitting model is 1.07″, and the pixel error is 0.06 pixels; the errors under the physical model are 1.08″ and 0.07 pixels. The correction effect under the two distortion models is basically the same, but the averaged operation speed based on the physical model is 19.45% faster.

In recent years, Raman spectroscopy techniques have been successfully applied to the area of deep-sea exploration. However, there are still some problems impeding the further application of Raman systems. For example, the large size of an underwater Raman system makes it difficult to deploy on the underwater vehicle. Meanwhile, the sensitivity is often a disadvantage, requiring improvement for detecting more trace components. To solve these problems, a new compact deep-sea in situ Raman spectroscopy system is presented in this paper. The whole system weighs 60 kg and is housed in an L800 mm×ϕ258 mm pressure vessel with an optical window on the front end cap. The main components include a 532 nm Nd:YAG laser, an optics module, a high-throughput spectrograph with 0∼4900 cm−1 spectral range and 8 cm−1 spectral resolution, a TEC-cooled 2000 pixel×256 pixel CCD detector, a PC104 embedded computer, and an electronics module. To evaluate the performance of the newly developed Raman system, systematic experiments have been carried out with solutions in laboratory, and the results have shown that the system limit of detection of SO42− is 0.4 mmol/L. The Raman system has been successfully deployed on a remote-operated vehicle on the Kexue research vessel in June 2015. The typical in situ detection results are presented in this paper, and it is shown that the Raman system is capable of detecting the Raman signal of SO42− and fluorescence of chlorophyll a (chl-a) and chromophoric dissolved organic matter (CDOM) in seawater. With 500 spectra accumulations and some data processing, the Raman signal of HCO3− is obtained. This is the first report of direct measurement of HCO3− by Raman system in in situ experiments. After further optimization, it is hoped to apply the Raman system in seafloor observation networks for long-time carbon cycling research.

A Mach-Zehnder interferometer (MZI) fiber sensing and positioning system based on common optical path technology that combines the advantages of the positioning method of the conventional MZI and the common optical path technology is proposed to improve the performance of the system in this paper. The feasibility of the interferometer has been proved by simulation and experiment. In the conventional MZI, the temperature and environment have an effect on the system performance due to the interference light transmitted through different optical fibers. The system proposed in this paper overcomes the disadvantages of the conventional MZI.

A ground-testing method and an algorithm are presented to demonstrate how to predict the image quality for an orbiting space telescope under 0 g. By using a mathematical model of the ground-testing system, one has to change the gravity conditions to get a 0 g wavefront. For the Hinode space telescope, one can change the gravity acceleration from +1 g to −1 g by rotating the telescope upside down, which is difficult for larger optical space telescopes. In this paper we introduce a new algorithm to get 0 g results by measuring the wavefronts under different gravity acceleration sets. In this way we can predict the 0 g image quality under any gravity acceleration value. With the algorithm, we propose to use oscillation in the vertical direction to mimic the change of the telescope figure under acceleration caused by gravity. Criteria of tests and estimates of errors are discussed in this paper. A test experiment is designed and performed for a scaled model of the space solar telescope (SST). The optical test system includes a 1.4-mm-thick, 101.6-mm-diameter flat mirror, and has almost the same gravity sag as the SST’s 1-m-diameter primary has; thus, it can be compared to the Hinode method. As a suspending spring mass oscillation system, it provides a gravity environment varying sinusoidally around 1 g. Gravity accelerations and response wavefronts are aligned in time. Test results and comparisons to Hinode’s are achieved and listed. The differences between our method and Hinode’s results is less than 1/20λ RMS, which is sufficient for testing a diffraction limited space optical system.

Most investigations of polarizers consider a normal angle of incidence only. This paper expands our investigation to also include an oblique angle of incidence. Essential problems are encountered for an oblique angle of incidence: there is an upward shift of the center frequency, and the impedance match gets worse as the angle of incidence increases. So it is apparent that polarizers gradually deteriorate for higher angles of incidence. The new contribution given in this paper is that it considers ways to greatly improve oblique incidence performance. These ways are well confirmed by the design process of the proposed graphene-based polarizer for large-angle oblique incident stability and high efficiency.

Phacoemulsification technique with intraocular lens implantation has been a common treatment for cataract patients. With rising demand among the public, new technologies for lens design have emerged to minimize intraocular aberrations, improving visual quality to the largest extent. This paper systematically reviews the development of materials applied in lens manufacturing, the different categories of intraocular lenses, and respective design principles. The advantages and potential drawbacks of intraocular lenses are illustrated in the paper, and prospective research to improve the design are presented in the end.

Recently, an enhanced computer program was applied to explain in detail the influence of different recombination mechanisms (Auger, radiative, and Shockley-Read-Hall) on the performance of high-operation-temperature, long-wavelength, infrared p-i-n HgCdTe heterojunction photodiodes. It is shown that the photon recycling effect drastically limits the influence of radiative recombination on the performance of small pixel HgCdTe photodiodes. The computer program is based on a solution of the carrier transport equations, as well as the photon transport equations for semiconductor heterostructures. Both the distribution of thermal carrier generation and recombination rates, and spatial photon density distribution in photodiode structures have been obtained. In comparison with two previously published papers in the Journal of Electronics Materials [J. Electron. Mater.45, 4587 (2016)JECMA50361-523510.1007/s11664-016-4566-6 and J. Electron. Mater.46, 6295 (2017)JECMA50361-523510.1007/s11664-017-5736-x], our paper provides an additional insight on the ultimate performance of long-wavelength infrared, high-operation-temperature HgCdTe arrays with pixel densities that are fully consistent with background- and diffraction-limited performance due to system optics.

Subwavelength gratings are gratings with periods smaller than the incident wavelength. They possess form birefringence, which depends on the grating parameters. This paper presents the results of an experimental method designed to measure the birefringent properties of diamond subwavelength gratings in the mid-infrared. The method consists of monitoring the intensity transmitted through one polarizer, a subwavelength grating, and a second polarizer for various orientations of the first polarizer. By fitting the intensity variation as a function of the orientation of the first polarizer, one can compute the phase shift induced by the grating, its local fast axis orientation, and the ratio of the transverse electric and transverse magnetic transmission efficiencies. The paper describes the method principle and its mathematical model. Then, several numerical simulations of different subwavelength gratings are presented and their results are discussed. Finally, the optical setup is described and the measurements of one subwavelength grating are displayed and compared with the values expected from the manufacturing process.

The paper presents a theoretical analysis of properties of a specific liquid membrane lens composed of two axially symmetric membranes of different thicknesses and double curvature. These membranes enclose a space where an optical liquid is filled. Mechanical and optical properties of the lens are then changed by varying the volume of the liquid. The paper presents new formulas for calculation of membrane deflections, radii of curvatures of the membranes, and axial geometry, which offer to minimize the third-order spherical aberration of the lens for an object at infinity. The presented theory is examined on specific examples.

In this paper, one-dimensional (1D) photonic crystals (PCs) based on InSb and nonlinear materials are studied using the transmission matrix method. It is found that in the terahertz band, due to the magneto-optical characteristics of InSb, when the incident light propagates through such 1D PCs in two different directions (forward and backward propagation), an asymmetric optical bistable state can be obtained. Propagating from the forward direction, the bistable state is achieved. Spreading from the backward direction, the multistable state can be observed. Compared with the bistable threshold value for the case of forward incidence, the similar value that appeared in the multistable curve is significantly reduced. The polarization-sensitive features of the asymmetric optical bistability of the presented 1D PCs are also investigated under TM waves, which focuses on the tuning effects of incident angle, external magnetic field, temperature, and the thicknesses of the InSb and nonlinear dielectric layers on the asymmetric optical bistability. The results show that when the incident light enters from two different directions, the tailoring effects of the incident angle and thickness of the InSb layer on the bistable state are obviously different, but the tuning influences of the magnetic field, temperature, and the thickness of the nonlinear material layer on the bistable state are similar. The asymmetric optical bistability we made in this paper can be applied to multifunctional devices and nonreciprocal optical isolators.

This paper discusses noise and bias in the method of holographic interferometry applied to the study of acoustics phenomena. The influence of noise on the measurement of acoustic pressure is described by an analytical approach. Relationships to quantify the minimum measurable fluid density and acoustic pressure are given by taking into account the experimental parameters of the setup. These parameters are related to the spatial bandwidths, number of electrons in pixels, readout noise, and quantization noise. Experimental results show that theoretical relations are relatively close to experimental data and that the lower pressure measurement limit is on the order of 15 Pa for the acoustics pressure. The case of waveguides excited by an internal or external acoustic source is investigated. Specifically, for the case of studies in thermoacoustics, this paper demonstrates that the parasitic coupling of vibrations can be compensated. The proposed method is based on the determination of the amplitude and phase of the parasitic oscillation, requiring a few assumptions related to the physics of the underlying phenomenon. Successful compensation is obtained and yields experimental data in agreement with the theoretical predictions.

In addition to utilizing traditional aspheric surfaces, complicated geometric curves for meeting stringent design requirements can also be adopted in optical systems. In this paper, we investigate two geometric shape modeling schemes, namely, pedal and cosine curves, which allow for representation of an S-shaped profile for the optical design of a camera lens. To obtain a powerful tool for representing a quasi-aspheric surface (QAS) to resemble the designed form surface, we linearly combine the pedal/cosine function with a base conic section. The detailed parameterization process of representation is discussed in this paper. Subsequently, an existing starting point that has similar specifications to that of the design requirements is selected. During the optimization process, a least-squares fitting algorithm is implemented to obtain the optimal coefficient values of the proposed QAS representation, and then the parameters (radii, air thickness, lens thickness, coefficients, materials, etc.) of the optical system are set to optimize the optical performance, gradually aiming to minimize the predefined merit function. We demonstrate the applicability of the proposed geometric modeling schemes via two design examples. In comparison to a conventional aspheric camera lens of the same specifications, the optical performance with respect to field of view and distortion has been improved due to higher degrees of design freedom. We believe that the proposed technology of geometric modeling schemes promises to improve optical performance due to these higher degrees of freedom and appears to be applicable to many different camera lenses.

The Lyot coronagraph is a widely known astronomical instrument used to realize direct imaging of exoplanets, and designing transmittance of an apodizer and Lyot stop is the key to obtaining high-contrast imaging. In this paper a new (to the best of our knowledge) optimization procedure used to design the apodizer and Lyot stop in the Lyot coronagraph is proposed. A two-step optimization program is established to obtain the optimum transmittance of an apodizer and Lyot stop in a sequential way. By using the optimized apodizer and Lyot stop obtained through the proposed optimization procedure, both the stellar light and its diffraction light could be strongly suppressed. Numerical results indicate that such an optimized Lyot coronagraph can produce a 1e-10 extinction of the stellar light near the diffraction limit ( 1.59 λ / D ), and a high contrast imaging of 1e-07 could still be obtained even with the influence of light intensity of planets themselves. In addition, the two-step optimization procedure brings in two benefits. First, the two-step optimization is approximately 1000 times faster than the joint optimization method [J. Astron. Telesc. Instrum. Syst. 2, 011012 (2016)2329-412410.1117/1.JATIS.2.1.011012]. Second, the optimum transmittance of the Lyot stop is binary, and therefore, the requirements of the production process are reduced, resulting in a greatly reduced cost. At the same time, the performance of the optimized Lyot coronagraph is also analyzed in the case of a monochromatic light incident and bandwidth light incident, and the effect of the diameter of the Lyot stop on the results is also discussed in this paper, which makes sense when designing a coronagraph.

Computer-aided alignment is very important for the correction of aberrations due to construction imperfections of microlithographic optical systems. The compensation results mostly depend on the selection of compensators. In this paper, an effective method for compensation selection considering optomechanical constraints is presented. The techniques are based on the linearity of compensators and treat compensator selection as a combinatorial optimization problem with the objective of minimum residual aberrations and compensator adjustment ranges. The method is reliable and offers a better combination of compensators under constraints of optomechanical structure. As an example, the method was applied to a lithographic lens with a numerical aperture (NA) of 0.75. The results show that compensators with minimum objective function value would get minimum residual aberrations and adjustment ranges compared to those with larger objective function values. This method presented in this paper could be a good solution for compensation selection in lithographic lenses and other similar optical systems.

The geometrical propagation of a beam of light is treated in this paper using aberration theory. Stop shifting on the aberration function and on the irradiance function provides insight into how the geometrical field changes as it propagates in free space. The formulae discussed in this paper give as a function of the field and aperture of an optical system, and to the sixth order of approximation, the wavefront deformation and, to the fourth order, the irradiance at the exit pupil plane of the system. The use of the formulae is illustrated with a lens design for uniform illumination that is nearly insensitive to the location of the illuminated surface.

In this erratum we clarify our previously published paper [Appl. Opt. 57, 4008 (2018)APOPAI0003-693510.1364/AO.57.004008], where we used a solar spectrum truncated to a maximum wavelength of 830 nm in the numerical modelling, but did not state this in the paper. Here, we present a graph of the numerically modelled absorption in the Nd:YAG rod as a function of the diffuse reflectivity of the chamber walls using the full solar spectrum, confirming that the theoretical maximum possible absorption we predict is in agreement with literature values.

In a previous paper by Cebrian et al. [Opt. Eng.53, 092006 (2014)OPEGAR0091-328610.1117/1.OE.53.9.092006], the knife-edge interferometer (KEI) was used for testing lenses with a collimated beam illuminating the lens. In this paper, a 2f scheme is used to test lenses, eliminating the use of a collimation beam, and testing, for the first time, concave reflecting (spherical and parabolic) surfaces at the center of curvature with KEI.

The photovoltaic-thermoelectric (PV-TE) hybrid system can achieve full-spectrum utilization of the solar spectrum, but surface reflection has always been an important reason to suppress its power conversion efficiency. Therefore, a novel composite nanostructure (CN) is proposed by the finite-difference time-domain (FDTD) simulation method to reduce the surface reflection in the spectral range of 0.3-2.5 μm, which consists of a pyramid and grating structure. For the sake of generality, this paper studies the spectral reflectance of the CN under multiple parameters. The results show that the CN integrated pyramid and grating correspond to excellent anti-reflection performance in the short wavelength range and long wavelength range, respectively, compared to a unitary structure, achieving anti-reflection in the full spectral range. In addition, the CN expresses the insensitivity to the structural parameters, and has lower reflectivity compared with a commercial battery. The mechanism for achieving this full-spectrum anti-reflection is mainly to enhance the path of light in the medium to enhance absorption and achieve high transmission under the action of the waveguide. This paper implements ultra-broadband anti-reflection of a compound nanostructure for full-spectrum utilization of solar energy, and provides a solution to improve the power conversion efficiency of PV-TE hybrid systems.