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Semitransparent organic solar cells (STOSCs) are consisted of semitransparent active layer with a structure of both top and bottom transparent electrodes and can be used as power generation windows for both electricity generation and light transmission. In order to better realize these two functions, numerous attentions have been paid on the transparent top electrodes to acquire excellent transparency and maintain high conductivity, as well as the novel photoactive materials to achieve the absorption of near-infrared region. Herein, we review recent advances in a variety of transparent top electrodes and active materials for highly efficient STOSCs, moreover, we also further highlight the application of optical engineering in STOSCs, and give some thoughts about these STOSCs.

With the increase in dimensions of optical elements in addition to ever rising demand for aspherical optics, the millimeter-scale periodic waviness that is naturally produced by machining (such as diamond turning) process in precision optical engineering has been one of the most crucial issues in the development of high surface quality optical elements. Even an extremely small waviness can affect the laser beam profile significantly through interference caused by Bragg scattering. This paper presents a novel method for improving a laser beam profile by utilizing the characteristics of Bragg scattering without requiring established final surface finishing processes such as optical polishing. By engraving an artificial periodic structure with a period of a few hundred microns, the Bragg scattering angle that influences the formation of interference fringes in the laser beam profile was drastically enlarged. Consequently, the quality of the beam profile was improved at a propagation distance where the 0th and 1st (− 1st) order beam modes are spatially separated, only by diamond turning machining without the surface finishing process. In addition, this approach represents an important contribution to green technology, which seeks energy saving and waste reduction in the optical surface manufacturing process.

The sensitivity of pneumothorax diagnosis via handheld ultrasound is low, and there is no equipment suitable for use with life-threatening tension pneumothorax in a prehospital setting. This study proposes a novel technology involving optical fibers and near-infrared spectroscopy to assist in needle thoracostomy decompression. The proposed system via the optical fibers emitted dual wavelengths of 690 and 850 nm, allowing distinction among different layers of tissue in vivo. The fundamental principle is the modified Beer–Lambert law (MBLL) which is the basis of near-infrared tissue spectroscopy. Changes in optical density corresponding to different wavelengths (690 and 850 nm) and hemoglobin parameters (levels of Hb and HbO2) were examined. The Kruskal–Wallis H test was used to compare the differences in parameter estimates among tissue layers; all p-values were 2 levels relative to those observed in the vein and artery, all p-values were also

A MARX cascade circuit laser illumination source for underwater laser range-gated imaging was developed based on the avalanche cascade principle. Compared with the ordinary laser drivers, this MARX cascade circuit had the advantages of narrow output pulse, high peak voltage, short rising edge, high repetition frequency, low cost, small volume and light weight. The pulsed laser illumination source developed by the cascade circuit maintained the miniaturization of illumination source system volume on the basis of realizing the pulse width performance with nanosecond (ns) magnitude. The experiment of range-gated imaging of underwater was carried out by the pulsed illumination source combined with laser shaping and homogenizing optical technology. With a pulse width of 10 ns, the range-gated imaging in the range of 7 times attenuation length under the water was achieved. The improvement of circuits and optics is of great significance to the reduction of volume and cost, and the application of laser range-gated imaging system.

Recent rapid progress in automotive lighting technology led to the emergence of headlamps featuring a large variety of light distributions that are highly adapted to provide best possible road illumination in particular traffic situations. Visual assistance systems which highlight relevant objects or project symbols to communicate with other traffic participants, further improve road safety. Implementing all these functions within a single headlamp usually requires the use of several additional modules with high and low resolution. This multitude of modules impacts the installation space, styling and cost of automotive headlamps. This paper presents a high-resolution red-green-blue (RGB) laser headlamp module which provides a good illumination of the road and can also be used for external communication purposes. A specially developed laser scanning unit, based on a bi-axial resonant micro-electro-mechanical systems (MEMS) scanner and a high-power RGB laser, serves as the technical basis. Three module concepts are designed using light simulation, constructed as computer-aided design (CAD) models and integrated into a serial headlamp package. The concepts are based on design, simulation and measurement data of the scanning unit.

Plasmonics has attracted considerable interest due to its promising applications in optical technology, with particular attention recently being focused on the plasmon-enhanced emission of phosphor...

Freeform surfaces are gaining popularity in vast engineering applications including optical engineering, aerospace, automotive, and biomedical. Success of freeform surfaces lies with its complex de...

Optical tweezers (OTs) are an important tool for the viscosity measurements in microrheology, and passive techniques have the features of being simple and need no external force generations. Current passive methods using OT always first calibrate the potential stiffness and then do parameter fittings to obtain the viscosity. Here, we introduced and demonstrated a passive viscosity estimation method for low-viscous microfluids using OTs without stiffness calibration and parameter fitting. By Brownian trajectory tracking of single trapped bead, the viscosity coefficients of water and NaCl solutions are quickly obtained with small deviations (typical

Given the importance of the 0.1- to 1-THz range in the security detection and diagnosis of cancer, we propose a structure for graphene-based terahertz (THz) photodetectors. We use the finite-difference time-domain and mathematical methods to calculate the light absorption in the graphene layers (GLs) and the detector’s figure of merits, including responsivity and detectivity. The proposed photodetector is based on single-layer and multilayer graphene absorbers within a p-type-intrinsic-n-type (PIN) photodiode structure. This detector is designed to achieve maximum absorption at the THz frequencies by creating adjustable Fabry–Perot resonances. Results show that it has two distinct and adjustable detection peaks in THz. So we set the operating frequency to 0.35 and 0.83 THz by adjusting the geometric parameters of the device, which also fit the atmospheric windows. Despite the low number of GLs, high absorption is provided at room temperature. It has high responsivity peaks of ∼1220 AW − 1 at the frequency of 0.35 THz and 420 AW − 1 at 0.83 THz, respectively, while we have achieved these characteristics with fewer GLs than other previous detectors.

A fiber-optic temperature sensor configuration is presented. This configuration consists of a fiber structure made from a no-core optical fiber coated with a thermochromic material as a transducer element between two multimode fibers. The excitation wavelength selected was in the absorption spectrum of the thermochromic material. The proposed sensor had a sensitivity of −0.08895 dB / ° C with a linear adjusted R-square of 0.9964 in a temperature range of 27°C to 63°C. The sensor response was characterized and validated with a commercial electronic temperature sensor.

Recently, indium tin oxide has been very attractive for thermo-optic (TO)-controlled silicon photonic devices, due to its high transparency, strong TO phase dependency, high conductivity, and CMOS compatibility. These properties enable the reduction of the gap between the silicon core and the heater, leading to a considerably low electric power consumption and high switching speed. We present an investigation of a numerical simulation to design and optimize a compact ITO microheater for tuning the TO phase shift in a proof-of-concept of a three-mode converter (TMC) with broadband and ultralow loss properties. We show that the TMC can operate the 3-dB bandwidth up to 100 nm. In addition, the designed device can attain relatively large fabrication tolerances for width and height of ±50 and ±5 nm, respectively. In addition, the proposed mode converter consumes a total power of less than 90 mW and obtains a fast switching time of less than 8 μs. Moreover, the device can be integrated into an estimated compact footprint of 8 μm × 2160 μm. Such excellent performances make ITO a strong candidate for low-loss TO phase shifters and open up an alternative method for realizing ultrafast and high-speed mode division multiplexing systems and large-scale applications.

Recording and monitoring electrically-excitable cells is critical to understanding the complex cellular networking within organs as well as the processes underlying many electro-physiological pathologies. Biopotential recording using an optical-electrode (optrode) is a novel approach which has potential to significantly improve interface-instrumentation impedance mismatching as recording contact-sizes become smaller and smaller. Optrodes incorporate a conductive interface that can sense extracellular potential and an underlying layer of liquid crystals that passively transduces electrical signals into measurable optical signals. This study investigates the impedance properties of this optical technology by varying the diameter of recording sites and observing the corresponding changes in the impedance values. The results show that the liquid crystals in this optrode platform exhibit input impedance values (1 MΩ - 100 GΩ) that are three orders of magnitude higher than the corresponding interface impedance, which is appropriate for voltage sensing. The automatic scaling of the input impedance enabled within the optrode system maintains a relatively constant ratio between input and total system impedance of about one for sensing areas with diameters ranging from 40 µm to 1 mm, at which the calculated signal loss is predicted to be1%. This feature preserves the interface-transducer impedance ratio, regardless of the size of the recording site, allowing development of passive optrode arrays capable of very high spatial-resolution recordings.

To improve the deficiencies of the current pressure-sensing structure, such as temperature crosstalk and large size, a cascaded polymer microcavity structure is prepared in the optical fiber end surface, which combined with the fiber forms an ultracompact three-beam Fabry–Perot interferometer. Two different size interferometers are prepared to monitor the details of their interference peak changes with temperature and pressure, and the sensitivity matrix method is used to measure the ambient temperature and pressure simultaneously. The proposed sensing probe effectively avoids the crosstalk problem caused by the temperature during the pressure measurement process. In addition, the two fiber polymer probes are very compact, and the axial lengths along the fiber are only 25 and 30 μm, respectively. Therefore, the sensing probe can be applied to the sensing detection of pressure in narrow areas.

All-dielectric waveguide modulators nowadays are critical for on-chip photonic circuit’s integration. We propose and theoretically demonstrate a graphene-based all-dielectric waveguide modulator with offset nanowires. The displacement between the nanowires causes the electric field parallel to the graphene to increase, thereby realizing an enhanced field modulation effect. We obtain the best modulation performance by optimizing the structural parameters and changing the offset distance of the nanowires. Analysis of the simulation results indicate that the structure offers a high modulation depth (>0.13 dB / μm) covering the S , C, and L bands. Benefitting from the strong subwavelength confinement and excellent broadband modulation performance, the proposed optical waveguide modulators offer a significant potential to realize various long-wave integrated modulators, interconnects, and optoelectronic devices.

Multi-camera stereo-digital image correlation (stereo-DIC) methods have gained popularity as non-contact methods for measuring high-spatial-resolution deformation of large engineering structures. Common multi-camera stereo-DIC methods can be classified into two types: target-based and calibration-based methods. Considering the wide application prospects of multi-camera stereo-DIC methods, it is important to study and compare the performances of these two types of multi-camera stereo-DIC methods. A four-point bending test of reinforced seawater sea-sand coral concrete (Coral-SWSSC) beams was conducted in this study to investigate the performance of multi-camera stereo-DIC in deformation measurement of slender components, and the measurement accuracy, robustness, and applicability of the two types of multi-camera stereo-DIC methods were compared and discussed. Furthermore, deformation analysis of reinforced Coral-SWSSC beams based on high-resolution multi-camera stereo-DIC methods was performed. The analysis showed that beams strengthened with basalt fiber-reinforced polymer wrapped steel tube and ultra high performance concrete (UHPC) can fully exploit the properties of Coral-SWSSC; the two strengthening materials demonstrated a higher compatibility, which compensates for the low strength defect of the Coral-SWSSC, making it a viable strengthening method. This study may promote the application of multi-camera stereo-DIC methods to measuring high-resolution deformation of large engineering structures.

We numerically calculated and analyzed the influence of a 7 × 1 fiber power combiner on supercontinuum (SC) laser beam quality in the range of 0.5 to 2.3 μm. The calculation results show the M2 oscillates within a range for a specific wavelength as the length of the output fiber changes. When the length of the output fiber is fixed, whether single input fiber or all fibers are injected with SC lasers, the M2 of the SC shows a nonlinear change and oscillates continuously throughout the entire spectrum, while it first decreases and then increases as the wavelength increases as a whole. Analysis of the numerical results shows that by changing the type of input fiber and the taper waist structure, the beam quality of both long-band and short-band parts of the SC laser can be improved. To verify theoretical calculations, the divergence angle of SC was measured as the beam quality after being transmitted by one 7 × 1 fiber power combiner in the spectral range from 0.5 to 2.3 μm. The divergence angle first decreases but then increases with a prolonging wavelength, and the curve of the experimental result renders a basic match with the calculation. To the best of our knowledge, currently no overall evaluation is reported on the beam quality of combined SC sources.

Breast cancer is one of the leading causes of death throughout the world. Early detection of breast cancer can prevent the death of many women throughout the world. There are many methods to detect tumor in breast tissue samples. Plasmonic-based sensors are of great importance in recent optical technology. A perfect semiconductor metamaterial absorber based on surface plasmon resonance is designed, and its sensing capability to detect breast cancer is investigated using numerical simulations. The indium antimonide (InSb) is used as an optimized semiconductor in the structure and the absorption value of 99.22% is obtained. The thermal, material, optical, and geometrical tunability of the structure is investigated. The maximum refractive index sensitivity as high as 24,680 nm/RIU is obtained. Moreover, it is shown that the structure can effectively work as a breast cancer detector. Furthermore, the temperature sensitivity of the structure is also analyzed, and the ultra-high value of 10,830 nm/K is obtained for thermo-optical sensitivity of this design/device.

Compared to traditional optical technology, Mueller matrix imaging can obtain sample’s complete polarization properties, thus can better characterize the microstructure and anisotropy information of the sample. For thick biological tissues or insitu living organs, backscattering Mueller matrix imaging is particularly attractive. In previous studies, we have established the collinear reflection Mueller matrix microscope based on dual rotating retarders (DRR-CRMMM), whose long acquisition time makes it difficult to characterize the polarization properties of the dynamically changing sample. In this paper, we propose and implement a fast collinear reflection Mueller matrix microscope based on dual DoFP polarimeters (DoFPs-CRMMM) and the corresponding calibration scheme to achieve accurate measurements. The system, which takes a Mueller matrix image within a few seconds, is tested for polarization monitoring of biological tissues during tissue optical clearing, and various polarization feature parameters are derived from the Mueller matrix images to reveal the characteristic microstructure variation of the tissues during the dynamic process of tissue optical clearing.

The fabrication and modeling of bow-tie antenna integrated uni-traveling carrier photodiodes (UTC-PD) are presented. The experimental results show that a −10.68 dBm RF power can be obtained from the 4 × 50 μm2 area UTC-PD at 100 GHz. The device is modeled by high frequency simulation software. The trend of variation of the measured terahertz (THz) power with frequency matches well with the simulation results. Based on the model, the effects of the shape and the contact pads of the antenna on the THz power emission properties of the device are studied numerically, which helps to further optimize the device design.

We present a wavelength division multiplexing-passive optical network (WDM-PON) that uses a graphene-based ultrashort pulsed fiber laser (USPL) as multi-wavelength source. The performance of this WDM-PON system is analyzed in two stages: at first, the USPL was designed, implemented, and characterized experimentally. Then experimental data from the USPL spectrum were then introduced into a simulated network using the software VPItransmissionMaker™, for testing the WDM-PON system performance. The results show that it is possible to achieve an error-free transmission (BER

Three different designs of plasmonic photonic crystal filters (two-channel, three-channel, and four-channel) are proposed and considered. The photonic crystal structures consist of standing rods made of Ag and GaAs, whereby introducing different simple or ring-shaped defects, two-, three-, or four-port filters are realized. Optical fluid is used instead of air as the background material, owing to its versatile benefits. By utilizing different combinations of optical fluids and plasmonic materials, multichannel filters are obtained which can function better by improving the structural parameters such as the rod’s radius. Considering the four-port filter, its applications as the power splitter are also investigated. For tuning the filter properties such as the resonance peak’s value and wavelength, impacts of Ag and GaAs rod radius on the transmission spectrum are examined. The following resonance peak’s value and FWHM are obtained for the proposed structures: two-channel filter (0.9, 4 nm), three-channel filter (0.8, 2 nm), four-channel filter (0.5, 10 nm). The proposed designed filters can be utilized in the photonic integrated circuits as well as the nanophotonics devices for medical and industrial applications.

The nanoscale modulation of light can be achieved by integrating plasmonic nanostructures with phase change materials. A dynamic and tunable perfect absorber is designed by combining VO2–Au hybrid nanodisc array with metal–insulator–metal structure. The finite-difference time-domain method is used to simulate the absorption curves under different structural parameters and temperatures. In the near-infrared band of 700 to 1800 nm, the average absorption rate and absorption bandwidth of the absorber in the insulating phase of VO2 are 87.6% and 939 nm, respectively. And the maximum absorption modulation depth before and after phase transition of VO2 reaches 63.8%. The absorber can tolerate a wide range of incident angles and exhibits polarization-independent features. We envisage that the overall advantages of this absorber will open new opportunities for optical modulation and optoelectronics.

We present a method for measuring the van der Waals force between two microspheres based on photonic force microscopy. We trapped a microsphere as probe by optical tweezers. The restricted Brownian motion of Gaussian distribution could be found in this system. The vibration center of the probe was affected by the van der Waals force when a target microsphere was closer to the probe. We measured the vibration center of the probe at different separation between the pair of microspheres. Based on this, the measurement of the van der Waals force between the two microspheres was realized with a high precision. Our method can realize the direct measurement of van der Waals force without using the variation rules of it. This method results in a simple structure, would not damage the sample, and can be suitable for the surface of any shape. It is general and has a wide range of applications in other fields of micro-force measurement.

Detection of ammonia concentration in exhaled human breath is one of the early diagnoses of renal disease. A photonic crystal fiber (PCF) gas sensor is designed, which gives the highest relative sensitivity from the wavelength of 1.1 to 1.7 μm. The structure of the proposed PCF consists of five layers with elliptical holes rotated circularly around a core region. The core region consists of two layers with circular holes, which have a hexagonal layer and a central hole. The finite element method is used to investigate the optical properties of PCF. The results show that the proposed PCF gives the highest relative sensitivity of 81.05% at the wavelength of 1.544 μm, which is the absorption line of the ammonia gas. Other optical properties of the proposed PCF, such as confinement loss and effective area, are calculated at the wavelength of 1.544 μm, which equal to 0.31 dB / m and 8.71 μm2, respectively. The impact of optical properties of the proposed PCF is investigated when the diameter of holes in the core and cladding region is changed. The results show that this structure shows good reliability for the manufacturing errors.

A highly sensitive monolithic optical receiver, applicable in optical fiber and wireless communication is presented. The proposed chip is capable of processing data rates of up to 10 Mb / s and offers compatibility to standard CMOS logic by creating full 3.3-V output swing. The photodetector of the system is carried out as a large-area fully integrated avalanche photodiode with a diameter of 800 μm and a high responsivity to red light with a wavelength of 675 nm. The receiver features pseudo differential signal processing with offset cancellation feedback to achieve desensitization to background light irradiation usually appearing with optical wireless communication. Additionally, common-mode feedback was implemented to prevent pulse width distorted output signals. Measurements at 2.5, 5, and 10 Mb / s reveal high sensitivities of −50.4, −47.65, and −42.7 dBm, respectively, for BER

Ultraflattened dispersion of optical fibers is urgently needed for ultrawideband and ultralong-haul transmission in dense wavelength division multiplexing (DWDM) systems. A systematic solution is finely developed to adjust and control the ultraflattened dispersion curves in high accuracy. The validity is verified by designing two photonic crystal fibers (PCFs) with ultraflattened chromatic dispersion across the whole telecom band (1260 to 1625 nm). Numerical results confirm that line PCF with near-zero, all-positive, and ultraflatten dispersion ranging 0.32 ± 0.17 ps / ( nm · km ) can support 1600-km line transmission in DWDM, whereas the dispersion-compensating PCF with low negative and ultraflattened dispersion ranging −15.57 ± 0.37 ps / ( nm · km ) has a high dispersion compensation efficiency of up to 33 times for line PCF. An improved PCF structure is proposed by introducing three extra small air-holes between the standard lattices of odd rings. Moreover, other fiber parameters such as nonlinear coefficient ( 0.189), and confinement loss (

Laser-based additive manufacturing (LBAM) is a group of advanced manufacturing processes used to produce metal components and functionally graded products. Production in LBAM is either limited to the formation of thin or thick coatings on a substrate by laser metal deposition or the production of a fully functional metallic product by selective laser melting. In every case, LBAM fabricated components require optimization for the process parameters to avoid defects, such as porosity, crack holes, thermal deformation, and mechanical strength. As a key link in the laser additive manufacturing (LAM) process, laser scanning path planning is an effective strategy for balancing the temperature field of the formed part, avoiding stress concentration, and preventing deformation and cracking. Efficient, accurate, and reasonable planning of the laser scanning path is of great significance for improving the processing efficiency of the process data, prolonging the life of the laser scanning system, and improving the forming quality of the specimen. Through many studies, it was found that the scanning pattern of the lasers has a significant impact on the mechanical properties and deformations caused by a thermal mismatch during the process. Therefore, it is essential to have in-depth knowledge about path planning in LBAM. Our review mainly focuses on the influence of scanning patterns on deformation, temperature, and mechanical properties in LBAM. Finally, our paper discusses the current study limitations and some future studies in LAM technology.

Calcium fluoride and zinc sulfide crystals exhibit broad multispectral transparency and are used for a multitude of optical applications. However, they both belong to a soft brittle crystal category and are mechanically challenging to process. Thus, a fabrication protocol using a single-point diamond turning method was developed, which can yield surfaces with optical quality for these materials. By using a diamond turning tool with low waviness (≤100-nm waviness) and by using feed rates of 1 and 0.2 μm / rev, CaF2 and ZnS surfaces with surface roughness of 6 and 5 nm were manufactured, respectively. Design and fabrication of a miniature objective with 0.5 NA are also presented, which was developed for the ultrafast laser microsurgery application. The objective consists of CaF2 and ZnS lenses to withstand the high power from ultra-short laser pulses and to provide a tightly focused beam with 1.23 μm 1 / e2 spot radius for laser ablation. Based on the spot size measurement of the objective, its performance was considered to be near diffraction limited.

Diffuse correlation spectroscopy (DCS) is a non-invasive optical technology for the assessment of an index of cerebral blood flow (CBFi). Analytical methods that model the head as a three-layered medium (i.e., scalp, skull, brain) are becoming more commonly used to minimize the contribution of extracerebral layers to the measured DCS signal in adult cerebral blood flow studies. However, these models rely on a priori knowledge of layer optical properties and thicknesses. Errors in these values can lead to errors in the estimation of CBFi, although the magnitude of this influence has not been rigorously characterized. Herein, we investigate the accuracy of measuring cerebral blood flow with a three-layer model when errors in layer optical properties or thicknesses are present. Through a series of in silico experiments, we demonstrate that CBFi is highly sensitive to errors in brain optical properties and skull and scalp thicknesses. Relative changes in CBFi are less sensitive to optical properties but are influenced by errors in layer thickness. Thus, when using the three-layer model, accurate estimation of scalp and skull thickness are required for reliable results.

The development of portable and inexpensive analyzers allowing fast determination of the integral sample characteristics is a current trend in analytical chemistry. Optical spectroscopy in visible and near infrared (NIR) range has a great potential due to the advances of modern optical engineering. Optical multisensor systems (OMS) are devices working on the principle of optical spectroscopy, but optimized for a specific analytical task and composed of cheaper elements: light-emitting diodes (LEDs), optical fibers, 3D-printed parts, stamped optics, and etc. Such specialization enables essential reduction of analyzers’ price, size and weight, thus, making the analysis widely available for both real-time application and field measurements. In the present work, a novel platform for construction of OMS was suggested. The idea is to use a combination of molecular emitters as a multichannel light source with tunable intensity and wavelength range. Cyclometalated Ir(III) complexes [1] and Cu(II)-based complexes were synthetized and tested in order to obtain such a light source. Each individual complex has its own emission spectrum in the visible range. This enables selection and optimization of the light source for a specific analytical application. Several optical setup designs of OMS were developed. The proposed prototype was applied to analyze the metal ions in aqueous mixtures. The practical application of the OMS was demonstrated for the quantification of fluoride and phosphate in real surface and tap waters. The proposed approach to OMS development allows reducing analysis time and does not require additional sample preparation. Moreover, OMS based on molecular emitters can be adopted for the particular analytical task by selecting the appropriate wavelength region. Despite the relative technical simplicity of OMS, its application in combination with modern chemometric methods provides high accuracy of analysis, comparable with that of full-featured spectrometers. This study was supported by the RSF project #19-79-00076. References [1] Gitlina A.Yu., Surkova A., Ivonina M.V., Sizov V.V., Petrovskii S.K., Legin A., Starova G.L., Koshevoy I.O., Grachova E.V., Kirsanov D.O. Dyes and Pigments, 180 (2020) 108428.

A sphere precessions polishing (SPP) method is proposed to perform the precessions polishing function like the bonnet polishing technique. A compliant inflated hollow ball is adopted as the sphere polishing tool, and three motors are used to collaboratively drive the sphere tool rotating around a desired axis tilting with a precessions angle. A prototype is developed to validate the technical feasibility and demonstrate the polishing removal functions. The polishing spots of vertical polishing show a typical W shape-like profile, and tilted polishing results reveal a D shape-like profile. This proposed SPP method can be regarded as a potential candidate technique to realize the precision precessions polishing in the optical precision engineering.

An approach that employs the aperture in front of the Raman crystal for the generation of high-order stimulated Raman scattering (SRS) was proposed. Furthermore, first- to fifth-order anti-Stokes components (508, 486, 465, 447, and 430 nm) and first- to fifth-order Stokes components (559, 588, 621, 658, and 700 nm) were generated by a potassium gadolinium tungstate (KGW) Raman generator, which were the highest-order SRS generated in KGW. The effect of the aperture was discussed, and the angular dependence of Stokes was calculated theoretically and experimentally.

An L-band single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) is proposed and experimentally demonstrated to exhibit an ultranarrow linewidth and a high optical signal-to-noise ratio. A multistage filter, which is composed of a thin film filter, a fiber Bragg grating, and a saturation absorption, is utilized as an effective mode-selecting filter to achieve an SLM EDFL. The SLM EDFL with an ultranarrow linewidth of 205 Hz is obtained at the measurement resolution bandwidth of 100 Hz. In addition, the stability performance of the EDFL is measured during 30 min. The maximum fluctuations of the center wavelength and the output power of the proposed EDFL are 0.04 nm and 0.01 dB.

We present the evaluation and comparison of four different polymers (VeroClear, ClearVue, LOCTITE 3820, and WaterShed) to produce macro transparent optical components using additive manufacturing. The refractive indices were measured at increasing temperatures. The Cauchy and Sellmeier coefficients were fitted subsequently. We used the measured and calculated parameters to determine the Abbe numbers of materials at increasing temperatures. Several different lenses of the mentioned polymers with varying orientations were printed and evaluated according to transmission, imaging quality, and temperature-dependent behavior. The results were used to build an illumination demonstrator to simulate the sunlight as it is created by a roof window.

High-power and high-quality pulsed fiber lasers with low repetition frequency are widely applied to various fields ranging from basic science to industrial applications. Coherent beam combining (CBC) is a significant method to obtain that beam, but few methods used for large-scale CBC of pulsed fiber lasers with low repetition frequency were presented. To realize it, a new method based on a continuous carrier was designed, where the continuous wave worked as the beacon signal, and the stochastic parallel gradient descent algorithm was employed for phase locking and tilt correction. The beam combining experiment revealed that the combining efficiency of two lasers with a repetition frequency of 15 kHz and a pulse width of 100 ns was 95%, and the fringe contrast in the center of the far-field spot was improved about three times. This method promises to be furtherly applied to combine the pulsed lasers with lower repetition frequency and narrower pulse width. These results pave the way for large-scale CBC of high-power and high-quality pulsed fiber lasers.

The measurement of the refractive index of optical glass samples is a common and fundamental activity in numerous fields of expertise. Several measurement techniques exist with relative accuracies from 10 − 2 to, at least, 10 − 7 with complexities that are inversely related to the corresponding uncertainty. We describe an implementation of a technique based on the measurement of the lateral displacement variation of a collimated beam caused by the rotation of a parallel plate glass sample. The method was aimed to achieve an uncertainty in the range from 10 − 3 to 10 − 4 without increasing the complexity normally associated with techniques with this level of accuracy. The system was designed and optimized based on a detailed analysis of the uncertainty budget. We describe the implementation, the data processing, and the results obtained with calibrated samples, showing a relative uncertainty at the level of 10 − 4.

Current optofluidic devices are analog focus-tunable elements with a continually varying focus between foci. An innovative digitized optofluidic element was developed to enable fast switching between the foci. The operation involves an internally placed elastic membrane of changing shape between the refractive and diffractive forms with a tiny amount of fluid transfer by a micro-actuator. This allows for switching the digitized optofluidic element between the refractive and diffractive states of the preset optical powers. A multimodal relief surface design was used in the diffractive state to manage the diffractive grooves and improve the chromatic characteristics. We applied finite element analysis to establish the membrane mechanical properties. The proof-of-concept prototypes were made using material bonding fabrication processes and were used to demonstrate an elastic membrane shape change between the refractive and diffractive forms for switching between the corresponding optical states. The design of the digitized optofluidic element allowed for bistate or tristate switching by a single actuator. The switchable element can be fairly thin, enabling conversion of a fixed lens into a dynamic lens switchable between two or three foci. The application of the tristate design to eyewear for presbyopia correction is discussed.

The present work introduces the concept of a total-internal-reflection (TIR)-based optical rotation, quasi-phase-matching (QPM) technique for generating highly efficient second-harmonic optical output in a rectangular slab of magnesium oxide-doped lithium niobate crystal coated with a thin layer of yttrium oxide. Combinational effects of TIR optical rotation QPM and fractional QPM techniques are experienced at certain bounce points inside the slab, thereby enhancing the conversion efficiency. In this analysis, the thin-film is used for controlling the phase-shifts accompanying the propagation of p- and s-polarized light at the slab-film interface during TIR. A conversion efficiency of 32%, corresponding to a second-harmonic wavelength of 532 nm has been observed using computer-aided simulation. Optical losses such as surface roughness, absorption, and interference effect due to the nonlinear law of reflection have also been incorporated.

A planar lightwave circuit-based multi-channel arrayed waveguide grating (AWG) is used as a critical part of the fiber Bragg grating (FBG) interrogation unit and designed to be integrated into the fiber grating sensing system. We designed and fabricated a high-performance, 40 channels AWG in the device, enabling whole C-band wavelength demodulation while maintaining high-measurement resolution. The AWG was designed to have 100-GHz channel spacing; the channel crosstalk was measured to be −45 dB. An AWG-based FBG interrogation system was built to analyze the characteristics of our unit. The testing result shows that our system has the capability of demodulating wavelength from 1526.438 to 1563.863 nm with wavelength accuracy within ±10 pm; the wavelength resolution is measured to be 1 pm. Our testing result confirms that an AWG-based FBG interrogator is an excellent choice for FBG sensing systems.

Single-material flexible actuators that can produce non-uniform deformation in response to external stimuli have attracted considerable interests due to their facile fabrication process and excellent actuation behavior. However, the recognition of actuation state with easily perceived and detectable signal is still a challenge. In this paper, we report an actuator behavior of single-material inverse opal photonic crystal films, which are in response to a variety of solvents based on swelling/de-swelling process. The actuator exhibits improved responsiveness due to the enhanced mass transport of solvent molecules in periodic inverse opal with macroporous structure. Especially, peaks in reflective spectra and corresponding structure colors are obviously changed, providing a simple and effective optical technology for optical recognition of micro-locomotion. Based on the above characteristics, we demonstrate the potential applications of this photonic crystal actuator as solvent-driven gripper, walking device and rolling motor, showing great promise in advanced soft robot for many important intelligent areas.

Summary The realization of semitransparent photovoltaics (ST-PVs) with optimal power conversion efficiency (PCE) and visible light transmittance (VLT) is an important step toward new applications such as power-generating windows for buildings and automobiles. A high-performing ST-PV should be wavelength selective, which best utilizes the ultraviolet (UV) and near-infrared (NIR) photons for photocurrent generation while balancing the absorption and transmission of visible photons. Semitransparent organic solar cells (STOSCs), coupled with wavelength-selective, one-dimensional photonic crystals (PCs), can meet such criteria, as organic semiconductors can achieve localized NIR absorption and PCs can further optimize device optical properties. Herein, by introducing a high-throughput optical model, we simulated over tens of millions of device configurations for PC-enhanced STOSCs to investigate their optical properties. Computationally guided fabrication of PC-enhanced PTB7-Th:IEICO-4F STOSC exhibited nearly 11% PCE and 30% VLT. The results exhibit the wide potential applications of high-throughput optical engineering, especially as related to designs including multi-objective and multi-layer thickness optimizations.