Small Optical Devices Research Articles

Multi-component 20La2O3–20TiO2–20Nb2O5-20(Al2O3/ZrO2)-20(ZrO2/Ta2O5) glasses with ultra-high refractive index and mechanical properties inspired by high-entropy design

The highly refractive glasses with excellent mechanical properties (hardness, Young's modulus, and fracture toughness) are highly desired for the lenses used in small optical devices. In this study, a series of five-primary-component 20La2O3–20TiO2–20Nb2O5-20(Al2O3/ZrO2)-20(ZrO2/Ta2O5) (LTNAZ, LTNAT, LTNZT) glasses were designed by using high-entropy strategy and successfully elaborated through a containerless melting-solidification process. The highest refractive index (nd) of the glasses reach up to 2.25. The maximum vickers hardness (HV), Young's modulus (E), and indentation fracture toughness (KIFT) are 10.74 GPa, 157.5 GPa, and 1.23 MPa m0.5 respectively. The glasses exhibit good glass forming ability with kinetic window (ΔT) ranging from 80 to 116 °C. The excellent comprehensive performances of the glasses are attributed to the high electronic polarizability and dissociation energy, as well as the synergistic effect of multiple components in the high-entropy effect. The glasses will be promising host materials for optical applications such as digital product lenses, endoscopes and mini size lasers.

Effect of Protective Layer on the Performance of Monocrystalline Silicon Cell for Indoor Light Harvesting.

The development of renewable energy sources has grown increasingly as the world shifts toward lowering carbon emissions and supporting sustainability. Solar energy is one of the most promising renewable energy sources, and its harvesting potential has gone beyond typical solar panels to small, portable devices. Also, the trend toward smart buildings is becoming more prevalent at the same time as sensors and small devices are becoming more integrated, and the demand for dependable, sustainable energy sources will increase. Our work aims to tackle the issue of identifying the most suitable protective layer for small optical devices that can efficiently utilize indoor light sources. To conduct our research, we designed and tested a model that allowed us to compare the performance of many small panels made of monocrystalline cells laminated with three different materials: epoxy resin, an ethylene-tetrafluoroethylene copolymer (ETFE), and polyethylene terephthalate (PET), under varying light intensities from LED and CFL sources. The methods employed encompass contact angle measurements of the protective layers, providing insights into their wettability and hydrophobicity, which indicates protective layer performance against humidity. Reflection spectroscopy was used to evaluate the panels' reflectance properties across different wavelengths, which affect the light amount arrived at the solar cell. Furthermore, we characterized the PV panels' electrical behavior by measuring short-circuit current (ISC), open-circuit voltage (VOC), maximum power output (Pmax), fill factor (FF), and load resistance (R). Our findings offer valuable insights into each PV panel's performance and the protective layer material's effect. Panels with ETFE layers exhibited remarkable hydrophobicity with a mean contact angle of 77.7°, indicating resistance against humidity-related effects. Also, panels with ETFE layers consistently outperformed others as they had the highest open circuit voltage (VOC) ranging between 1.63-4.08 V, fill factor (FF) between 35.9-67.3%, and lowest load resistance (R) ranging between 11,268-772 KΩ.cm-2 under diverse light intensities from various light sources, as determined by our results. This makes ETFE panels a promising option for indoor energy harvesting, especially for powering sensors with low power requirements. This information could influence future research in developing energy harvesting solutions, thereby making a valuable contribution to the progress of sustainable energy technology.

Super strong wide TM Mie bandgaps tolerating disorders

This study demonstrates the appearance of super intense and wide Mie bandgaps in metamaterials composed of tellurium, germanium, and silicon rods in air that tolerate some disordering of rod position and rod radius under transverse magnetic (TM) polarized light waves. Tellurium metamaterials reveal {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, {mathrm{TM}}_{21}, {mathrm{TM}}_{02}, {mathrm{TM}}_{12} Mie bandgap modes in which {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, and {mathrm{TM}}_{21} tolerate high rod-position disordering of 50% and rod-radius disordering of 34 and 27%, respectively. Results for germanium metamaterials show Mie bandgap modes {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, and {mathrm{TM}}_{21}, in which {mathrm{TM}}_{01} and {mathrm{TM}}_{11} tolerate rod-position disordering of 50%, and rod-radius disordering of 34 and 20%, respectively. Using these characteristics of {mathrm{TM}}_{11} in germanium metamaterials under position and radius disordering, ultra-narrow straight, L-shaped, and crossing waveguides that contain 14, four, and two rows of germanium rods in air are designed. Also, it is shown that {mathrm{TE}}_{01} Mie bandgap appears in metamaterials containing a high refractive index, and disappears in metamaterials with a lower refractive index such as silicon; in contrast, a new phenomenon of intense and broadband {mathrm{TM}}_{01}, {mathrm{TM}}_{11}, and {mathrm{TM}}_{21} in metamaterials with a lower refractive index such as silicon appear. In silicon-based metamaterials, {mathrm{TM}}_{01} tolerates high rod-position and rod-radius disordering of 40% and 34%, respectively, and {mathrm{TM}}_{11} shows robustness to rod-position and rod-radius disordering of 20%. This strong tolerance of disordering of TM modes in tellurium, germanium, and silicon metamaterials opens a new way to design small, high-efficient, and feasible fabrication optical devices for optical integrated circuits.

Wireless Sensor Networks Using Sub-Pixel Optical Camera Communications: Advances in Experimental Channel Evaluation.

Optical wireless communications in outdoor scenarios are challenged by uncontrollable atmospheric conditions that impair the channel quality. In this paper, different optical camera communications (OCC) equipment are experimentally studied in the laboratory and the field, and a sub-pixel architecture is raised as a potential solution for outdoor wireless sensor networks (WSN) applications, considering its achievable data throughput, the spatial division of sources, and the ability of cameras to overcome the attenuation caused by different atmospheric conditions such as rain, turbulence and the presence of aerosols. Sub-pixel OCC shows particularly adequate capabilities for some of the WSN applications presented, also in terms of cost-effectiveness and scalability. The novel topology of sub-pixel projection of multiple transmitters over the receiver using small optical devices is presented as a solution using OCC that re-uses camera equipment for communication purposes on top of video-monitoring.

Compact and high-speed Stokes polarimeter using three-way polarization-preserving beam splitters.

We present a new real-time Stokes parameter measurement technique using three polarized beam splitters without mechanical motion or electrical tuning. This system can analyze the polarization state of light at 30kHz, limited only by the speed of the detector analog to digital converters. The optical system is also compact (52×30×25 mm) because it consists only of small volume optical devices. We show that the system can measure arbitrary polarization states with an accuracy of better than 0.006 in the normalized Stokes parameters. We also demonstrate the ability to measure fast dynamic polarization states by analyzing the state produced by a fast rotating quarter-wave plate and the time-dependent stress induced in a PMMA block by hitting the block with a hammer.

Significant reduction in propagation loss in electrospun polymer fibers by adopting thermal drawing

Electrospun polymer submicroscale fibers normally have flexible cylindrical waveguide geometries and can be produced with ultra-long and functional materials. Hence, they are promising building blocks for small optical devices. However, the propagation loss in the fibers is still higher than that in submicroscale polymer fibers produced by melt and solution drawing. In this study, thermal drawing of electrospun fibers was found to reduce their propagation loss. Fivefold thermal drawing of as-electrospun polymer fibers significantly reduced their diameters (e.g., from 1.121 μm to 0.497 μm) and propagation loss (e.g., from 16 dB cm−1 to 6.6 dB cm−1 at 521-nm wavelength). Because fluctuations in the fiber diameter significantly reduced after thermal drawing, the propagation loss reduction could be attributed to the reduced fluctuations in addition to the reduced density inhomogeneity in the fibers. These findings pave the way for low-loss electrospun fiber waveguides and their application in small optical devices.

Luminescence of III-IV-V thin film alloys grown by metalorganic chemical vapor deposition

III-IV-V heterovalent alloys have the potential to satisfy the need for infrared bandgap materials that also have lattice constants near GaAs. In this work, significant room temperature photoluminescence is reported for the first time in high quality III-IV-V alloys grown by metalorganic chemical vapor deposition. Pronounced phase separation, a characteristic suspected to quench luminescence in the alloys in the past, was successfully inhibited by a modified growth process. Small scale composition fluctuations were observed in the alloys; higher growth temperatures resulted in fluctuations with a striated morphology, while lower growth temperatures resulted in fluctuations with a speckled morphology. The composition fluctuations cause bandgap narrowing in the alloys—measurements of various compositions of (GaAs)1-x(Ge2)x alloys reveal a maximum energy transition of 0.8 eV under 20% Ge composition rather than a continuously increasing transition with the decreasing Ge composition. Additionally, luminescence intensity decreased with the decreasing Ge composition. The alloys appear to act as a Ge-like solid penetrating a GaAs lattice, resulting in optical properties similar to those of Ge but with a direct-bandgap nature; a decrease in the Ge composition corresponds to a reduction in the light-emitting Ge-like material within the lattice. An energy transition larger than 0.8 eV was obtained through the addition of silicon to the (GaAs)1-x(Ge2)x alloy. The results indicate significant promise for III-IV-V alloys as potential materials for small bandgap optical devices with previously unachievable lattice constants.

Adjusting third-order nonlinear properties in silicon triply resonant nanobeam cavities

We propose the use of triply resonant silicon photonic structures, based on a set of three coupled silicon nanobeam cavities, to engineer third-order nonlinearities. We show that a judicious selection of the opto-geometrical parameters allows a nearly independent tuning of the linear and nonlinear properties of the system. We demonstrate that longitudinally shifting the central cavity weakly affects the system nonlinear properties while strongly changing its resonance wavelengths. In contrast, longitudinally shifting one of the side cavities leads to a significant variation of the self-phase modulation, cross-phase modulation, and four-wave mixing nonlinear overlaps, while the linear properties of the three-cavity photonic molecule are then only moderately tuned. This geometrical control of the nonlinear properties of photonic molecules opens new degrees of freedom for the realization of small footprint and efficient optical switching and frequency conversion devices.

Effect of nanosectioning on surface features and stiffness of an amorphous glassy polymer

Sectioning of a glassy polymer, poly(methyl methacrylate), at nanoscale was carried out by means of an ultramicrotome. The effects of sectioning thickness and speed on the morphology and stiffness over the sectioned surface were then investigated by atomic force microscopy. A critical sectioning thickness and speed were identified, below which flat and smooth surfaces were created with homogeneous elasticity. Above the critical thickness or speed, periodic localized structures formed on the sectioned surfaces, leading to a nonhomogeneous distribution of the mapped elasticity. Finite element simulation reproduced the periodic structures observed in the experiments. The influence of sectioning speed on the surface stiffness was predicted by a phenomenological damage model and was found to correlate with the experimental results. The study lends confidence that critical sectioning conditions (e.g., the sectioning thickness and speed) can be identified to avoid undesirable local deformation and damage in the manufacture of small scale optical and photonic components and devices. POLYM. ENG. SCI., 58:1849–1857, 2018. © 2017 Society of Plastics Engineers

OP.8D.06] OCULAR FUNDUS PHOTOGRAPHY WITH A SMARTPHONE DEVICE IN ACUTE HYPERTENSION

Objective: The ocular fundus (FO) examination is infrequently and poorly performed in the emergency department (ED) clinical settings, placing patients at risk for missed diagnosis of hypertensive emergencies. Aim: to investigate the feasibility of the FO photography with a smartphone small optical device (D-Eye; J Ophtalmol. 2015) in a ED setting and to compare it to a traditional FO examination. Design and method: The study included 41 consecutive patients (mean age 69 ± 16 years, 50% women) presenting to an hospital ED with an acute increase in blood pressure (SBP >180 and/or DBP >100 mmHg). When admitted to the ED all patients had mydriatic FO examination obtained by an Emergency physician (EP) using both a traditional ophtalmoscope and a commercially available FO smartphone device (D-Eye, Si14 S.p.A., Padova). All FO images and videos recorded with the D-Eye system were analysed by 2 independent expert (ophthalmologist) and inexpert (EP) observers. A quantitative score of hemorrages, exudates and/or papillary edema was used (0 absent, 1 early, 2 moderate, 3 severe, 4 very severe). The Cohen K coefficient (Ki) was used to assess the inter-observer concordance index. Results: Six patients had headache, 6 had focal neurologic symptoms, and 4 had acute visual changes. The mean duration of FO examination was 130 ± 39 and 74 ± 31 seconds for traditional ophtalmoscopy and for smartphone D-Eye, respectively. No relevant abnormalities of their FO were detected by traditional ophthalmoscopy, performed by the EP, while a signifcant number of abnormal FO findings were detected by the use of the D-eye device in 17 and 19 patients by the EP and ophthalmologist, respectively. The Ki value ranged from 0,66 to 0,77 (good concordance) for the assessment of hemorrages and exudates, and from 0,89 to 0,90 (optimal concordance) for the evaluation of presence and severity of papilledema. Conclusions: Our results show that a new small smartphone device (D-Eye) may be feasible in an ED setting for the fundoscopic examination, detecting a signifcant number of abnormal FO. The reliability of relevant FO abnormalities seems to be superior in respect to traditional fundoscopy.

Photonic crystal and photonic quasicrystal patterned in PDMS surfaces and their effect on LED radiation properties

We present results of fabrication and implementation of thin polydimethylsiloxane (PDMS) membranes with patterned surface for the light emitting diode (LED). PDMS membranes were patterned by using the interference lithography in combination with embossing technique. Two-dimensional photonic crystal and photonic quasicrystal structures with different period were patterned in the surface of thin PDMS membranes with depth up to 550nm. Patterned PDMS membranes placed on the LED chip effectively diffracted light and increased angular emission of LED radiation pattern. We presented effective technique for fabrication of patterned PDMS membranes, which could modify the emission properties of optoelectronic devices and can be applied directly on surface LEDs and small optical devices.

Development of method for quantifying essential tremor using a small optical device

BackgroundClinical assessment scales are the most common means used by physicians to assess tremor severity. Some scientific tools that may be able to replace these scales to objectively assess the severity, such as accelerometers, digital tablets, electromyography (EMG) measurement devices, and motion capture cameras, are currently available. However, most of the operational modes of these tools are relatively complex or are only able to capture part of the clinical information; furthermore, using these tools is sometimes time consuming. Currently, there is no tool available for automatically quantifying tremor severity in clinical environments. New methodWe aimed to develop a rapid, objective, and quantitative system for measuring the severity of finger tremor using a small portable optical device (Leap Motion). ResultsA single test took 15s to conduct, and three algorithms were proposed to quantify the severity of finger tremor. The system was tested with four patients diagnosed with essential tremor. Comparison with existing methodThe proposed algorithms were able to quantify different characteristics of tremor in clinical environments, and could be used as references for future clinical assessments. ConclusionsA portable, easy-to-use, small-sized, and noncontact device (Leap Motion) was used to clinically detect and record finger movement, and three algorithms were proposed to describe tremor amplitudes.

A Novel Device to Exploit the Smartphone Camera for Fundus Photography.

Purpose. To construct an inexpensive, convenient, and portable attachment for smartphones for the acquisition of still and live retinal images. Methods. A small optical device based on the principle of direct ophthalmoscopy was designed to be magnetically attached to a smartphone. Representative images of normal and pathological fundi were taken with the device. Results. A field-of-view up to ~20° was captured at a clinical resolution for each fundus image. The cross-polarization technique adopted in the optical design dramatically diminished corneal Purkinje reflections, making it possible to screen patients even through undilated pupils. Light emission proved to be well within safety limits. Conclusions. This optical attachment is a promising, inexpensive, and valuable alternative to the direct ophthalmoscope, potentially eliminating problems of poor exam skills and inexperienced observer bias. Its portability, together with the wireless connectivity of smartphones, presents a promising platform for screening and telemedicine in nonhospital settings. Translational Relevance. Smartphones have the potential to acquire retinal imaging for a portable ophthalmoscopy.

Sn–ZnO nanoneedles grown on Zn wire as a pointed field emitter and switching device

Sn–ZnO nanoneedles were grown by cathodic electrodeposition and an annealing process on Zn wire as a substrate. Scanning electron microscope studies showed the formation of ZnO nanoneedles. From the field emission studies, the field required to draw an emission current density of ~15.2mA/cm2 was observed at an applied field of ~0.14V/μm. In addition, field emission behavior of specimen grown on wire substrate demonstrates the applicability of Sn–ZnO as an electron current source with small optical size and switching device. The observed results suggest the suitability of this synthesis route for fabrication of pointed emitter.

Analysis and characterization of Er–Yb codoped-depressed inner cladding fiber

A 125 μm-diameter erbium-ytterbium-codoped single-mode fiber is reported. The utilization of depressed inner cladding guarantees the improvement of trade-off between the effective area and bending sensitivity compared to step-index profiles. Changes of cutoff wavelength, effective area, and macrobend loss under the influence of various structural parameters, and the balancing selection of core radius and subsidence layer width are investigated systematically. For the laboratory-made depressed inner cladding fiber, a macrobend loss of 0.06 dB/loop for a bending radius as tight as 10 mm was achieved, while maintaining an effective area of 164.22 μm² with intact single-mode properties at 1550 nm. The maximum small signal gain was achieved at 40.9 dB, and the gain fluctuation was less than 1 dB at the C-band. The fiber is suitable for high-power, small, portable, and handy optical fiber devices.

Spacecraft Attitude Determination System Using Nano-Optical Devices and Linux Software Libraries

This paper presents a new spacecraft attitude determination system based on small optical devices and Linux-based software. This technology intends to support nanosatellite operations by providing low-cost, low-mass, low-volume, low-power, and redundant attitude determination capabilities with quick and straightforward onboard programmability for real-time spacecraft operations. The chosen commercial-off-the-shelf optical devices perform sensing and image processing on the same circuit board, and they are biologically inspired by insects’ vision systems, which measure optical flow and/or track objects while navigating the environment. The firmware on the devices is modified here to enable communication with PC/104 form-factor embedded computers running RealTime Application Interface for Linux. Algorithms are developed for operations using optical flow mode and point-tracking mode, and an application programming interface, along with Simulink® S-functions, is created. The performances of the proposed system, used in optical flow mode, point-tracking mode, and a combination of the two, are assessed using a spacecraft simulator at Rensselaer Polytechnic Institute, and they are compared with measurements from the PhaseSpace® motion-tracking system.

Micro Energy Source Using WGMs of Wave in Small Scale Optical Device

Simulation results of forms of waves in a ring resonator system known as a PANDA ring resonator for coated and uncoated materials have been proposed and discussed. The input waves (lights) can be in the forms of soliton, Gaussian pulses, photon or matter wave. The trapped electron motion around the PANDA ring can also be generated, in which the matter wave concept is formed within the PANDA ring waveguide. From the results, we found that the whispering gallery mode (WGM) can be generated due to coupling effects of the two nonlinear side rings, which have shown many interesting results and aspects, especially for energy applications, which can be fabricated and tested on-chip.

Muscle Sensor Model Using Small Scale Optical Device for Pattern Recognitions

A new sensor system for measuring contraction and relaxation of muscles by using a PANDA ring resonator is proposed. The small scale optical device is designed and configured to perform the coupling effects between the changes in optical device phase shift and human facial muscle movement, which can be used to form the relationship between optical phase shift and muscle movement. By using the Optiwave and MATLAB programs, the results obtained have shown that the measurement of the contraction and relaxation of muscles can be obtained after the muscle movements, in which the unique pattern of individual muscle movement from facial expression can be established. The obtained simulation results, that is, interference signal patterns, can be used to form the various pattern recognitions, which are useful for the human machine interface and the human computer interface application and discussed in detail.

Development of a novel façade sandwich panel with low-density wood fibres core and wood-based panels as faces

The paper explores, experimentally and theoretically, the possibility of producing a novel cladding sandwich panel comprised of a low-density wood fiber (WF) core and faces made of wood-based panels. Tests on small specimens, using physical and optical devices, were performed for the basic mechanical characterization of WF. Shear modulus (G) was the main target; and values for a range of nominal densities (ρ) from 110 to 190 kg/m3 were obtained. Short term load tests on real scale WF sandwich (WFS) specimens of 3.2 m span were also performed. An initial simple analytical structural linear model, taking into account the shear deformation of the core, was used to evaluate the data obtaining a reasonable agreement. The results show that WFSs are a viable solution at least for claddings; special care must be taken, however, in the selection of the face panels due to the influence of hygro-thermal changes. The line of work is especially attractive as WF is a natural and sustainable product.

A study on manufacturing technology for an inclined polygon mirror

Generally, the core component of small precise optical device demands high accuracy of manufacturing processes. Although, the geometry of it is simple, the manufacturing technique to materialize is categorized as the ultra precision machining and it must be done with the specialized machines and by the trained operator. Typical examples of small precise optical device are laser printer and phone camera. The shape is very simple but required manufacturing technology is very difficult. It belongs to fine precision machining technique and needs an ultra precision machining center and an assignment researcher. Laser printers and phone cameras are representative examples in small precise optical device. Recently, small sized display device is being developed and has an inclined polygon mirror as core part. The inclined polygon mirror is different with the previous polygon mirror in the point of view that it has a variety of reflection angle. With the result that, multi lines were achieved at screen. It could not be fabricated with conventional machine for a typical polygon mirror. It was manufactured in the process of fly-cutting with Al material on which was coated electroless-Ni for enhancement of hardness. Owing to process of polishing has bad influence on reflection angle, the inclined polygon mirror must be only fabricated with fly-cutting and have surface roughness R max = 10 nm and form error R a = λ /10 ( λ = 632 nm).