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Significance: The estimation of tissue optical properties using diffuse optics has found a range of applications in disease detection, therapy monitoring, and general health care. Biomarkers derived from the estimated optical absorption and scattering coefficients can reflect the underlying progression of many biological processes in tissues. Aim: Complex light--tissue interactions make it challenging to disentangle the absorption and scattering coefficients, so dedicated measurement systems are required. We aim to help readers understand the measurement principles and practical considerations needed when choosing between different estimation methods based on diffuse optics. Approach: The estimation methods can be categorized as: steady state, time domain, time frequency domain (FD), spatial domain, and spatial FD. The experimental measurements are coupled with models of light--tissue interactions, which enable inverse solutions for the absorption and scattering coefficients from the measured tissue reflectance and/or transmittance. Results: The estimation of tissue optical properties has been applied to characterize a variety of ex vivo and in vivo tissues, as well as tissue-mimicking phantoms. Choosing a specific estimation method for a certain application has to trade-off its advantages and limitations. Conclusion: Optical absorption and scattering property estimation is an increasingly important and accessible approach for medical diagnosis and health monitoring. [ABSTRACT FROM AUTHOR]

The use of bioluminescence as a reporter for physiology in neuroscience is as old as the discovery of the calcium-dependent photon emission of aequorin. Over the years, luciferases have been largely replaced by fluorescent reporters, but recently, the field has seen a renaissance of bioluminescent probes, catalyzed by unique developments in imaging technology, bioengineering, and biochemistry to produce luciferases with previously unseen colors and intensity. This is not surprising as the advantages of bioluminescence make luciferases very attractive for noninvasive, longitudinal in vivo observations without the need of an excitation light source. Here, we review how the development of dedicated and specific sensor-luciferases afforded, among others, transcranial imaging of calcium and neurotransmitters, or cellular metabolites and physical quantities such as forces and membrane voltage. Further, the increased versatility and light output of luciferases have paved the way for a new field of functional bioluminescence optogenetics, in which the photon emission of the luciferase is coupled to the gating of a photosensor, e.g., a channelrhodopsin and we review how they have been successfully used to engineer synthetic neuronal connections. Finally, we provide a primer to consider important factors in setting up functional bioluminescence experiments, with a particular focus on the genetic model Caenorhabditis elegans, and discuss the leading challenges that the field needs to overcome to regain a competitive advantage over fluorescence modalities. Together, our paper caters to experienced users of bioluminescence as well as novices who would like to experience the advantages of luciferases in their own hand. [ABSTRACT FROM AUTHOR]

We present practical laboratory work for master's students in photonics. The laboratory session is based on the construction of a telescope, emulating the one used by Galileo Galilei and analyzing the effect of aberrations and other practical limitations on the quality of the image. Different situations and configurations are analyzed, and the recreation of historical observations is carried out to generate a debate on the limitations of real telescopes with the students. The impact on the learning procedure of the students is analyzed by means of the results they have obtained during several academic years. [ABSTRACT FROM AUTHOR]

This communication analyzes the potential for immersive virtual reality (IVR) to improve efficiency in optics education. We first critically review the common motivations to use IVR in education. Second, we highlight the two capabilities of IVR that distinguish it from the other visualization technologies that can be used in education: immersion and analysis of the learner's movement. Then, we identify four characteristics of situations in which IVR can efficiently support optics learning: large equipment, operating with distraction, security training, and feedback for motor skills. We illustrate these findings with 11 concrete examples. [ABSTRACT FROM AUTHOR]

Public educational outreach is critical for introducing students to the field of optics. Video-sharing platforms, including YouTube and TikTok, are powerful tools for introducing optics to young students, especially as video consumption rates continue to rise. The proliferation of short, casual videos shot vertically on a cell phone on these applications and other social media platforms has greatly reduced the barriers to entry for educating through video. This work will cover the strategies and tactics used by Edmund Optics in recent years to establish and rapidly scale up a video-based outreach program that now reaches up to 13 million views per month. While this scale may at first seem unattainable, short-form video on social media provides a low-cost, low-time-requirement method for achieving this level of reach. In addition to practical guidance for educational video creation, the benefits of such an effort to the company or institution who sponsors it and tips to get buy-in from organizational leadership will be shared. A digital video-based optics outreach program can serve as the foundation for a larger outreach effort that develops the future photonics workforce. [ABSTRACT FROM AUTHOR]

Robot-guided laser ablation for surgical applications potentially offers many advantages compared to by-hand mechanical tissue cutting. However, given that tissue can be rough and/or uneven, ablation quality can be compromised if the beam waist deviates significantly from the target tissue surface. Therefore, we present a method that uses optical coherence tomography (OCT) for dynamic refocusing of robot-guided surgical laser ablation. A 7-DOF robotic manipulator with an OCT-equipped optical payload was used to simulate robotic guided laser osteotomy. M-mode OCT feedback is used for continuous surface detection to correct for axial deviations along the ablation path due to surface nonuniformity. We were able to show that such a correction scheme could maintain the beam waist within the depth of focus for surface variation as aggressive as 45 deg with feed rates up to 1 mm/s. Strategies for implementation in surgical and nonsurgical applications are examined. [ABSTRACT FROM AUTHOR]

We describe the design and ground-based performance of the two-color calibration lamp for the Michelson Interferometer for Global High-Resolution Thermospheric Imaging (MIGHTI) instrument on the NASA Ionospheric Connection (ICON) satellite. The calibration lamp assembly contains radio frequency excited krypton and neon lamps, which generate emission lines at 557 and 630 nm, respectively, and which are used to monitor thermal drifts in the two MIGHTI Doppler asymmetric spatial heterodyne interferometers. The lamps are coupled to two mixed optical fiber bundles that deliver the calibration signals to the two MIGHTI optical units. The assembly starts reliably, consumes <8 W, and has passed environmental testing for the ICON satellite. The total mass of the lamp assembly is 1.8 kg. Special features of the assembly and its implementation are described along with results of life tests. [ABSTRACT FROM AUTHOR]

High on the list of desired capabilities for warfighters noted at the 2008 Fort Benning "Lab Day" was the development of combat protective eyewear with lenses that would instantly change the amount of light they transmit, based on incident lighting conditions. We reviewed the investigation regarding the effect of four different protective spectacle lens designs [clear, standard sunglass, step filter (SF), and electro-optical (EO)] on a soldier's ability to rapidly transition from bright to dim environments. The dependent measures were selected to specifically permit the findings to be evaluated in both clinical and operational terms. A multifactorial analysis of variance revealed global statistically significant interactive effects regarding the viewing lenses, subject marksmanship, and subject visual acuity. The subjective preference ratings indicated a clear preference for the SF and the EO eyewear over no eyewear, the Authorized Protective Eyewear List (APEL) clear eyewear, and the APEL sun eyewear. Operational performance results while wearing either of these two optical devices (the SF eyewear and the electronic eyewear) are equally effective. Consequently, the fielding of either transition strategy provides equal acceptance and utility by the soldiers using this transitional gear. [ABSTRACT FROM AUTHOR]

A software for fast rendering the visual appearance of a blood vessel located in human skin was developed based on a numerical solution of the radiative transfer equation. The user can specify geometrical properties, such as the depth and the diameter of the vessel, and physiological properties, such as the oxygen saturation of the vessel or the blood concentration in the skin. From these data, the spatially and spectrally resolved reflectance from the skin containing the blood vessel is calculated via Monte Carlo simulations, by which a two-dimensional image is generated. The short calculation time of about a second is achieved by precalculating and storing the spatially resolved reflectance for a variety of combinations of the optical and geometrical properties. This concept gives the user the opportunity to rapidly explore the influence of the physiological and geometrical properties of the investigated blood vessel on its visual appearance. The correctness of the lookup table was validated by comparison with independent Monte Carlo simulations. Rendering examples of different blood vessels in human skins are given. [ABSTRACT FROM AUTHOR]

Background: Many MEMS and optical sensor devices can benefit from layers that block transmission and suppress reflection of light across the visible spectrum. Because these devices can include complicated topography, many existing methods for depositing antireflective layers are difficult, impractical, or unusable. Aim: To create a light-blocking antireflective layer that works well with complicated MEMS and sensor devices, a layer should be made that is cheap, simple, and can be deposited and patterned with high resolution at low temperatures. Approach: Light blocking is achieved using an aluminum layer. Suppressing reflection is achieved by mixing aluminum oxide nanoparticles in photoresist to create a layer that partially absorbs and partially scatters light. Results: The combination of a layer of metal and a layer of nanoparticles and photoresist completely blocks transmission of light and significantly reduces reflections across the visible spectrum, particularly for shorter wavelengths. The layer is also patternable to sizes as small as a few microns with high resolution. Conclusion: By combining a metal layer and a layer of nanoparticles in photoresist, a simple, cheap, and effective light-blocking antireflective layer can be created that is compatible with planar devices with complex topography. [ABSTRACT FROM AUTHOR]

We report the design, fabrication, and measurement of waveguide lattice filters for use in integrated Raman- or fluorescence-based spectroscopy and sensing systems. The filters consist of a series of broadband directional couplers and optical delay sections that create an n-stage unbalanced Mach-Zehnder interferometer specifically designed to segregate pump light and redshifted signal light in the two output ports. We first report the design criteria for optimal filter performance. Then, we use these criteria with numerical beam propagation methods to design specific broadband couplers. The filters were fabricated by a photonic integrated circuit foundry and measured using white-light spectroscopy. We report both four-stage and eight-stage filters, with the eight-stage filter demonstrating a 190-nm-wide signal passband (1100 cm-1) on the "through" port with <1.5 dB of ripple and a 17-nm-wide, 20-dB extinction band at the filter resonance. [ABSTRACT FROM AUTHOR]

This work presents a highly sensitive hybrid-integrated optical receiver with a custom designed linear transimpedance amplifier (TIA). The choice of the circuit and diode technology, considering the impact of process parameters on the optical sensitivity and the input referred noise current, are elaborated. The TIA has been designed in a 55-nm complementary metal oxide semiconductor process and was combined with a commercial InGaAs/InP PIN-diode. Measurements resulted in a transimpedance of 9.2 kΩ and a bandwidth of 1.4 GHz. The optical sensitivity of the hybrid receiver is −27.45 dBm for 2 Gbps, with a wavelength of 1550 nm and a bit error rate of 10 − 9. The input referred root mean square (RMS) noise current results in 110 nA. The fabricated chip has an area of 410 μm × 410 μm and a power consumption of 31 mW at a 1 V supply voltage. The performance of the designed TIA is able to match other designs used in high sensitivity applications such as continuous variable quantum key distribution or optical wireless communication, while consuming significantly less power and having a smaller chip area. [ABSTRACT FROM AUTHOR]

We used intravital multiphoton microscopy to study the recovery of hepatobiliary metabolism following carbon tetrachloride (CCl4) induced hepatotoxicity in mice. The acquired images were processed by a first order kinetic model to generate rate constant resolved images of the mouse liver. We found that with progression of hepatotoxicity, the spatial gradient of hepatic function disappeared. A CCl4-induced damage mechanism involves the compromise of membrane functions, resulting in accumulation of processed 6-carboxyfluorescein molecules. At day 14 following induction, a restoration of the mouse hepatobiliary function was found. Our approach allows the study of the response of hepatic functions to chemical agents in real time and is useful for studying pharmacokinetics of drug molecules through optical microscopic imaging. [ABSTRACT FROM AUTHOR]

Optical technologies may be applied to multiple facets of spinal surgery from diagnostics to intraoperative image guidance to therapeutics. In diagnostics, the current standard remains cross-sectional static imaging. Optical surface scanning tools may have an important role; however, significant work is required to clearly correlate surface metrics to radiographic and clinically relevant spinal anatomy and alignment. In the realm of intraoperative image guidance, optical tracking is widely developed as the current standard of instrument tracking, however remains compromised by line-of-sight issues and more globally cumbersome registration workflows. Surface scanning registration tools are being refined to address concerns over workflow and learning curves, and allow real-time update of tissue deformation; however, the line-of-sight issues plaguing instrument tracking remain to be addressed. In therapeutics, optical applications exist in both visualization, in the form of endoscopes, and ablation, in the form of lasers. Further work is required to extend the feasibility of laser ablation to multiple tissues, including disc, bone, and tumor, in a safe and time-efficient manner. Finally, we postulate some of the short- and long-term opportunities for future growth of optical techniques in the context of spinal surgery. Particular emphasis is placed on intraoperative image guidance, the area of the authors’ primary expertise. [ABSTRACT FROM AUTHOR]

We present an overview of the applications of self-mixing interferometer (SMI) to tasks of interest for mechanical engineering, namely high-resolution measurement of linear displacements, measurements of angles (tilt, yaw, and roll), measurements of subnanometer vibrations, and absolute distance, all on a remote target--representative of the tool-carrying turret of a tool-machine. Along with the advantages of SMI--compactness, low cost, minimum invasiveness, ease of use, and good accuracy, we illustrate the typical performance achieved by the basic SMI sensors, that is, the versions requiring a minimum of signal processing and discuss special features and problems of each approach. [ABSTRACT FROM AUTHOR]

Photoplethysmography (PPG) is a widely used technique for measuring blood oxygen saturation, commonly using an external pulse oximeter applied to a finger, toe, or earlobe. Previous research has demonstrated the utility of direct monitoring of the oxygen saturation of internal organs, using optical fibers to transmit light between the photodiode/light emitting diode and internal site. However, little research into the optimization and standardization of such a probe has yet been carried out. This research establishes the relationship between fiber separation distance and PPG signal, and between fiber core width and PPG signal. An ideal setup is suggested: 1000-μm fibers at a separation distance of 3 to 3.5 mm, which was found to produce signals around 0.35 V in amplitude with a low variation coefficient. [ABSTRACT FROM AUTHOR]

We report the design, fabrication, and characterization of 1310-nm-emission buried-heterostructure (BH) spot-size-converter (SSC)-integrated distributed-feedback (DFB) laser diode (LD) with record power efficiency of 20% at optical power of more than 100 mW at 75°C and current of 400 mA. The SSC also functions as semiconductor optical amplifier so that with laser oscillation takes place in the DFB section, the SSC provides optical gain while shaping the optical mode to give a lowest possible far-field (FF) of 9 ° (h) × 14.5 ° (v). The measured coupling loss of the SSC-integrated DFB LD output to 10 μm-radius-of-curvature lensed single-mode-fiber is ∼0.9 dB. For Co-Package Optics application, the SSC-integrated DFB LD is a potentially viable candidate for External-Laser-Source module, or for hybrid-integrated laser-source on silicon photonics (SiPh) platform via flip-chip and butt-coupling of light to SiPh waveguide. [ABSTRACT FROM AUTHOR]

The use of objective speckles as patterns is of high interest for the ongoing development of stereo photogrammetry. The depth of focus of the projected speckle patterns, which can be found to be several meters, can hardly be matched by other projection principles. On the downside, the use of coherent light leads to subjective speckles generated by the rough surface of the object under test. This effect decreases the accuracy under which objects can be reconstructed. We show how laser-based stereo photogrammetry can be adjusted to increase the measurement accuracy of three-dimensional (3-D)-surface measurements while preserving the advantages of speckles projection. Therefore, we present a method to decrease the contrast of subjective speckles in the images by pixel-wise shifting the cameras orthogonally to their viewing direction and back shifting the taken images numerically, accordingly. This leads to an increase in 3-D-reconstruction quality, as seen in a decrease in standard deviation, peak-to-valley value and in an increase in the number of reconstructed points for measured test objects. [ABSTRACT FROM AUTHOR]

A framework is presented for the analysis of average symbol error rate (SER) for M-ary quadrature amplitude modulation in a free-space optical communication system. The standard probability density function (PDF)-based approach is extended to evaluate the average SER by representing the Q-function through its Meijer's G-function equivalent. Specifically, a converging power series expression for the average SER is derived considering the zero-boresight misalignment errors in the receiver side. The analysis presented here assumes a unified expression for the PDF of channel coefficient which incorporates the M-distributed atmospheric turbulence and Rayleigh-distributed radial displacement for the misalignment errors. The analytical results are compared with the results obtained using Q-function approximation. Further, the presented results are supported by the Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The recent developments in time-domain diffuse optics that rely on physical concepts (e.g., time-gating and null distance) and advanced photonic components (e.g., vertical cavity source-emitting laser as light sources, single photon avalanche diode, and silicon photomultipliers as detectors, fast-gating circuits, and time-to-digital converters for acquisition) are focused. This study shows how these tools could lead on one hand to compact and wearable time-domain devices for point-of-care diagnostics down to the consumer level and on the other hand to powerful systems with exceptional depth penetration and sensitivity. [ABSTRACT FROM AUTHOR]

Quantum-based technologies have been instrumental in the development of a whole range of devices that are used these days (such as lasers, transistors, LiDAR, GPS, MRI, and many more). These technologies that emanated from the Quantum 1.0 Revolution have become ubiquitous in modern civilization over the past 50 years. The product commercialization and mass production were enabled by scientists, researchers, engineers, and most importantly, by the skilled technological workforce. This workforce played a critical support role in transforming inventions into high-volume, marketable products. We are currently at the heart of the Second Quantum Revolution, which is fueled by the research in quantum computing, quantum communication, quantum cryptography, and quantum sensing. The scientific progress that is currently taking place in these areas is going to fundamentally change the way we sense the world around us, approach our security, and process critical information. Governments and private entities across the world have recognized the strategic importance of quantum research-enabled technologies and have invested a significant amount of money to support graduate programs and research institutions where scientists, engineers, and other professionals are earning advanced degrees and immediately being engaged in active Quantum 2.0 research. To the best of our knowledge, and despite considerable investment in quantum research, no active efforts or programs exist that would train a quantum technological workforce at the technician level to support Quantum 2.0. The quantum industry, on the other side, has clearly identified the need for highly skilled quantum technicians that are able to support the commercialization of the new products and inventions. The lack of a trained quantum technician workforce is a major shortcoming that may have a profound negative impact on the long-term prospects and sustainability of the emerging quantum industry. The EdQuantum project, funded through the National Science Foundation (NSF) Advanced Technological Education (ATE) program, is an effort to close this shortcoming and propose a well-defined curriculum through which the incumbent photonic and laser technicians in the United States will be upskilled with the new skills and competencies from quantum research-enabled technologies. This paper presents the results of the first phase of the EdQuantum project—the quantum industry survey. Over the last few months, we sought input from the quantum industry as to what skills and competencies should a future quantum technician possess to support its emerging needs. The results collected during the survey are presented in this paper along with their impact on the proposed educational curriculum. This paper also elaborates on the alignment of the proposed curriculum with a few ongoing initiatives in the skilled technical workforce education (such as NSB Vision 2030, Convergence Accelerators Initiative, and Skilled Technical Workforce Initiative). [ABSTRACT FROM AUTHOR]

RGB (red-green-blue) technique for mapping skin chromophores by smartphones is proposed and studied. Three smartphones of different manufacturers were tested on skin phantoms and in vivo on benign skin lesions using a specially designed light source for illumination. Hemoglobin and melanin indices obtained by these smartphones showed differences in both tests. In vitro tests showed an increment of hemoglobin and melanin indices with the concentration of chromophores in phantoms. In vivo tests indicated higher hemoglobin index in hemangiomas than in nevi and healthy skin, and nevi showed higher melanin index compared to the healthy skin. Smartphones that allow switching off the automatic camera settings provided useful data, while those with "embedded" automatic settings appear to be useless for distant skin chromophore mapping. [ABSTRACT FROM AUTHOR]

An easy to realize L3 photonic crystal nanocavity that exhibits ultrahigh quality factor (Q-factor), ultrasmall mode volume, and a large Q/Vmode is proposed. A resonant cavity mode at 910.625 nm wavelength with Q-factor 4.93 x 105, mode volume 0.802 (λ/n)³, and Q/Vmode6.15 x 105 (λ/n)-3 is reported. The proposed design improves Q-factor by a factor of 84 and Q/Vmode by a factor of 70 in comparison to unoptimized L3 photonic crystal nanocavity. Such a high-quality nanocavity can be used to realize a strongly interacting quantum dot-nanocavity coupled system. [ABSTRACT FROM AUTHOR]

This work demonstrates the use of adaptive polymer lenses (APLs) for short-wavelength infrared (SWIR) applications. First, we present a push-button adaptive optical zoom system for variable magnification with a SWIR focal plane array. We then present a push-button, variable divergence, SWIR laser system for pointing and illumination. Last, we outline a system that combines the two: an SWIR adaptive zoom coupled with an APL-enhanced designator/illuminator. The result would allow a user to toggle between different fields of view (magnification), while optimizing illumination (beam divergence) for each field of view. This could be critical for situational awareness and target identification/designation in tactical applications. [ABSTRACT FROM AUTHOR]

A mid-IR amplifier consisting of a tapered chalcogenide fiber coupled to an Er3+-doped chalcogenide microsphere has been optimized via a particle swarm optimization (PSO) approach. More precisely, a dedicated three-dimensional numerical model, based on the coupled mode theory and solving the rate equations, has been integrated with the PSO procedure. The rate equations have included the main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions. The PSO has allowed the optimal choice of the microsphere and fiber radius, taper angle, and fiber-microsphere gap in order to maximize the amplifier gain. The taper angle and the fiber-microsphere gap have been optimized to efficiently inject into the microsphere both the pump and the signal beams and to improve their spatial overlapping with the rare-earth-doped region. The employment of the PSO approach shows different attractive features, especially when many parameters have to be optimized. The numerical results demonstrate the effectiveness of the proposed approach for the design of amplifying systems. The PSO-based optimization approach has allowed the design of a microsphere-based amplifying system more efficient than a similar device designed by using a deterministic optimization method. In fact, the amplifier designed via the PSO exhibits a simulated gain G = 33.7 dB, which is higher than the gain G = 6.9 dB of the amplifier designed via the deterministic method. [ABSTRACT FROM AUTHOR]

We present the design, simulation, evaluation, and technological verification of various low-index optical demultiplexers based on arrayed waveguide gratings (AWGs). When designing such optical demultiplexers, a set of input geometrical parameters must be first calculated. They are essential to create AWG layout that will be then simulated using commercial photonics tools. However, these tools do not support or support only partially such a fundamental calculation. Therefore, a new stand-alone tool called AWG-Parameters was developed, which strongly reduces the time needed for the design. From the calculated geometrical parameters, the AWG layouts were created and simulated using three commercial photonic tools: Optiwave, (Ottawa, Ontario, Canada), Apollo Photonics, (Ancaster, Ontario, Canada), and R-Soft, (Pasadena, California). The designs were also technologically verified. The simulated/measured transmission characteristics were evaluated by our newly developed AWG-Analyzer tool. This tool provides calculations of AWG transmission parameters, which are also missing in commercial photonic tools. Additionally, the tool provides clear definitions of calculated transmission parameters together with their textual and graphical representations. Finally, the transmission characteristics and parameters achieved from different photonic tools were compared with each other and discussed in detail. The simulated results were also compared with the measurements. Very good agreement was achieved between theoretical (AWG-Parameters tool), simulated (commercial photonic tools), and fabricated AWG transmission parameters. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to establish radiation-safe scanning of passersby at high security areas, such as airports and customs. The stomach was selected as the organ to be analyzed. In order to determine whether a substance found inside a human body as wrapped in a plastic bag is filled narcotics or not, many substances in white powder form including morphine-HCL were inspected. Inspection was carried out with on-ionizing radiation by irradiating stomach tissue with laser light. Optical transmittance of lamb stomach tissue was analyzed at different wavelengths. We showed that detection by 650-nm diode laser irradiation would be suitable for such a radiation-safe scan. Different materials were also investigated for absorptive properties, and closed system Raman studies were performed. The spectrum of a molecule found inside white powder placed behind the lamb stomach tissue was detected as a fingerprint. This allowed the detection of target substances without any physical contact or damage to the biological tissu [ABSTRACT FROM AUTHOR]

A small, portable, high-flux correlated photon-pair source has been designed and constructed from simple opto-mechanical parts. Unique to this device is its straightforward alignment process, together with the direct coupling of signal and idler photons into polarization-maintaining single-mode optical fibers. Spontaneous parametric down-conversion is used to produce photon pairs in β-barium borate (BBO) at a center wavelength of 810 nm. Owing to the applied type-I phase-matching, coincident photons have identical polarization. The estimated fiber-coupling efficiency is 51%, the measured photon and coincidence flux are 636 and 130 kHz/mW, respectively, normalized to pump power (44 mW). The source has an extremely wide wavelength spectrum of 202-nm FWHM, measured at the fiber output, which limits the actual heralding ratio to 20%. [ABSTRACT FROM AUTHOR]

Aero-optical beam control relies on the development of low-latency forecasting techniques to quickly predict wavefronts aberrated by the turbulent boundary layer around an airborne optical system, and its study applies to a multidomain need from astronomy to microscopy for high-fidelity laser propagation. We leverage the forecasting capabilities of the dynamic mode decomposition (DMD) — an equation-free, data-driven method for identifying coherent flow structures and their associated spatiotemporal dynamics — to estimate future state wavefront phase aberrations to feed into an adaptive optic control loop. We specifically leverage the optimized DMD (opt-DMD) algorithm on a subset of the Airborne Aero-Optics Laboratory-Transonic experimental dataset, characterizing aberrated wavefront dynamics for 23 beam propagation directions via the spatiotemporal decomposition underlying DMD. Critically, we show that opt-DMD produces an optimally debiased eigenvalue spectrum with imaginary eigenvalues, allowing for arbitrarily long forecasting to produce a robust future state prediction, while exact DMD loses structural information due to modal decay rates. [ABSTRACT FROM AUTHOR]

A metalens is a planar optical device that can accurately control the phase, polarization, and amplitude of light. Aiming at the application requirements of polarization imaging equipment for miniaturization, integration, and common field of view, we designed and fabricated two kinds of orthogonally polarized metalenses based on amorphous silicon and fused quartz. These metalenses can achieve orthogonal linear or circular polarization light imaging with a common field of view. The samples with a 2-mm diameter and 20-mm focal length were fabricated by electron beam exposure. The test results show that these metalenses can realize the imaging of orthogonal linearly or circularly polarized light simultaneously; the focusing efficiency is more than 50%, and the polarization contrast is >22 dB. [ABSTRACT FROM AUTHOR]

For industrial three-dimensional (3D)-measuring applications as well as for other applications such as driver assistance systems in vehicles, a high-quality reproduction in a depth map calculation is of paramount importance. Yet to date, light field cameras still exhibit severe problems in imaging homogeneous surfaces such as smooth metallic surfaces, plastics, or semiconductor materials. On those, the necessary contrast for determining the topography is not present or too weak. Here, we present an innovative approach to improve the performance of light field cameras (also called plenoptic cameras) for various applications in 3D measurement technology. More specifically, we show that this disadvantage can be avoided using structured lighting pattern and analyze various lighting patterns (with respect to geometry, size, regularity, etc.) used to improve the performance of the algorithm in greater detail. In addition, different ways of projecting the pattern have been examined with regard to their advantages and disadvantages. We perform a systematic investigation of the impact of structured light illumination with regard to different object materials, object geometries, and illumination patterns as well as illumination sources. These examinations further comprise the analysis of environmental influences and magnitude of measurement deviations in a light field camera measuring set-up. Summing up, we investigated experimentally the influence of structured illumination on the performance of 3D depth information without the need of additional phase information. [ABSTRACT FROM AUTHOR]

Matrices provide a practical and elegant tool for describing the transformation properties of beam splitters and waveguide couplers acting on single-mode optical fields. Using a systematic approach, we show how the application of various physical constraints determines the form of the matrix for both classical fields and quantum number states. The goal is to provide a clear explanation of the conditions under which various matrix forms are appropriate to represent four-port couplers and beam splitters. Examples of calculations using the matrices are provided. [ABSTRACT FROM AUTHOR]

The dissipative soliton resonance (DSR) pulses are demonstrated experimentally in an all polarization-maintaining (PM) thulium-doped mode-locked fiber laser. The mode-locked operation is achieved using of the nonlinear amplifying loop mirror mechanism (NALM). Each loop of the apparatus includes an independently controlled amplifier and a section of gain fiber. The experiment is carried out at a central wavelength of 1969.8 nm and 3.5 ns as the maximum output pulse width. The time domain and spectrum characteristics of output pulse are analyzed with different positions of PM-1950 fiber in the NALM loop. In addition, the DSR pulse properties are experimentally verified by changing the length of the PM-1950 fiber spliced into the NALM loop. We have achieved environmentally stable mode-locked pulses at 3, 2.1, and 1.62 MHz corresponding to the maximum pulse energies of 6.8, 20, and 29.1 nJ. The output pulse is stable and robust at different ambient temperatures. [ABSTRACT FROM AUTHOR]

Digital micromirror devices (DMDs) have become ubiquitous as spatial light modulators in the optics community, but ambiguity remains on how best to implement them in a laboratory environment. Here, we explicitly tackle the problem of generating high fidelity modes of structured light while maintaining optical efficiency. We present a theoretical characterization of the diffractive properties of the DMD, allowing us to motivate an alignment procedure that improves optical efficiency. We also present a set of best practice recommendations that cover aspects of DMD operation that are not immediately intuitive, these best practice recommendations ensure structured light is generated with the correct spatial profile and wavefront. We present experimental results that show efficiency improvements of up to 20%. Further, we demonstrate the creation of modes of structured light with fidelities in excess of 96%. The best practices presented here provide a pragmatic set of procedures for ensuring DMDs are used to their fullest potential. [ABSTRACT FROM AUTHOR]

Photonic millimeter wave (mm-wave) signal generation employing a differential Mach-Zehnder modulator (DMZM) and a semiconductor optical amplifier (SOA) is proposed and evaluated by theoretical analysis and simulation. This paper presents the theoretical study of the generation of a co-polarized and phase-locked dual-pump for four-wave mixing and optical mm-wave signal, the propagation of the optical mm-wave signal in single mode fiber, and the coherent demodulation of the electrical mm-wave signal at the base station. Performance analysis and optimization design of the proposed scheme are conducted via simulations. The generation of mm-wave signals at 30, 40, and 60 GHz is simulated and analyzed. The influence of SOA and the input optical signal on the mm-wave generation and transmission is investigated. Simulation results present useful insight for the practicality of photonic mm-wave signal generation and distribution in the next-generation access network. [ABSTRACT FROM AUTHOR]

Abstract not available [ABSTRACT FROM AUTHOR]

A simple modal interferometer is proposed, to be produced by splicing a section of a novel ring-core photonic crystal fiber (RPCF) and two segments of single-mode fibers. Owing to the effects of the collapsed region, the ring modes in the RPCF can be effectively activated. This is the first demonstration of an interferometer based on the interference between ring modes, as opposed to previously reported interferometer based on the interference of core modes or cladding modes. The effects of the length of RPCF and the wavelength on the temperature and strain characteristics of the interferometer are investigated. The strain sensitivity increases with RPCF length and with wavelength. Based on the interferometer, a strain sensor with low temperature sensitivity is proposed, which has strain sensitivity of 1.777 pm(mm). [ABSTRACT FROM AUTHOR]

We present a sapphire photonic crystal fiber structure. The structure consists of six holes symmetrically arranged within the outer single crystal sapphire layer surrounding the solid single crystal sapphire core. The single crystal sapphire fibers produced are approximately 200 min diameter with hole sizes in the range of 10 m. This represents the first time that a photonic crystal fiber has been fabricated in single crystal sapphire. [ABSTRACT FROM AUTHOR]

Over the years, numerous methods have been proposed separately for restoring images corrupted by either impulse noise or Gaussian noise. Nevertheless, because of the distinct nature of both types of degradation processes, not much work has been developed to effectively remove mixed noise from images, a problem that is commonly found in practice. To alleviate this problem, we propose a two-stage approach based on impulse detectors and detail-preserving regularization. We employ the detectors to identify impulse noise, and then restore them and smooth the remaining Gaussian noise simultaneously based on regularization framework. A novel error norm that can adaptively mimick traditional l1and l2norms is used in the regularization process. This adaptivity enables our approach to be universally capable of removing various degrees of impulse noise and mixed noise, while preserving fine image details well. Extensive experiments have been conducted to test the proposed approach and shown its improvements over the algorithms existing in the literature. [ABSTRACT FROM AUTHOR]

A tunable intracavity fiber laser has been widely used for gas sensing. In order to design a better performance sensor by use of this tunable intracavity fiber laser, the influence factors, including output power such as pump power, intracavity loss, output splitting ratio, and emission wavelength, are investigated based on a theoretical model using the propagation equation. The tunable intracavity fiber laser is set up, and the effects of pump power, intracavity loss, output splitting ratio, and emission wavelength are measured. The experimental results indicate that the theoretical analysis is in good agreement with the experimental measurements; in the process of designing the sensor, the intracavity loss and splitting ratio should be given more attention. [ABSTRACT FROM AUTHOR]

We integrate transmitting and receiving parallel optical subassemblies (POSAs) that are suitable for high-speed and parallel optical modules between optical components by using a simple and high-accuracy alignment technique. Characteristics of the proposed POSAs include a low coupling loss of 0.75 dB, a wide bandwidth for 10 Gbitsstransmission per channel, and low optical and electrical crosstalk of less than 30 dB. As a result, a data transmission rate of 10 Gbitss×12channels is well demonstrated with clean eye diagrams. [ABSTRACT FROM AUTHOR]

Coherence-free microwave photonic filter configurations are presented. The configurations are based on a Sagnac loop interferometer containing an electro-absorption modulator (EAM) without a nonreciprocal bias unit. Notch responses are obtained by modulating the clockwise and counterclockwise propagating waves inside the Sagnac loop at different times. Measured results verify the theoretical expressions and demonstrate a robust notch filter response extending to high frequency without reducing notch depth. [ABSTRACT FROM AUTHOR]