Optical Subsystems Research Articles

Facile approach towards the fabrication of compact and miniature Er3+-doped waveguide amplifiers

Compact and miniature optical amplifiers operating in the near-infrared wavelength range are in ever-increasing-demand for integrated optical communication devices and subsystems. Due to low dopant concentration and the relatively large size of conventional fiber amplifiers, however, much effort is shifting toward compact and miniature waveguide structures. We hereby demonstrate a simple and effective method for the fabrication of optical waveguide devices. The devices can be fabricated by using a miniature rare-earth-ion-doped-glass microneedle coupled with two fiber collimators at the input and output ends of the waveguide. The experimental results show that, with a pump power of 500 mW, a small-signal net gain of 13.20 dB at 1530 nm is achieved in the 1.0 cm-length active microneedle with a more than 1.0×1026 ion/m3 dopant concentration. This approach can be considered as a new gateway for the fabrication and wide application of compact and miniature waveguide devices in the future.

Performance evaluation of a downlink MIMO wideband code‐division multiple access‐based radio‐over‐fibre system using Alamouti space‐time block code

In this work, the effect of a radio-over-fibre (RoF) subsystem on the bit error rate (BER), total degradation (TD) and system capacity performances of downlink multiple-input multiple-output (MIMO) wideband code division multiple access (WCDMA) are assessed. The research investigates the use of maximal ratio combining (MRC) in single-input multiple-output (SIMO) schemes and Alamouti space-time block coding (STBC) in MIMO systems to compensate for the collective effects of the optical subsystem and the radio channel for different channel conditions and number of users. Results show that the aforementioned techniques are effective methods to compensate for both the non-linearity of the optical subsystem and the time-varying wireless radio frequency (RF) channel. It is also demonstrated that by increasing the number of users for severe non-linearity conditions, the BER performance of the system is significantly affected. Also, an appropriate quiescent point can always be found for the optical subsystem which improves the system performance irrespective of different conditions.

Site-resolved imaging of beryllium ion crystals in a high-optical-access Penning trap with inbore optomechanics.

We present the design, construction, and characterization of an experimental system capable of supporting a broad class of quantum simulation experiments with hundreds of spin qubits using 9Be+ ions in a Penning trap. This article provides a detailed overview of the core optical and trapping subsystems and their integration. We begin with a description of a dual-trap design separating loading and experimental zones and associated vacuum infrastructure design. The experimental-zone trap electrodes are designed for wide-angle optical access (e.g., for lasers used to engineer spin-motional coupling across large ion crystals) while simultaneously providing a harmonic trapping potential. We describe a near-zero-loss liquid-cryogen-based superconducting magnet, employed in both trapping and establishing a quantization field for ion spin-states and equipped with a dual-stage remote-motor LN2/LHe recondenser. Experimental measurements using a nuclear magnetic resonance (NMR) probe demonstrate part-per-million homogeneity over 7 mm-diameter cylindrical volume, with no discernible effect on the measured NMR linewidth from pulse-tube operation. Next, we describe a custom-engineered inbore optomechanical system which delivers ultraviolet (UV) laser light to the trap and supports multiple aligned optical objectives for topview and sideview imaging in the experimental trap region. We describe design choices including the use of nonmagnetic goniometers and translation stages for precision alignment. Furthermore, the optomechanical system integrates UV-compatible fiber optics which decouple the system's alignment from remote light sources. Using this system, we present site-resolved images of ion crystals and demonstrate the ability to realize both planar and three-dimensional ion arrays via control of rotating wall electrodes and radial laser beams. Looking to future work, we include interferometric vibration measurements demonstrating root-mean-square trap motion of ∼33 nm (∼117 nm) in the axial (transverse) direction; both values can be reduced when operating the magnet in free-running mode. The paper concludes with an outlook toward extensions of the experimental setup, areas for improvement, and future experimental studies.

Impact of time-variant turbulence behavior on prediction for adaptive optics systems.

For high-contrast imaging systems, the time delay is one of the major limiting factors for the performance of the extreme adaptive optics (AO) sub-system and, in turn, the final contrast. The time delay is due to the finite time needed to measure the incoming disturbance and then apply the correction. By predicting the behavior of the atmospheric disturbance over the time delay we can in principle achieve a better AO performance. Atmospheric turbulence parameters, which determine wavefront phase fluctuations, have time-varying behavior. We present a stochastic model for wind speed and model time-variant atmospheric turbulence effects using varying wind speeds. We test a low-order, data-driven predictor, the linear minimum mean square error predictor, for a near-infrared AO system under varying conditions. Our results show varying wind can have a significant impact on the performance of wavefront prediction, preventing it from reaching optimal performance. The impact depends on the strength of wind fluctuations with the greatest loss in expected performance being for high wind speeds.

Rotation effect on spin current in curved space-time

The spin-orbit interaction and spin Hall effect have drawn special attention. Not only theoretical predictions have been made, but also the generation of spin currents has been achieved in experiment. In this paper, we study the spin current and the spin Hall conductivity under the influence of rotation in the curved space-time. Our work shows that the nontrivial geometries could modify the spin-orbital interaction. By using the extended Drude model, we calculate the spin-dependent force and obtain a correction to this force by non-mediocre geometry. When considering the rotation effect, the general Dirac equation is given. The Hamiltonian under the non-relativistic approximation is obtained by the Foldy-Wouthuysen transform. According to this, we calculate the spin current and spin Hall conductance. The polarization vector is deformed due to the effect of the rotation in the curved space-time. The magnitude and direction of the spin current are changed because of the correction to rotation, and the spin Hall conductivity. The nontrivial space-time geometry leads to the anisotropic nature of the spin current. Our work uses a general method that does not depend on the model, so the result can be used to analyze the electromagnetic dynamics of charged spin particles in quantum Hall systems, and it also helps to theoretically study the defects in crystals. Our results can also be extended to the optical subsystem. Considering the spin effect of photons, based on the spin-orbit coupling of photon, a light splitting phenomenon emerges in an inhomogeneous medium, which is the spin hall effect of photon. Our discussion has a certain reference value for studying the behavior of the photonic spin Hall effect in the static gravitational field. At the same time, using the optical chips to simulate curved space-time, photon manipulation and precision measurement can give some theoretical support.

SAMSON: Spectral Absorption-fluorescence Microscopy System for ON-site-imaging of algae

This paper presents SAMSON, a Spectral Absorption-fluorescenceMicroscopy System for ON-site-imaging of algae within a watersample. Designed to be portable and low-cost for on-site use,the optical sub-system of SAMSON consists of a mixture of low-cost optics and electronics, designed specifically to capture bothfluorescent and absorption responses from a water sample. Thegraphical user interface (GUI) sub-system of SAMSON was de-signed to enable flexible visualisation of algae in the water samplein real-time, with the ability to perform fine-grained exposure con-trol and illumination wavelength selection. We demonstrate SAM-SON’s capabilities by equipping the system with two fluorescentillumination sources and seven absorption illumination sources toenable the capture of multispectral data from six different algaespecies (three from the Cyanophyta phylum (blue-green algae) andthree from the Chlorophyta phylum (green algae)). The key benefitof SAMSON is the ability to perform rapid acquisition of fluores-cence and absorption data at different wavelengths and magnifica-tion levels, thus opening the door for machine learning methods toautomatically identify and enumerate different algae in water sam-ples using this rich wealth of data.

Experimental Study of the Subsystems in a Microscale Additive Manufacturing Process

High-throughput manufacturing of complex 3D architectures for microscale products such as microelectronics is limited by the resolution of existing additive manufacturing processes. This paper presents experimental testing and validation of the major subsystems in a microscale selective laser sintering (µ-SLS) process that is capable of fabricating true-3D metallic micro-architectures with microscale feature size resolutions. In µ-SLS, the part quality and throughput of the sintering process are largely determined by the precision, accuracy, and speed of the subsystems including: (1) the optical subsystem, (2) the global positioning mechanism, (3) the XY nanopositioning stage, and (4) the powder bed dispensing system. This paper shows that each of these subsystems can maintain the sub-micrometer precision and accuracy required to produce metal parts with microscale resolutions. Preliminary sintering results with optimized process parameters show the potential of the µ-SLS process to fabricate complex metal parts with sub-10-μm resolution at high rates.

Thermodynamic consistency of the optomechanical master equation

We investigate the thermodynamic consistency of the master equation description of heat transport through an optomechanical system attached to two heat baths, one optical and one mechanical. We employ three different master equations to describe this scenario: (i) The standard master equation used in optomechanics, where each bath acts only on the resonator that it is physically connected to; (ii) the so-called dressed-state master equation, where the mechanical bath acts on the global system; and (iii) what we call the global master equation, where both baths are treated non-locally and affect both the optical and mechanical subsystems. Our main contribution is to demonstrate that, under certain conditions including when the optomechanical coupling strength is weak, the second law of thermodynamics is violated by the first two of these pictures. In order to have a thermodynamically consistent description of an optomechanical system, therefore, one has to employ a global description of the effect of the baths on the system.

Adaptive wavefront interferometry for unknown free-form surfaces

The primary problem of conventional wavefront interferometers is limited dynamic range. Unknown free-form surface figure error with large amplitude or slope is not measurable for too dense or invisible fringes. To troubleshoot this problem, we propose adaptive wavefront interferometry (AWI). AWI utilizes a wavefront sensor-less adaptive optics (AO) subsystem to intelligently speculate and compensate the unknown free-form surface figure error. In this subsystem, adaptive null optics is utilized to iteratively generate adaptive wavefronts to compensate the unknown severe surface figure error. The adaptive null optics is close-loop controlled (i.e., wavefront sensor-less optimization algorithms are utilized to control it by real time monitoring the compensation effects to guarantee convergence of the iteration). Ultimately, invisible fringes turn into resolvable ones, and null test is further realized. To demonstrate the feasibility of AWI, we designed one spatial light modulator (SLM) based AWI modality as an example. The system is based on a commercial interferometer and is easy to establish. No other elements are required besides the SLM. Principle, simulation, and experiments for the SLM based AWI are demonstrated.

Design of a Hybrid Fiber Optic Daylighting and PV Solar Lighting System

Residential buildings with limited natural lighting are generally lit by fuel-based electricity which contributes to increase of CO2 concentration in the atmosphere. This paper presents the design of a hybrid fiber-optic daylighting and PV solar lighting system for household applications. The system is composed of a light collecting subsystem, a light guiding subsystem, an optical fiber light diffuser subsystem and corresponding control system. Preliminary system performance shows that, the developed system could provide comfortable and natural indoor illumination. Meanwhile, the hybrid lighting system can provide an average of 9h of electric lighting under clear sky conditions, and reduce 158.2kg of carbon dioxide emission in a year within the tested dark room of 5m2.

AIRCRAFT FAULT DIAGNOSIS SYSTEM DEVELOPMENT

Dichotomizing algorithms of diagnostics and reconfiguration of the navigation system which process indicators of inertial, satellite and optical subsystems in real time for typical types of refusals are considered in the work. The given approach provides majority diagnostics of measuring system with system and hardware redundancy at a minimum necessary set of sensors. The main idea of a method is the comparative analysis of all measuring subsystems behind reference value. The reference value is the parameter which is synthesized from all diagnosable subsystems, in this work – a course corner. When obtaining the only parameter by gages of the different nature it is possible to provide firmness of an algorithm. Also reasonably the possibility of the introduction of optical systems with the use of algorithms of computer sight for ensuring system redundancy of the navigation system is described. The system is intended for identification only of one type of refusal for a unit of time. A positive factor of an invention is the universality that allows using system on any operating small autonomous aircraft. For the introduction of a system, there is no requirement in finishing the hardware. Use of system of failure diagnostics will reduce the risk of loss of the aircraft when performing a task, will increase its efficiency and accuracy of indicators. As a result of researches, the algorithmic dependence of signals of the navigation system was established that allowed to make the analysis and diagnostics with the following renewal of the lost parameter thanks to system and hardware redundancy of devices. Practical use of the system in actual practice with an influence of artificially created obstacles and noise is shown. Developments in area of aircraft safety are necessary due to the need for an increase in level, at the emergence of emergency situations

Understanding the reliability of LED luminaires

The purpose of this paper is to educate both manufacturers and end users on what constitutes the overall reliability of an LED luminaire and the reliabilities of individual subsystems. Wide ranges of LED luminaires are available in the market to meet the needs of a specific applications, hence a potentially wide range of product performance characteristics exist. The different subsystems in an LED luminaire introduce other potential reliability issues that will be critical in deciding the overall system lifetime. The mutual dependency of subsystems and their interactions make the prospect of characterizing LED luminaire reliability challenging. Best design practices ensure that the overall luminaire reliability will be decided by a small number of subsystems, thus reducing the complexity. In this paper, a general theory of assessing the reliability of the optical, electrical and thermal subsystems of an LED luminaire is discussed. How the remaining useful lives of the subsystems are obtained from their degradation profile and how the remaining useful life of the entire system is derived from them are explained. The theory explained in this paper is useful in designing experiments to express the reliability of an LED luminaire and its subsystems in terms of remaining useful life.

OVERVIEW OF DIGITAL FORENSICS ALGORITHMS IN DSLR CAMERAS

Abstract. The widespread usage of the mobile technologies and the improvement of the digital photo devices getting has led to more frequent cases of falsification of images including in the judicial practice. Consequently, the actual task for up-to-date digital image processing tools is the development of algorithms for determining the source and model of the DSLR (Digital Single Lens Reflex) camera and improve image formation algorithms. Most research in this area based on the mention that the extraction of unique sensor trace of DSLR camera could be possible on the certain stage of the imaging process into the camera. It is considered that the study focuses on the problem of determination of unique feature of DSLR cameras based on optical subsystem artifacts and sensor noises.

Super-resolution visible photoactivated atomic force microscopy

Imaging the intrinsic optical absorption properties of nanomaterials with optical microscopy (OM) is hindered by the optical diffraction limit and intrinsically poor sensitivity. Thus, expensive and destructive electron microscopy (EM) has been commonly used to examine the morphologies of nanostructures. Further, while nanoscale fluorescence OM has become crucial for investigating the morphologies and functions of intracellular specimens, this modality is not suitable for imaging optical absorption and requires the use of possibly undesirable exogenous fluorescent molecules for biological samples. Here we demonstrate super-resolution visible photoactivated atomic force microscopy (pAFM), which can sense intrinsic optical absorption with ~8 nm resolution. Thus, the resolution can be improved down to ~8 nm. This system can detect not only the first harmonic response, but also the higher harmonic response using the nonlinear effect. The thermoelastic effects induced by pulsed laser irradiation allow us to obtain visible pAFM images of single gold nanospheres, various nanowires, and biological cells, all with nanoscale resolution. Unlike expensive EM, the visible pAFM system can be simply implemented by adding an optical excitation sub-system to a commercial atomic force microscope.

Real-time Triple-modal Photoacoustic, Ultrasound, and Magnetic Resonance Fusion Imaging of Humans.

Imaging that fuses multiple modes has become a useful tool for diagnosis and therapeutic monitoring. As a next step, real-time fusion imaging has attracted interest as for a tool to guide surgery. One widespread fusion imaging technique in surgery combines real-time ultrasound (US) imaging and pre-acquired magnetic resonance (MR) imaging. However, US imaging visualizes only structural information with relatively low contrast. Here, we present a photoacoustic (PA), US, and MR fusion imaging system which integrates a clinical PA and US imaging system with an optical tracking-based navigation sub-system. Through co-registration of pre-acquired MR and real-time PA/US images, overlaid PA, US, and MR images can be concurrently displayed in real time. We successfully acquired fusion images from a phantom and a blood vessel in a human forearm. This fusion imaging can complementarily delineate the morphological and vascular structure of tissues with good contrast and sensitivity, has a well-established user interface, and can be flexibly integrated with clinical environments. As a novel fusion imaging, the proposed triple-mode imaging can provide comprehensive image guidance in real time, and can potentially assist various surgeries.

Horizon-T experiment status

Horizon-T is an innovative detector system constructed to study Extensive Air Showers (EAS) in the energy range above 1016 eV coming from a wide range of zenith angles (0°–85°). The system is located at the Tien Shan High-altitude Science Station of the Lebedev Physical Institute of the Russian Academy of Sciences at ∼ 3340 meters above sea level. It consists of eight charged particle detection points separated by distances up to one kilometer as well as an optical detector subsystem to measure the Vavilov-Cherenkov light from the EAS. The time resolution of charged particles and Vavilov-Cherenkov light photons passage of the detector system is a few ns. This level of resolution allows conducting a research of the atmospheric development of individual EAS. This report focuses on a general description of the detector system and the individual sub-systems providing an overview of the operations and latest results.

Horizon-T experiment status

Horizon-T is an innovative detector system constructed to study Extensive Air Showers (EAS) in the energy range above 10 16 eV coming from a wide range of zenith angles (0 ° –85 ° ). The system is located at the Tien Shan High-altitude Science Station of the Lebedev Physical Institute of the Russian Academy of Sciences at ∼ 3340 meters above sea level. It consists of eight charged particle detection points separated by distances up to one kilometer as well as an optical detector subsystem to measure the Vavilov-Cherenkov light from the EAS. The time resolution of charged particles and Vavilov-Cherenkov light photons passage of the detector system is a few ns. This level of resolution allows conducting a research of the atmospheric development of individual EAS. This report focuses on a general description of the detector system and the individual sub-systems providing an overview of the operations and latest results.

84-, 100-, and 107-GBd PAM-4 Intensity-Modulation Direct-Detection Transceiver for Datacenter Interconnects

We report on an ultrahigh-speed PAM-based IM/DD optical subsystem featuring compact signal generation and tractable digital-processing complexity. The proposed transceiver is based on two main technologies: an InP DHBT selector power DAC for electrical signal generation, and a complexity-optimized receiver processing chain. We show how the complexity of the feed-forward equalizer can be considerably reduced by stacking a <3-symbol memory sequence estimator. Finally, we experimentally demonstrate successful signal recovery for 107-GBd PAM-4 in back-to-back configuration, and after 500 m and 1 km of transmission over standard single-mode fiber for 100- and 84-GBd PAM-4 configuration, respectively. A power-budget margin above 2 dB is attained in all cases.

All-Optical Virtual Private Network in OFDM-PON Using Microwave Photonic Filter

We propose and demonstrate a novel all-optical virtual private network (VPN) using a microwave photonic filter, which enables inter-communications among optical network units in a passive optical network system. In our scheme, an optical coupler based recirculating delay line is used at optical line terminal as an optical subsystem to implement a microwave photonic-bandpass filter (MP-BPF). The periodic passbands of an MP-BPF are used to transmit VPN signal, whereas stopbands are used for conventional upstream transmission. The proposed system has two critical issues, optical phase-induced intensity noise in the MP-BPF and Rayleigh back-scattering interference by a single-fiber loop back link. To overcome the issues, an RF clipping tone based spectrum-broadening technique is applied to uplink transmitter. The proposed all-optical VPN system is tolerant to wavelength of VPN optical carrier, and enables multi-VPN data transmission using multi-passbands of MP-BPF.

Optical Switches Based on Silicon Photonics for ROADM Application

We demonstrate compact and low-loss 8 × 8 silicon photonic switch modules, which are applicable to transponder aggregators (TPAs) in colorless, directionless, and contentionless reconfigurable optical add-drop multiplexers. Newly designed silicon optical switch chips incorporating spot size converters with polarization insensitive and wavelength insensitive properties over C/L bands are packaged. The developed module shows about 6-dB average excess optical loss, including optical coupling loss, on all 64 optical paths with low-polarization-dependent loss and low crosstalk. Using these compact optical switch modules, we construct a TPA prototype featuring over 100-port optical switch subsystem densely mounted on one board and confirm its feasibility.