Optical Source Research Articles

NP-doped Optical Fibers for All-Fiber Integrated Optical Sources, Sensors and Actuators with Self-Sensing Capabilities

NP-doped Optical Fibers for All-Fiber Integrated Optical Sources, Sensors and Actuators with Self-Sensing Capabilities

Near‐Infrared Dual‐Band Frequency Comb Generation from a Silicon Resonator

AbstractBenefitting from the mature, cost‐effective, and scalable manufacturing capabilities of complementary metal‐oxide‐semiconductor (CMOS) technology, silicon photonics has facilitated the seamless and monolithic integration of diverse functionalities, including optical sources, modulators, and photodetectors. Microresonators can generate multiple coherent optical frequency comb lines and serve as optical sources. However, at the telecom band, silicon suffers from two‐photon absorption and free‐carrier absorption, which severely hampers the realization of microcombs from a single silicon chip at telecom wavelengths until now. In this paper, a novel approach is presented and demonstrated with near‐infrared dual‐band frequency combs from a multimode silicon resonator. With a single pumping configuration, dual‐band combs are generated from the interaction between the pump and Raman Stokes fields by involving two different optical mode families but with similar group velocities. It is observed that the pump power required to generate dual‐band combs is as low as 0.7 mW. The work in bringing telecom microcombs to the silicon platform will advance silicon photonics for the next generation of monolithically integrated technology based on a single silicon chip, enabling new possibilities for further exploring silicon photonics‐based applications in optical telecommunications, sensing, and quantum metrology in the telecom band using a monolithic single silicon chip.

60-GHz Millimeter-Wave over Visible Light Communications for Downlink Wireless Networks

Background and Objective: In this paper, we address potential solution for downlink wireless communications by integrating visible light communications (VLC) with the broadband radio frequency (RF) networks operating at 60 GHz-millimeter wave (mmWave) band. For this hybrid design, the outdoor 60 GHz-mmWave based RF link is utilized to ensure backhaul connectivity for VLC indoor system, while the VLC exploiting the lighting infrastructure that essentially used LEDs as optical source to provide low-cost and high-speed data access. Methods: The hybrid 60 GHz-mmWave/VLC system is analyzed by using 16-QAM OFDM signal, and its performance is investigated by evaluating the signal to noise ratio (SNR) and the received signal power distributions, for regular placement of LEDs and random location of receivers within the room. The impact of the transmitter-receiver parameters, and their orientations and directivities are also considered. Results: Numerical results show the efficiency of the proposed system, which can retransmit RF signals at 60 GHz-mmWave band using visible optical carriers in the indoor environment. Conclusion: The results suggest that the hybrid 60 GHz-mmWave/VLC system is able to provide reliable wireless data transmission, making it an attractive solution for downlink indoor communications.

Phase synthesis method in multi-aperture optical systems based on iterative image processing algorithms

Background. Modern technologies in the field of optics and photonics place high demands on the quality and output power of the radiation source. The fulfillment of these requirements can currently be achieved by creating multi-aperture laser systems with coherent beam addition. The main problem of creating such systems is the development of phase synthesis methods in a multichannel optical system. Aim. In this paper, we consider a phase synchronization method without a reference beam for a coherent addition system with active feedback, which is based on the Gerchberg–Saxton algorithm. This algorithm makes it possible to reconstruct complex field amplitudes in the aperture and focal planes from intensity distributions in these fields. The application of this algorithm for multichannel systems is analyzed and its features, such as the occurrence of stagnation and ambiguity of the solution, are revealed. Methods. Solutions are proposed to eliminate the problem of convergence of the algorithm to side solutions and getting the iterative procedure into the local extremum using global optimization algorithms, methods of reducing the dimension of the problem and the introduction of antisymmetric amplitude modulation. Results. The paper demonstrates the results of phase field reconstruction for a large number of optical sources. For a seven-aperture system, a physical simulation was performed to restore phase information, confirming the results of numerical modeling. Conclusion. The proposed approach is a reasonable alternative to currently existing methods and can be used in the problem of coherent addition in multichannel optical systems.

Energy-Efficient and Smart Bicycle Lamps: A Comprehensive Review

In this review paper, information about bicycle lamp technical parameters is provided. The review is based on the searched Web of Science (WoS) and Scopus bibliographic databases and Transportation Research Information Services, which include references to books, technical reports, conference proceedings, and journal articles. This review showed that these papers about bicycle lighting legal rules in given countries are very easy to reach, but deep searching must be performed to find this research paper having the information about types of optical systems and light sources used in bicycle lamps. This research was conducted using PRISMA 2020 assumptions in the area of bicycle lighting technologies and innovations. The information about bicycle lamp technical parameters was obtained on the basis of the examination of technical documents and papers from high-impact journals. The author’s review shows that contemporary bicycle lamps are becoming increasingly smarter and more energy efficient, while also enhancing safety and comfort for cyclists on their routes in and beyond urban environments.

Long organic persistent luminescence triggered by photo-induced charge-separation for water-resistant information encryption.

The long persistent luminescence (LPL) phenomenon in the water environment presents us with a broad blueprint to struggle for a new generation of optical materials. However, the realization of water-resistant LPL remains a formidable challenge due to severe quenching of triplet excitons inflowing media. Here, an electron donor-acceptor system is designed based on a B2O3 host and carbon dot (CD) guest, which exhibits deep-blue LPL with a lasting time of about 21 s to the naked eye. The average LPL lifetime is over 2 s, and the LPL quantum yield is 10.78%. This host-guest system possesses charge-separated states and charge-transferred states triggered by an optical source, which is the foundation for LPL. Importantly, in water environments (HCl, NaOH, electrolyte NaCl, and H2O), the LPL of as-obtained CDs@B2O3 can still remain due to high environmental stability of B2O3. Based on the excellent LPL with ultra-long lifetime and water-resistant feature, the CDs@B2O3 successfully applies in water-resistant information encryption.

Quantum-limited superresolution of two arbitrary incoherent point sources: Beating the resurgence of Rayleigh's curse

Superresolution has been demonstrated to overcome the limitation of Rayleigh's criterion and achieve significant precision improvement in resolving the separation of two incoherent optical point sources. However, in recent years, it was found that, if the photon numbers of two incoherent optical sources are unknown, the precision of superresolution vanishes when the photon numbers are actually different. In this work, we first analyze in detail the estimation precision of the separation for two incoherent optical sources with the same point-spread functions and show that, when the two photon numbers are different but sufficiently close, the superresolution can still be realized but with different precisions. We find the condition on how close the photon numbers need to be to realize the superresolution and derive the precision of superresolution in different regimes of the photon number difference. We further consider the superresolution for two incoherent optical sources with different point-spread functions and show that the competition between the difference of photon numbers, the difference of point-spread functions, and the separation of source locations determines the precision of superresolution. The results exhibit precision limits distinct from that of two identical point-spread functions with equal photon numbers and extend the realizable regimes of quantum superresolution. Finally, the results are illustrated by Gaussian point-spread functions. Published by the American Physical Society 2024

Time-delay signature elimination of chaotic laser via a self-feedback antisymmetric resonator.

A scheme for generating a chaotic output from a semiconductor laser while eliminating the time-delay signature (TDS) is proposed, leveraging the multi-path feedback provided by a self-feedback antisymmetric coupling fiber ring resonator (SACFRR). A theoretical model is developed to elucidate the feedback perturbation process in the proposed structure. The multi-path feedback can be modeled by incorporating the unit impulse response of the SACFRR into the modified Lang-Kobayashi-based model. We successfully eliminated the TDS using the SACFRR structure in our experimental demonstration. Further investigation into the impact of the coupling coefficient on the TDS revealed that the optimal value is 0.3, which results in the largest mapping area with the TDS below 0.03. The proposed structure is highly effective and simple to implement and integrate. As a result, the chaotic laser generated by this structure can serve as an efficient optical source for encrypted communications, chaotic Lidar, and random bit generation.

Multifunctional Microwave Photonic Processor With Sideband-Dependent Filtering and Phase Shifting Based on Broadband Optical Source and Hybrid Spectrum Slicer

Multifunctional Microwave Photonic Processor With Sideband-Dependent Filtering and Phase Shifting Based on Broadband Optical Source and Hybrid Spectrum Slicer

Performance advantage of quantum hypothesis testing for partially coherent optical sources

Determining the presence of a potential optical source in the interest region is important for an imaging system and can be achieved by using hypothesis testing. The previous studies assume that the potential source is completely incoherent. In this paper, this problem is generalized to the scenario with partially coherent sources and any prior probabilities. We consider quantum-optimal error probability and a classical benchmark of two scenarios depending on the number of available temporal modes M. For M=1, we calculate the quantum Helstrom bound and the error probability of prior-based direct decision. For M≫1, we analyze the quantum Chernoff bound as well as the Chernoff bound of intensity-based direct imaging. In addition, we propose binary spatial-mode demultiplexing and the result demonstrates asymptotically optimal detection performance. Our findings may shed new light on super-resolution imaging in partially coherent scenarios.

Environmental Impacts on the RSS-Based Visible Light Indoor Positioning System

To address the shortcomings of the global positioning system (GPS) operating within indoor scenarios, a range of indoor positioning systems (IPS) have been proposed. Among these, visible light IPS garners substantial research interest for its potential as a cost-effective IPS solution. However, susceptibility to environmental influences like external light and non-line-of-sight that can significantly affect its performance hindered its adoption. Hence, a simulation framework capable of simulating these influences becomes crucial in supporting the effective deployment and promoting the adoption of visible light IPS. This paper investigates the feasibility of using a simulation framework to replicate environmental factors affecting the system, including external optical sources and blocked transmitters. The research involved the development of a received signal strength (RSS) based visible light IPS prototype and an associated simulation framework. Subsequently, the prototype was tested in three distinct environments: no influences, with an external optical source, and non-line-of-sight. The prototype achieved an accuracy of 0.0836 m, 0.3541 m, and 1.1519 m for 50% of the time respectively in these three environments. Ultimately, the simulation framework developed is capable of reproducing similar effects for all three environments with a difference in the accuracy of 76.08%, 74.86% and 867%, respectively. Thus, the findings support the use of the developed simulation framework for the effective development of visible light IPS in environments with no influences and with external optical sources.

Enhance Hydrogen Production from Water Using 532 Lasers

ABSTRACT: hydrogen production via water electrolysis under the influence of laser sounds fascinating with its unique properties, was particularly effective in promoting hydrogen production. The mechanism by which the laser promotes hydrogen production The electrolytic cell used in this work contains 270 ml of distilled water stimulated with different amounts of alcohol (2 ml - 4 ml - 6 ml - 8 ml - 10 ml). This chamber consists of two vertically oriented cylinders. Inside each cylinder there are graphite electrodes, each measuring 10 x 5 x 7 mm3, connected to the positive and negative terminals of a direct current power source, in addition to using a green laser source (532). An efficiency study was conducted using a green laser with a wavelength of 532 nanometers as an optical light source for water analysis through electrolysis. Results were obtained using both the standard electrolysis method and with the green laser source (532 nm). In the case of standard electrolysis, we obtained (When adding 5 ml of cohol, we get 6.63 hydrogen ), while (Adding 10 ml of ill we get 7.44 of hydrogen ) was obtained when using the laser source. The results indicate that using the laser source enhances hydrogen production significantly compared to standard electrolysis, demonstrating the laser's high effectiveness in electrolysis due to its non-absorptive property in water. This could have significant implications for renewable energy and hydrogen fuel production.

High-efficiency mid-infrared CW-seeded optical parametric generation in PPLN waveguide

Mid-infrared optical sources have been extensively used in a variety of applications, including gas sensing and metrology, by exploiting the fingerprint fundamental vibrational absorption bands of molecules in this spectral region. Parametric frequency conversion techniques, such as optical parametric generation (OPG) and optical parametric oscillator (OPO), represent common methodologies for mid-infrared generation. Notably, continuous-wave (CW)-seeded OPG exhibits superior stability and performance compared to conventional OPG. Here, we present a simple method for mid-infrared source generation based on femtosecond OPG in periodically poled lithium niobate (PPLN) waveguides. In addition to its robustness and simplicity, mid-infrared CW-seeded OPG features a high quantum conversion efficiency of 46.5% and a low threshold. The phase of CW-seeded OPG was passively referenced to the CW laser, making it suitable for dual-comb applications. This system shows great promise in the miniaturization of mid-infrared combs and will be applied to non-laboratory applications, including open-path atmospheric gas sensing and portable environmental monitoring.

Optical Transmission in Single-Layer Brain Tissues under Different Optical Source Types: Modelling and Simulation.

The human brain is a complex organ controlling daily activity. Present technique models have mostly focused on multi-layer brain tissues, which lack understanding of the propagation characteristics of various single brain tissues. To better understand the influence of different optical source types on individual brain tissues, we constructed single-layer brain models and simulated optical propagation using the Monte Carlo method. Based on the optical simulation results, sixteen optical source types had different optical energy distributions, and the distribution in cerebrospinal fluid had obvious characteristics. Five brain tissues (scalp, skull, cerebrospinal fluid, gray matter, and blood vessel) had the same set of the first three optical source types with maximum depth, while white matter had a different set of the first three optical source types with maximum depth. Each brain tissue had different optical source types with the maximum and minimum full width at half maximum. The study on single-layer brain tissues under different optical source types lays the foundation for constructing complex brain models with multiple tissue layers. It provides a theoretical reference for optimizing the selection of optical source devices for brain imaging.

Nonlinear Damping as the Fourth Dimension in Optical Fiber Anemometry

AbstractIn this study, nonlinear damping is introduced as the fourth dimension in the operation of a fiber tip optomechanical anemometer. The flow sensing element, featuring a 3D rotor measuring 110 µm in diameter and fabricated through a two‐photon nanomachining process, is monolithically integrated onto the cleaved face of the optical fiber, which serves as an integrated waveguide. As the rotor encounters airflow, it spins, and mirrors on its blades reflect light across the fiber core at each pass. This setup permits precise measurement of gaseous fluid flow with minimal sensor footprint at the point of detection and accommodates a variety of optical sources and measurement apparatuses without the need for specific wavelength or broad‐spectrum capabilities. To stabilize the rotation of the rotor and facilitate consistent frequency‐domain analysis, a polydimethylsiloxane hydrocarbon stabilizing agent is infused into the gap between the rotor and stator of the sensing element via dual‐function microfluidic channels. This enhancement allows for the measurement of gaseous nitrogen flow rates from 10 to 20 liters per minute (LPM), with a consistent periodic response. Comprehensive characterizations of the fiber tip anemometer are presented with and without the stabilizing medium, demonstrating its crucial role in regulating the dynamics between the rotor and the stator.

Tbps wide-field parallel optical wireless communications based on a metasurface beam splitter

Optical wireless communication (OWC) stands out as one of the most promising technologies in the sixth-generation (6G) mobile networks. The establishment of high-quality optical links between transmitters and receivers plays a crucial role in OWC performances. Here, by a compact beam splitter composed of a metasurface and a fiber array, we proposed a wide-angle (~120°) OWC optical link scheme that can parallelly support up to 144 communication users. Utilizing high-speed optical module sources and wavelength division multiplexing technique, we demonstrated each user can achieve a communication speed of 200 Gbps which enables the entire system to support ultra-high communication capacity exceeding 28 Tbps. Furthermore, utilizing the metasurface polarization multiplexing, we implemented a full range wide-angle OWC without blind area nor crosstalk among users. Our OWC scheme simultaneously possesses the advantages of high-speed, wide communication area and multi-user parallel communications, paving the way for revolutionary high-performance OWC in the future.

Feasibility Study and Results from a Baseline Multi-Tool Active Seismic Acquisition for CO2 Monitoring at the Hellisheiði Geothermal Field

CO2 capture and underground storage, combined with geothermal resource exploitation, are vital for future sustainable and renewable energy. The SUCCEED project explores the feasibility of re-injecting CO2 into geothermal fields to enhance production and store CO2 for climate change mitigation. This integration requires novel time-lapse monitoring approaches. At the Hellisheiði geothermal power plant in Iceland, seismic surveys utilizing conventional geophones and a permanent fiber-optic helically wound cable (HWC) for Distributed Acoustic Sensing (DAS) were designed to provide subsurface information and CO2 monitoring. This work details the feasibility study and active seismic acquisition of the baseline survey, focusing on optical fiber sensitivity, seismic modeling, acquisition parameters, source configurations, and quality control. Post-acquisition signal analysis using a novel electromagnetic vibrating source is discussed. The integrated analysis of datasets from co-located sensors improved quality-control performance and geophysical interpretation. The study demonstrates the advantages of using densely sampled DAS data in space by multichannel processing. This experimental work highlights the feasibility of using HWC DAS cables in active surface seismic surveys with an environmentally friendly electromagnetic source, providing also a unique case of joint signal analysis from different types of sensors in high-temperature geothermal areas for energy and CO2 storage monitoring in a time-lapse perspective.

A Swift X-Ray View of the SMS4 Sample. II. X-Ray Properties of 17 Bright Radio Sources

Based on a proposal to observe 18 bright radio sources from the SMS4 catalog with the Neil Gehrels Swift Observatory (hereafter Swift), we obtained X-ray observations of 17 targets (one target was not observed). Following up our first paper that discussed 31 sources (see Maselli et al.; 20 sources detected as point sources and one very extended source), we present results for this final sample of 17 radio sources that previously lacked dedicated, pointed narrow-field-of-view (FOV) X-ray observations. One of these 17 sources, undetected by Swift due to a very short exposure, was instead detected by eROSITA, and given in the Data Release 1 (DR1) Catalog. No 1eRASS source was found in the DR1 for the remaining source, unobserved by Swift. The new Swift observations led to 11 X-ray source detections in the 0.3–10 keV band and six upper limits. We investigated the extent of the X-ray emission and the hardness ratio, and when statistics allowed, we carried out a spectral analysis. The X-ray emission of eight sources is consistent with pointlike emission, while three sources show clear evidence of extent, each with peculiar properties. We used the X-ray determined positions and uncertainties of the 12 detected sources to establish associations with infrared and optical sources from the AllWISE and the GSC 2.4.2 catalogs. Requiring a detection in both the infrared and the optical bands to establish a candidate counterpart for our X-ray detections, we identify counterparts for all 12 sources. Following this X-ray-based approach to derive the position of the active nucleus, we are able to confirm the same IR counterparts previously proposed by White et al. for eight sources, and provide four new IR candidates. In the optical, we identify counterparts that match the candidates previously given by Burgess & Hunstead for all sources. We discuss the interesting structure of MRC B0344−345 and PKS B2148−555, two of the six extended X-ray sources that we detected in both our Swift campaigns, and suggest they are very promising for further X-ray and radio investigations. For the 38 SMS4 sources that lack pointed, narrow-FOV X-ray telescope observations, after our Swift campaigns, we list 18 likely counterparts from the eROSITA DR1 catalog.

Identification of Decedents by Restoring Mummified Fingerprints: Forensic Dermatology in the Investigation of Mummy Dermatoglyphics

Fingerprints are created by elevations and depressions on the fingertip pads. Each person has their own unique fingerprints, which can be used in the identification of that individual when alive, during the immediate postmortem period, or even after the digits have become mummified. Mummification can occur naturally; it can be partial (such as localized to only the hands and feet), extensive, or complete. Obtaining fingerprints after the skin has become mummified can be attempted while the digits remain attached to the hand, but the digits may need to be removed from the hand, and the finger pads may also need to be separated from the underlying bone to secure an adequate fingerprint. The mummified tissue often needs to be rehydrated; numerous solutions have been used that increase the turgor of the digits, provide softening and pliability of the tissue, and enhance the details of the finger pad ridges. An aqueous solution of sodium carbonate (either combined with acetic acid or combined with 95% ethanol and distilled water) was found to be most effective for rehydration. Thereafter, various techniques can be attempted to obtain the fingerprint. These include the traditional method of inking and rolling of the finger or photographing the finger. Powders (such as aluminum powder, black fingerprint powder, white cornstarch-based powder, or fluorescent powder) can be used to enhance the ridge features; adhesive tape can be pressed against the powdered digit and the print pattern preserved by applying the adhesive tape to a clear transparency sheet. Molds (using modeling clay or silicone rubber) and casts (using plaster of paris, dental casting materials, or putty) of the digits can be created; either the molds or the casts or both can be photographed with or without prior application of fingerprint powder. Transillumination, using a fiber optic light source to illuminate the epidermis and underlying remaining dermis of a scraped and defleshed finger pad, can be used to demonstrate the finger ridge pattern when photographing the tip of the digit. Forensic dermatology can play an integral role in obtaining fingerprints from mummified digits, which can be successfully used for the identification of a decedent.

Quantum dot fourth-harmonic colliding pulse mode-locked laser for high-power optical comb generation

Quantum-dot mode-locked lasers have advantages such as high temperature stability, large optical bandwidth, and low power consumption, which make them ideal optical comb sources, especially for wavelength-division multiplexing (WDM) telecommunications, and optical I/O applications. In this work, we demonstrate an O-band quantum dot colliding pulse mode-locked laser (QD-CPML) to generate optical frequency combs with 200 GHz spacing with maximum channels of 12 within 3 dB optical bandwidth. To achieve the high output power of individual comb lines, four channel conditions are implemented at central wavelength of 1310 nm for WDM transmission experiments. Each channel exhibits more than 10 dBm output power with 200 Gb/s PAM-4 and 270 Gb/s PAM-8 modulation capability via thin-film LiNbO3 Mach–Zehnder interferometer modulator without the requirement of any optical amplifications. This high-order QD-CPML is an ideal comb source for power-efficient optical interconnects and large bandwidth optical data transmission.