Controlled Light Source Research Articles

Efficient polarization emission from metasurface-integrated resonant cavity light-emitting diodes

Abstract The pursuit of advanced illumination and display technologies has driven the development of beam manipulation for GaN micro-sized light-emitting diodes (LEDs). To realize an efficient polarization emission light source, we propose metasurface-integrated resonant cavity light-emitting diodes (RCLEDs), incorporating a dual-layer embedded photonic crystal (PhC) within the GaN cavity, and placing a resonant-cavity reflector (RCR) on top of the existing distributed Bragg reflector (denoted as PhC-RCR-RCLED). Numerical simulations reveal a significant enhancement in emission efficiency along with an improved ability to manipulate the emission beams. The averaged transmittance, deflection efficiency, and collection efficiency at the central wavelength for both x- and y-polarizations are 66.9%, 79.6%, and 53.6%, respectively. Compared to the traditional RCLED, our PhC-RCR-RCLED achieves 5.3, 1.2, and 6.3 times enhancements in these three efficiencies. Our scheme paves the way for more efficient and controllable light sources.

On-chip topological transport of integrated optical frequency combs

Optical frequency combs in integrated photonics have widespread applications in high-dimensional optical computing, high-capacity communications, high-speed interconnects, and other paradigm-shifting technologies. However, quantum frequency combs with high-dimensional quantum states are vulnerable to decoherence, particularly in the presence of perturbations such as sharp bends. Here we experimentally demonstrate the robust on-chip topological transport of quantum frequency combs in valley photonic crystal waveguides. By measuring the time correlations and joint spectral intensity of the quantum frequency combs, we show that both quantum correlations and frequency entanglement remain robust against sharp bends, owing to the topological nature of the quantum valley Hall effect. We also demonstrate that dissipative Kerr soliton combs with a bandwidth of 20 THz maintain their spectral envelope and low-noise properties even in the presence of structure perturbations. These topologically protected optical frequency combs offer robust, complex, highly controllable, and scalable light sources, promising significant advances in high-dimensional photonic information processing.

All-optical control of high-order harmonic generation in correlated systems

Solid-state high-order harmonic generation (HHG) presents a promising approach for achieving controllable broadband coherent light sources and dynamically detecting materials. In this study, we demonstrate the all-optical control of HHG in a strongly correlated system, vanadium dioxide (VO2), through photo-carrier doping. It has been discovered that HHG can be efficiently modified using a pump laser, achieving modulation depths approaching 100% (extinction ratio ≥40 dB) on femtosecond timescales. Quantitative analysis reveals that the driving forces behind pump-dependent HHG are attributed to two distinct many-body dynamics: the scattering-induced dephasing and the insulator-to-metal transition (IMT) caused by photo-induced electron shielding. These two dynamics play a crucial role in defining the intensity and transient response of the HHG. Furthermore, we demonstrate that it is possible to quantitatively extract the metallic phase fraction from time-resolved HHG (tr-HHG) signals throughout the IMT. This study highlights the benefits of utilizing many-body dynamics for controlling HHG and underscores the necessity for further theoretical research on HHG in strongly correlated systems.

Enhancing solar cell productivity with MgAl2O4–ZnAl2O4 blended anti-reflection coatings

The enhancement of productivity in solar cells primarily relies on the application of anti-reflection coatings. The current research employs coating materials such as MgAl2O4, ZnAl2O4 and blended MgAl2O4–ZnAl2O4 as an anti-reflective layer on the monocrystalline Si solar cells by employing RF sputter coating method. Magnesium nitrate hexahydrate and aluminium nitrate nonahydrate were utilized for the synthesis of MgAl2O4 by the sol-gel technique. ZnAl2O4 was synthesized using zinc nitrate hexahydrate and aluminum nitrate nonahydrate by sol–gel procedure. The performance of coated photovoltaic cells was evaluated through different characterization techniques. From the optical study, the blended MgAl2O4-ZnAl2O4 coating shows the maximum absorbance of around 93 % and lowest reflectance of 9 %. The MgAl2O4–ZnAl2O4 blend achieves a maximum power conversion efficiency (PCE) of 22.12 % in a controlled light source and 19.21 % in direct sunlight. Compared to other solar cells, blended MgAl2O4–ZnAl2O4 demonstrates low resistivity (4.23 × 10−3 Ω-cm), high carrier concentration (35.81 × 1020 cm−3) and maximum hall mobility (12.96 cm2/Vs). From the surface temperature measurement, it is evident that the MgAl2O4–ZnAl2O4 blend coated solar cell exhibits lowest temperature of 38.2 °C under simulated light. The experimental results indicate that the blended MgAl2O4–ZnAl2O4 coated photovoltaic cells exhibits superior productivity than the various coated and uncoated solar cells. Therefore, it can be stated that MgAl2O4–ZnAl2O4 blends are the excellent antireflective materials for achieving desired PCE in solar photovoltaic cells.

Controlled alignment imaging optical MIMO communication system based on light spot detection of arrayed light sources.

Visible light communication (VLC) technology has become one of the potential key technologies for 6 G due to its unique features, such as abundant license-free spectrum, high confidentiality, and low electromagnetic interference. In this paper, an optical multiple-input multiple-output (MIMO) communication system based on imaging reception is proposed, which can improve the data transmission rate and reduce interference between different sub-channels. To overcome the problem of optical communication link alignment, in this paper, we established an imaging optical MIMO communication system with a controlled light source array (CLSA) and proposed an optical alignment strategy to address the alignment issue. The scheme decouples the constraint that the light spot cannot be aligned with the detector in the communication system under the influence of optical parameters. Based on the light spot detection CLSA module, the communication system can ensure the stability of the link alignment when the communication distance changes. Experimental results show that when the communication distance is 20-80 m, the bit error rate (BER) of the communication system remains below 10-6. The single-channel communication rate of the system is 5 Mbps, and the total communication rate is 20 Mbps through the four-channel rate multiplexing. Moreover, if the communication distance increases to the range of 80-100 m, the BER increases, but it is always lower than the forward error correction (FEC) threshold.

Comparison of Thermal and Mechanical Pain Testing Modalities in Sprague Dawley and Fischer 344 Rats (Rattus norvegicus).

While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechanical pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague-Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.

Mode-dependent analysis of a fiber optic curvature sensor with sensitive zone

In this paper, mode-dependent analysis of fiber optic curvature sensor with precision machined structural imperfections (teeth) as sensitive zone is conducted. Using controlled input or light source launching conditions sensor response is measured for different modes excited in the multimode optical fiber. Study shows that as curvature changes there is significant difference in how sensitive zone affects low and high order modes propagating through the fiber. Obtained measurement results provide further insight into FOCS response and open possibilities for development of new measurement approaches which represent a significant step forward for FOCS based measurement systems. Guidelines for maximizing sensor sensitivity, increasing measurement reliability and even avoiding intensity based measurement by measuring changes in the width of the sensor’s output light intensity distribution are discussed in this work.

Comparison of Thermal and Mechanical Pain Testing Modalities in Sprague Dawley and Fischer 344 Rats (Rattus norvegicus).

While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechanical pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague-Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.

Surface engineering of Sio2-Zro2 films for augmenting power conversion efficiency performance of silicon solar cells

Improving solar cell performance hinges significantly on the application of anti-reflective surface coatings. A wide variety of coating techniques, including blade coating, spin coating, dip coating, and others were employed. The present research investigation employed various coating materials, namely SiO2 (Silicon dioxide), ZrO2 (Zirconium dioxide), and SiO2–ZrO2 blends, to apply a protective layer onto polycrystalline silicon solar cells using the sputter coating process. The efficiency of these solar cells with multilayer coating was assessed through diverse characterization methods. The uniform thin films were obtained using a 45-min coating process using an input voltage source of 17 kV, which was confirmed through analyses conducted using FESEM and AFM techniques. The UV–Vis spectroscopy and current-voltage source metre were employed to examine the light absorption and transmittance of bare and coated silicon solar cells. When compared to alternative solar cells, the solar cell coated with a combination of SiO2 and ZrO2 demonstrated uniform deposition and a low light reflectance of only 6 %. SiO2–ZrO2 gains a highest power conversion efficiency (PCE) of 17.6 % under controlled light source. This superior performance was due to the increase in photon transmittance in to the depletion region. Furthermore, the electrical resistivity of the SiO2–ZrO2 blend coated solar cell was measured using the four-probe method was found to be 2.89 × 10−3 Ω-cm, which was lower than that of other solar cells. From the experimental results, it was clear that SiO2 - ZrO2 blend-coated solar cells outperformed both other coated and uncoated solar cells. Consequently, SiO2–ZrO2 blends emerged as superior anti-reflective materials for achieving peak performance.

LOW-HEAT STERILIZATION SYSTEM ON FRUIT AND VEGETABLE PICKLING LINE PRODUCTION WITH PULSED LIGHTING

Automatic control system for pulsed lighting in sterilization of low-heat fermented food packaging. This paper aims to design and prototype an automatic control system for xenon lamps in pulsed lighting, specifically for sterilizing packages of low-heat fermented foods. The system comprises various components, including lamp holders, lenses, ballasts, heat dissipation mechanisms, power supplies, electronic controller boards, power electronic boards, and touch display control boards. The system’s effectiveness is evaluated through the application of a cultured bactericidal test, focusing on Escherichia coli. Variables such as control light source distance, the number of pulses, light intensity, and energy per unit area are considered. Results indicate that the application of pulsed light, with variations in frequency, leads to a reduction in the number of Escherichia coli colonies observed after the optical test

Interferometric metrology probe for highly sloped freeform optics.

A wide variety of systems are employed to measure the surface profile of aspheric and freeform optical surfaces. Freeform metrology systems must accurately characterize the full surface under test, which can be difficult with steep surface slopes. Here we present an interferometric surface metrology probe for highly sloped aspheric and freeform optical surfaces. The optical design of this probe allows the measurement of surface slopes up to 50deg without tilting the probe, which simplifies stage design and increases the accuracy of the system. A spectrally controlled light source is used to create a virtual ball in front of the probe tip to measure the surface distance and angle. This system produces a cloud of points, to which Zernike polynomials are fit and used to reconstruct the surface. We will show sensitivity tests and accuracy results.

NIR light-facilitated bone tissue engineering.

In the last decades, near-infrared (NIR) light has attracted considerable attention due to its unique properties and numerous potential applications in bioimaging and disease treatment. Bone tissue engineering for bone regeneration with the help of biomaterials is currently an effective means of treating bone defects. As a controlled light source with deeper tissue penetration, NIR light can provide real-time feedback of key information on bone regeneration in vivo utilizing fluorescence imaging and be used for bone disease treatment. This review provides a comprehensive overview of NIR light-facilitated bone tissue engineering, from the introduction of NIR probes as well as NIR light-responsive materials, and the visualization of bone regeneration to the treatment of bone-related diseases. Furthermore, the existing challenges and future development directions of NIR light-based bone tissue engineering are also discussed. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

An electroluminescent and tunable cavity-enhanced carbon-nanotube-emitter in the telecom band

Emerging photonic information processing systems require chip-level integration of controllable nanoscale light sources at telecommunication wavelengths. Currently, substantial challenges remain in the dynamic control of the sources, the low-loss integration into a photonic environment, and in the site-selective placement at desired positions on a chip. Here, we overcome these challenges using heterogeneous integration of electroluminescent (EL), semiconducting carbon nanotubes (sCNTs) into hybrid two dimensional – three dimensional (2D-3D) photonic circuits. We demonstrate enhanced spectral line shaping of the EL sCNT emission. By back-gating the sCNT-nanoemitter we achieve full electrical dynamic control of the EL sCNT emission with high on-off ratio and strong enhancement in the telecommunication band. Using nanographene as a low-loss material to electrically contact sCNT emitters directly within a photonic crystal cavity enables highly efficient EL coupling without compromising the optical quality of the cavity. Our versatile approach paves the way for controllable integrated photonic circuits.

Non-line-of-sight imaging and location determination using deep learning

Non-line-of-sight (NLOS) imaging methods have been proposed and rapidly developed to address the challenge of detecting objects hidden from the direct line of sight. One critical issue in NLOS imaging is acquiring the spatial position of hidden objects. Active NLOS imaging methods solve this problem using complex designs and sophisticated equipment while the conventional passive NLOS imaging scheme, which does not have a controllable light source and time-gating detector, rarely captures the spatial information of objects. Using speckle patterns and the assistance of a deep learning method, we experimentally demonstrated that the passive NLOS imaging system could simultaneously visualize and locate objects hidden in corners like an active NLOS imaging system could. High-fidelity reconstructed images and high-accuracy location recognition were realized using the proposed network. The network could provide 99% recognition accuracy for the object's position with an axis spacing of 36 μm. These results were significant for NLOS imaging with high-accuracy positioning requirements.

Frequency conversion in a hybrid cavity-optomechanical system

We propose a scheme to realize frequency conversion of photons, using a hybrid system with a qubit coupled to both a resonator cavity and an optomechanical cavity. In this system, a high-energy photon can be converted into a low-energy photon plus a phonon and vice versa; the qubit works as an intermediate medium with its states unchanged. Moreover, the process can be exquisitely tuned by changing the frequency of the qubit or the resonator mode, providing additional control for the conversion. We further analyze the system dynamics and demonstrate two Rabi oscillation behaviors with dissipations. With the state-of-the-art techniques in cavity quantum electrodynamics and optomechanical systems, our proposal would be implemented and an efficient and controllable quantum light source can be achieved.

Application of Partial Least Squares (PLS) Regression to Control Light Source for <i>Solanum lycopersicum</i> Seedling Growth in Plant Factory with Artificial Lighting

The use of LEDs as a light source in plant factories with artificial lighting is expected to reduce costs, but it has been reported that some crops do not grow as expected due to differences in the wavelength of the light source. Therefore, it is necessary to design LEDs with the appropriate wavelength for each crop to be grown. On the other hand, there is research toward the realization of smart plant factories that utilize artificial intelligence, and artificial intelligence may contribute to the design of the light environment in plant factories. In this study, we selected mini-tomatoes as a model crop, and prepared fluorescent lamps and LEDs as the light environment during seedling growth, respectively, and searched for suitable light source wavelengths while investigating the relationship with growth conditions using statistical analysis methods, one of the artificial intelligence techniques. We investigated the relationship between multiple light environments, PPFD, R/B ratio, and spectrum of wavelengths respectively, using LEDs, fluorescent lamps, and dimming filters, and growth indices stem diameter in order to clarify the light environments that contribute to growth. The correlation between the measured light environment and crop growth results was objectively shown by PLS regression analysis, and the contributing wavelengths were explored by calculating the selectivity ratio and regression coefficient. As a result, it was suggested that stem diameter was promoted at around 550 nm and 630 nm, and suppressed at around 460 nm.

Intelligent synthesis of hyperspectral images from arbitrary web cameras in latent sparse space reconstruction

<abstract><p>Synthesizing hyperspectral images (HSI) from an ordinary camera has been accomplished recently. However, such computation models require detailed properties of the target camera, which can only be measured in a professional lab. This prerequisite prevents the synthesizing model from being installed on arbitrary cameras for end-users. This study offers a calibration-free method for transforming any camera into an HSI camera. Our solution requires no controllable light sources and spectrometers. Any consumer installing the program should produce high-quality HSI without the assistance of optical laboratories. Our approach facilitates a cycle-generative adversarial network (cycle-GAN) and sparse assimilation method to render the illumination-dependent spectral response function (SRF) of the underlying camera at the first part of the setup stage. The current illuminating function (CIF) must be identified for each image and decoupled from the underlying model. The HSI model is then integrated with the static SRF and dynamic CIF in the second part of the stage. The estimated SRFs and CIFs have been double-checked with the results by the standard laboratory method. The reconstructed HSIs have errors under 3% in the root mean square.</p></abstract>

The performances of partial shading adjuster for improving photovoltaic emulator

A photovoltaic (PV) emulator (PVE) is essential equipment for the research and diagnostic of PV generation. It is a convenient, highly efficient, and low-cost approach when compared to controllable light sources. Nonetheless, the implementation of the partial shading capability in a PVE is highly limited in terms of efficiency, computation burned, number of power converters, and flexibility to change in the ambient condition. This paper proposes a partial shading adjuster for a PVE that can overcome the aforementioned limitations. The adjuster is applicable to the conventional PVE since it is based on an algorithm that can be added to the controller of the PVE. By adding the adjuster, the conventional PVE can emulate partial shading. The partial shading adjuster is added into a PVE that uses the direct referencing control strategy with the buck controller regulated by the proportional-integral controller. The results show that the PVE maintains its accuracy and produces a stable output voltage and current during the load changes when the adjuster is added. In conclusion, the proposed partial shading adjuster able to improve th

Evolution of the frequency-comb structure and coherence from a Keldysh multiphoton into a tunneling regime.

We present a theoretical study of the characteristics of the frequency-comb structure and coherence via high-order harmonic generation (HHG) driven by the laser pulse trains when the ionization process is pushed from Keldysh multiphoton into tunneling regime. HHG is obtained by solving accurately the time-dependent Schrödinger equation by means of the time-dependent generalized pseudospectral method. We find that the nested comb structures are formed from each harmonic order in the Keldysh multiphoton ionization regime. But it is severely suppressed or even disappeared in the Keldysh tunneling ionization regime. It implies that the temporal coherence of the emitted frequency comb modes is very sensitive to the Keldysh ionization regime. To understand the evolution of frequency-comb structure and coherence, we perform the calculation of the time-dependent ionization probability and the spectral phase of frequency-comb HHG. We find that the frequency-comb HHG driven by the laser pulse trains in the Keldysh multiphoton regime has a good coherence because the ionization probability of the atom driven by each laser pulse is stable, leading to a phase-coherent frequency-comb structure rather than those cases in the Keldysh tunneling regime with high laser intensity. Our results shed light on current interest and significance to the experimental realization of controllable and frequency-comb vacuum-ultraviolet light sources.

Igneous rock powder identification using colour cameras: A powerful method for space exploration

Powdered rocks are commonly present at the surface of extraterrestrial bodies and are widely analysed by in situ space probes. Moreover, a number of rovers exploring the surface of Mars are equipped with drills enabling them to access unaltered material and collect samples. During drilling operations, a cone of powder made of the drilled materials forms at the surface. These powders will be particularly large during the ESA/Roscosmos ExoMars 2022 mission since the rover Rosalind Franklin will drill to 2 m depth below the Martian surface. These fines are generally observed by the rovers' cameras after the drilling process and analysed by a limited range of instruments. In order to maximise the scientific return of planetary missions to Mars and other bodies in the solar system, we propose to use the images taken by rover cameras to identify the composition of the powdered materials. This could be particularly useful during the ExoMars 2022 mission where the CLUPI camera will take pictures during drilling and could thus document changes in the regolith composition (Josset et al., 2017). In the absence of a controlled light source, we used an image processing method called CaliPhoto that we previously developed for generic purposes. To test the ability of the method to identify volcanic rocks, more than twenty Mars-analogue samples were crushed at various grain sizes and photographed. The images were then processed via the CaliPhoto method and used to construct a database of reference images. New images were then taken under different lighting conditions, processed using the same method, and compared to the database. We show that it is possible to estimate igneous rock powder lithology with greater than 90% accuracy considering the uncertainties. Furthermore, when using images of polished and powdered samples, identification reaches 100%. We also show that the method permits precise lithological identification of samples that are not in the initial database. Finally, we demonstrate that the proposed method is extremely efficient, while at the same time very easy to implement on any in situ space probe. It could thus be used to help in identifying powdered igneous rocks during future missions to Mars or other rocky body in the solar system.