Light Generation Research Articles

Continuous-wave second harmonic generation of green light in periodically poled thin-film lithium tantalate

Continuous-wave second harmonic generation of green light in periodically poled thin-film lithium tantalate

Projection-type holographic display with observation area expanded using time-division reproduced light generation system

Projection-type holographic display with observation area expanded using time-division reproduced light generation system

Recent advances and future prospects in oxidative-reduction low-triggering-potential electrochemiluminescence strategies based on nanoparticle luminophores.

The oxidative-reduction electrochemiluminescence (ECL) potential of a luminophore is one of the most significant parameters during light generation processes when considering the growing demand for anti-interference analysis techniques, electrode compatibility and the reduction of damage to biological molecules due to excessive excitation potential. Nanoparticle luminophores, including quantum dots (QDs) and metal nanoclusters (NCs), possess tremendous potential for forming various ECL sensors due to their adjustable surface states. However, few reviews focused on nanoparticle luminophore-based ECL systems for low-triggering-potential (LTP) oxidative-reduction ECL to avoid the possible interference and oxidative damage of biological molecules. This review summarizes the recent advances in the LTP oxidative-reduction ECL potential strategy with nanoparticle luminophores as ECL emitters, including matching efficient coreactants and nanoparticle luminophores, doping nanoparticle luminophores, constructing donor-acceptor systems, choosing suitable working electrodes, combining multiplex nanoparticle luminophores, and employing surface-engineering strategies. In the context of the different LTP ECL systems, potential-lowering strategies and bio-related applications are discussed in detail. Additionally, the future trends and challenges of low ECL-triggering-potential strategies are discussed.

Electrically Pumped h-BN Single-Photon Emission in van der Waals Heterostructure.

Atomic defects in solids offer a versatile basis to study and realize quantum phenomena and information science in various integrated systems. All-electrical pumping of single defects to create quantum light emission has been realized in several platforms including color centers in diamond and silicon carbide, which could lead to the circuit network of electrically triggered single-photon sources. However, a wide conduction channel which reduces the carrier injection per defect site has been a major obstacle. Here, we realize a device concept to construct electrically pumped single-photon emission using a van der Waals stacked structure with atomic plane precision. Defect-induced tunneling currents across graphene and NbSe2 electrodes sandwiching an atomically thin h-BN layer allow robust and persistent generation of nonclassical light from h-BN. The collected emission photon energies range between 1.4 and 2.9 eV, revealing the electrical excitation of a variety of atomic defects. By analyzing the dipole axis of observed emitters, we further confirm that emitters are crystallographic defect structures of h-BN crystal. Our work facilitates implementing efficient and miniaturized single-photon devices in van der Waals platforms toward applications in quantum optoelectronics.

Simultaneous on-chip generation of violet, blue, cyan, green, yellow, orange, and red light from an octave-spanning infrared frequency comb

Simultaneous on-chip generation of violet, blue, cyan, green, yellow, orange, and red light from an octave-spanning infrared frequency comb

Improving the performance of quantum well solar cells with photonic crystal.

The fabrication of quantum well solar cells with surface photonic crystal (SPC) and embedded photonic crystal (EPC) structures has resulted in solar cells with improved properties. When compared to reference solar cells (RSCs), the photoluminescence (PL) intensities of SPC solar cells and EPC solar cells have been enhanced by 89% and 114%, respectively. This indicates improved light absorption and emission characteristics in the presence of the periodic patterns (PCs). The short-circuit current (Isc) of EPC solar cells is 31% higher than that of RSCs, suggesting improved light absorption and carrier generation. On the other hand, SPC solar cells exhibit a 6% higher Isc compared to RSCs, and the open-circuit voltage has increased simultaneously. The fill factors (FF) of the solar cells are 84% for RSCs, 86% for SPC solar cells, and 76% for EPC solar cells. The higher FF in SPC solar cells suggests improved charge carrier collection efficiency. In terms of photoelectric conversion efficiency, SPC solar cells demonstrate a 10.6% increase, while EPC solar cells show a 7.7% increase. These improvements indicate that the incorporation of PCs in the solar cells enhances their ability to convert light into electrical energy. These findings highlight the potential of photonic crystals engineering for enhancing the performance of solar cells.

Robust single-photon generation for quantum information enabled by stimulated adiabatic rapid passage

The generation of single photons using solid-state quantum emitters is pivotal for advancing photonic quantum technologies, particularly in quantum communication. As the field continuously advances toward practical use cases and beyond shielded laboratory environments, specific demands are placed on the robustness of quantum light sources during operation. In this context, the robustness of the quantum light generation process against intrinsic and extrinsic effects is a major challenge. Here, we present a robust scheme for the coherent generation of indistinguishable single-photon states with very low photon number coherence using a three-level system in a semiconductor quantum dot. Our approach combines the advantages of adiabatic rapid passage and stimulated two-photon excitation. We demonstrate robust quantum light generation while maintaining the prime quantum-optical quality of the emitted light state. Moreover, we highlight the immediate advantages of the implementation of various quantum cryptographic protocols.

Design and Assessment of a Linear Drive‐Controlled Tilt‐Roll Heliostat with Sun Tracking Algorithm for Small‐Scale Solar Installation

Heliostats are devices used for solar concentration that use mirrors oriented according to the position of the sun. A heliostat's main function is to redirect sunlight for use in a variety of applications, including heating, lighting, scientific research, and solar power generation. The two‐axis tracking employed in the device ensures that the reflected irradiance is aimed at a predetermined target. The design and evaluation of a tilt‐roll two‐axis tracking heliostat are presented in this article. The model consists of a mirror 0.45 m in width and 0.45 m in length installed on a pedestal of height 0.75 m. The motion of the heliostat is controlled using two separate linear drives via a sun‐tracking algorithm implemented in a microcontroller. A small‐scale tilt‐roll design with a reflective area (mirror) of 0.2025 m2 is established. This novel design eliminates the need for commercially available solar tracking systems and can be deployed in areas of limited installation space. Dual‐axis heliostat design used here provides an effective way to track the sun's movement for maximum solar energy capture by combining tilt and roll mechanisms. This design ensures tracking precision for optimal solar energy concentration making it well‐suited for experimental and smaller‐scale deployments.

Microsecond triplet emission from organic chromophore-transition metal dichalcogenide hybrids via through-space spin orbit proximity effect

Efficient light generation from triplet states of organic molecules has been a hot yet demanding topic in academia and the display industry. Herein, we propose a strategy for developing triplet emitter by creating heterostructures of organic chromophores and transition metal dichalcogenides (TMDs). These heterostructures emit microsecond phosphorescence at room temperature, while their organic chromophores intrinsically exhibit millisecond phosphorescence under vibration dissipation-free conditions. This enhancement in phosphorescence is indicative of significantly enhanced spin-orbit coupling efficiency through coupling with TMDs. Through detailed studies on these hybrids from various perspectives, we elucidate key features of each component essential for generating microsecond triplet emission, including 2H-TMDs with heavy transition metals and aromatic carbonyl with an ortho-hydroxy group. Our intriguing findings open avenues for exploring the universal applicability of fast and stable hybrid triplet emitters.

A Review On The He-Ne Laser System

Abstract: The first continuous-wave (CW) laser to be created was the He-Ne laser. Ali Javan and his colleagues W. R. Bennet and D. R. Herriott revealed the production of a cw He-Ne laser a few months after Maiman declared his invention of the pulsed ruby laser. Neon atoms are excited by helium atoms in this four-level gas laser. The laser light is produced by the neon's atomic changes. Red light with a wavelength of 632.8 nm is produced by these lasers' most popular neon transition. In addition to producing various UV and IR wavelengths, these lasers may also produce green and yellow light in the visible spectrum (Javan's first He-Ne operated in the IR at 1152.3 nm). It is feasible to make a given He-Ne's output work at a single wavelength by utilizing highly reflecting mirrors that are intended for one of these numerous possible lasing transitions.He-Ne lasers normally produce a few to tens of mW (milli-Watt, or 10−3 W) of power; they are not generators of high-power laser light. These lasers' extreme stability, both in terms of output light intensity (minimal jitter in power level) and wavelength (mode stability), is likely one of its most notable characteristics. He-Ne lasers are frequently used to steady other lasers for these reasons. They are also utilized in applications, like as holography, where mode stability is vital. He-Ne lasers dominated the market until the mid-1990s when they were manufactured for low-power uses, such as range finding, scanning, optical transmission, laser pointers, etc. However, due to lower costs, other types of lasers most notably semiconductor lasers seem to have emerged victorious in the recent rivalry. [30]

Optical investigation of Dy3+/ Eu3+ co-activated K2NaAlF6 fluorophosphor for color tunable lighting system: Structural analysis and warm light generation

Nowadays, research is mostly focused on developing luminous materials. Specifically, compounds based on inorganic phosphorus have found widespread use in a variety of applications, like radiation dosimetry, field emission displays (FEDs), cathode ray tubes (CRTs), lamp industries, and white light emitting diodes (WLEDs). In order to achieve white light emission, we successfully synthesized single-host K2NaAlF6 co-doped with Dy3+/Eu3+ in this study utilizing the pechini sol-gel approach. Under UV light, the synthesized samples' luminescence characteristics were examined. XRD analysis verified K2NaAlF6's phase purity. The phosphor materials have a tendency to aggregate, as seen by SEM pictures. The K2NaAlF6:Dy3+ doped phosphors showed good excitation at 349 nm in photoluminescence (PL) experiments, with strong emission bands at 489 nm (blue) and 576 nm (yellow). Strong orange emissions were seen for K2NaAlF6: Eu3+ doped phosphors at 595 nm and 614 nm, which correspond to the 5D0→7F1 and 5D0→7F2 transitions in Eu3+ ions. When these rare earths were co-doped, intense red, yellow, and blue emissions were produced. The Commission Internationale de l'Eclairage (CIE) coordinates were used to calculate the colour characteristics of the luminous produced samples. Consequently, these results imply that Dy3+/Eu3+ co-doped K2NaAlF6 phosphors, when stimulated by UV LEDs, could be appropriate for creating reddish-orange and warm white lighting systems.

Polarization squeezing in chalcogenide fibers.

We experimentally demonstrate the generation of polarization-squeezed light in a short piece of solid-core chalcogenide (ChG) (As2S3) fiber via the Kerr effect for femtosecond pulses at 1.56 µm. Directly measured squeezing of -2.8 dB is obtained in a setup without active stabilization. Numerical simulations are in good agreement with the experimental results and indicate that the measured squeezing in our setup is mainly limited by the losses in the detection system rather than by the fiber properties.

Improving Solar Cell Efficiency of Silicon and Silicon Tandem Structure by Using Surface Modification

Silicon heterojunction (SHJ) solar cells face challenges in maximizing energy capture due to limitations in light collection and surface passivation. To address this, the use of SHJ tandem solar cells in a back‐to‐back configuration is explored, allowing illumination from both sides to enhance light absorption and energy generation. This study aims to improve the stability and efficiency of these cells through Al2O3 and Nafion surface treatments. Al2O3 is deposited to enhance bifacial light collection, while Nafion is applied for surface passivation to increase the fill factor (FF). The method involves adding 0.1–0.6 units of incident light to the rear of the cells to evaluate the effects of these treatments. The results show a 2.06% increase in efficiency with Al2O3 and a 1.72% improvement with Nafion under standard illumination conditions. The optimized tandem SHJ with Al2O3 and Nafion achieves a Jsc of 62.01 mA cm−2, Voc of 650.63 mV, FF of 76.49%, and an efficiency of 30.86%. These findings demonstrate the significant potential of these surface treatments to enhance the overall performance of bifacial back‐to‐back tandem SHJ solar cells.

Observation of temporal optical solitons in a topological waveguide

Photonic topological systems may be exploited in topological quantum light generation, the development of topological lasers, the implementation of photonic routing systems and optical parametric amplification. Here, we leverage the strong light confinement of an ultra-silicon-rich nitride (USRN) topological waveguide adopting the 1D Su-Schrieffer-Heeger (SSH) system with a topological domain wall. We present the formation and propagation of temporal optical solitons in the topological waveguide, exhibiting two-fold temporal compression. We further observe a saturation in the output power at sufficiently high input powers. It is further observed that pulse propagation through a trivial, non-topological waveguide does not lead to similar temporal soliton dynamics. The demonstrated topological system allows for the temporal compression to be manipulated through power tuning via topological control of delocalization of the topological mode. This design degree of freedom allows temporal solitons to be generated in a topological waveguide while providing straightforward control of temporal pulses in practical applications.

Titanium Dioxide: A Versatile Earth‐Abundant Optical Material for Photovoltaics

AbstractTitanium dioxide (TiO2) has long been receiving attention as a promising material for enhancing the performance of photovoltaic devices due to its tunable optoelectronic properties. This paper reviews the utilization of TiO2 in recent photovoltaic applications, focusing primarily on its role as an optical material. The fundamental properties of TiO2 are reviewed, such as its wide bandgap and unique property of tunable refractive index. Furthermore, various strategies are discussed to harness the fundamental properties of TiO2 to improve light absorption and charge carrier generation within various photovoltaic devices. Overall, the pivotal role of TiO2 as an Earth‐abundant and non‐critical optical material is highlighted for future advances in the power conversion efficiency and viability of photovoltaic technologies, paving the way for future research and developments aimed at achieving sustainable and cost‐effective solar energy conversion.

Advancements in halide perovskite photonics

Halide perovskites have emerged as a new class of materials for photoelectric conversion, attracting an ever-increasing level of attention within the scientific community. These materials are characterized by expansive compositional choices, ease of synthesis, an impressively high light absorption coefficient, and extended carrier recombination lifetimes. These attributes make halide perovskites an ideal candidate for future optoelectronic and photonic applications, including solar energy conversion, photodetection, electroluminescence, coherent light generation, and nonlinear optical interactions. In this review, we first introduce fundamental concepts of perovskites and categorize perovskite photonic devices by the nature of their fundamental mechanisms, i.e., photon-to-electron conversion devices, electron-to-photon conversion devices, and photon-to-photon devices. We then review the significant progress in each type of perovskite device, focusing on working principles and device performances. Finally, future challenges and outlook in halide perovskite photonics will be provided.

White Light Generation and Stability Analysis of High-Power Blue LDs with Remote YAG Phosphors

This paper presents a comprehensive analysis of white light generation and the associated aging dynamics using high-power blue laser diodes (LDs) combined with transmissive single crystal remote YAG phosphors. By systematically varying input currents (ranging from 0.6 A to 3 A) and phosphor thicknesses (250 μm and 500 μm), this study elucidates the optical and electrical characteristics of LD-phosphor systems under diverse operating conditions. The results highlight the system’s potential for stable and efficient white light generation, making it suitable for high-power lighting applications. Experimental setups included both single LDs and a 4 × 2 LD array. For the single LD, a peak optical output of 4.16 W was achieved at 3 A, corresponding to an initial luminous flux of approximately 700 Lm and a correlated color temperature (CCT) of 4653 K, with minimal color temperature shift observed during a 60 min aging process. The 4 × 2 LD array demonstrated consistent white light output across varying phosphor thicknesses, with maximum luminous fluxes of 1857 Lm at 1.4 A and 2622 Lm at 1.6 A for phosphor thicknesses of 250 μm and 500 μm, respectively. Importantly, the phosphor exhibited excellent thermal stability throughout the aging process, with the CCT maintained within a range of 4600 K to 5500 K. These findings underscore the reliability and applicability of LD-based white light systems in demanding high-power lighting environments, offering a promising alternative to conventional light sources for automotive, industrial, and specialized lighting applications.

Measurement and analysis of photoacoustic pressure induced by weak microsecond pulsed light.

The photoacoustic effect (PAE) of weak microsecond pulsed light (WMPL) has immense potential for application to biomedical engineering. However, practical measurements and theoretical analysis of the photoacoustic pressure of WMPL are lacking. Hence, we constructed a WMPL photoacoustic pressure measurement system using an electret piezoelectric sensor and multi-wavelength parameter-adjustable pulsed light generator. Based on the system, the photoacoustic pressure interacting with the air medium induced by the WMPL with different optical parameters was measured. The measured pressure data were analyzed using the fixed variable method, and the pressure response characteristic was obtained. It was found that the measured results conform to the law of energy conversion but have a specific trend for some wavelengths. The analysis and discussion were conducted based on the classical wave equation of the PAE, and the extended wave equation was presented. It is shown that the proposed approach provides a reliable basis for the measurement and analysis of WMPL photoacoustic pressure.

Innovative synthesis of Tm³⁺/Er³⁺-doped Yb-YGG single crystals for upconversion-based white light emission

In recent years, there has been a growing interest in developing advanced materials for photonics applications, particularly for efficient white light emission, which is crucial for technologies like solid-state lighting and display devices. One interesting approach for emitting white light is Upconversion (UC) luminescence. This study focuses on synthesis, by a new and alternative method, and characterization of yttrium ytterbium gallium garnet (Yb-YGG) single crystals, specifically Y1.8Yb1.2Ga5O12, doped with various concentrations of Er3+ and Tm3+ ions. These crystals were studied intending to enhance UC luminescence properties for white light generation by modifying their respective emissions in the red, green, and blue (RGB) regions. Unlike traditional methods such as Czochralski, these crystals were produced by controlled nucleation and growth through gradual cooling of a specific glass mixture, leading to Yb-YGG single crystals doped with different concentrations of Yb3+, Er3+, and Tm3+ ions. By optimizing the Yb3+/Tm3+/Er3+ ratio, the study allowed to obtain micrometric single crystals that efficiently emit white light via UC. The crystals were characterized by X-ray diffraction, optical and electronic microscopies, EDS and luminescence spectroscopy.

Processable Circularly Polarized Luminescence for the Synthesis of Chiral Plasmonic Nanoparticles

AbstractCircularly polarized light is previously shown as a chiral bias to enable the synthesis of chiral plasmonic nanomaterials through light‐matter interactions. The traditional approach for circularly polarized light generation relies on a “top‐down” approach by removing undesired light polarization through optics, which suffers from energy loss and compatibility issues. An alternative approach is to develop chiral phosphors that emit efficient circularly polarized luminescence (CPL). However, most materials fail to produce processable CPL with both high quantum yield and dissymmetry factors, let alone the synthesis of chiral nanomaterials. Herein, a liquid‐crystal‐templated framework is developed to assemble halide perovskite nanocrystals, CsPbX3 (X = Cl, Br, I), and achieved efficient CPL with the record‐high figure of merit (FM) for three primary colors (Red, Green, Blue). The fidelity of the CPL is further demonstrated in the synthesis of chiral gold nanoparticles, where a five‐fold increase in optical activity is achieved.