High-brightness Light Sources Research Articles

Double Perovskite Single Crystals with High Laser Irradiation Stability for Solid-State Laser Lighting and Anti-counterfeiting.

Laser lighting devices, comprising an ultraviolet (UV) laser chip and a phosphor material, have emerged as a highly efficient approach for generating high-brightness light sources. However, the high power density of laser excitation may exacerbate thermal quenching in conventional polycrystalline or amorphous phosphors, leading to luminous saturation and the eventual failure of the device. Here, for the first time, we raise a single-crystal (SCs) material for laser lighting considering the absence of grain boundaries that scatter electrons and phonons, achieving high thermal conductivity (0.81 W m-1 K-1) and heat-resistance (575 °C). The SCs products exhibit a high photoluminescence quantum yield (89%) as well as excellent stability toward high-power lasers (>12.41 kW/cm2), superior to all previously reported amorphous or polycrystalline matrices. Finally, the laser lighting device was fabricated by assembling the SC with a UV laser chip (50 mW), and the device can maintain its performance even after continuous operation for 4 h. Double perovskite single crystals doped with Yb3+/Er3+ demonstrated multimodal luminescence with the irradiation of 355 and 980 nm lasers, respectively. This characteristic holds significant promise for applications in spectrally tunable laser lighting and multimodal anticounterfeiting.

Energy transfer driven brightening of MoS2 by ultrafast polariton relaxation in microcavity MoS2/hBN/WS2 heterostructures

Energy transfer is a ubiquitous phenomenon that delivers energy from a blue-shifted emitter to a red-shifted absorber, facilitating wide photonic applications. Two-dimensional (2D) semiconductors provide unique opportunities for exploring novel energy transfer mechanisms in the atomic-scale limit. Herein, we have designed a planar optical microcavity-confined MoS2/hBN/WS2 heterojunction, which realizes the strong coupling among donor exciton, acceptor exciton, and cavity photon mode. This configuration demonstrates an unconventional energy transfer via polariton relaxation, brightening MoS2 with a record-high enhancement factor of ~440, i.e., two-order-of-magnitude higher than the data reported to date. The polariton relaxation features a short characteristic time of ~1.3 ps, resulting from the significantly enhanced intra- and inter-branch exciton-exciton scattering. The polariton relaxation dynamics is associated with Rabi energies in a phase diagram by combining experimental and theoretical results. This study opens a new direction of microcavity 2D semiconductor heterojunctions for high-brightness polaritonic light sources and ultrafast polariton carrier dynamics.

Interfacial engineering boosted narrow-band ultraviolet LED based on n-PtNPs@ZnO:Ga microwire/AlN/p-GaN heterojunction

Low-dimensional ZnO micro/nanocrystals having high optical gain, self-constructed microcavity and large-bandgap, is the largest potential constituent for constructing droop-free and high-brightness ultraviolet light sources. In this study, we reported a workable scheme to construct high-monochromatic ultraviolet electroluminescence devices including a Ga-doped ZnO microwire decoated with platinum nanoparticles (PtNPs@ZnO:Ga MW), an AlN electron blocking layer and p-GaN layer substrate. The device exhibits a robust narrow-band ultraviolet electroluminescence peaking at around 374.8 nm and a narrowing bandwidth ∼ 13.5 nm. The electroluminescence profile is comparable with photoluminescence spectrum of ZnO:Ga MW. The device properties can be interpreted by the working mechanism of plasmonic effects, heterojunction interface engineering and optimization strategies. The AlN intermediate layer appeared in the optimized device enables effectively to tune the paths of current traveling and carrier recombination, yielding the band-edge luminescence of ZnO:Ga MW. As the device is further modified using PtNPs with desired plasmons, the optimization of heterojunction interface is significantly boosted, like the observable enhancement of holes injection efficiency, electroluminescence efficiency and interface contact, etc. Thereby, the boosted band-edge luminescence of ZnO:Ga MW can contribute to the well-being of the enhanced ultraviolet electroluminescence in our constructed LED devices. The findings are looking forward to bringing new opportunities toward the implementation of ultra-bright and high-efficiency narrow-band ultraviolet light sources, especially for the achievement of electrically-pumped microlaser devices.

Speckle control for electro-holographic display using high-brightness yellow phosphor light source in projector

Speckle control for electro-holographic display using high-brightness yellow phosphor light source in projector

Microstructured interface modification of laser-driven phosphor-in-glass-film for ultra-high-efficiency white lighting

Phosphor-converted white laser lighting has been regarded as a potential high-brightness light source in lighting and display. Nevertheless, the traditional phosphor-in-glass-film (PiGF) converter suffers the roadblock of low luminous efficiency owing to the low phosphor conversion from small laser spot and the light scattering loss from film-substrate interface. Herein, a laser-driven PiGF with microstructured interface modification was proposed for ultra-high-efficiency white lighting. The effects of PiGF thickness and laser power on the optical performance of PiGF-MS based laser lighting were assessed and compared with the conventional PiGF based laser lighting. The PiGF-MS converter has higher phosphor conversion efficiency and suitable thermal stability originating from the light field strengthening effect of microstructured interface and the outstanding thermal conductivity of sapphire. At the PiGF thickness of 80 µm, the luminous efficacy of PiGF-MS based laser lighting is enhanced by 11% compared with that of PiGF based laser lighting. At this thin PiGF thickness, the PiGF-MS converter adequately emits a cold white light while the PiGF converter still yields a blue light due to its insufficient blue-yellow light conversion. The PiGF-MS converter enables an ultra-high luminous efficacy of 249.1 lm/W and a suitable correlated color temperature (CCT) of 6500 K under a laser power of 3.15 W. The results indicate that the presence of microstructure interface in the PiGF significantly reduces the blue intensity and enhances yellow intensity in the emitted light. The PiGF-MS converter provides a promising roadmap to enhance the light conversion and efficiency of white laser lighting.

Preparation and Thermal Conductivity Enhancement of Boron Nitride Nano-Material PiG Composite

With the improvement of the conversion efficiency of LED chip and fluorescent material and the increasing demand for high-brightness light sources, LED technology has begun to move toward the direction of high-power. However, there is a huge problem that high-power LED must face with a large amount of heat generated by high power causing a high temperature thermal decay or even thermal quenching of the fluorescent material in the device, resulting in a reduction of the luminous efficiency, color coordinates, color rendering index, light uniformity, and service life of LED. In order to solve this problem, fluorescent materials with high thermal stability and better heat dissipation were prepared to enhance their performance in high-power LED environments. A variety of boron nitride nanomaterials were prepared by the solid phase-gas phase method. By adjusting the ratio of boric acid to urea in the raw material, different BN nanoparticles and nanosheets were obtained. Moreover, the control of catalyst amount and synthesis temperature can be used to synthesize boron nitride nanotubes with various morphologies. By adding different morphologies and quantities of BN material in PiG (phosphor in glass), the mechanical strength, heat dissipation, and luminescent properties of the sheet can be effectively controlled. PiG prepared by adding the right number of nanotubes and nanosheets has higher quantum efficiency and better heat dissipation after being excited by high power LED.

Spontaneous emission enhancement and directional emission by an optical nanonatenna array on a metallic mirror

Optical nanoantennas support surface plasmon polariton (SPP) with a confinement of light breaking through the diffraction limit, and thereby achieving an enhancement and regulation of electromagnetic field on a deep-subwavelength scale. In this paper, a periodic array of optical nanoantennas on a metallic mirror is proposed, where the antennas are gold nanocubes forming a two-dimensional periodic array, and a single point emission source is located in the nanogap between the antenna of gold nanocube and the gold mirror. The nanogap between the antenna and mirror can support gap surface plasmon, which results in an enhanced spontaneous emission rate. Meanwhile, the periodic array of nanoantennas can support the surface lattice resonance (SLR), which can achieve directional far-field radiation perpendicular to the substrate or in a specified direction by properly designing the array period. To design the antenna that can simultaneously achieve an enhancement of spontaneous emission rate and a directional radiation of far field, the calculation of the radiation field of a single point source in a periodic structure is transformed into the calculation of the radiation fields of a set of pseudoperiodic point-source arrays by combining the array scanning method (ASM) and full-wave rigorous numerical method, thus giving the spontaneous emission rate of the emitter and the near-field distribution of the antenna. Concerning the calculation of the angular distribution of far-field radiation intensity, we start from the Maxwell’s equations and provide a rigorous formulation and proof of the reciprocity-theorem method. This proof is different from those reported in existing literature and has a more rigorous applicability for infinite-extent periodic structures or has a lower amount of computational work. Based on the reciprocity-theorem method, the antenna parameters are designed so that the enhancement factor of far-field radiation intensity reaches a maximum value of 2756 in the direction perpendicular to the substrate, and simultaneously, the enhancement factors of total spontaneous emission rate and far-field spontaneous emission rate of the point source reach 1097 and 55.50, respectively. The proposed antenna has a simple structure that is easy to design and fabricate, and the proposed design method is intuitive and easy to implement, which can be used to guide the design of high-speed, high-brightness and directional-radiation light sources.

Heat-conducting LSN:Ce-in-glass film on AlN substrate for high-brightness laser-driven white lighting

Laser diodes (LDs) combined with color converters have been considered as new-generation high-brightness white light source. Whereas, the luminescence of phosphor materials is easily influenced by accumulated heat originating from laser-driven conversion. In order to alleviate the thermal effect under focused laser of high-power, we proposed a high-luminescence laser-driven color converter of heat-conducting La3Si6N11:Ce3+ (LSN:Ce) phosphor-in-glass (PiG). The LSN:Ce nitride phosphor exhibits excellent opto-thermal property. The LSN:Ce-PiG-AlN converter was fabricated by sintering the LSN:Ce-PiG layer (∼50 μm) upon a AlN ceramic substrate. Due to excellent luminescence of LSN:Ce and high thermal conductivity of AlN, the LSN:Ce-PiG-AlN converter achieves a luminous flux (LF) of 376.1 lm, a luminous efficiency (LE) of 158 lm/W, and a correlated color temperature (CCT) of 4462 K under 2.39 W laser excitation. In addition, the temperature of PiG film surface still stays low level (<150 °C) when driven by 4.82 W laser irradiation. The proposed LSN:Ce-PiG-AlN converter is a high-performance and promising phosphor converter for high-luminescence white laser lighting.

Lanthanoid-doped quaternary garnets as phosphors for high brightness cathodoluminescence-based light sources

Gadolinium-yttrium- aluminum-gallium garnets (GYAGG) doped and codoped with Eu, Tb, and Ce were manufactured as ceramics to develop long-wavelength phosphors for high-brightness white light sources based on cathodoluminescence (CL). The CL light yield (LY) of Tb-doped ceramics at high-intensity electron beam excitation is shown to be more than twice as high as that of the conventional phosphor YAG:Ce, whereas codoping with Eu to redshift the chromaticity results in reducing the LY approximately to the level of YAG:Ce. The LY might be substantially improved by using a mix of Tb- and Eu-doped GYGAG powders instead of a single codoped GYGAG to produce ceramic phosphor. The high LY is explained by favorable contribution of Gd sublattice in excitation transfer to activator ions. Chromaticity of phosphors GYGAG:Tb, Eu can be tuned in a wide range by varying the ratio of Tb to Eu concentration. They are radiation resistant and stabile in the temperature range from 300 to 450 K.

Research of continuous fiber laser sustained Xe plasma

High-speed optical inspection of wafers requires a high-brightness and broadband light source. The brightness of traditional arc discharge lamps is difficult to increase, which is limited by the cathode current density. Laser sustained plasma (LSP) is a promising method to overcome the limitations of existing light source technologies. Then the characteristics of fiber laser sustained plasma in a xenon bulb were investigated, the absorption coefficient was measured, and the spectrum was analyzed. The results show that with the increase of laser power, the volume of plasma gradually increases and moves towards the direction of laser incident. With the increase of Gaussian beam focusing number F, the threshold laser power required to maintain the stable existence of plasma decreases gradually. There are upper and lower limits for laser power at which the LSP could be sustained. When the laser incident at the optimal incident angle, the laser propagation in the plasma is the optimal path for laser energy deposition, and the plasma has higher absorption coefficient, temperature and brightness. When F ≥ 10, the Xe plasma will show spatial instability due to refraction effect. Compared with the traditional short-arc xenon lamp, the LSP spectrum has a higher proportion in short wavelength.

Optically active Fe2+-doped ZnSe particles in a chalcogenide glass matrix

High brightness light sources in the mid-infrared are of particular interest for a host of different applications. However, the selection and availability of laser gain media in this spectral region are severely lacking. In this manuscript, we demonstrate broadband optical emission in the 3520-5200 nm region from Fe2+-doped ZnSe microparticles dispersed in a chalcogenide glass matrix which is amenable to fiber drawing. A conformal alumina shell was applied to the Fe:ZnSe particles which prevented ZnSe dissolution and preserved normal Fe2+ optical absorption and emission properties during the composite material manufacturing process. The broadband emission properties of the Fe:ZnSe-doped chalcogenide glass material observed here are promising for the future development of fiber lasers operating at wavelengths &gt; 4 µm.

Interfacial modulation and plasmonic effect mediated high-brightness green light sources in a single Ga-doped ZnO microwire based heterojunction

High-brightness, stable and nearly droop-free green LEDs based on a carefully constructed n-AuNPs@ZnO:Ga MW/MgO/p-InGaN heterojunction were proposed and investigated experimentally.

Phase-Programmable Gaussian Boson Sampling Using Stimulated Squeezed Light.

We report phase-programmable Gaussian boson sampling (GBS) which produces up to 113 photon detection events out of a 144-mode photonic circuit. A new high-brightness and scalable quantum light source is developed, exploring the idea of stimulated emission of squeezed photons, which has simultaneously near-unity purity and efficiency. This GBS is programmable by tuning the phase of the input squeezed states. The obtained samples are efficiently validated by inferring from computationally friendly subsystems, which rules out hypotheses including distinguishable photons and thermal states. We show that our GBS experiment passes a nonclassicality test based on inequality constraints, and we reveal nontrivial genuine high-order correlations in the GBS samples, which are evidence of robustness against possible classical simulation schemes. This photonic quantum computer, Jiuzhang 2.0, yields a Hilbert space dimension up to ∼10^{43}, and a sampling rate ∼10^{24} faster than using brute-force simulation on classical supercomputers.

Research of pulsed Xenon lamp power supply based on STM32

Novel coronavirus pneumonia affects the health of people all over the world. In this study, UV pulse high-light sterilization technology was used to combat coronavirus. The light source of the ultraviolet pulsed high-light disinfection robot is a kind of high-brightness flash light source using pulsed xenon lamps as the output load. This paper developed a pulsed xenon lamp power supply with a high-voltage pulse synchronous trigger function, a DC charging voltage of 1kV-3kV, an output pulse current range of 1kA-3kA, and a pulse width of 50μS for a pulsed xenon lamp with a 196mm×Φ10mm and a resistivity of 12Ω⋅A1/2. This paper presented the experimental results of charging voltage of 1kV, output pulse current peak value of 1kA, and pulse width of 50μS. The power supply design was based on the phase-shifting voltage regulation mode of UC3825 control power MOS tube, through the sampling isolation module and the closed-loop feedback formed by STM32 control, the energy storage capacitor was linearly charged through the DC voltage sampling and voltage regulation control module; the trigger pulse signal was generated by the SCR switch, and the xenon lamp was turned on and emits flash light after the pulse transformer was boosted. The sample test results verified the feasibility of the power supply design principles and technical solutions.

High field X-ray laser physics

High field X-ray laser physics

Single microwire based smart color-switchable light-emitting diode

Achieving high-brightness and high-efficiency low-dimensional light sources remains a challenging issue due to the lack of high electrical conductance electrodes, as well as the efficient charge injection into the luminescent layer. Herein, by employing chemical vapor deposition methods, individual ZnO microwires with heavily Ga-impurity (GZO MWs) have been successfully synthesized, and then directly assembled on p-GaN substrate to form a heterostructure light-emitting device. In the device, the single GZO MW, which possessing metallic behavior, can function as an outstanding conductance electrode, whilst an efficient luminescence layer. Electroluminescence (EL) characteristics of the single GZO MW-diode operated under forward bias were performed, yielding bright, blue/green lighting with the main peaks positioned at 450 nm and spectral line width of 90 nm. While it also can emit strong broadband, stable and monochromatic white emission under reverse bias. The dual-color-illuminating can be switched repeatedly by reversing the bias polarity. The bias-polarity-switched light source enables independent control over the EL illuminating-color and brightness. The fabrication of single MW based color-switchable light-emitting diode can afford a promising scheme toward the miniaturized, and smart light sources, which hold tremendous power in optical communication, optoelectronic devices and photoelectricity encoders.

High-Luminance Mid-Air Image Display for Outdoor Viewing by Focusing Sunlight

The mid-air image is a very powerful method for presenting computer graphics in a real environment, but it cannot be used in bright locations owing to the decrease in brightness during the imaging process. Therefore, to form a mid-air image with a high-brightness light source, a square pyramidal mirror structure was investigated, and the sunlight concentration was simulated. We simulated the tilt angle and combination angle of the condenser as parameters to calculate the luminance of the surface of a transparent liquid crystal display. The light collector was installed at 55∘ from the horizontal plane and mirror. A high level of illumination was obtained when these were laminated together at an angle of 70∘. To select a suitable diffuser, we prototyped and measured the brightness of the mid-air image with an LED lamp to simulate sunlight in three settings: summer solstice, autumnal equinox, and winter solstice. The maximum luminance of the mid-air image displayed by collecting actual sunlight was estimated to be 998.6 cd/m2. This is considerably higher than the maximum smartphone brightness to allow for outdoor viewing, and it can ensure fully compatible visibility.

Vertically-aligned ZnO microrod for high-brightness light source

ZnO-microrod array with well-aligned orientation prepared on p-GaN template can be utilized to construct high-performance near-ultraviolet emitters due to desired high optical quality and well-defined geometries.

Mid-infrared supercontinuum generation in chalcogenide fibers with high laser damage threshold.

Laser damage thresholds (Ith) at 1.03 µm, as well as third-order nonlinear refractive indices (n2) and two photon absorption coefficients (β) at 1.55 µm of a number of Ge-As-S glasses were measured and systematically studied. The glass with the composition Ge0.12As0.24S0.64 showed a high Ith and the maximum figure of merit (fm= n2/(β·λ)), and therefore was selected as the core material for the fabrication of a step-index fiber. A compatible glass with the composition Ge0.18As0.1S0.72 was chosen as the cladding material. Based on the dispersion calculations, the fiber with a core diameter of ∼7-10 µm was designed. The designed fiber was fabricated by a multiple step rod-in-tube method. When the fiber with a core diameter of ∼9 µm and a length of ∼13.5 cm was pumped by ∼170 fs pulses (1 MHz) at 4.5 µm, the mid-infrared supercontinuum (SC) covering 1.3-8.1 µm was generated. These results demonstrate the good potential of Ge-As-S chalcogenide fibers for producing high-brightness broadband mid-infrared SC light sources.

Memory and CPU efficient computation of the Fresnel free-space propagator in Fourier optics simulations.

We describe a version of the paraxial free-space Fourier optics propagator for numerical wave propagation simulations that eliminates the need for a dense sampling of an input electric field with phase dominated by quadratic terms developing at some distance from the source or from the radiation beam waist. This propagator requires considerably (two to three orders of magnitude as observed in routine simulations) less memory and CPU resources than the standard Fresnel free-space propagator while preserving its levels of accuracy and generality. This method has been successfully used in "Synchrotron Radiation Workshop" code for more than a decade. It has greatly contributed to the applicability of the code, and more generally the applicability of the Fourier optics methods, to wave-optics based simulations of radiation propagation through optical systems of beamlines at high-brightness and high-coherence synchrotron light sources.