Light-emitting Modules Research Articles

Toward Intelligent Display with Neuromorphic Technology.

In the era of the Internet and the Internet of Things, display technology has evolved significantly toward full-scene display and realistic display. Incorporating "intelligence" into displays is a crucial technical approach to meet the demands of this development. Traditional display technology relies on distributed hardware systems to achieve intelligent displays but encounters challenges stemming from the physical separation of sensing, processing, and light-emitting modules. The high energy consumption and data transformation delays limited the development of intelligence display, breaking the physical separation is crucial to overcoming the bottlenecks of intelligence display technology. Inspired by the biological neural system, neuromorphic technology with all-in-one features is widely employed across various fields. It proves effective in reducing system power consumption, facilitating frequent data transformation, and enabling cross-scene integration. Neuromorphic technology shows great potential to overcome display technology bottlenecks, realizing the full-scene display and realistic display with high efficiency and low power consumption. This review offers a comprehensive summary of recent advancements in the application of neuromorphic technology in displays, with a focus on interoperability. This work delves into its state-of-the-art designs and potential future developments aimed at revolutionizing display technology.

Tunable Multicolor Fluorescence of Perovskite-Based Composites for Optical Steganography and Light-Emitting Devices.

Multicolor fluorescence of mixed halide perovskites enormously enables their applications in photonics and optoelectronics. However, it remains an arduous task to obtain multicolor emissions from perovskites containing single halogen to avoid phase segregation. Herein, a fluorescent composite containing Eu-based metal-organic frameworks (MOFs), 0D Cs4PbBr6, and 3D CsPbBr3 is synthesized. Under excitations at 365 nm and 254 nm, the pristine composite emits blue (B) and red (R) fluorescence, which are ascribed to radiative defects within Cs4PbBr6 and 5D0→7FJ transitions of Eu3+, respectively. Interestingly, after light soaking in the ambient environment, the blue fluorescence gradually converts into green (G) emission due to the defect repairing and 0D-3D phase conversion. This permanent and unique photochromic effect enables anticounterfeiting and microsteganography with increased security through a micropatterning technique. Moreover, the RGB luminescence is highly stable after encapsulation by a transparent polymer layer. Thus, trichromatic light-emitting modules are fabricated by using the fluorescent composites as color-converting layers, which almost fully cover the standard color gamut. Therefore, this work innovates a strategy for construction of tunable multicolor luminescence by manipulating the radiative defects and structural dimensionality.

Dual-functional transparent adhesive films with modified titanium dioxide nanoparticles for UV protection and wide viewing

A new type of dual-functional optically clear adhesive (OCA) with UV protection and wide viewing capabilities was fabricated using TiO2 nanoparticles. UV-visible spectroscopy was used to determine the transmittances of OCA films, and a laser oscilloscope and a bar-type LED lamp were used for light-diffusion studies. Modified TiO2 nanoparticles with core-shell structures have different refractive indices to the unmodified particles and exhibit improved UV protection and light-scattering abilities. Therefore, dual-functional OCAs, rather than normal OCAs, help to protect light-emitting modules or the naked eye, and images emitted from such modules are observed more clearly from a variety of angles.

High-Throughput Visual MIMO Systems for Screen-Camera Communications

Screen-camera communications, using a liquid crystal display (LCD) screen and camera image sensors, have been attractive variants of visible light communications (VLC) since any external light-emitting modules and photo detectors are required for recent mobile devices, which are usually equipped with display and camera. A major issue in screen-camera communications is a performance loss in transmission rate due to nonlinear channel impairments with ambient noise. To improve transmission rates, we investigate the impact of nonlinear channel equalization, nonbinary channel coding, probabilistic shaping, and nonlinear precoding for high-order modulation schemes. Experimental evaluations using an LCD screen and camera demonstrate that our proposed scheme achieves 3.8–3.3 times higher transmission rates compared to existing schemes for a communication distance of 60–160 cm.

The Surveillance Transceiver Module Design for Improvement of Irradiance Coverage and Image Grayscale Quality

Night image quality is gradually emphasized in surveillance industry in past years, and the requirement for the night image definition standards is enhanced. A traditional flashlight-like circularly symmetric light is gradually not suitable for the industry, and the optical design equipped secondary optical elements also encounters the difficulty in space restriction. Package lenses are used for the optical design in this study, mainly replacing the functions of secondary optics and solve the restriction of inadequate internal space of a camera. Meanwhile, the light design of a light-emitting module is proceeded to match the characteristic of a camera image capturing 4:3 or 16:9. Radiant coverage and irradiance efficiency are two parameters to judge the light quality. A new design, under the irradiance efficiency 100%, could enhance the original radiant coverage from 0.366 to 0.825, increasing up to 2.25 times. Besides, the image irradiance uniformity also increases from 0.47 to 0.714, with the increase up to 1.52 times. The package lens design is gradually accepted by international surveillance manufacturers.

Single-transverse-mode near-IR superluminescent diodes with cw output power up to

A series of light-emitting modules based on single-mode quantum-well superluminescent diodes with centre emission wavelengths of about 790, 840, 960 and and a cw output power up to in free space is developed. A sufficiently long service life of these devices is demonstrated.

Investigation of light extraction from light emitting module chip-on-board

A research has been carried out on the optimization of the shape of encapsulating cover to minimize optical losses in light-emitting modules fabricated with the “chip-on-board” (COB) technology. Optical properties of the components of a typical COB were taken into account including those of the substrate, light-emitting chips, encapsulating material and phosphor particles. Light losses were analyzed for various types of encapsulant surface structuring in an attempt to design an optical element with maximum light extraction efficiency. Calculations were complemented with experimental measurements. The results of the research showed that structuring the surface of the encapsulant can enhance light extraction by 10 to 15% for the material without phosphor particles and by 10 to 14% for the material with phosphor particles.

Broadband superluminescent diodes with bell-shaped spectra emitting in the range from 800 to

Quantum-well superluminescent diodes (SLD) with extremely thin active (AlGa)As and (InGa)As layers and centre wavelengths about 810, 840, 860 and are experimentally studied. Their emission spectrum possesses the shape close to Gaussian, its FWHM being depending on the length of the active channel and the level of pumping. Under cw injection, the output power of light-emitting modules based on such SLDs can amount to at the output of a single-mode fibre. It is demonstrated that the operation lifetime of these devices exceeds 30000 hours. Based on the light-emitting modules the prototypes of combined BroadLighter series light sources are implemented having a bell-shaped spectrum with the width up to .

Effect of optical feedback on the output parameters of quantum-well superluminescent diodes

The effect of a weak optical feedback on the power and spectral parameters of light-emitting modules based on near-IR quantum-well superluminescent diodes (SLDs) is studied. It is shown that even very weak parasitic feedback (kfb < -30 dB) distorts the emission spectrum of high-power SLDs and noticeably reduces their output power.

Broadband radiation sources based on quantum-well superluminescent diodes emitting at 1550 nm

The emission spectra of superluminescent diodes (SLDs) based on a multilayer quantum-well (InGa)PAs heterostructure are studied in the wavelength range from 1450 to 1650 nm. The FWHM of these spectra exceeds 120 nm in certain operating regimes. The experimental samples of light-emitting modules with output single-mode fibres are fabricated based on the SLDs studied, which produce the output power spectral density above -45 dBm nm-1 within the band over 200 nm. The spectrum of such an emitter covers the main bands (S, C, and L) of WDM telecommunication systems. The possibilities of a further broadening and flattening of the emission band of these SLDs are considered.

Analysis of the emission parameters of low-power superluminescent diodes in the temperature range from -55°C to +93°C

The main physical parameters of superluminescent diodes are studied in the spectral range 800 — 850 nm and temperature range from -55°C to +93°C for an output power of the order of 0.1 mW. It is shown that such diodes can be used in low-power miniature light-emitting modules that can operate in a wide temperature range without thermal stabilisation of the active element.

Passive mode locking in a multisegment laser diode with an external cavity

The structure and operating conditions of multisegment laser (GaAl)As diodes with passive locking of the modes of an external cavity (bulk and fibre) were optimised. Regular trains of optical single pulses of picosecond duration were generated in a spectral range 850 — 860 nm. The peak power of these pulses was several watts and the repetition rate was near 1 GHz. Under certain conditions these output pulses were linearly chirped, i.e. they were suitable for subpicosecond time compression. Laboratory prototypes were made of miniature light-emitting modules with these characteristics.

Superluminescent diodes based on single-quantum-well (GaAl)As heterostructures

Theoretical and experimental investigations were made of the power, spectral, and polarisation characteristics of superluminescent diodes based on (GaAl)As heterostructures with separate confinement and a quantum-well active layer. The technical characteristics of these diodes were not inferior to those of superluminescent diodes based on traditional double-sided heterostructures. The new diodes were superior to the traditional heterostructures in respect of the half-width of the emission spectrum which was up to 100 nm, corresponding to a coherence length less than 7 μm. Test samples of light-emitting modules based on the investigated diodes were constructed.