Laser wireless power transmission (WPT) is one of the most important technologies in the field of long-range power transfer. This technique uses a laser as a transmission medium instead of conventional physical or electrical connections to perform WPT. It has the characteristics of long transmission distance and flexible operation. The existing laser wireless power transmission system uses photovoltaic cells as a receiver, which convert light into electricity. Due to the contradiction between the Gaussian distribution of laser and the uniform illumination requirements of photovoltaic cells, the laser wireless power transmission technology has problems such as low transmission efficiency and small output power. Therefore, understanding the energy distribution changes in the laser during transmission, especially the energy change after the laser is transmitted to each key device, and analyzing the influencing factors of the energy distribution state, are of great significance in improving the transmission efficiency and reducing the energy loss in the system. This article utilizes the optical software Lighttools as a tool to establish a laser wireless power transmission model based on a powersphere. This model is used to study the energy distribution changes in the laser as it passes through various components, and to analyze the corresponding influencing factors. To further validate the simulation results, an experimental platform was constructed using a semiconductor laser, beam expander, Fresnel lens, and powersphere as components. A beam quality analyzer was used to measure and analyze the laser energy distribution of each component except for the powersphere. The output voltage and current values of various regions of the powersphere were measured using a multimeter. The energy distribution of the powersphere was reflected based on the linear relationship between photo-generated current, voltage, and light intensity. The experimental results obtained were in good agreement with the simulation results. Simulations and experiments have shown that using a beam expander can reduce divergence angle and energy loss, while employing large-aperture focusing lens can enhance energy collection and output power, providing a basis for improving the efficiency of laser wireless power transfer.

With the development of underwater exploration, underwater networking is in urgent demand. At present, underwater wireless optical communication (UWOC) is primarily based on line-of-sight (LOS) communication links. However, the underwater environment is so complicated that LOS communication links are easily affected by a couple of factors such as air bubbles, turbidity, oceanic turbulence, and so on. We put forward novel UWOC links using the total reflection at the air-water interface, which can mitigate those phenomena. This paper aims to investigate a UWOC link based on the total reflection at the air-water interface. In our work, we achieved the maximum data rate of 300 Mb/s and a bit error rate (BER) of 3.10 × 10⁻³ under the forward error correction (FEC) with the total reflection angle of 7°. Furthermore, we verified the performance of the total reflection-based UWOC links at the air-water interface in the presence of waves and evaluated the impact on the UWOC links when the frequency and amplitude of the waves varied.

A photovoltaic panels is a device used for converting solar and other energy into electrical energy. In laser wireless power transmission, there is a problem that the conversion efficiency of the photovoltaic panel is not as high as that of a single photovoltaic cell, and the output power is not as large as expected. This is not conducive to the popularization and use of wireless power transmission via laser. It is important to find out why the output power of the photovoltaic panel irradiated by lasers is not high. According to the laser intensity distribution equation, it is deduced that the laser in a very small area has an equivalent uniformity intensity distribution through the comparative calculation of the light intensity of two adjacent points. Then, the input non-uniform laser can be broken down into many equivalent uniform small lasers with different light intensity values. Based on this theory, the photovoltaic array model under laser was established, and it was simulated by MATLAB/Simulink. The simulation results reveal that the greater the difference between the light intensity values of these small spots, that is to say, the more non-uniform the laser, the lower the output power of the photovoltaic module illuminated by it. A multi-wavelength experimental platform was built, and comparative experiments of laser wireless power transmission were carried out using three kinds of lasers: 808, 532, and 1030 nm. The experimental result was in good agreement with the simulation result. The above results show that the deduced theory and the model based on it are correct.

The powersphere is a spherical enclosed receiver composed of multiple photovoltaic cells. It serves as a replacement for traditional photovoltaic panels in laser wireless power transmission systems for optoelectronic conversion. The ideal powersphere aims to achieve a uniform distribution of light within the cavity through infinite reflections, reducing energy losses in the circuit. However, due to the high absorption rate of the photovoltaic cells, the direct irradiation area on the inner surface of the powersphere exhibits a significantly higher light intensity than the reflected area, resulting in a suboptimal level of light uniformity and certain circuit losses. To address the aforementioned issues, a method of intra-cavity beam splitting in the powersphere is proposed. This solution aims to increase the area of direct illumination and reduce the intensity difference between direct and reflected lights, thereby improving the light uniformity on the inner surface of the powersphere. Utilizing the transformation matrix of Gaussian beams, the q parameters for each optical path with beam splitting were calculated, and the equality of corresponding q values was demonstrated. Further, based on the q parameter expression for the electric field of Gaussian beams, the intensities for each optical path were calculated, and it was demonstrated that their values are equal. Additionally, an optical software was utilized to establish a model for intra-cavity beam splitting in the powersphere. Based on this model, a beam-splitting system was designed using a semi-transparent and semi-reflective lens as the core component. The light uniformity performance of the proposed system was analyzed through simulations. To further validate the effectiveness of the calculations, design, and simulations, multiple lenses were employed to construct the beam-splitting system. An experimental platform was set up, consisting of a semiconductor laser, monocrystalline silicon photovoltaic cells, beam expander, Fresnel lens, beam-splitting system, and powersphere. An experimental verification was conducted, and the results aligned with the theoretical calculations and simulated outcomes. The above theory, simulations, and experiments demonstrate that the intra-cavity beam-splitting method effectively enhances the optical uniformity within the powersphere.

In laser wireless power transmission systems, the powersphere serves as a spherical enclosed receiver that performs photoelectric conversion, achieving uniform light distribution within the cavity through infinite internal light reflection. However, in practical applications, the high level of light absorption displayed by photovoltaic cells leads to significant disparities in light intensity between directly irradiated regions and reflected regions on the inner surface of the powersphere, resulting in poor light uniformity. One approach aimed at addressing this issue uses a spectroscope to split the incident beam into multiple paths, allowing the direct illumination of all inner surfaces of the powersphere and reducing the light intensity difference between direct and reflected regions. However, experimental results indicate that light transmission through lenses introduces power losses, leading to improved uniformity but reduced output power. To address this limitation, this study proposes a method that utilizes multiple incident laser beams combined with a centrally positioned spherical reflector within the powersphere. A wireless power transmission system model was developed using optical simulation software, and the uniformity of the intracavity light field in the system was analyzed through simulation. To validate the design and simulation accuracy, an experimental system incorporating semiconductor lasers, spherical mirrors, and a powersphere was constructed. The data from the experiments aligned with the simulation results, jointly confirming that integrating a spherical reflector and distributed incident lasers enhances the uniformity of the internal light field within the powersphere and improves the system’s efficiency.

In visible light communication (VLC) systems, lenses are typically used to collimate light at the transmitter. However, due to the wide light emission angle of mini-LEDs, capturing light at large angles using a lens at the transmitter can be challenging. This paper presents a design of a reflective cup at the mini-LED-based VLC transmitter. The redesigned reflective cup can collect most of the light and collimate it, achieving an efficiency of approximately 86% at a distance of 10 m in the simulation. In the experiment, error-free communication was achieved at a distance of 100 m with a data rate of 190 Mbps. To the best of our knowledge, a long-distance VLC system based on mini-LEDs is investigated for the first time. The reflective cup offers advantages, including high efficiency, low cost, and a simple structure. It holds reference value for addressing the issue of limited communication distance in underwater wireless optical communication (UWOC).