Laser wireless power transmission (LWPT), which can realize long-range power transmission, has been received widespread attention in recent years. The influence of high-power laser nonuniform irradiation on the output power and conversion efficiency of photocells has attracted much attention. This article conducted simulations and experiments on nonuniform irradiation with a constant power density and on nonuniform irradiation with constant incident power. The current I, voltage V, output power PL, conversion efficiency ηL, internal resistance R0, and maximum power point resistance RLmax of a 1 cm × 1 cm single-junction gallium arsenide photocell under nonuniform irradiation were studied. Under the condition of nonuniform irradiation with a constant laser power density, the conversion efficiency of the photocell remained constant, but R0 increased nonlinearly from 0.5 to 5 Ω. The ηL decreased from 45% to 5% when the load resistance is constant. Under the condition of nonuniform irradiation with constant laser power, the photoelectric conversion efficiency and R0 changed little, and the ηL remained about 45%, for it is not affected by nonuniform irradiation. The output characteristics of the photocells under uniform irradiation were also studied, and the results were consistent with the above conclusions. When the photocells with constant temperature were irradiated in-homogeneously, it was also revealed that the internal resistance increased and that the conversion efficiency decreased due to the irradiation power variation. The empirical formula was derived through circuit transformation and curve fitting.
High power diode lasers are widely used as the pump sources for fiber lasers and solid-state lasers, or the light sources for direct diode laser systems. To meet the emerging needs of fiber lasers, solid state lasers and direct diode laser systems, diode lasers are moving towards higher volume manufacturing, along with higher performance and lower cost. In this paper, we will present our progresses in these areas. We have set up a 6" GaAs wafer production line for high power diode laser chips, which includes MOCVD epitaxy and wafer fabrication. With the 6" wafer production line, we are producing multi-million chips per month for fiber laser pumping. The 6" wafers show great uniformity and reproducibility. Device performance is outstanding, with near 70% efficiency and high CW roll-over power.
KEYWORDS: Liquids, Disk lasers, Thermal effects, High power lasers, Temperature metrology, Convection, Thermal modeling, Analytical research, Nd:YAG lasers, Refractive index
The thermal effects of a liquid direct cooled split disk laser are modeled and analytically solved. The analytical solutions with the consideration of longitudinal cooling liquid temperature rise have been given to describe the temperature distribution in the split disk and cooling liquid based on the hydrodynamics and heat transfer. The influence of cooling liquid, liquid flowing velocity, thickness of cooling channel and of disk gain medium can also be got from the analytical solutions.
For the nonuniform distribution of pump and temperature in the large-aperture, high-power, thin-disk laser medium, a cooling method of multiannular channel liquid cooling was proposed and examined both experimentally and theoretically. The temperature distribution in the gain medium becomes uniform utilizing the method of multiannular channel liquid cooling, which is proved by a numerical model using Ansys software. In the modeling, the distribution of temperature in the medium varies with the changes of the flow rate and temperature of the coolant in each annular channel. An excellent uniform temperature distribution could be obtained in the gain medium with arbitrary power and profile of pump light by setting a tailored parameter of the coolant in each annular channel. The highest temperature difference in the gain medium with multiannular channel liquid cooling reduces about 88% compared with evenly cooling. Also, the thermal effect has been suppressed; the experimental result is consistent with numerical modeling. This method could be a new idea for designing the thin-disk laser’s cooling system.
For the non-uniform distribution of pump and temperature in the large aperture, high-power thin disk laser medium, a novel cooling method of multi-annular channel liquid cooling is proposed and examined both experimentally and theoretically. The temperature distribution in the gain medium is getting into uniform utilizing the method of multi-annular channel liquid cooling, which is proved by a numerical model using ANSYS software. In the modeling, the distribution of temperature in the medium varies with the changes of the flow rate and temperature of the coolant in each annular channel. A wonderful uniform temperature distribution could be obtained in the gain medium with arbitrary power and profile of pump light by setting a tailored parameter of the coolant in each annular channel. The highest temperature difference in the gain medium with multi-annular channel liquid cooling reduces about 88% compared with an evenly cooling. And the thermal effect has been suppressed, the experimental result is consistent well with numerical modeling. This method could be a new idea for designing the thin disk laser’s cooling system.
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