Low-loss light source for photovoltaic power station optical power meter

Laser diodes emitting in the 750–980 nm range, coupled with GaAs-based or III-V photovoltaic cells, are the preferred low-loss light sources for optical power measurement in photovoltaic power stations.

Optimal Light Source Selection

For high-efficiency optical power meters, monochromatic or narrow-band laser diodes are ideal because they provide coherent, directional light that can be efficiently coupled into optical fibers or free-space systems, minimizing propagation losses.

LE

Ds are generally less suitable due to their incoherent emission, which reduces coupling efficiency and increases losses. Typical laser wavelengths for short-range applications are 750–980 nm, which match the absorption peaks of GaAs-based photovoltaic cells. For longer distances, longer wavelengths reduce Rayleigh scattering and fiber attenuation, further lowering transmission losses.

Photovoltaic Receiver Materials

Gallium arsenide (GaAs) is widely used for optical power conversion due to its direct bandgap of 1. 42 eV, high optical absorption, and fast carrier mobility, which reduces series resistance and improves conversion efficiency. For higher-power or specialized applications, indium gallium nitride (InGaN) and indium aluminum nitride (InAlN) are emerging as promising wide-bandgap alternatives, offering better spectral matching and lower recombination losses in high-power optical transmission systems.

Multijunction designs can further enhance efficiency by tailoring subcells to specific photon energies.

Efficiency Considerations

Photovoltaic cells optimized for quasi-monochromatic light can achieve efficiencies above 50%, with some systems approaching 70% under ideal conditions. Key factors to minimize losses include: Wavelength matching: Photon energy should slightly exceed the bandgap of the photovoltaic material to reduce thermalization losses. Optical alignment: Especially critical for free-space transmission to avoid beam divergence and misalignment losses.

Fiber coupling: Using multimode fibers with large cores can transmit high optical powers with minimal scattering and absorption. Multijunction or segmented cells: These reduce junction capacitance and improve bandwidth while maintaining high light collection efficiency.

Practical Recommendations

Use laser diodes over LEDs for coherent, low-divergence light.

Select Ga

As or III-V multijunction photovoltaic cells for high conversion efficiency. Match the laser wavelength to the photovoltaic bandgap for minimal energy loss. For long-distance fiber transmission, consider longer wavelengths and large-core multimode fibers to reduce scattering.

Implement optical mirrors or resonant layers in the cell design to enhance absorption and reduce reflection losses. By combining a narrow-band laser source with a bandgap-optimized photovoltaic receiver, optical power meters in photovoltaic power stations can achieve low-loss, high-accuracy measurements suitable for both laboratory calibration and field deployment.