Source: MDPI
Understanding Coherent Beam Combining in High-Power Laser Systems
Introduction
Coherent beam combining is a technique used in high-power laser systems to combine multiple laser beams into a single beam with increased power while maintaining beam quality and brightness. This process results in a more powerful and focused laser beam, which is crucial for various industrial and scientific applications.
Techniques of Coherent Beam Combining
Coherent beam combining techniques can be categorized into side-by-side combining and filled-aperture techniques. Side-by-side combining involves combining beams using a phased array, leading to a larger beam size but reduced divergence. Filled-aperture techniques combine multiple beams into a single beam with the same size and divergence using devices like diffraction gratings.
Coherent Polarization Beam Combining
A special case of filled-aperture technique is coherent polarization beam combining, where linearly polarized beams are combined to achieve higher power output. This technique is particularly useful when only two input beams are available, but the output can be repeated as needed.
Methods for Obtaining Mutual Coherence
To ensure the coherence of combined beams, various techniques are employed, such as active stabilization of laser arrays and passive beam combining methods. It is essential for the input beams to maintain stable linear polarization and minimal amplitude fluctuations for successful coherent beam combining.
Coherent Beam Combining with Non-monochromatic Waves
While coherent beam combining is typically done with monochromatic waves, it can also be applied to non-monochromatic input beams, such as ultrashort pulses with broad optical spectra. Precise matching of path lengths is crucial for combining non-monochromatic waves effectively.
Challenges and Considerations
Coherent beam combining faces challenges in maintaining phase coherence at high power levels and in noisy environments. Additionally, precise wavefront and polarization alignment are critical for successful beam combining. Techniques using single-frequency signals and high-power amplifiers may require additional measures to mitigate issues like stimulated Brillouin scattering.
Conclusion
Coherent beam combining is a powerful technique for increasing the power and brightness of laser beams in high-power laser systems. By effectively combining multiple laser beams while maintaining coherence, researchers and engineers can achieve enhanced laser performance for a wide range of applications.
By understanding the principles and challenges of coherent beam combining, advancements in laser technology can continue to push the boundaries of what is possible in fields such as materials processing, communication, and scientific research.
Source: PowerPhotonic
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