{'fraction_non_alphanumeric': 0.017826825127334467, 'fraction_numerical': 0.0, 'mean_word_length': 5.108808290155441, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Laser beam filtering by refractive or diffractive microstructures

Lateral intensity fluctuations of laser beams can be removed by spatial frequency filtering using a pinhole. Beams with a high divergence have a very small and narrow focus, therefore the pinhole must be both very small and thin. Conventional pinholes, based on absorption or reflection of the unwanted parts of the beam, have several limitations in this case. Their disadvantages can be overcome by a new kind of pinholes that are based on microstructures. They are characterized by a higher laser damage threshold, only limited by the bulk material, and a constant visibility of the beam, making the adjustment process of the pinhole a lot easier. The microstructures can be circular, binary gratings working mainly in a diffractive way, as we described earlier. This paper will summarize and update the results for this diffractive, dielectric pinholes and introduce a new idea of using cone-like structures, working mainly in a refractive way. We present the design, fabrication and characterization of pinholes, realized with both of these new concepts and we asses their performance and their limitations.