Nanostructured Multilayer Coatings for Spatial Filtering

Spatial filtering is an important mechanism to improve the spatial quality of laser beams. Typically, a confocal arrangement lenses with diaphragm in focal plane used for intracavity filtering. Such conventional requires access far-field domain. In microlasers, however, impossible due lack space microresonators far-field. Therefore, novel concept more compact and efficient necessary. this study, conceptually near-field domain proposed demonstrated, by nanostructured multilayer coating—a 2D photonic crystal structure periodic index modulation along longitudinal transverse directions beam propagation. The built on nanomodulated substrate, provide periodicity. physical vapor deposition self-repeating direction. A 5 µm thick composed multiple layers alternating high- low-index materials providing near-infrared frequencies 2° low angle passband experimentally demonstrated. can be considered as ideal component microlasers.