Nanostructured Multilayer Coatings for Spatial Filtering

Abstract

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

Guided mode resonance optimization for spatial dispersion control

“…There exists a vast number of optical components recently developed that are of similar scale to the wavelength of interest and mimic the function of classical bulky elements, making complex optical and laser systems more compact. 1 Examples include meta-optical components such as metalenses based on metaatoms, 2 surface relief holographic elements, 3 and thin film grating elements. 4 The former can replace classical Bragg gratings in a lossless dielectric configuration and is successfully used in compact laser systems such as vertical-cavity surfaceemitting lasers (VCSELs) to stabilize their time-like spectrum, emission direction, and laser beam's spatial characteristics.…”

Spatially Structured Optical Pump for Laser Generation Tuning

“…Photonic crystal (PhC) spatial filters are a potential solution to suppress multimode operations in microcavity semiconductor surface-emitting lasers, increasing the output beam spatial quality and its brightness [ 48 , 49 , 50 , 51 ]. The other alternative is photonic crystal structures integrated with the gain medium, as in photonic crystal surface-emitting lasers (PCSELs) [ 52 , 53 , 54 , 55 , 56 ].…”

Anti-Reflective Coatings Produced via Atomic Layer Deposition for Hybrid Polymer 3D Micro-Optics

“…Highly curved substrates or stacked structures cannot be uniformly coated. For instance, the ion beam sputtering method has been successfully utilized to deposit single-layer [ 9 ] and multilayer [ 10 ] coatings on nanostructured planar surfaces (gratings). However, significant progress has been made in designing and fabricating optical components over the past few decades.…”