Optical characterizations and thermal analyses of HfO₂/SiO₂ multilayered diffraction gratings for high-power continuous wave laser

Abstract

Spectral beam combining technique is a simple and straightforward method to obtain a high-power laser beam. The beam combining system typically consists of three parts: fiber laser array, transform optical system and diffraction grating. Performance of the system (diffraction efficiency and laser induced damage threshold) is mainly determined by the diffraction grating. This paper describes a multilayer dielectric diffraction gating with high diffraction efficiency and low laser-induced damage threshold, which can be potentially used to obtain a high-power laser by combing laser beams. The diffraction grating is designed by coupled-wave analysis, and single-beam laser interference lithography is used to fabricate diffraction gratings. To verify the optical and thermal characteristics of the beam, we measure diffraction efficiency and the threshold for laser-induced damage. Finite element method simulation accurately represented temperature distribution in the grating during laser irradiation. This work provides integrated methods that include design of multilayer dielectric gratings, thermal analysis and device characterization using high-power laser.

Scalable and High-Throughput Top-Down Manufacturing of Optical Metasurfaces

“…Through the miniaturization and performance enhancement of bulk optical components, metasurfaces have been used in imaging applications such as resolution-enhanced fluorescence microscopy [ 21 , 22 ] and laser scanning microscopy [ 23 ]. Furthermore, the extraordinary optical properties of metasurfaces enable the perfect absorption of light [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ], and light manipulating applications such as beam splitting [ 31 , 32 , 33 ], verification and enhancement of the spin Hall effect [ 34 , 35 , 36 ], asymmetric transmission [ 37 ], multifunctional waveguides [ 38 ], and other light-manipulation applications [ 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. In addition, the researches on various materials of the metasurfaces have been actively reported: a metasurface-based solar reflector using vanadium dioxide (VO 2 ) [ 43 , 50 , 51 , 52 , 53 ], a study on the manufacturing of graphene oxide film for anisotropic photoresponse [ 54 ], and the scalable nanostructures of molybdenum disulfide (MoS 2 ) [ 55 ].…”

Damage Characteristics of Aluminum-Coated Grating Irradiated by Nanosecond Pulsed Laser

“…Damage to thin-film materials by nanosecond pulsed lasers involves complex physical mechanisms, such as impurity-induced phase explosion [7,8], phase transition-induced mass removal [9], plasma-induced plasma expansion [10], plasma shielding [11], and shock wave effects [12][13][14]. To date, with the improvement of laser technology, researchers have studied the damage mechanisms and damage thresholds of various lasers acting on different gratings [15][16][17], including those of continuous lasers on multilayer dielectric film gratings [18][19][20], and those of nanosecond pulsed lasers and ultrafast lasers acting on gold, multilayer dielectric, and hybrid multilayer dielectric film gratings [21]. However, aluminum-coated gratings are also widely used in spectrometers, aperture cameras, and detection devices because of their low cost, high practicability, stable reliability, and high diffraction efficiency, but there are few reports on the damage caused to aluminum-coated gratings irradiated by 1064 nm nanosecond pulsed lasers.…”