Submicrometer grating fabrication in fused silica by interferometric laser-induced backside wet etching technique

摘要

Submicrometer period fused silica gratings were produced by two-beam interferometric laser-induced backside wet etching technique (TWIN LIB WE). The fourth harmonic of a Nd:YAG laser beam was spatially filtered in two steps, and the smoothened beam was split into two parts and interfered at incident angles of 60°, 30°, 14°, and 7.7°, respectively, on the backsides of fused silica plates that were in contact with a liquid absorber. The periods of the produced fused silica gratings were, respectively, 154 nm, 266 nm, 550 nm, and 990 nm. In the next step, TWIN-LIB WE setup was completed by using a coupling rectangular prism in order to reach immersion setup, which made possible to fabricate 104 nm period fused silica grating. This is the smallest laser-generated grating constant in fused silica at present.rnThe morphology of the etched gratings was characterized by atomic force microscope. Important parameters (modulation depth, low-pass filtered waviness, quality factor) of the produced gratings were determined. Evolution of the grating parameters was also studied in the 990 nm case: the dependence of modulation depth, waviness, and quality factor on the number of laser pulses was investigated.