Femtosecond pulse laser beam shaping and power control for freespace optical material properties measurements

摘要

With the development of lasers, laser sources have been well adopted in spectrophotometry and optical materialmeasurement. Especially in the ultraviolet range, ultraviolet laser has broad application prospects in the fields of opticaldata storage, lithography, micromachining, photobiology and medical treatment. The previously used xenon lamps havelimited reliability, high energy consumption, and poor beam direction stability. NIM's new facility uses Ti: sapphirelasers as a source of monochromatic beams. Femtosecond pulse lasers can be tuned in a wide spectral range viaparametric oscillation and high efficiency frequency conversions. For (280-340) nm femtosecond pulses generated viatwo nonlinear conversion of a (680-1080) nm Ti:Sapphire laser, the average power can be well controlled from 1 mW tosub-nW level using a polarizer-based attenuator. The laser beam quality was significantly improved using a spatial filterconsists of an objective lens, a silica optical fiber, and an off-axis parabolic reflective collimator. The spatial filter wasmounted on a two-dimension linear stage to accommodate the spatial beam shift. A spatially stabilized, quality beamover (280-340) nm spectral range was obtained and suitable for free-space optical materials measurements.