Nonlinear beam shaper for femtosecond laser pulses, from Gaussian to flat-top profile

Efficient cross polarized wave generation for compact, energy-scalable, ultrashort laser sources

“…Pointing instabilities are transformed into coupling efficiency variations whereas for hard aperture filtering, they cause distortions of the beam profile by diffraction. At high input energies, it is difficult to improve the beam profile simply with a hard aperture because the filtering process occurs abruptly at the pinhole and requires complicated nonlinear beam shaping in the polarizer [4]. Both are required to obtain a super Gaussian profile thus achieving the best results [3].…”

“…Smooth, flat-top like beam profiles are preferable for high conversion efficiencies, theoretically reaching up to 37% with Z-cut crystallographic orientation crystals [2] (45% with holographic-cut [3]), and in addition, higher energy transmission in the crystal is possible due to reduced self-focusing [3]. The conversion efficiency of a single crystal setup was improved to 28% for sub-mJ pulses with a sophisticated, nonlinear technique for beam shaping combined with pinhole filtering [3,4]. Energy scalability is possible but not simple due to the complexity of the technique incorporating nonlinear beam shaping.…”

On the different ways for defining the effective focal length of a Kerr lens effect

“…It is seen that the incident GB is reshaped by the phase profile ∆φ(ρ) especially for the highest values of φ 0 the on-axis phase shift. The longitudinal evo lution of the transverse intensity distribution of a Gaussian femtosecond laser beam diffracted upon a positive Kerr medium has already been reported [24].…”

Fluidic Optical Devices Based on Thermal Lens Effect

“…For CW beams, several approaches to spatially shape Gaussian beams have been developed, such as the use of aspheric lenses, implement beam shaping or the use of diffractive optical devices [20]. However, these methods have some disadvantages: a refractive beam shaping system lead to large aberration [21] and implemental beam shaping has low energy efficiency and lacks of flexibility [22]; and the use of refractive optical devices requires complex configuration design and high cost [23]. In practice, a low-cost and flexible method to convert a Gaussian beam into a flat-top beam is required.…”