Experimental characterization of multifocal diffractive lenses for femtosecond laser applications

We report on the design, experimental realization, and high-resolution spatial analysis of dynamically reconfigurable multifocal diffractive lenses based on computer-generated holography. While conventional diffractive optics are often limited by static focal parameters and low damage thresholds, our platform utilizes a phase-only liquid-crystal-on-silicon spatial light modulator to achieve real-time, coaxial focal control with a structural stability threshold of up to 10 11 W cm −1 . We implemented a spatial multiplexing strategy to encode independent Fresnel-type quadratic phase functions, allowing for the simultaneous generation of multiple focal points without any mechanical adjustment. A key contribution of this work is the rigorous 3D spatial characterization of propagation dynamics using a motorized ω − z profiling technique based on a high-resolution CMOS camera. Quantitative analysis confirms that the multiplexed holographic lenses maintain near-perfect Gaussian integrity and beam circularity, effectively eliminating quantization-induced artifacts and phase crosstalk. By combining this high spatial precision with real-time programmability and high-power handling capabilities, this software-defined lensing method establishes itself as a robust tool for advanced laser applications, including laser filamentation, high-harmonic generation, and real-time holographic steering in nonlinear media.