Spatiotemporal noise characterization for chirped-pulse amplification systems.

Area of Science:

• Optics and Photonics
• Laser Physics
• Ultrafast Science

Background:

• Optical noise is a critical challenge for achieving high pulse contrast in ultra-high peak power femtosecond lasers.
• Spatiotemporal (ST) coupling, induced by angular dispersion, is a key characteristic of this noise.
• Previous noise characterization was limited to temporal domain measurements, lacking ST information.

Purpose of the Study:

• To experimentally characterize spatiotemporal (ST) noise in ultra-high peak power femtosecond lasers.
• To understand the origin and nature of ST noise, specifically its coupling behavior.
• To identify methods for improving laser pulse contrast by mitigating ST noise.

Main Methods:

• Extended temporal cross-correlation measurements to the spatiotemporal (ST) domain.
• Experimental investigation of noise originating from pulse stretcher/compressor optical surface imperfections.
• Analysis of ST noise coupling in the far-field plane.

Main Results:

• Successfully characterized ST noise in the ST domain for the first time.
• Demonstrated that ST noise originates from optical surface imperfections in the stretcher/compressor.
• Observed a linear ST coupling of the noise in the far-field plane.
• Showed that avoiding far-field optics in the stretcher improves contrast on the far-field axis.

Conclusions:

• The study provides a novel method for ST noise characterization, crucial for understanding laser pulse contrast.
• Identified optical surface imperfections as the source of ST noise, enabling targeted improvements.
• Results pave the way for designing femtosecond lasers with enhanced pulse contrast and higher peak power.