Pulse characterization by THG d-scan in absorbing nonlinear media.

Area of Science:

• Optics and Photonics
• Materials Science
• Ultrafast Lasers

Background:

• Accurate characterization of ultrashort laser pulses is crucial for scientific research.
• Third Harmonic Generation (THG) is a nonlinear optical process sensitive to pulse properties.
• Developing robust THG-based methods is essential for reliable pulse measurements.

Purpose of the Study:

• To demonstrate few-cycle pulse characterization using THG dispersion scan (THG d-scan).
• To investigate the use of TiO(2)-SiO(2) thin films with varying compositions as nonlinear media for THG d-scan.
• To assess the impact of material band gap and absorption edges on pulse retrieval accuracy.

Main Methods:

• Performing THG d-scan measurements using thin films of TiO(2)-SiO(2) with controlled compositions.
• Varying the TiO(2) concentration to tune the band gap and absorption edge of the nonlinear media.
• Employing a robust retrieval algorithm that accounts for wavelength-dependent nonlinearity via a spectral weight function.

Main Results:

• Achieved agreement in retrieved pulse durations within 5% across different nonlinear media.
• Demonstrated that reconstructed pulse shapes are immune to the material's absorption edges.
• Validated the effectiveness of the spectral weight function in the retrieval algorithm.

Conclusions:

• TiO(2)-SiO(2) thin films are suitable nonlinear media for THG d-scan pulse characterization.
• The THG d-scan method, coupled with a robust algorithm, provides accurate ultrashort pulse measurements.
• The technique's resilience to absorption edges broadens its applicability in ultrafast optics.