Fringe-free, background-free, collinear third-harmonic generation frequency-resolved optical gating measurements for...

Area of Science:

• Optics and Photonics
• Ultrafast Laser Science
• Nonlinear Optics

Background:

• Frequency-resolved optical gating (FROG) is a standard technique for characterizing ultrashort laser pulses.
• Traditional FROG methods can suffer from background noise and interference fringes, complicating data analysis.
• Characterizing ultrashort pulses at the focus of high numerical aperture (NA) objectives presents unique challenges.

Purpose of the Study:

• To develop and demonstrate a simplified, robust FROG technique for ultrashort pulse characterization.
• To achieve background-free and fringe-free measurements.
• To characterize 100 femtosecond (fs) pulses focused by a high NA objective.

Main Methods:

• Utilized a glass coverslip to generate a third-harmonic signal.
• Employed a background-free, fringe-free frequency-resolved optical gating (FROG) configuration.
• Focused 100 fs pulses using a 0.65 NA objective lens.

Main Results:

• Successfully characterized 100 fs laser pulses.
• The method provided background-free and fringe-free spectral data.
• Demonstrated the feasibility of FROG at the focus of a high NA objective.

Conclusions:

• The third-harmonic generation from a glass coverslip offers a practical approach for simplified FROG.
• This technique effectively overcomes common limitations of traditional FROG methods.
• It is suitable for characterizing ultrashort pulses in demanding optical configurations like high NA focusing.