High-sensitivity ultrashort mid-infrared pulse characterization by modified interferometric field autocorrelation

Area of Science:

• Ultrafast optics
• Nonlinear optics
• Spectroscopy

Background:

• Accurate characterization of ultrashort laser pulses is crucial for many scientific applications.
• Measuring the spectral phase of infrared (IR) pulses presents unique challenges due to detector limitations and material properties.

Purpose of the Study:

• To develop and demonstrate a simple, yet effective method for spectral phase retrieval of femtosecond pulses at 3.3 μm.
• To achieve high-resolution pulse characterization at low pulse energies.

Main Methods:

• A modified interferometric field autocorrelation technique was employed.
• The setup utilized a Michelson interferometer, a silver gallium selenide (AgGaSe2) crystal, and a custom spectrometer with an InGaAs point detector.
• The method was validated against simulations and frequency-resolved optical gating (FROG).

Main Results:

• Successful spectral phase retrieval of 43 MHz, ~100 fs, 3.3 μm pulses was achieved down to energies of 8.9 pJ.
• The system demonstrated the capability to measure pulses as short as 20 fs (1.8 cycles) at 3.3 μm.
• The method accurately characterized spectral phase modulation induced by a germanium plate.

Conclusions:

• The developed modified interferometric field autocorrelation method offers a practical and accessible approach for ultrashort IR pulse characterization.
• This technique is suitable for measuring low-energy, few-cycle pulses in the mid-infrared region.
• The findings pave the way for advanced studies in nonlinear optics and spectroscopy using ultrashort IR sources.