Correction of broadband terahertz electro-optic sampling with GaSe crystals

Area of Science:

• Solid-state physics
• Nonlinear optics
• Terahertz (THz) spectroscopy

Background:

• Gallium selenide (GaSe) is a key nonlinear crystal for electro-optic (EO) sampling in the multi-terahertz (THz) range.
• Lattice resonances in GaSe crystals distort broadband THz pulse waveforms, limiting sampling accuracy.
• Understanding frequency-dependent responses is crucial for accurate THz transient analysis.

Purpose of the Study:

• To experimentally evaluate the frequency-dependent response function in GaSe for EO sampling.
• To investigate and compensate for the effects of phonons, phase mismatch, and gate pulse waveforms.
• To improve the accuracy of multi-THz pulse waveform characterization.

Main Methods:

• Experimental evaluation of the frequency-dependent response function in GaSe.
• Modeling phonon effects using an effective Faust-Henry coefficient.
• Determining the Faust-Henry coefficient for both substrate-mounted and free-standing GaSe samples.

Main Results:

• The effective Faust-Henry coefficient was determined to be -0.19 for thin GaSe on a substrate and -0.23 for free-standing GaSe.
• Corrected multi-THz pulse field amplitudes showed agreement with average power and beam diameter measurements.
• Demonstrated successful compensation of frequency characteristics in GaSe.

Conclusions:

• The study successfully compensated for frequency-dependent limitations in GaSe for THz EO sampling.
• Accurate characterization of multi-THz transients is achievable by accounting for phonon interactions.
• This work advances the precision of THz spectroscopy and transient measurements.