Cross-polarized common-path temporal interferometry for high-sensitivity strong-field ionization measurements.

Area of Science:

• Plasma Physics
• Laser-Induced Phenomena
• Quantum Optics

Background:

• Accurate plasma density measurements are vital for understanding laser-matter interactions.
• Applications include strong-field physics, laser pulse propagation, and Lidar technology.
• Existing methods often lack the required sensitivity for low-density plasmas.

Purpose of the Study:

• To develop a highly sensitive interferometer for absolute plasma density measurements.
• To investigate strong-field ionization yields in noble gases using different laser polarizations.
• To study photoionization and photodissociation of molecular hydrogen.

Main Methods:

• A cross-polarized common-path temporal interferometer with balanced detection was employed.
• Measurements utilized 800 nm, 55 fs laser pulses for noble gas ionization studies.
• Experimental data were compared against Ammosov-Delone-Krainov (ADK) and Perelomov-Popov-Terent'ev (PPT) theoretical models.

Main Results:

• The interferometer achieved a sensitivity of ~0.6 mrad, enabling density-length product measurements of ~2.6 x 10^13 cm^-2.
• Measured phase changes for noble gases aligned with ADK theory in the adiabatic tunneling regime.
• The PPT model demonstrated applicability across various ionization regimes.
• Ionization pathways for molecular hydrogen were determined using different pump laser wavelengths (800, 400, 267 nm).

Conclusions:

• The developed interferometer offers high sensitivity for plasma density diagnostics.
• Experimental results provide insights into the validity of ADK and PPT models for laser-driven ionization.
• The study elucidates ionization mechanisms in noble gases and molecular hydrogen under varying laser conditions.