Phase-interfacial stimulated Raman scattering generated in strongly pumped water

Area of Science:

• Nonlinear Optics
• Laser-Induced Plasma Physics
• Condensed Matter Physics

Background:

• Stimulated Raman scattering (SRS) is a well-known nonlinear optical phenomenon in liquids like water.
• Laser-induced breakdown in water can create plasma, altering the optical properties of the medium.

Purpose of the Study:

• To investigate unusual blue-shifted radiations observed in water subjected to intense laser pumping.
• To characterize the properties of these radiations and compare them with standard SRS.
• To elucidate the underlying physical mechanism responsible for the observed phenomenon.

Main Methods:

• Experimental observation of blue-shifted radiations in water using a 532-nm nanosecond laser.
• Measurement of radiation properties: divergence, polarization, and pulse shape.
• Comparison of measured properties with those of regular stimulated Raman scattering (SRS) in water.

Main Results:

• Observation of anomalous blue-shifted radiations distinct from typical SRS.
• Characterization reveals unique divergence, polarization, and pulse shape properties.
• The unusual radiations are experimentally differentiated from standard SRS in water.

Conclusions:

• The observed blue-shifted radiations are attributed to parametric anti-Stokes SRS.
• This process is proposed to occur at the interface between water and the laser-induced ionization plasma or gas.
• The findings offer new insights into nonlinear optical interactions at plasma interfaces.