Stimulated rotational Raman scattering from para-H(2) pumped by a CO(2) TEA laser

Area of Science:

• Physics
• Laser Science
• Quantum Optics

Background:

• Stimulated Raman scattering (SRS) is a nonlinear optical process.
• Rotational Raman scattering involves changes in molecular rotational energy levels.
• Para-hydrogen (para-H2) is a spin isomer of molecular hydrogen with unique properties.

Purpose of the Study:

• To investigate stimulated rotational Raman scattering (SRRS) in para-H2.
• To explore the efficiency of SRRS pumped by a CO2 TEA laser.
• To achieve high gain for the Stokes wave in a para-H2 medium.

Main Methods:

• Utilizing a carbon dioxide (CO2) transversely excited atmospheric (TEA) laser as the pump source.
• Operating the CO2 laser on strong P- and R-branch transitions at 9.4- and 10.6-micrometer bands.
• Employing a multiple-pass gain cell cooled to liquid-nitrogen temperatures.

Main Results:

• Observed SRRS from para-H2.
• Achieved small signal gain exceeding 80 dB for the Stokes wave.
• Demonstrated high gain with TEM00 pump powers of 8.5 MW.

Conclusions:

• Para-H2 is an effective medium for achieving high gain SRRS.
• CO2 TEA lasers can efficiently pump SRRS in para-H2.
• The experimental setup demonstrates a viable method for generating intense Stokes waves.