Externally triggered coherent two-photon emission from hydrogen molecules

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We report coherent enhancement of two-photon emission from the excited vibrational state of molecular hydrogen triggered by irradiating mid-infrared pulses externally.

• We previously observed the two-photon emission triggered by the internally generated fourth Stokes photons.
• By injecting independent mid-infrared pulses externally, it is possible to control experimental parameters and investigate the mechanism in more detail.
• In this article, we describe the two-photon emission using the external trigger pulses.