Frequency dependence of coherently amplified two-photon emission from hydrogen molecules

Abstract

We investigate how the efficiency of coherently amplified two-photon emission depends on the frequency of one of the two emitted photons, namely the signal photon. This is done over the wavelength range of 5.048-10.21 μm by using the vibrational transition of parahydrogen. The efficiency increases with the frequency of the signal photon. Considering experimental errors, our results are consistent with the theoretical prediction for the present experimental conditions. This study is an experimental demonstration of the frequency dependence of coherently amplified two-photon emission, and also presents its potential as a light source.

Coherent two-photon emission from hydrogen molecules excited by counter-propagating laser pulses

“…The energy level differences between |g or |e and |j , ω jg and ω je are much larger than ω eg (far-off-resonance condition). In the previous coherent two-photon emission (TPE) signal generation experiments via oneside excitation [29][30][31], coherence between |g and |e was prepared using the Raman process, where lasers with different frequency were necessary. In this experiment, in contrast, we generate coherence using identical-frequency photons which originate from a single laser.…”

“…In the previous experiments, we observed the TPE signal from vibrational states of parahydrogen (p-H 2 ) molecules [29][30][31][32], which have long decoherence time (O(1) ns).…”

“…In the previous experiments, we observed the TPE signal from vibrational states of parahydrogen (p-H 2 ) molecules [29][30][31][32], which have long decoherence time (O(1) ns). In these experiments two lasers of different colors were injected coaxially in the same direction for the Raman excitation of p-H 2 .…”

“…As in the case of the previous experiments [29][30][31], it is helpful for understandings of properties of the coherent amplification to compare actual data to results of the numerical simulation. These simulations are based on Maxwell-Bloch equations, which represent developments of the laser fields and the coherence among the ensemble.…”

Superradiant searches for dark photons in two stage atomic transitions

“…The use of two stage superradiant atomic transitions for the production and detection of weakly coupled particles was proposed and studied extensively by Yoshimura et al [32][33][34][35][36][37][38][39][40]. These authors have pointed out that macroscopic quantities of coherently excited atoms may be employed to measure neutrino properties [36,39,41]. The use of multi-stage atomic transitions for the discovery of axion dark matter has recently been considered in [42,43].…”