Abstract

A two-photon laser [1] is a device that allows the transfer of energy stored in the atoms into the field via the stimulated two-photon processes. It works as follows. A strong triggering field of frequency ωw₁ along with a weak probe field of frquency ωw_p interact with the atoms that posess a population inversion betwen levels 2 and 1 of the same parity. If the sum of (ωw₁ and ωw_p equals the 2 ->1 atomic transition frequency, the probe field will be amplified as a result of the competition between two-photon emissions and absorptions. The main advantage of this laser is that the frequency of the generated field can be widely varied. The difficulty in making such a device stems from the conflicting requirements of the level schemes. Having a metastable level as level 2 is ideal for the purpose of population inversion, but implies that the intermediate levels that have dipole connecitons with level 2 must lie above level 2. This will exclude the opportunity of enhancing the two-photon gain by single-photon near-resonance interactions.

© 1996 Optical Society of America