K. Matsushima, K. Hirata and
Department of Electrical Engineering, Kansai University
Department of Applied Physics, Osaka City University
We report directional anisotropy of the outputs of an
optically pumped far-infrared ring laser, which operates on 119
micro meter line of CH3OH, with special emphasis on
the effect of Raman-type two-photon process on unidirectional
operation. By use of a Doppler broadened 3-level system which
allows coexistence of two counterpropagating far infrared (fir)
fields as well as a pump field in the cavity, expression for the
fir intensity determining equations is derived.
Numerical calculation has been carried out to map the threshold contours on the parameter plane spanned by cavity and pump detuning frequencies. The output directionality is shown to be a direct consequence of the gain anisotropy due to two-photon process. Furthermore, it is also noted that how dynamic Stark effect modifies the threshold contours of the forward output.
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