Dependence of gain and phase-shift on crystal parameters and pump intensity in unidirectional photorefractive ring resonators |
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Authors: | M K Maurya T K Yadav and R A Yadav |
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Institution: | (1) Lasers and Spectroscopy Laboratory, Department of Physics, Banaras Hindu University, Varanasi, 221 005, India |
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Abstract: | The steady-state amplification of light beam during two-wave mixing in photorefractive materials has been analysed in the
strong nonlinear regime. The oscillation conditions for unidirectional ring resonator have been studied. The signal beam can
be amplified in the presence of material absorption, provided the gain due to the beam coupling is large enough to overcome
the cavity losses. Such amplification is responsible for the oscillations. The gain bandwidth is only a few Hz. In spite of
such an extremely narrow bandwidth, unidirectional oscillation can be observed easily at any cavity length in ring resonators
by using photorefractive crystals as the medium and this can be explained in terms of the photorefractive phase-shift. The
presence of such a phase-shift allows the possibility of the non-reciprocal steady-state transfer of energy between the two
light beams. Dependence of gain bandwidth on coupling constant, absorption coefficient of the material’s cavity length (crystal
length) and modulation ratio have also been studied.
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Keywords: | Two-wave mixing unidirectional ring resonator photorefractive phase-shift non-reciprocal energy transfer |
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