On the quantum phase fluctuations of coherent light in a chain of two anharmonic oscillators coupled through a linear one

•Coupled anharmonic oscillator.•Quantum phase fluctuations.•Phase fluctuation parameters.•Barnett–Pegg formalism.

We investigate the quantum phase fluctuations of input coherent light involving two quartic anharmonic oscillators coupled through a linear one. The analytical expressions for various phase fluctuation parameters due to Carruthers and Nieto are expressed as functions of coupling constant, anharmonic constant, initial excitation numbers, and the initial phase of the input coherent field. By using some numerical estimates of the analytical expressions, the effects of anharmonic and coupling constants are clearly indicated. In one of the two anharmonic modes (say mode a1), it is found that the presence of coupling causes the reduction of phase fluctuation parameters U1, and S1, compared to their counterparts at t=0. In sharp contrast to these results, the increase and the decrease (at least in the axis range of kt) of the phase fluctuation parameters U1, S1 and Q1 compared to their initial value counterpart are attributed by the strong field and hence the nonlinearity. We establish that the signature of anharmonicity (β≠0)(β≠0) is realized only for intense field situations. It corroborates the fact that the nonlinearity of the medium is invoked only if the field strength is quite strong. Interestingly, for significantly strong field situation, the reduction of the phase fluctuation parameters compared to their initial values is exhibited for the harmonic mode. These reductions are attributed partly by the strong field and partly by the coupling between the oscillators. In spite of the modes corresponding to two anharmonic oscillators which are in vacuum, we report the generation of excitation for nonzero coupling constant with β=0. It may be attributed by the quantum state transfer through the chain of harmonic oscillators.