Phase-dependent scaling law for signal amplification and squeezing near period-doubling bifurcation in a CO<inf>2</inf> laser

We study experimentally and numerically the effect of the phase of a periodic resonant perturbation-signal on a scaling law for signal amplification and classical squeezing in a CO2 laser with modulated losses in the vicinity of a period-doubling bifurcation. We obtain a π-periodical phase dependence in the scaling power which for maximal signal amplification has the value - 2/3. Experimental results are in a good agreement with numerical calculations. The numerical simulations also show that in the phase range corresponding to classical squeezing the scaling power can take either negative or positive values, depending on the signal phase.