A nonlinear dynamics of stimulated phonon emission in a nonautonomous acoustic quantum generator under superlow-frequency-modulated pumping conditions

Abstract

A nonlinear resonance was experimentally observed in a ruby acoustic quantum generator operating in the region of 10¹⁰ Hz with electromagnetic pumping modulated at a superlow frequency. The resonance is manifested by slow regular self-detunings in the microwave spectra of stimulated phonon emission. The self-detuning period T _SD strongly depends on Δ_L≡ω_m-ω_L, where ω_m is the modulation frequency and ω_L is the resonance frequency varying from 9.8 to ∼5 Hz when the magnetic field detuning grows from 0 to 60 Oe. The direction of motion of a mode cluster along the frequency axis is uniquely determined by the sign of Δ_L. As the ¦Δ_L¦ value decreases to 0.05 Hz, the self-detuning period increases to very large values T _SD > 100 s. These large-scale collective motions take place against the background of small-scale low-frequency chaotic oscillations in intensity of the generated phonon modes, while the mode widths remain almost as narrow (<1 kHz) as those in the autonomous regime.