We study the peculiarities of the nonstationary Casimir effect (creation of
photons in cavities with moving boundaries) in the special case of two res
onantly coupled modes with frequencies omega (0) and (3 + Delta)omega (0) p
arametrically excited due to small amplitude oscillations of the ideal cavi
ty wall at the frequency 2 omega (0)(1 + delta) (with \ delta \, \ Delta \
much less than 1). The effects of thermally induced oscillations in time de
pendences of the mean numbers of created photons and the exchange of quantu
m purities between the modes are discovered, Squeezing and photon distribut
ions in each modes are calculated for initial vacuum and thermal states. A
possibility of compensation of detunings is shown. (C) 2001 Elsevier Scienc
e B.V. All rights reserved.