CHARACTERISTIC SCALING PARAMETERS FOR TUNNELING IN STRONG TIME-DEPENDENT ELECTRIC-FIELDS

Tunneling through a single driven barrier is studied where the ac pote ntial on either side of the barrier is of the general form V-ac(z,t)=( <(a)over cap (l,r)>z + <(b)over cap (l,r))cos omega t (l,r: left,right ). Analytic expressions for the transmission and reflection amplitudes are obtained in the delta-barrier limit. The omega(-1) characteristic scaling behavior of the Tien-Gordon theory is recovered in the specia l case of vanishing ac fields, (a) over cap(l,r)=0, while an omega(-2) scaling is found for finite ac fields, (a) over cap(l,r)not equal 0> which is not contained in the Tien-Gordon theory. An analogy with the Fabry-Perot interferometer is used to extend the theory to multiple ba rriers. Implications for experiments are discussed.