Equivalence of Doppler and quantum frequency shifting in Bragg cells

The modified Bragg equation is used to calculate the Doppler shift of light diffracted by a Bragg cell. The calculation yields a solution which agrees exactly with the frequency shift obtained quantum mechanically. This result is in contradistinction to the approximate result published recently. (See R. F. Adrion in Proc. IEEE (Lett.), vol. 58, Sept. 1970, pp. 1391-1393).