  There is significant current interest in spintronic devices fashioned after a
spin analog of the electro-optic modulator proposed by Datta and Das [Appl.
Phys. Lett., \underline{56}, 665 (1990)]. In their modulator, the
``modulation'' of the spin polarized current is carried out by tuning the
Rashba spin-orbit interaction with a gate voltage. Here, we propose an
analogous modulator where the modulation is carried out by tuning the
Dresselhaus spin orbit interaction instead. The advantage of the latter is that
there is no magnetic field in the channel unlike in the case of the Datta-Das
device. This can considerably enhance modulator performance.
