  We report experiments on electron interferometer devices in the quantum Hall
regime, where edge channels circle a 2D electron island. The main confinement
is produced by etch trenches, into which front gate metal is deposited. We find
a linear dependence of the Aharonov-Bohm period on gate voltage for electrons
(integer filling f=1) and for Laughlin quasiparticles (fractional 2/5 embedded
in 1/3). The capacitance of a large 2D electron island with respect to the
front gates is approximately proportional to the island radius. Comparing the
experimental data for the integer and the fractional fillings and for two
samples, we find the magnetic field period and its slope scale with the radius
of the Aharonov-Bohm orbit. Analysis of the directly measured integer and
fractional slope data allows to determine the interferometer area in the
fractional regime, and thus the Laughlin quasiparticle flux period of 5h/e,
within the experimental accuracy.
