  We present dust opacity spectral indexes (beta) of the youngest protostellar
systems (so-called Class 0 sources), L1448 IRS 2, L1448 IRS 3, and L1157,
obtained between 1.3 mm and 2.7 mm continua, using the Combined Array for
Research in Millimeter-wave Astronomy (CARMA). The unprecedented compact
configuration and image fidelity of CARMA allow a better detection of the dust
continuum emission from Class 0 sources, with a less serious missing flux
problem normally associated with interferometry. Through visibility-modeling at
both 1.3 mm and 2.7 mm simultaneously, as well as image- and
visibility-comparison, we show that beta of the three Class 0 sources are
around or smaller than 1, indicating that dust grains have already
significantly grown at the Class 0 stage. In addition, we find a radial
dependence of beta, which implies faster grain growth in the denser central
regions and/or dust segregation. Density distributions of the Class 0 sources
are also addressed by visibility-modeling.
