Three-dimensional pseudo-bandgap polystyrene photonic crystals (PhCs) fabricated by the self-assembly technique are used to design two models of microcavities, namely the double-layered and the triplelayered PhC heterostructures, to study the laser-induced emission from the embedded Rhodamine-B dye. The dye molecules in the colloids of these PhC matrices are excited with a Q-switched frequencydoubled Nd:YAG laser at 532 nm, and the emission is recorded in different directions for different input powers. The spontaneous emission of the dye gets modified due to the inhomogeneous distribution of density of states in the PhC. The Bragg crystal planes serve as reflecting cavity mirrors for the embedded gain medium, and at higher pump powers, direction-dependent spectral narrowing of the emission spectrum is clearly observed.