Photocurrent, electroluminescence, and photoluminescence spectroscopy were used for the characterisation of laser structures containing ultrathin InAs δ-layers in GaAs matrix surrounded by AlGaAs waveguide and grown by low-pressure metal organic vapour phase epitaxy. Three types of δ-layer structures for laser active layers were investigated: single layers with different thickness (W L ), different numbers of identical layers (N), and seven identical δ-layers separated by GaAs spacers of variable thickness (S L ). Measurement revealed two fundamental optical transition between electron and heavy and light hole states in the δ-layers. Both transitions are shifted to lower energies by hundreds of meV when W L and N increases or S L decreases. While the effect of W L can be explained by a quantum model accounting for the influence of stress and quantum state coupling, data obtained from multilayer structures exhibit significant deviation from theory.