Effect of hydroxy groups on nonlinear optical behaviour of encapsulated freebase porphyrin thin films in a borate glass matrix

•Structure of the Porphyrin is strongly perturbed due to encapsulation in the borate glass matrix.•Red shift in the B and Q-bands are tuned by varying the number of hydroxy groups on the phenyl ring of the Porphyrin.•Reverse saturable absorption (RSA) behaviour at low intensity regions and crossover to saturable absorption (SA) at high intensities.•Optical limiting behaviour with intensity range less than 10 GW/cm2 and an optical switch behaviour at high intensity range above ∼ 10 GW/cm2.