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

Abstract

The development of nonlinear optical (NLO) materials are crucial for technological advancement in the field of optoelectronics and photonics. In this direction, porphyrin molecules are appeared to be a possible building material to play a key role in the light-matter interactions owing to their high degree of delocalized π-electrons. In this report, our primary focus is to understand the effect of hydroxy phenyl derivatives of meso-substituted porphyrins in an encapsulated borate glass matrix through linear and nonlinear optical measurements. The encapsulated porphyrin molecules show strong red shifted Soret (B) and Q-band absorption pattern in the range 455–460 nm and 680–700 nm, respectively, and structure is modified. The Q-band is able to tune by varying the number of hydroxy groups on the phenyl ring of the porphyrin molecule. A similar red shift is observed in the emission spectra of the encapsulated porphyrin along with the appearance of a new emission peak due to impede N-B vibrations in the glass matrix. The NLO behaviour of the encapsulated porphyrin thin films in borate glass matrix show reverse saturable absorption (RSA) at lower intensity region and crossover to saturable absorption (SA) at higher intensity. With the tunable intensity variations across the focal region, these porphyrin thin films exhibit switching behaviour from RSA to SA unclog its potential to act as an optical limiter (in the intensity range less than 10 GW/cm2) and an optical switch (in the high intensity range above ∼ 10 GW/cm2).