Shock wave-induced optical band gap engineering on pure and dye-doped potassium dihydrogen phosphate crystals

Abstract

At this point in time, there are only a few studies available which deal with the investigation on the effect of shock waves in structural, electrical, thermal, and optical properties of potassium dihydrogen phosphate (KDP) crystal that has been analyzed systematically in the previous publications (Sivakumar et al. in Opt Laser Technol 111:284, 2019; Sivakumar et al. in J Eelectron Mater 47:4831, 2018; Sivakumar et al. in Mater Res Express 6:086303, 2019; Sivakumar et al. in J Electron Mater 48:7868, 2019; Sivakumar et al. in Z. Kristallogr Cryst Mater, 2020, https://doi.org/10.1515/zrki-2020-0017 ). In this study, the prime interest is to explore the band gap engineering of pure and dye-doped KDP (methylene blue and rhodamine B) crystals by shock waves which would enable to get the deep insight so that better understanding of the relation between shock wave and optical physics could be arrived at and it would pave the way to get acquainted with more knowledge of the material itself. Optical band gap energies are calculated from Tauc plot relations and it is observed that the values of band gap energies are reduced with respect to number of shock pulses for all the test crystals. The reduction of band gap energy is due to the formation of surface defects and oxygen vacancies by the impact of shock waves and this effect is called as Franz–Keldysh effect (Strain Lattice effect). Among the three crystals, RB + KDP crystal is found to be the best such that it could be tuned for the range of band gap energy from 4.89 to 3.3 eV as compared to the other two crystals. Hence, an alternate method is proposed to understand band gap engineering of non-linear optical materials which are suitable for photonic applications.