Determination of the dispersive parameters of PVA/methyl red composite irradiated by 532 nm green laser

Abstract The absorption spectra of the polyvinyl alcohol (PVA)/methyl red (MR) composite have been measured to investigate the dispersion properties. The composite was prepared with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>9000</mml:mn> <mml:mrow> <mml:mtext> </mml:mtext> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mtext>nm</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> thickness using the casting method. The semiconductor green laser irradiated the thick films at a power of 32 mW and a wavelength of 532 nm for varying durations of 0, 20, 30, and 40 min. Wemple–DiDomenico method was utilized to compute the dispersion parameters prior to and following laser exposure. The dispersion energy values exhibited a decreasing trend with increasing irradiation time, declining from 12.5 for irradiated thick films to 5.203 at 40 min. The single oscillator energy of the electronic transition <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:msub> <mml:mi>E</mml:mi> <mml:mrow> <mml:mtext>o</mml:mtext> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow/> </mml:mrow> </mml:math> increased with the increasing in irradiating time for PVA, MR and PVA/MR composite. For PVA/MR thick films, the optical energy gap increased with prolonged laser irradiation, rising from 3.98 for the non-irradiated films to 4.24 after 40 min of exposure, while Urbach energy decreased. The optical and dispersive properties of the irradiated thick films can be adjusted for different medical and industrial applications.