Eur. Phys. J. Spec. Top. (2022) 231: 781-789
https://doi.org/10.1140/epjs/s11734-022-00462-4

Regular Article

High-quality-factor dye-doped polymeric microdiscs fabricated by soft imprint lithography

¹ Department of Physics, Indian Institute of Technology Kharagpur, 721302, Kharagpur, India
² School of Nano-Science and Technology, Indian Institute of Technology Kharagpur, 721302, Kharagpur, India

Received: 31 October 2021
Accepted: 19 January 2022
Published online: 7 February 2022

Abstract

We present a study on the photophysical properties of pyrromethene 570-doped polymethyl methacrylate (PMMA) thin films with varying dye concentrations. The emission and absorption spectra are analyzed to identify the optimum dye concentration in the polymer matrix for efficient light emission. The refractive index and the gain coefficient of pyrromethene 570-doped PMMA thin film was estimated by ellipsometry technique and variable stripe length method, respectively. The fabrication of high optical quality microdiscs is demonstrated by soft imprint lithography technique. Further, the lasing characteristics of the whispering gallery mode (WGM) microdisc resonator are evaluated. The high power density built within these microdisc resonator due to the WGM, combined with the high fluorescence quantum yield of pyrromethene 570 dye in PMMA matrix, gives rise to the lasing threshold pump fluence of $\sim$ 37.5 mJ/cm${}^2$ under nanosecond pulsed excitation. WGMs with a quality factor of $2.89\times {10}^4$ were recorded indicating the high morphological and optical quality of the fabricated microdisc.