Tunable and low-threshold random lasing emission in waveguide aided Rhodamine-6G dye incorporated silica embedded thin films

Abstract

A simple and low-cost approach for producing tunable and low threshold RL emission in the visible region is reported by using a fluorescent laser dye as gain medium and light scattering is achieved in silica nanospheres (SNS) under the pump light of 532 nm, obtained by second harmonic generation of a Q-switched Nd: YAG laser fundamental radiation of 1064 nm wavelength. Depending upon the size (a) of the scatterer particles in comparison to the wavelength (λ) of the pump light, the scattering mechanism can be classified into different categories. However, to demonstrate various RL parameters for scatterer particles residing in Rayleigh scattering (a <λ) and Geometrical optics regime (a >>λ) in Rh6G dye doped PVA film, we have deliberately synthesized two different sized SNS (notably, 400 nm and 1000 nm). Also, to demonstrate the tuning in the RL emission by enhancement in pump photon density the gain medium has been enclosed within two glass slides. The performances of developed three RL systems, one made with bare film (S1), one cover with one glass slide (S2) and another one in which the gain medium is enclosed between two glass slides (S3) have been compared. It has been demonstrated experimentally that in the developed RL system with 400 nm SNS particles, RL emission in the incoherent regime is obtained. On the other hand, in the case of 1000 nm SNS particles, RL emission in the coherent regime is demonstrated. The tunable random lasing emission covering 585–592 nm wavelength regions with the lowest emission line-width of 4.2 nm and the lowest RL threshold of 1.59 mJ/cm2 is obtained from the developed RL systems. The demonstrated low cost and simple strategy for the development of tunable RL devices provided here will find novel applications in laser-based imaging, RL based sensing, and other optoelectronic devices.