Sensing based on random lasers via Pearson correlation dynamics of intrinsic emission modes

Abstract

Random Lasers, or LA's, are characterized by a wide range of applications in the scientific world today, both in a practical and theoretical sense, being responsible for the miniaturization of sensors, cheaper laser formation processes, diagnosis of cancer cells and many others. Its main distinction in relation to common lasers is that it does not require an optical cavity, a set of mirrors, one fully reflective and the other partially, which will promote a re-interaction of photons generated by a gain medium, thermally or electrically excited. , via stimulated emission emission and thus create the laser effect. In the case of LA's, the optical cavity is located within the gain medium, by scattering particles that increase the propagation time of spontaneously emitted photons from the gain medium and the probability of the cascade effect of photon generation occurring. In this sense, the theoretical framework of LA's indicates the existence of two fundamental modes: the incoherent and the coherent, the first with an emission spectrum similar to a Gaussian FWHM in nanometers and the second with several peaks in subnanometers, whose spectra are correlated by a process of coupling the intrinsic electromagnetic modes of the gain medium set and scattering particles via their spatial superposition. Through local production of Rhodamine 6G samples imbued with TiO2 or ZnO particles, which is cheap and easy to handle, using a double-frequency Nd:YAG Q-Switched laser at 532 nm, we want to use a technique based on the dynamics of Pearson correlations (or coefficients) of the wavelengths in the emission spectrum, in which when we modify conditions such as temperature and topological degradation of the sample, which we will do in this project, we see the movement of the phases of the electromagnetic modes and, therefore, the correlations in the spectrum are modified. The idea is to observe how a heat map of the coefficients reacts to the proposed changes and, thus, generate highly responsive and miniaturized sensors of different physical magnitudes, as many previous works demonstrate a high power of reaction of LA's to the conditions of the external and internal environment.