Yüzey destekli sıvı mikrodamlacıklarda ışımayan erk dönüşümlü optoakışkan mikrolazerler

Optofluidics is a recently established research field combining the microfluidic chip technology with optics. It allows for a broad range of applications aiming to develop new photonic devices whose functions are defined by the liquid or to build new integrated photonic devices in which light is used for excitation, analysis, or manipulation of the fluid and the particles in the fluid. In particular, optofluidic lasers hold great promise for developing biological sensors thanks to the high sensitivity of stimulated emission to small perturbations in the laser cavity and gain medium. In an optofluidic dye laser, the gain medium can be directly excited by tuning the pump laser into dye absorption band or non-radiative Förster resonance energy transfer (FRET) can be employed exciting donor molecules which transfer their energy efficiently to acceptor molecules. Optofluidic dye lasers based on FRET enable the extension of the lasing wavelength range and provide new ways of biological sensing thanks to the high sensitivity of FRET efficiency to the donor-acceptor pair separation. In this thesis, the behavior of energy-transfer dye lasers using a mixture of saturable absorber and laser dye as an active medium is investigated theoretically by using rate-equation model. The rate equation model describing the working principle of such dye laser consists of coupled differential equations for the population of energy levels of the dye and the absorber and photon density inside the cavity. Here, we study the temporal characteristics and power of the output lasing pulses as a function of the fluence of the pulsed excitation beam. In the second part, we demonstrate optofluidic microlasers using highly efficient non-radiative FRET for pumping of the gain medium placed within glycerol/water microdroplets situated on a superhydrophobic surface. These droplets can serve as natural microcavities hosting whispering gallery modes (WGMs). Droplets are doped with the FRET donor-acceptor dye pair Rhodamine 6G-Rhodamine 700. FRET lasing is characterized for different acceptor and donor concentrations, and low threshold pump fluences of acceptor lasing are demonstrated. We also verify the nature of the energy transfer (non-radiative vs. radiative) for the range of parameters studied in the experiments.