Süperhidrofobik yüzeylerde duran mikrodamlacıklarda yüksek Q-faktör ölçümü ve sürdürülebilir Raman lazeri

Optical microcavities are platforms in which the light-matter interactions are investigated and novel photonic and optoelectronic device concepts are introduced and tested. From the basic scientific point of view, they are important for quantum and nonlinear optical studies, whereas from a technological perspective, future computers and telecommunication components can benefit from microcavity based devices. The results of this thesis are presented in two parts; i) characterizing liquid microdroplets as optical microcavities and ii) sustainable microdroplet Raman laser, both with the help of recently demonstrated reversible photothermal tuning of a droplet.High Quality factors (Q-factors) are essential for studies in especially quantum and nonlinear optics. Previous attempts of Q-factor measurements were limited by the resolution (0.07 nm) of the monochromator present in the laboratory which corresponds to a Q-factor of about 8100 around 650 nm. In the first part of the thesis, we made use of reversible photothermal tuning to overcome this limitation. When heated, certain amount of water evaporates, thus changes the equilibrium size of the microdroplet. In order to measure the Q-factor, we continuously change the power of the IR laser in very small steps, which enables tuning of the size of the microdroplet accordingly. WGMs of a dye-doped microdroplet are simultaneously excited by a probe laser and dye emission is monitored with an avalanche photo diode (APD). A peak is observed in the APD signal when the resonance condition is satisfied. Q-factors up to 105 are measured with this method. We achieved a resolution around 0.004 nm, which implies that we have the ability to tune the droplet?s radius with a precision of ?1Å.In the second part of the thesis, we demonstrate sustained Raman lasing from NaCl-water microdroplets with time periods as long as 25 minutes. In principle, there is no upper limit and all the experiments were terminated after sufficient amount of data were gathered. The technique we present relies on two lasers: a cw IR laser for photothermal tuning, and a pulsed green laser for size stabilization and excitation of the Raman band. It was previously shown that resonant heating of a droplet can lead to size stabilization due to size-dependent absorption. In this study, we combine this effect with photothermal tuning to sustain Raman lasing in long time scales. By photothermal tuning, the size of the droplet is tuned to a specific size in resonance with the green laser. From then on, resonant heating of the green laser leads to size stabilization, which eliminates the previously observed on-off behavior. However, long term fluctuation in the chamber still needs to be suppressed and it is compensated by slight manual adjustments of IR laser power after Raman lasing is detected.