Yeni bir mikrokovuk tanıtımı: Su tutmayan yüzey üzerinde duran yağ/su mikrodamlacığı

Optical microcavities confine light into small volumes in high quality resonances. They have found various applications in both fundamental and applied research areas such as cavity quantum electrodynamics, optoelectronics, and biological sensing. Up to date various geometries have been demonstrated to function as optical microcavities. Cylindrical, spherical, spheroidal/toroidal, ring, and other shapes and topologies with various confining principles have been used in these demonstrations. With their specific truncated microsphere geometry, glycerol/water microdroplets standing on a superhydrophobic surface can also provide a three dimensional confinement for light, specifically in the equatorial plane paralel to the substrate. Provided a large contact angle, the whispering gallery modes (WGMs) of these optical microcavities can possess relatively high quality factors. Besides, no additional position control technique such as electrodynamic trapping or optical tweezing is necessary to analyze the optical properties of these microdroplets. In this thesis we present the following results obtained using single glycerol/water microdroplets standing on a superhydrophobic surface. (i) We demonstrate the observation of largely tunable WGMs in water microdroplets. Larger than 9.6 nm spectral tunability was achieved by evaporation/condensation in a current controlled mini humidity chamber. (ii) We demonstrate a self-control mechanism stabilizing the volume of these microdroplets with femtoliter resolution. The mechanism relied on the interplay between the condensation rate that was kept constant and the size dependent laser induced heating. By blocking the laser excitation for 500 msec, we were able to change the stable volume of individual microdroplets stepwise. (iii) We demonstrate lasing in Rhodamine B doped glycerol/water microdroplets. In these experiments, a pulsed, frequency-doubled Nd:YAG laser operating at 532 nm was used as the excitation source. (iv) Using the same pulsed excitation source, we demonstrate Raman lasing in glycerol/water microdroplets. The observed Raman lasing was not sustained; rather, oscillation would occur in temporally separated bursts. Inter-burst separations were determined to decrease from 2.3 sec to 0.4 sec by using nitrogen purging. Large spectral tunability of the WGMs can inspire novel applications in optical communication systems, e.g. tunable filters, switches, and lasers. The observed Raman lasing can also pave way to the development of very compact, cost-effective light sources for short-haul communications systems at around 650 nm. Besides due to the sensitivity of the WGMs to the size and shape of the microdroplets, our results can find applications in characterizing superhydrophobic surfaces and investigating liquid-solid surfaces.