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2024-11-27 9:50

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Conference: Bucharest University Faculty of Physics 2014 Meeting

Section: Optics, Spectroscopy, Plasma and Lasers

Title:

Tunable lasers with pendant micro-droplets active media

Authors:

M. BONI(1,2), I. R. ANDREI(1), Angela STAICU (1),M. L. PASCU (1,2)

Affiliation:

1)National Institute for Laser, Plasma and Radiation Physics, Romania

2)Faculty of Physics, University of Bucharest, Romania

E-mail

mihai.boni@inflpr.ro

Keywords:

micro-droplets, lasing, fluorescence, WGMs

Abstract:

In this paper is presented a tunable laser based on microfluidics technology. The lasing effect is achieved in pendant droplets which contain ultra-pure water seeded with a laser dye, Rhodamine 6G. When the laser beam is partially or fully absorbed by the droplet’s components and laser induced fluorescence (and lasing) effects are produced, the interaction is called resonant. If the laser beam is not absorbed by the droplet materials exerting only pressure (mechanical) effects on the droplet itself, the interaction is defined as unresonant. In the reported experiments it was studied the resonant interaction, where the droplets behave as optical spherical cavities in which the fluorescence signal is amplified. This effect is known as the whispering gallery modes (WGMs). The typical volume used in the experiments was 10µl, so that the diameter of the droplet was 2.67 mm. The droplets were irradiated at 532 nm emitted by a pulsed Nd:YAG laser which makes available the second harmonic of the fundamental beam (1.064µm); the pulse FWHM was 5 ns and the pulse repetition rate was 10pps. The average energy of the laser beam was typically 2.2 mJ. The droplets, which were simple droplets containing only the dye solution were generated using a computer controlled system Hamilton Microlab 500. In order to observe and measure the lasing emission the fluorescence/lasing signal was collected using an optical fiber (400 μm core). This was analysed with a high resolution spectrograph (Princeton Instruments; Acton SpectraPro 2750). For tuning the lasing, different parameters were varied such as the concentration of the laser dyes and the droplet’s volume. The interaction angle of the pumping laser beam with the droplet’s surface and the geometry of the collection point are also parameters which may influence the lasing obtained from a pendant droplet. Acknowledgements: The authors from NILPRP acknowledge the financing of the research by MEN-CDI Nucleu project: PN0939/2009 and CNCS – UEFISCDI by project number PN-II-ID-PCE-2011-3-0922, and University of Bucharest, Faculty of Physics.