Tunable optofluidic microlasers based on optically stretched emulsion droplets

0422303 - ÚPT 2014 RIV US eng C - Conference Paper (international conference)
Aas, M. - Jonáš, Alexandr - Kiraz, A. - Brzobohatý, Oto - Ježek, Jan - Pilát, Zdeněk - Zemánek, Pavel
Tunable optofluidic microlasers based on optically stretched emulsion droplets.
Optical Trapping and Optical Micromanipulation X (Proceedings of SPIE Vol. 8810). Bellingham: SPIE, 2013, 88101Y:1-12. ISSN 0277-786X.
[Optical Trapping and Optical Micromanipulation /10./. San Diego (US), 25.08.2013-29.08.2013]
R&D Projects: GA ČR GPP205/11/P294; GA TA ČR(CZ) TA03010642; GA MŠMT ED0017/01/01
Institutional support: RVO:68081731
Keywords : lasers * optical trapping * water * wavelength tuning
Subject RIV: BH - Optics, Masers, Lasers

We introduce tunable optofluidic microlasers based on optically stretched, dye-doped emulsion droplets confined in a dual-beam optical trap. Optically trapped microdroplets of oil emulsified in water and stained with fluorescent dye act as active ultrahigh-Q optical resonant cavities hosting whispering gallery modes (WGMs) which enable dye lasing with low threshold pump powers. In order to achieve tunable dye lasing, the droplets are pumped with a pulsed green laser beam and simultaneously stretched by light in the dual-beam trap. For a given stretching power, the magnitude of the droplet deformation is dictated by the interfacial tension between the droplet and the host liquid which is adjustable by adding surfactants. Increase of power of the dual-beam trap causes a directly proportional change of the droplet stretching deformation. Subsequently, resonant path lengths of different WGMs propagating in the droplet are modified, leading to shifts in the corresponding microlaser emission wavelenghts. Using this technique, we present all-optical, almost reversible spectral tuning of the lasing WGMs and show that the direction of wavelength tuning depends on the position of the pump beam focus on the droplet, consistent with the deformation of originally spherical droplet towards a prolate spheroid. In addition, we study the effects of changes of the droplet and immersion medium temperature on the spectral position of lasing WGMs and demonstrate that droplet heating leads to red-tuning of the droplet lasing wavelength.
Permanent Link: http://hdl.handle.net/11104/0228483