Abstract
Engineering photonic devices from liquid has been emerging as a fascinating research avenue. Reconfigurably tuning liquid optical micro-devices are highly desirable but remain extremely challenging because of the fluidic nature. In this article we demonstrate an all-liquid tunable whispering gallery mode microlaser floating on a liquid surface fabricated by using inkjet print technique. We show that the cavity resonance of such liquid lasers could be reconfigurably manipulated by surface tension alteration originated from the tiny concentration change of the surfactant in the supporting liquid. As such, remarkable sensing of water-soluble organic compounds with a sensitivity of free spectral range as high as 19.85 THz / (mol · mL−1) and the detectivity limit around 5.56 × 10−3 mol · mL−1 is achieved. Our work provides not only a novel approach to effectively tuning a laser resonator but also new insight into potential applications in biological, chemical and environmental sensing.
Highlights
Optical microresonators confine light into tiny volumes where the light‒matter interactions are strongly enhanced
The evanescent field inherent with a whispering gallery mode (WGM) resonator can be further exploited to couple among waveguides and resonators, leading to important devices such as optical filter and add-drop routers for optical communication[2]
A WGM resonator is a ring laser cavity which exhibits two whispering gallery modes degenerate in frequency corresponds to clockwise and counterclockwise travelling waves
Summary
Gallery Mode Microlasers received: 25 February 2016 accepted: 16 May 2016 Published: 03 June 2016. In a WGM microresonator, an evanescent field exists tens to hundreds of nanometers near the cavity’s interface This evanescent field can interact with the surrounding environment and dramatically change the resonator characteristics such as resonant wavelength, intensity and Q-factor, which allows for extremely sensitive detection down to even a single molecule level[13,14,15,16]. A WGM resonator is a ring laser cavity which exhibits two whispering gallery modes degenerate in frequency corresponds to clockwise and counterclockwise travelling waves Bistability between these two counter-propagating travelling waves has been demonstrated for semiconductor ring lasers and it is the corner stone on which all-optical memories and logic gates devices have been proposed[17,18]. The resonator shape as well as size of the quasi-disk WGM lasers can be changed by the variation of surface tension of water through employing surfactant, which provide reconfigurable tuning of resonance and output envelop. The sensing application for water-soluble organic compounds exemplified by ethanol is proposed and demonstrated with the FSR sensitivity as high as 19.85 THz/(mol · mL−1) and detectivity limit around 5.56 × 10−3 mol · mL−1
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