Photothermal/photoacoustic (PT/PA) spectroscopy provides useful knowledge about optical absorption, as well as the thermal and acoustical properties of a liquid sample. For microfluidic biosensing and bioanalysis where an extremely small volume of liquid sample is encapsulated, simultaneous PT/PA detection remains a challenge. In this work, we present a new optofluidic device based on a liquid-core optical ring resonator (LCORR) for the investigation of PT and PA effects in fluid samples. A focused 532 nm pulsed light optically heats the absorptive fluid in a capillary to locally create a transient temperature rise, as well as acoustic waves. A 1550 nm CW laser light is quadrature-locked to detect the resonance spectrum shift of the LCORR and study thermal diffusion and acoustic wave propagation in the capillary. This modality provides an optofluidic investigative platform for biological/biochemical sensing and spectroscopy.
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