Bio-integrated lasers, that are lasers implanted into cells and tissues, are gaining interest from the research community. Here we show how microlasers and microcavities based on whispering gallery modes can be used for sensing different processes in biological materials including inside cells. By making microcavities of a predefined size they can also be used to encode some information and for cell tracking. Sensing and tracking can be applied to highly scattering tissues.
We demonstrate non-contact temperature measurement with 0.1 K precision at distances of several meters using omnidirectional laser emission from dye-doped cholesteric liquid crystal droplets freely floating in a fluid medium. Upon the excitation with a pulsed laser the liquid crystal droplet emits laser light due to 3D Bragg lasing in all directions. The spectral position of the lasing is highly dependent on temperature, which enables remote and contact-less temperature measurement with high precision. Both laser excitation and collection of light emitted by microlasers is performed through a 20 cm aperture optics at a distance of up to several meters. The optical excitation volume, where the droplets are excited and emit the laser light, is approx. 10 cubic millimeters. The measurement is performed with sub-second speed when several droplets pass through the excitation volume due to their thermal motion. Since the method is based solely on measuring the spectral position of a single and strong laser line, it is quite insensitive to scattering, absorption and background signals, such as auto-fluorescence. This enables a wide use in science and industry, with a detection range exceeding tens of meters.
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