Spatially selective DNA deposition on the fiber core by optically trapping an aqueous droplet and its application for ultra-compact DNA Fabry-Perot temperature sensor

We developed a new method to deposit deoxyribonucleic acid (DNA) solid film selectively only on the core of an optical fiber facet with a variable thickness, by optically trapping an aqueous DNA droplet during an optimal drying process. We experimentally demonstrated an ultra-compact DNA Fabry-Perot interferometer (FPI) on the fiber core in a columnar shape with a diameter of ~10 μm and variable height from 2.0 to 4.5 μm. Utilizing the highly confined DNA-FPI and its unique thermo-optical properties with a large negative thermo-optical coefficient of -5.91 × 10⁻⁴/ °C at λ = 1550 nm, we realized a very large temperature sensitivity of -2.42 nm/ °C in the spectral domain and a power change of -0.43 dB/ °C in the biologically important temperature range from 30 to 80 °C. The proposed sensor also showed a fast temporal response with an average rise time of 0.62 s and fall times of 1.16 s. The proposed device structure can be readily applied in situ real-time temperature monitoring applications in microscopic environment as well as in various bio-chemical sensing.