TiO2 freestanding thin film as evanescent waveguide sensor for biomedical application

In this paper, an evanescent waveguide is employed as sensor for biomedical application especially for post surgery to diagnostic anastomosis leakage (AL) by detecting bacteria in drain fluid. Atomic Layer Deposition (ALD) is used to deposit thin film of TiO₂ as waveguide material. We design and fabricate the waveguide in a freestanding configuration in order to obtain evanescent tale in front and back side so that the sensitivity of the sensor is higher than slab waveguide. An optical measurement is carried out to measure the propagation loses by `cut back´ method. An annealing at 700°C in oxygen atmosphere for 1 hour is conducted as treatment to improve the optical properties of the material. The results show that the annealing reduces the propagation loss from 6.7dB/cm to 5.4 dB/cm. The sensitivity of the sensor is presented as dB per unit volume percent (% v/v) of IPA diluted in H₂O. The sensitivity of the sensor is 1.6 dB/%.