Abstract
An on-chip optical humidity sensor using Nano-anatase TiO2 coating is presented here. The coating material was prepared so that the result is in solution form, making the fabrication process quick and simple. Then, the solution was effortlessly spin-coated on an SU8 straight channel waveguide. Investigating the sensitivity and performance (response time) of the device revealed a great linearity in the wide range (35% to 98%) of relative humidity (RH). In addition, a variation of more than 14 dB in transmitted optical power was observed, with a response time of only ~0.7 s. The effect of coating concentration and UV treatment was examined on the performance and repeatability of the sensor. Interesting observations were found, and the attributed mechanisms were described. In addition, the proposed sensor was extensively compared with other state-of-the-art proposed counterparts from the literature and remarkable advantages were found. Since a high sensitivity of ~0.21 dB/%RH and high dynamic performances were demonstrated, this sensor is proposed for use in biomedical applications.
Highlights
Humidity monitoring is a necessary activity in many industry fields [1]
In a higher relative humidity (RH) range (35% to 90%), monolayers of water molecules will be adsorbed onto the walls of the holes in the cladding, which may change the real part of cladding refractive index (RI)
An optical humidity sensor is presented here based on the effect of the evanescent field in an anatase TiO2 nanoparticle coating
Summary
Humidity monitoring is a necessary activity in many industry fields [1]. Measurement of humidity is of great importance in chemical and medical industries such as respiration monitoring [2,3]. Humidity sensing is essential in civil and aerospace engineering It is frequently monitored in giant structures such as planes and bridges to control the possible risk of leakage due to corrosion [4]. In situations where humidity changes rapidly, sensors with low response and recovery times are needed Such applications include process control in industry, meteorology and a variety of other medical applications such as human respiration monitoring [11,12]. This shows the need for fast, highly sensitive and low-cost humidity sensors. The advantages of the proposed sensor are its high sensitivity, low response and recovery times, and simple fabrication process
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