Ultra-sensitive pressure sensor using double stage racetrack silicon micro resonator
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Ultra‑sensitive pressure sensor using double stage racetrack silicon micro resonator Abbas Kalate Seyfari1 · Mahdi Bahadoran1 · Alireza Aghili2 Received: 9 April 2020 / Accepted: 29 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Three layouts of add-drop double stage racetrack microring resonators (ADSRMRR) located on the centre of the flexible silicon diaphragm were introduced as microscale optomechanical pressure sensors. The light propagation through all of the proposed ADSRMRR layouts were simulated using the signal flow graph method and the variational finite difference time domain (varFDTD) analysis. To achieve optimum transmission, a formula was derived for a critical coupling coefficient in the presence of the coupling loss factor for each coupling region. The pressure was measured from a wavelength shift in the output drop port signals considering the change in the optical length of the ADSRMRR due to the diaphragm shear stress. The pressure sensitivity of 48.5 pm/kPa, 42.4 pm/kPa and 33.2 pm/kPa with the limit of detection of 4.1 × 10−2 kPa, 4.7 × 10−2 kPa and 6.0 × 10−2 kPa were measured for the symmetric-large layout, the asymmetric and the symmetricsmall layout of ADSRMRR pressure sensor, respectively. We introduced the ratio of the total optical length rather the sum of the resonant mode numbers (R-ratio) as a key factor in designing of the microscale Vernier based-pressure sensors. It is found that, using an ADSRMRR layout with a higher R-ratio provides a higher sensitivity with a lower detection limit, which are required in altitude sensors in satellites, aircraft, and weather balloons. Keywords Pressure sensor · Coupler loss · Double stage racetrack microring resonator · Optomechanical sensor · Vernier based sensor
1 Introduction Optical sensors have found many applications on the basis of interferometry (Bing et al. 2012), surface plasmon resonance (SPR) (Cao et al. 2014), refractive index-based sensors (Vakili and Noori 2019), waveguide-based sensors (Dutta et al. 2014), optical fibers (Wang et al. 2018), photonic crystals (PCs) (Zhou et al. 2016) and microring resonators (Butt et al. 2020). The optical and electrical pressure sensors convert the measured pressure to * Mahdi Bahadoran [email protected] 1
Department of Physics, Shiraz University of Technology, Shiraz, Fars 31371555, Iran
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Department of Polymer Engineering, Faculty of Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran
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detectable optical or electrical signals (Chao et al. 2009). In the last decades, the electrical pressure sensors had found numerous applications in different fields of engineering, however the electric-based pressure sensors suffer from some disadvantages like sensitivity of electrical devices and circuits to humidity, spark, electromagnetic (EM) field, temperature, pressure, etc. (Oh et al. 2009). Contrary to the electric-based pressure sensors, the optical-based pressure s
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