Sensitivity enhancement of polymeric Mach–Zehnder interferometers by use of thin high-index films

Multifunctional waveguide interferometer sensor: simultaneous detection of refraction and absorption with size-exclusion function

“…phase shift per RI unit, that can be used is only limited to the loss of the sensor. By using a short wavelength laser (450 nm), a large increase in phase shift is realized in comparison to most of previous works [9,14,15,18,21,26,[28][29][30], which operates with a laser above 630 nm. The sensitivity for homogeneous bulk RI sensing of this sensor is comparable to those made by only polymers [9,19,31] or optical fiber [5].…”

“…The sensitivity for homogeneous bulk RI sensing of this sensor is comparable to those made by only polymers [9,19,31] or optical fiber [5]. We remark that approaches like coating with high RI dielectrics can be employed to enhance the LoD [14,17]. However, it may compromise the size-exclusion functionality of the sensor.…”

“…Recently, polymer waveguides have gained much attention owing to their interesting properties including high transparency in the UV-visible range, versatile process-abilities, cost effectiveness, and mechanical flexibility [8][9][10]. Different designs including ring resonators [11][12][13], interferometers [14][15][16][17][18][19] and guided mode resonance filters [20] have been demonstrated. In order to enhance the sensitivity of the polymeric sensor, various strategies have been demonstrated.…”

“…Organic-inorganic polymer slot waveguides have been developed to enable large light-liquid interaction [15,17,21]. Some polymer waveguides have shown enhanced sensitivity by incorporating additional high RI material like TiO 2 and Ta 2 O 5 at the interface to the liquid, [2,14,16,17]. However, simultaneous measurement of both the real and imaginary component of refractive index has been less explored.…”

A Polymer Asymmetric Mach–Zehnder Interferometer Sensor Model Based on Electrode Thermal Writing Waveguide Technology

“…The prototype showed a detection limit of 3 × 10 −3 refractive index units for homogeneous sensing at a total system length of 9.3 mm and a total waveguide core thickness of 3 μm [23]. In 2017, a polymer-based effective index sensor based on tailored high-index thin films was reported to enhance the sensitivity of asymmetric MZIs [24]. The core layer of this M–Z structure was fabricated with a single material, resulting that the phase difference of the two waveguide arms can only be realized by changing the length and width of the waveguide.…”