Silicon photonics in the mid-infrared: Waveguide absorption sensors

Mode Sensitivity Analysis of Subwavelength Grating Slot Waveguides

“…In general, high S mode over a wide range of n c is preferred for many applications. For example, it corresponds to higher sensitivity in photonic sensors; a higher n eff change due to a cladding index perturbation translates into a higher spectral shift in wavelength-based detection sensors [15] or higher absorption in intensity detection sensors [20]. In the case of electro-optic modulators, higher S mode facilitates faster switching with low power consumption [11].…”

Investigation of dual-bend serpentine/spiral waveguides coupled to a microchannel system for competent, evanescent-wave-absorption-based, on-chip, biological-/chemical-sensing applications

“…The loss of optical power per unit length (L N ) was calculated (using eqn (19)) at the xed values of W ¼ 200 mm, 3 ¼ $8 m À1 M À1 (extinction coefficient for methylene blue at 0.625 m wavelength), l ¼ 0.625m and q cc ¼ 33 (for n 2 ¼ 1.33 of D.I. water).…”

“…Upper ðj 0 1 Þ and lower limit ðj 0 1 Þ values (i.e. the complementary angles of the minimum and maximum values of the angles of incidences F or d) were put in to the eqn (19) to calculate the L N values for the C 1 and C 2 bends of S-bend/spiral waveguides. The total loss due to all the TIRs was calculated by multiplying the L N value with the corresponding equal interaction lengths (i.e.…”

“…Lavchiev et al also showed a sensor design based on a single-mode straight Si waveguide (WG) on a low refractive index Si 3 N 4 /SiO x /Si 3 N 4 membrane, where the waveguide interacted with the fluid sample by means of the evanescent field that extended into the sample. 19 However, these reported devices seemed to be not suitable for liquid analyte samples, because the designs did not contain suitable closed microchannel structures (around the waveguide sensor probe) allowing for placement of a constant volume of fluid samples to interface with the fixed length of waveguide during the detection process. Further, the absence of possible close microchannel structures may allow the liquid samples to evaporate, which may not ensure the concentration of sample is constant, leading to an irregular real-time output of the sensing device for similar concentrations.…”

Fluidic Physical Sensors and Sensor Systems

“…We recently have worked on silicon based waveguides which interact with fluid samples placed in their evanescent fields, see, e.g. [30,31]. We expect that there will be significant developments in this spectral range as integrated photonics technology thus far is concentrated on the near infrared but condition monitoring applications would require mid-IR absorption data.…”