Single-channel Mach-Zehnder interferometric biochemical sensor based on two-lateral-mode spiral waveguide

Abstract

We propose and demonstrate a single-channel Mach-Zehnder interferometric (MZI) biochemical sensor consisting of two single-mode waveguides connected by a two-lateral-mode spiral sensing waveguide through two discontinuous junctions. The use of a two-lateral-mode waveguide offers the advantage of simple fabrication using single-step lithography and etching process. Meanwhile, the two-mode waveguide folded in a spiral layout can achieve high sensitivity of a long sensing waveguide while providing a compact sensing area compatible with commercial spotting machine and requiring small volume of sample. The sensor is demonstrated in silicon waveguides and the effect of the discontinuity offset distance on the interference visibility is studied. The bulk and surface sensitivity of a fabricated sensor with a 4582-μm-long two-mode spiral waveguide folded within a 185 μm diameter spot are characterized to be 461.6 π/RIU (refractive index unit) and 1.135 π/ng mm(-2), respectively. The biosensing capability of the sensor is verified by the measurement of biotin-streptavidin interaction of different concentrations.

Single waveguide silicon-organic hybrid modulator

“…by laterally shifted tapers (Hoppe et al, 2017a) as depicted in Fig. 1b, by lateral shifted waveguides (Liu et al, 2014), by waveguide steps (Zinoviev et al, 2011), by waveguide gratings (Bruck and Hainberger, 2014) or even simpler by a lateral shift of the external fibers with respect to the center of the grating couplers. Using the last approach, at a special fiber position, the first and second order modes are excited in the following dual-mode waveguide with the same power resulting in a balanced excitation (Hoppe et al, 2015).…”

“…The area can be minimized by using a different structure like spiral or meander shaped waveguides (Liu et al, 2014) but losses are still a limitation.…”

“…Whereas the MZM is an established element based on two waveguide arms, the modulator design can be simplified with the help of a dual-mode or bimodal interferometer (DMI), which is presented e.g. in (Zinoviev et al, 2011;Liu et al, 2014;Hoppe et al, 2017a). Using only one dual-mode waveguide, the novel design is a promising candidate to offer simplified, compact, parallelizable, broadband and thermal stable silicon modulators.…”

On‐Chip Spiral Waveguides for Ultrasensitive and Rapid Detection of Nanoscale Objects

“…The Si‐based optical sensors are thus highly reproducible and can be on‐chip integrated with high density. Note that, the present waveguide sensor exploits the elastic scattering of single nanoparticles, instead of the phase shift induced by the change of the bulk refractive index where the minute phase change has to be read out by a stable Mach–Zehnder interferometer …”

Analysis and investigations of differential interferometer based on a polymer optical bimodal waveguide

“…Particularly noteworthy are differential interferometers using a two-mode optical waveguide [2][3][4][5], which in some cases provide greater sensitivity than single-mode waveguides [6]. They operate utilizing the interference of two modes of different orders in the exemplary types of structures: spiral-type waveguides [7], silicon nanowire ridge waveguides (SNRW) [8], composite bimodal waveguides [9]. Modes propagating in a waveguide interfere with each other and the light intensity distribution at the output of the structure depends on the phase difference between the modes.…”