Long, stitch-free slot waveguide with s-bend tapered couplers for IR-sensing applications using electron beam lithography

We use the fixed beam moving stage (FBMS) electron beam lithography technique to pattern a 10 mm long slot waveguide with s-bend tapered double-tip couplers. The fabrication method solves two major limitations of the FBMS mode, namely, the requirement for fixed-width structures and the incidence of stage placement drift for patterns involving elements of different widths. This has been achieved by fracturing the outline of the structure into fixed-width elements of gradually increasing width and creating intermediate overlap areas between the elements to mitigate the stage placement drifts

Long, stitch-free slot waveguide with s-bend tapered couplers for IR-sensing applications using electron beam lithography

We use the fixed beam moving stage (FBMS) electron beam lithography technique to pattern a 10 mm long slot waveguide with s-bend tapered double-tip couplers. The fabrication method solves two major limitations of the FBMS mode, namely, the requirement for fixed-width structures and the incidence of stage placement drift for patterns involving elements of different widths. This has been achieved by fracturing the outline of the structure into fixed-width elements of gradually increasing width and creating intermediate overlap areas between the elements to mitigate the stage placement drifts.acceptedVersio

Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy

Nanophotonic waveguides are at the core of a great variety of optical sensors. These structures confine light along defined paths on photonic chips and provide light–matter interaction via an evanescent field. However, waveguides still lag behind free-space optics for sensitivity-critical applications such as trace gas detection. Short optical pathlengths, low interaction strengths, and spurious etalon fringes in spectral transmission are among the main reasons why on-chip gas sensing is still in its infancy. In this work, we report on a mid-infrared integrated waveguide sensor that successfully addresses these drawbacks. This sensor operates with a 107% evanescent field confinement factor in air, which not only matches but also outperforms free-space beams in terms of the per-length optical interaction. Furthermore, negligible facet reflections result in a flat spectral background and record-low absorbance noise that can finally compete with free-space spectroscopy. The sensor performance was validated at 2.566 μm, which showed a 7 ppm detection limit for acetylene with only a 2 cm long waveguide

Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy

Nanophotonic waveguides are at the core of a great variety of optical sensors. These structures confine light along defined paths on photonic chips and provide light–matter interaction via an evanescent field. However, waveguides still lag behind free-space optics for sensitivity-critical applications such as trace gas detection. Short optical pathlengths, low interaction strengths, and spurious etalon fringes in spectral transmission are among the main reasons why on-chip gas sensing is still in its infancy. In this work, we report on a mid-infrared integrated waveguide sensor that successfully addresses these drawbacks. This sensor operates with a 107% evanescent field confinement factor in air, which not only matches but also outperforms free-space beams in terms of the per-length optical interaction. Furthermore, negligible facet reflections result in a flat spectral background and record-low absorbance noise that can finally compete with free-space spectroscopy. The sensor performance was validated at 2.566 μm, which showed a 7 ppm detection limit for acetylene with only a 2 cm long waveguide.</p