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

• 作者: Marek Vlk Anurup Datta Sebastián Alberti Henock Demessie Yallew Vinita Mittal Ganapathy Senthil Murugan Jana Jágerská
• 来源期刊: 光：科学与应用（英文版）
• 年，卷（期）: 2021,（2）
• 所属期刊栏目: Letters
• 页码范围: 147-153
• 页数: 7页
• 语种: 英文

摘要

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 2.566μm, which showed a 7 ppm detection limit for acetylene with only a 2 cm long waveguide.