Slow light enhanced gas sensing in photonic crystals

• Published in: Optical materials 2018-02, Vol.76, p.106-110
• Main Authors: Kraeh, Christian, Martinez-Hurtado, J.L., Popescu, Alexandru, Hedler, Harry, Finley, Jonathan J.
• Format: Article
• Language: English
• Subjects: Gas sensor; Mid-infrared; Photonic crystals; Slow-light
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2017.12.024

Infrared spectroscopy allows for highly selective and highly sensitive detection of gas species and concentrations. Conventional gas spectrometers are generally large and unsuitable for on-chip applications. Long absorption path lengths are usually required and impose a challenge for miniaturization. In this work, a gas spectrometer is developed consisting of a microtube photonic crystal structure. This structure of millimetric form factors minimizes the required absorption path length due to slow light effects. The microtube photonic crystal allows for strong transmission in the mid-infrared and, due to its large void space fraction, a strong interaction between light and gas molecules. As a result, enhanced absorption of light increases the gas sensitivity of the device. Slow light enhanced gas absorption by a factor of 5.8 in is experimentally demonstrated at 5400 nm. We anticipate small form factor gas sensors on silicon to be a starting point for on-chip gas sensing architectures. [Display omitted] •A slow-light enhanced gas sensing device is demonstrated.•The millimetric device is built on a Si substrate ideal for on-chip applications.•A photonic crystal comprising hollow microtubes allows for mid-infrared light transmission.•Enhanced gas sensing is demonstrated for a hydrocarbon gas.