As our world becomes more complex and the effects of human activities on the environment and
their own health increases, the need to map and understand what we expel into our surroundings
grows. Especially gases, which are often color- and odorless, often have big implications on the
health of humans and the planet as a whole. Having a sensor that is both cheap and small enough
to be used ubiquitously would enable us to measure and understand the influences of human
This project aims to build such a cheap, chip-scale, sensitive gas sensor. The size and price are kept
low by employing silicon photonics. The sensitivity will be ensured by using photoacoustic
spectroscopy. Furthermore we operate in the terahertz frequency range which typically interacts
with gaseous molecules of many different species in a highly selective manner due to the typically
rotational nature of the excitations. This gives us an advantage over infrared spectroscopy which is
concerned with vibrational modes and hence is unsuited to discriminate between isomeres.
In photoacoustics a gas is modularly heated when it interacts with light (an effect inherent to
terahertz excitations), creating a pressure wave. This waves hits a mechanical resonator whose
frequency matches that of the soundwave and its movement forms the signal. We will improve
this technique by achieving better light concentrations and having an optical, acoustical and
mechanical resonator in one system.