Gas sensing demonstration by using silica high-mesa waveguide with amplified cavity ring down spectroscopy technique

For realizing compact breath sensing device, we have proposed a silica high-mesa waveguide for the gas-cell (breath detection part) because of its low propagation loss. It is, however, still difficult to make breath-sensing due to its total insertion loss because the required length of the waveguide reaches very long of approximately several 10 cm–1m for the small portion of gas, and thus gas-sensing has not been achieved so far. To compensate the insertion loss, we utilize “amplified” CRDS (cavity ring down spectroscopy) technique to realize gas-sensing in this paper. As a result, we could successfully confirm the gas-sensing of CO₂ with using the waveguide gas-cell for the first time.