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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-1 m 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 CO 2 with using the waveguide gas-cell for the first time.

A high-mesa waveguide is attractive as a certain portion of propagation light profiles out of the waveguide, which can be used for infrared absorption. One of the issues for a high-mesa waveguide is its propagation loss, since high propagation loss decreases the propagation light power, which restricts sensing capabilities. In this paper, we propose a silica high-mesa waveguide for infrared sensing and demonstrate its low propagation loss possibility. The implemented waveguide showed a low propagation loss of 0.02 dB/cm successfully.

No abstract

We propose a multiple-slot silica high-mesa waveguide for infrared sensing considering the possibility of realizing a higher portion of an optical field out of the waveguide (which is defined as "Γ air "). Low Γ air leads to less light power being used for sensing, which limits sensing capabilities. The simulated results showed a high Γ air of 20.3% for a quadruple structure under λ = 1550 nm. A scattering loss of 0.06 dB/cm was predicted theoretically as well.