High-mesa waveguide is attractive as a certain potion of propagation light profiles out of the waveguide, which can be used for infrared absorption. One of the issues for high-mesa waveguide is its high propagation loss, since high propagation loss consumes light power, which restricts sensing limitation. We tried to fabricate silica high-mesa waveguide for its low propagation loss possibility. The implemented waveguide showed the propagation loss of 0.65dB/cm (@λ=1550nm, w=2.3μm), which is higher than expected value of lower than O.1dB/cm. We investigated the reason of the high propagation loss and found that the radiation loss took a large part of the propagation loss. For further improvement, we propose under cladding layer thickness of more than 5μm to suppress the propagation loss.
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