Development principle of hollow infrared waveguide coupler

The guiding principle of optical coupling based on a hollow optical fiber was clarified to fabricate high-efficiency mid-infrared fiber coupler. In the side-polished fiber coupler structure that shares the core at the branch, the inserted light travels straight toward the branch. Therefore, it was found that the branching ratio of the coupler can be flexibly controlled by the bending angle of the input fiber.　Based on this principle, a fiber coupler based on the AgI/Ag hollow optical fiber was fabricated, and a low-cost, high-performance fiber coupler was realized. We have also demonstrated that the proposed fiber coupler can be used in heterodyne spectrometers for planetary observations.

量子カスケードレーザの技術革新により，小型堅牢で安価な赤外光源が入手可能となり，赤外ファイバとの組み合わせにより赤外光の応用領域が拡大しつつある．本研究で得られた知見は，それら装置から光の合分波に必要なミラー，ビームスプリッタ，レンズなどの光学素子を排除し，柔軟で小型な光計測装置の実現に寄与し，医療計測，宇宙・環境観測，光通信を含む広範な波及効果を有する．