| 摘要 |
PROBLEM TO BE SOLVED: To obtain optical information depending on the direction of a substance by controlling the directivity of an evanescent field that exists near a small opening. SOLUTION: Linear polarization light existing a light source is introduced into a polarization retention fiber 102 so that the polarization coincides with the polarization direction of the polarization retention fiber 102, enabling the light to reach an opening at the tip of the fiber while being propagated in the optical fiber with the polarization direction being retained. An evanescent field exists at distance that is approximately equal to a wavelength from the opening to the outside. The direction of the electromagnetic field of the evanescent field depends on the polarization direction of light from the optical fiber but does not have any special polarization surface in the optical fiber and the evanescent field is not directional up to now. However, in this case, light advancing immediately before the opening has a specific polarization surface, and the evanescent field formed near the tip also has directivity depending on it. When a sample 112 exists in the region of the evanescent field, the evanescent field becomes disturbed propagation light and the intensity of the light is detected by a photo detector.
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