High refractive index immersion liquid for super-resolution 3D imaging using sapphire-based aNAIL optics

摘要

Optically-transparent immersion liquids with refractive index (n ~ 1.77) tomatch sapphire-based aplanatic numerical aperture increasing lens (aNAIL) arenecessary for achieving deep 3D imaging with high spatial resolution. We reportthat antimony tribromide (SbBr$_{3}$) salt dissolved in liquid diiodomethane(CH$_{2}$I$_{2}$) provides a new high refractive index immersion liquid foroptics applications. The refractive index is tunable from n = 1.74 (pure) to n= 1.873 (saturated), by adjusting either salt concentration or temperature;this allows it to match (or even exceed) the refractive index of sapphire.Importantly, the solution gives excellent light transmittance in theultraviolet to near-infrared range, an improvement over commercially-availableimmersion liquids. This refractive index matched immersion liquid formulationhas enabled us to develop a sapphire-based aNAIL objective that has both highnumerical aperture (NA = 1.17) and long working distance (WD = 12 mm). Thisopens up new possibilities for deep 3D imaging with high spatial resolution.