Singlet oxygen luminescence detection with a fiber-coupled superconducting nanowire single-photon detector.

Direct monitoring of singlet oxygen (¹O₂) luminescence is a particularly challenging infrared photodetection problem. ¹O₂, an excited state of the oxygen molecule, is a crucial intermediate in many biological processes. We employ a low noise superconducting nanowire single-photon detector to record ¹O₂ luminescence at 1270 nm wavelength from a model photosensitizer (Rose Bengal) in solution. Narrow band spectral filtering and chemical quenching is used to verify the ¹O₂ signal, and lifetime evolution with the addition of protein is studied. Furthermore, we demonstrate the detection of ¹O₂ luminescence through a single optical fiber, a marked advance for dose monitoring in clinical treatments such as photodynamic therapy.