Singlet oxygen phosphorescence imaging by superconducting single-photon detector and time-correlated single-photon counting: publisher's note.

This publisher's note contains corrections to Opt. Lett.46, 1217 (2021) OPLEDP0146-959210.1364/OL.415229.

Singlet oxygen phosphorescence imaging by superconducting single-photon detector and time-correlated single-photon counting.

This Letter presents, to the best of our knowledge, a novel optical configuration for direct time-resolved measurements of luminescence from singlet oxygen, both in solutions and from cultured cells on photodynamic therapy. The system is based on the superconducting single-photon detector, coupled to the confocal scanner that is modified for the near-infrared measurements. The recording of a phosphorescence signal from singlet oxygen at 1270 nm has been done using time-correlated single-photon counting. The performance of the system is verified by measuring phosphorescence from singlet oxygen generated by the photosensitizers commonly used in photodynamic therapy: methylene blue and chlorin e6. The described system can be easily upgraded to the configuration when both phosphorescence from singlet oxygen and fluorescence from the cells can be detected in the imaging mode. Thus, co-localization of the signal from singlet oxygen with the areas inside the cells can be done.

Single photon detection system for visible and infrared spectrum range.

We demonstrate niobium nitride based superconducting single-photon detectors sensitive in the spectral range 452-2300 nm. The system performance was tested in a real-life experiment with correlated photons generated by means of spontaneous parametric downconversion, where one photon was in the visible range and the other was in the infrared range. We measured a signal to noise ratio as high as 4×104 in our detection setting. A photon detection efficiency as high as 64% at 1550 nm and 15% at 2300 nm was observed.

Sensitivity of a superconducting nanowire detector for single ions at low energy.

We report on the characterization of a superconducting nanowire detector for ions at low kinetic energies. We measure the absolute single-particle detection efficiency η and trace its increase with energy up to η = 100%. We discuss the influence of noble gas adsorbates on the cryogenic surface and analyze their relevance for the detection of slow massive particles. We apply a recent model for the hot-spot formation to the incidence of atomic ions at energies between 0.2 and 1 keV. We suggest how the differences observed for photons and atoms or molecules can be related to the surface condition of the detector and we propose that the restoration of proper surface conditions may open a new avenue for SSPD-based optical spectroscopy on molecules and nanoparticles.

A superconducting NbN detector for neutral nanoparticles.

We present a proof-of-principle study of superconducting single photon detectors (SSPD) for the detection of individual neutral molecules/nanoparticles at low energies. The new detector is applied to characterize a laser desorption source for biomolecules and allows retrieval of the arrival time distribution of a pulsed molecular beam containing the amino acid tryptophan, the polypeptide gramicidin as well as insulin, myoglobin and hemoglobin. We discuss the experimental evidence that the detector is actually sensitive to isolated neutral particles.