Light Sci Appl 2021 Sep 13;10(1):182. Epub 2021 Sep 13.
State Key Laboratory of Modern Optical Instrumentations, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, 310058, China.
Bright anti-Stokes fluorescence (ASF) in the first near-infrared spectral region (NIR-I, 800 nm-900 nm) under the excitation of a 915 nm continuous wave (CW) laser, is observed in Indocyanine Green (ICG), a dye approved by the Food and Drug Administration for clinical use. The dependence of fluorescence intensity on excitation light power and temperature, together with fluorescence lifetime measurement, establish this ASF to be originated from absorption from a thermally excited vibrational level (hot-band absorption), as shown in our experiments, which is stronger than the upconversion fluorescence from widely-used rare-earth ion doped nanoparticles. To test the utility of this ASF NIR-I probe for advanced bioimaging, we successively apply it for biothermal sensing, cerebral blood vessel tomography and blood stream velocimetry. Read More