Photoluminescence of Nitrogen-Vacancy Centers by Ultraviolet One- and Two-Photon Excitation of Fluorescent Nanodiamonds

• Published in: The journal of physical chemistry letters 2022-12, Vol.13 (48), p.11280-11287
• Main Authors: Yang, Teng-I, Huang, Yu-Wen, Bista, Prabesh, Ding, Chien-Fang, Chen, Jeson, Chiang, Cheng-Tien, Chang, Huan-Cheng
• Format: Article
• Language: English
• Subjects: Physical Insights into Light Interacting with Matter
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.2c03064

Fluorescent nanodiamonds contain nitrogen-vacancy (NV) centers as quantum defects. When exposed to a continuous-wave 325 nm laser or a femtosecond 344 nm laser, the particles emit red fluorescence from NV0 centers at ∼620 nm. Power dependence measurements of the emission strength revealed a predominantly linear behavior at the laser peak intensity lower than 1 GW·cm–2, contributed mainly by photoexcitation of electrons from the valence band of diamond to the NV0 centers, followed by relaxation via electron–hole recombination. In the higher power regions, however, nonresonant two-photon interband excitation of the diamond matrix dominates the photoluminescence processes. Best fits of the experimental data to semiempirical models revealed an ionization coefficient of ∼1 cm–1 for the one-photon valence-to-defect excitation and a saturation intensity of 180 ± 60 GW·cm–2 for the two-photon interband excitation. The study provides new insight into the photoionization of NV0 centers and the interband excitation properties of diamond in the UV region.