Two-Photon Excitation of Silicon-Vacancy Centers in Nanodiamonds for All-Optical Thermometry with a Noise Floor of 6.6 mK·Hz<sup>–1/2</sup>
Jiahua Zhang, Hongsen He, Tongtong Zhang, Lingzhi Wang, Madhav Gupta, Jixiang Jing, Zhongqiang Wang, Qi Wang, Kwai Hei Li, Kenneth K. Y. Wong, Zhiqin Chu
Abstract
In this paper, we introduce ultrasensitive all-optical nanothermometry using high figure-of-merit nanodiamonds with silicon-vacancy (SiV) centers. In contrast to the commonly used single-photon process, we have adopted a two-photon approach to achieve efficient excitation of SiV centers in nanodiamonds. Based on the developed intensity-projected scheme, we have experimentally achieved a noise floor of 6.6 mK·Hz –1/2 using nanodiamonds. This serves as a new record of temperature resolution in the relevant field. Particularly, this simplified method allows us to reflect the temperature-induced spectral shift without wavelength scanning via a spectrometer. Furthermore, we demonstrate that the two-photon excitation of SiV centers has been thermally activated, as indicated by an elevated fluorescence intensity accompanied by a temperature increase. Our findings offer an opportunity for harnessing SiV-based nanothermometry in an easy-to-use manner and open the road for the development of practical applications in complicated environments such as living cells.