JEOS RP ISSN01 | Page 72

J. Eur. Opt. Society-Rapid Publ. 21, 7( 2025) 67

Figure 8. Schematic of the STED microscope setup.

Table 1. Set of parameters adjusted for STED microscopy in practice.
Parameters	Definition
Pixel size	Dimension of each pixel of the image
Pinhole size	1 A. U.
Dwell time	The time during that light is detected from each volume element
Line accumulation	Repeating each line including several pixels(# pixels)
Excitation power %	Reported based on percentage of Excitation laser power
STED power %	Reported based on percentage of STED laser power
Excitation wavelength	561 nm
STED wavelength	775 nm
Frame size	Dimension of each image

Figure 9. Five different positions of the sample for obtaining PL spectra.

and are depicted in Figure 10. The PL measurements show that there are two peaks at k = 575 nm and k = 637 nm for the neutral charge state( NV 0) andthenegativecharge state( NV �) of the NV centres, respectively.

These peaks indicate a zero-phonon line( ZPL) at room temperature where purely electronic transition occurs. The spectra indicate a broad fluorescence emission in the spectral range from about 550 – 800 nm, with a maximum