1：Experimental Design and Method Selection:

A home-built confocal microscope was used to study NV centers under continuous wave green (532 nm) and IR (1064 nm) laser excitation. The methodology involved steady-state and time-resolved fluorescence measurements to analyze charge-state dynamics, with a rate equation model developed to describe the photodynamic processes.

2：Sample Selection and Data Sources:

Single shallow NVs were measured in a high-purity chemical vapor deposition (CVD) diamond sample (Element Six electronic grade, implanted with N15 and annealed) and bulk NVs in a high-pressure high-temperature (HPHT) sample (Element Six). Data were collected using fluorescence levels filtered for NV- and NV0 states.

3：List of Experimental Equipment and Materials:

Lasers: CNI MGL-III-532 100 mW (532 nm), II-VI SUWTECH DPIR 2200 (1064 nm). Modulators: Gooch and Housego AOMO 3080-

4：Objective:

1 Nikon Plan Apochromat 100X Oil Lambda NA

5：45 WD 13 mm. Detector:

Excelitas SPCM-700-13-FC single-photon counter. Filters: Semrock NF01-532U-25, Semrock FF01-736/128-25, Semrock FF01-600/52-

6：Samples:

Element Six CVD and HPHT diamonds.

7：Experimental Procedures and Operational Workflow:

The beam was focused to a diffraction-limited spot using an oil immersion objective. Fluorescence was collected and directed to the single-photon counter. Pulse sequences involved turning IR laser on and off while green laser was continuous, with measurements of fluorescence dynamics over time. Data were analyzed to extract ionization and recombination rates.

8：Data Analysis Methods:

Numerical optimization using ODE45 in MATLAB to solve rate equations based on an 8-level energy diagram. Cross sections were extracted from fits to experimental data using derived equations for quasi-steady-state populations.