1：Experimental Design and Method Selection:

The study involved synthesizing coumarin-benzoxazole derivatives via a multi-step chemical reaction, followed by characterization using various spectroscopic techniques and Z-scan measurements for NLO properties. Theoretical calculations using DFT, TDDFT, and ZINDO methods were employed to support experimental findings.

2：Sample Selection and Data Sources:

Seven coumarin-benzoxazole derivatives (4a-4g) were synthesized and dissolved in DMSO or CH2Cl2 for analysis. Samples were prepared with specific concentrations (e.g., 9×10-4 M for Z-scan).

3：List of Experimental Equipment and Materials:

Equipment included Bruker Avance III 500 MHz NMR spectrometer, Agilent 6210 Series Time-of-Flight mass spectrometer, Shimadzu UV-2550 UV-vis absorption spectrometer, SHIMADZU RF-5301PC spectrofluorometer, Nicolet 6700 IR spectrometer, TGA Q5000 thermogravimeter, Nd:YAG laser (PL2143B, EKSPLA), energy meter (Laser Probe Corporation, Rj-7620), and 2-mm quartz cuvette. Materials included analytical grade solvents, deuterated chloroform, deuterated DMSO, and various chemical reagents for synthesis.

4：Experimental Procedures and Operational Workflow:

Synthesis involved refluxing salicylaldehyde, ethyl cyanoacetate, and o-aminophenol with benzoic acid catalyst, followed by chlorination with oxalyl chloride and amidation with aromatic amines. Purification was done via silica gel column chromatography. Characterization included NMR, mass spectrometry, UV-vis, fluorescence, IR, TGA, and Z-scan measurements. Z-scan was performed with 120 fs laser pulses at 532 nm, 10 Hz repetition rate, focused with a 400 mm lens.

5：Data Analysis Methods:

Data were analyzed using standard Z-scan theory to calculate nonlinear absorption coefficient β, nonlinear refraction index n2, third-order nonlinear susceptibility χ(3), and hyperpolarizability γ. Theoretical calculations were done with Gaussian 09W (B3LYP/6-31G level) and ZINDO program.