1：Experimental Design and Method Selection:

The study involved preparing Cu3Nb2O8 via solid-state reaction at 700°C for various sintering times (3-12 hours) to achieve different morphologies and phases. Nonlinear optical properties were studied using Z-scan experiments with a Ti:Sapphire laser (800 nm, 150 fs, 80 MHz). Theoretical models such as Sheik-Bahae formalism were used for data fitting.

2：Sample Selection and Data Sources:

Samples were synthesized from stoichiometric mixtures of Nb2O5 and CuO precursors. Data were obtained from XRD, Raman spectroscopy, FESEM, UV-Vis absorption, and fluorescence measurements.

3：List of Experimental Equipment and Materials:

Equipment included a PAN analytical X-Ray powder diffractometer, FEI Quanta FEG 200 scanning electron microscope, Lamda UV-Vis spectrophotometer, FP-8000 spectrofluorometer, and a Ti:Sapphire laser system. Materials included Nb2O5 (Sigma Aldrich), CuO (Merck), and diethylene glycol as a dispersing agent.

4：Experimental Procedures and Operational Workflow:

Precursors were ground and sintered at 700°C for 3-12 hours. Structural and morphological analyses were performed using XRD, Raman, and FESEM. Linear optical properties were measured with UV-Vis and fluorescence spectroscopy. Nonlinear optical properties were assessed via Z-scan experiments, where samples were moved along the Z-axis of a focused laser beam, and intensity-dependent measurements were taken.

5：Data Analysis Methods:

Nonlinear absorption and refraction coefficients were derived from Z-scan data using theoretical fits. Band gaps were estimated from Tauc's plots. Statistical analysis included error estimation of around 10% for nonlinear parameters.