1：Experimental Design and Method Selection:

The study employed the vertical Bridgman method for crystal growth, using a double-wall ampoule to control thermal stress and nucleation. Characterization methods included TG-DTA for thermal analysis, SXRD and PXRD for structural analysis, NMR and FTIR for bonding and functional group analysis, UV-Vis-NIR for optical transparency, z-scan for nonlinear optical properties, and dielectric measurements for electrical properties.

2：Sample Selection and Data Sources:

The raw material 2H1N was purchased from Sigma Aldrich (Technical grade, H45353). Crystals were grown and analyzed in-house.

3：3). Crystals were grown and analyzed in-house. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included a vertical Bridgman furnace, double-wall borosilicate glass ampoule (Type

4：3 glass), KAPPA APEXII Bruker single crystal X-ray diffractometer, D8 Advance Bruker powder X-ray diffractometer, Bruker Avance III 500 MHz NMR spectrometer, Perkin Elmer Spectrum1 ATR-FT-IR instrument, Perkin-Elmer Lambda-35 UV-Vis-NIR spectrometer, z-scan setup with 532 nm diode-pumped Nd:

YAG laser, and HIOKI 3532-50 LCR HiTester for dielectric measurements.

5：Experimental Procedures and Operational Workflow:

The ampoule was loaded with 2H1N, sealed under vacuum, and translated at

6：3 mm/hr in the furnace. After growth, crystals were cut, polished, and subjected to various analyses:

TG-DTA from 38°C to 500°C, SXRD for lattice parameters, PXRD for phase analysis, NMR in acetone-d6, FTIR from 450-4000 cm?1, UV-Vis-NIR from 200-1100 nm, z-scan with closed and open apertures, and dielectric measurements from 50 Hz to 5 MHz.

7：Data Analysis Methods:

Data were analyzed using software for XRD indexing, theoretical fits for z-scan parameters (n2, β, χ3), and standard formulas for optical and dielectric properties.