The optically transparent single crystals of pure and amaranth dye-doped (0.1 and 0.2 mol%) sulphamic acid (SA) are grown by slow evaporation solution technique. The unit cell parameters of the grown crystals were calculated by single-crystal X-ray diffraction. The various planes and its crystallinity were analysed by powder X-ray diffraction studies. The presence of amaranth dye molecules in the grown SA crystal lattice was confirmed by energy dispersive X-ray analysis. The optical quality of the crystal was analysed by ultraviolet–visible analysis and it reveals that the grown crystals have the good optical transmission in the whole visible region. No weight loss observed up to 212 °C, 214 °C (0.1 mol%) and 215 °C (0.2 mol%) for pure and amaranth dye-doped SA crystals, respectively. The increasing hardness and laser damage threshold properties of the crystals may be due to the incorporation of amaranth dye in the SA crystal lattices. Photoconductivity analysis shows that the pure and doped SA crystals possess negative photoconductive nature. The third-order nonlinear optical susceptibility values also increased as an effect of amaranth dopant.