Profile control of femtosecond laser-fabricated moth-eye structures on Si substrate

•The AR characteristic of 1-D moth-eye structures has been successfully controlled by adjusting the effective refractive index distribution of micro tapers for THz waves, which is achieved by employing femtosecond laser processing.•The THz-TDS measured and FDTD simulated results showed good agreement for all the samples, which can induce the power reflectance nearly to 0.•The stair profile displayed the most stable reflectance distribution of nearly 0 maintained in the 0.5–1.0-THz range, as well as lower total power reflectance for a broadband THz region from 0.1–1.0 THz.