Provided is a nonlinear optical device manufactured with 4H silicon carbide crystal. The nonlinear optical crystal may be configured to alter at least a light beam (12) at a frequency to generate at least a light beam (16) at a further frequency different from the frequency. The nonlinear optical crystal comprises a 4H silicon carbide crystal (13). The nonlinear optical device is more compatible with practical applications in terms of outputting mid-infrared laser at high power and high quality and thus are more applicable in practice, because the 4H silicon carbide crystal has a relatively high laser induced damage threshold, a relatively broad transmissive band (0.38-5.9 μm and 6.6-7.08 μm), a relatively great 2nd-order nonlinear optical coefficient (d15=6.7 pm/V), a relatively great birefringence, a high thermal conductivity (490 Wm−1K−1), and a high chemical stability.