Pockel’s effect and optical rectification induced by the built-in electric field in the space charge region of a silicon surface layer are demonstrated in a {001}-cut high-resistance silicon crystal. The half-wave voltage is about 203 V, deduced by Pockel’s effect. The ratio χzxx(2)/χzzz(2) is calculated to be about 0.942 according to optical rectification. Our comparison with the Kerr signal shows that Pockel’s signal is much stronger. This indicates that these effects are so considerable that they should be taken into account when designing silicon-based photonic devices.