The object of the invention is a phase modulator including a modulation guide intended to guide die propagation of a light flow, said guide comprising a PN junction extending mainly along the main axis of propagation according to an oscillating continuous function. Advantageously, the oscillating continuous function is defined in such a way that the PN junction covers at least 50% of the light flow between the input and the output of the modulation guide. According to one possibility, the continuous function is sinusoidal. The object of the invention is also a switch and an intensity modulator each comprising a phase modulator.