Polarization beam splitter for guided light

Claim 1

Polarization beam splitter for guided light, which comprises a directional coupler (39) having an alternating delta beta electrode structure, said coupler incorporating two sections (40, 42) adjacent to one another and two light guides (44, 46), one end (64) of one (44) of the two guides serving to receive an input lightwave, which is a combination of the two optical guided modes, namely a transverse-electrical mode TE and a transverse-magnetic mode TM, characterized in that the coupler is produced on a substrate (38) made from a material having a refractive index associated with the TE mode and a refractive index associated with the TM mode and which makes it possible to induce opposite variations respectively on the refractive indexes and in that the coupler is able to introduce, in the absence of a voltage between the electrodes, a delta beta variation between the propagation constants respectively corresponding to the symmetrical and anti-symmetrical propagation modes of the coupler, which is on the one hand independent of the polarization state of the lightwave guided by the splitter and on the other is such that the representative point of the coupler (M1, M2, M3, M4) on its control diagram is the centre of a segment parallel to the abscissa axis of the reference frame in which the diagram is plotted and which is defined by two points (A1, B1; A2, B1; A1, B2; A2, B2) respectively belonging to a curve (I) corresponding to crossed states of the coupler and to a curve (II) corresponding to parallel states of said coupler, so that for an appropriate electrical polarization of the latter, one of the two TE and TM modes of the input lightwave is obtained at the other end of the guide (44), which receives said input lightwave and the other mode at the corresponding end of the other guide.