Polarization-insensitive optical switch and multiplexing apparatus

Claim 1

Polarization-insensitive optical switch apparatus for switching a collimated input beam between two output paths comprising a first polarization beam splitter (13) for receiving and splitting said collimated input beam (12) into two perpendicularly polarized first and second beams, means for reflecting (118) one of said first and said second beams so that the reflected beam and the other of said first and said second beams travel parallel paths, with means comprising an electro-optical crystal for varying the index of refraction in said path of said light beams and with a second polarization beam splitter (137) oper­ated in reverse, coupled to receive the perpendicularly polarized output beams, to provide a third single output light beam, which can be coupled to a first optical output means, characterized by a first polarization rotating means (14) for rotating the first of said two perpendicularly polarized beams by 90°, so that the rotated polarized beam (116) and the second one of said perpendic­ularly polarized beams (117) are each polarized in the same direction, further by a first electro-optical crystal, being part of the refraction index varying means, and having a first surface adapted to receive said reflected one beam (117) and said other beam (116) for transmission through said first crystal, a second surface adapted to receive such transmitted beams (116, 117) from said first surface of said first crystal (102) at a first pair of spots (121, 122) and to partly reflect the beams, a first reflective surface (123), oriented to receive the reflected light beams (216, 217) from said first pair of spots (121, 122) of said second surface (104) of said first crystal (102) and to reflect such light beams, a third surface adapted to receive such reflected light beams from said first reflective surface (123) of said first crystal upon a second pair of spots (126, 127) and to partly reflect the beams, and a fourth surface adapted to externally pass light beams (516, 517) impinged thereupon from said second pair of spots (126, 127) of said first crystal (102), further by a second electro-optical crystal (103), also being part of the refraction index varying means, having a first surface, a second surface oriented to receive transmitted light from said second surface (104) of said first crystal (102) at a first pair of spots (121, 122), a first reflective surface oriented to receive light (316, 317) from said first pair of spots (121, 122) of said second surface of said second crystal (103) and to reflect such received light, a third surface adapted to receive such reflected light from said first reflective surface of said second crystal (103) upon a second pair of spots and to partly reflect the beams, and a fourth surface adapted to externally pass light beams impinged thereupon from said second pair of spots of the second crystal, and further by a dielectric beam splitting coating (104) said first crystal (102), said second crystal (103) and said coating (104) being so positioned that said first pair of spots (121, 122) of said second surface of said first crystal (102) and said first pair of spots of said second surface of said second crystal (103) are substant­ially juxtaposed with a first portion of said coating (104) connecting said surfaces, and said second pair of spots (126, 127) of said third surface of said first crystal (102) and said second pair of spots of said third surface of said second crystal (103) being substantially juxtaposed with the second portion of said coating connecting said surfaces such that the transmitted and the reflected beams interfere with each other, said means for varying the index of refraction further comprising means (106, 107, 108, 109) for varying the index of refraction of one of said crystals (102, 103) with respect to the index of refraction of the other of said crystals (102, 103), means (136) being associated with said fourth surface of said first crystal (102) for reflecting one light beam (516) from one spot (126) of said second pair of spots (126, 127) of said first crystal (102) into the second polarization beam splitter (137), a second polarization rotating means being provided for rotating the polarization of one (517) of said light beams (516, 517) from said fourth surface of said first crystal (102) by 90° so that the rotated light beam (517) and the unrotated light beam (516) enter the second polarization beam splitter perpendicularly polarized with respect to each other, means being associated with said fourth surface of said second crystal (103) for reflecting one light beam (416) from one spot of said second pair of spots of said second crystal into a third polarization beam splitter (132), a third polarization rotating means (113) being provided for rotating the polarization of one (417) of said light beams from said fourth surface of said second crystal (103) by 90° so that the rotated light beam (417) and the unrotated beam (416) from said second crystal enter the third polarization beam splitter perpendicularly polarized with respect to each other and the third polarization beam splitter (132) being operated in reverse and coupled to receive the perpendicularly polarized output beams from said second crystal (103) and to provide a second single light beam (134).