Integrated optical polarization converter with enhanced periodic coupling and method of fabricating same
First Claim
1. Polarization converter for the conversion of a fraction of a signal component, propagating according to a first guided mode, of an optical signal into a signal component propagating according to a second guided mode, the first and second guided modes relating to different polarization modes, comprising a channel-type waveguide supported by a substrate, in which waveguide a periodic coupling takes place between the two guided modes of the optical signal propagating in the waveguide, said waveguide comprising:
- an incoming wave-guiding section;
an intermediary wave-guiding section; and
an outgoing wave-guiding section;
the intermediary wave-guiding section having a periodic geometrical structure including a periodic concatenation of, within a period length, two wave-guiding subsections, the lengths of the wave-guiding subsections and the number of periods of the periodic concatenation being tailored to a desired conversion fraction; and
wherein the two wave-guiding subsections each comprise different strip-type elements respectively provided with side walls which are at mutually different angles with respect to the plane of the substrate, said different strip-type elements defining different waveguide profiles for the two wave-guiding subsections, respectively.
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Abstract
Integrated optical polarization converter provided with a channel-type waveguide (B) defined by a strip-type structure (S4) supported by a substrate (S) and having a periodic concatenation of two different part strips having side walls which are at different angles with the plane of the substrate. The two part strips have as cross-sections either a trapezium (EFGH with Δ1, Δ2 ≠0) and a rectangle (EFGH with Δ1 =Δ2 =0), or both of them a right-angled trapezium with oblique sides situated opposite one another (EFGH with Δ1 0 and Δ2 ≠0, and EFGH with Δ1 ≠0 and Δ2 =0). Oblique and vertical side walls on such a strip-type structure supported by a substrate are fabricated, in the case of suitable crystal orientation, by means of two mutually complementary mask patterns, using etching steps, employing wet-chemical and dry etchants respectively.
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Citations
13 Claims
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1. Polarization converter for the conversion of a fraction of a signal component, propagating according to a first guided mode, of an optical signal into a signal component propagating according to a second guided mode, the first and second guided modes relating to different polarization modes, comprising a channel-type waveguide supported by a substrate, in which waveguide a periodic coupling takes place between the two guided modes of the optical signal propagating in the waveguide, said waveguide comprising:
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an incoming wave-guiding section; an intermediary wave-guiding section; and an outgoing wave-guiding section; the intermediary wave-guiding section having a periodic geometrical structure including a periodic concatenation of, within a period length, two wave-guiding subsections, the lengths of the wave-guiding subsections and the number of periods of the periodic concatenation being tailored to a desired conversion fraction; and wherein the two wave-guiding subsections each comprise different strip-type elements respectively provided with side walls which are at mutually different angles with respect to the plane of the substrate, said different strip-type elements defining different waveguide profiles for the two wave-guiding subsections, respectively. - View Dependent Claims (2, 3, 4, 5)
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6. Method for fabricating a channel-type waveguide on a substrate made of crystalline material and provided with a light-guiding layer, which waveguide comprises a concatenation of wave-guiding sections having alternately a first and a second mutually different waveguide profile, the mutually different waveguide profiles being defined at least by strip-type elements having different trapeziform cross-sections, the method comprising the steps of:
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(a) applying to the substrate a first strip-type mask pattern of a first mask material in a direction tailored to the crystal orientation of the light-guiding layer, (b) applying to the substrate, and partially over the first strip-type mask pattern, a second mask pattern of a second mask material, which second mask material comprises a number of parallel strip-type subpatterns which lie substantially transversely to, and at least partially over, the first strip-type mask pattern, (c) a first etching step, using first etchants, of parts of the substrate which are not covered by the first and second mask materials, (d) removing the second mask material, (e) covering the parts etched in the first etching step with a third mask material, (f) a, second etching step, using second etchants, of parts of the substrate which are;
not covered by the first and third mask materials,(g) removing the first and third mask materials, one of the first and second etching steps being carried out with wet-chemical etchants and the other of said first and second etching steps being carried out with dry etchants. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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Specification