Broadband dispersion controlling waveguide and controlling method

Abstract

An optical waveguide structure has a waveguide core including an inner and an outer layer with different refractive indices, and a refractive index ratio of the different refractive indices is greater than or equal to 1.15. A dispersion controlling method using the optical waveguide structure includes: first, obtaining a dispersion curve having up to 5 zero-dispersion wavelengths by calculating based on a set of preset structural size parameters of the optical waveguide; and then, adjusting one or more of the width (W) of a contact surface between the inner layer and the substrate, the thickness (H) of a higher refractive index material, and the thickness (C) of a lower refractive index material, so as to implement dispersion control.

Claims

1. A broadband dispersion controlling waveguide, comprising a waveguide core located on a substrate, wherein the waveguide core is provided with a cladding layer; the waveguide core comprises an A layer and a B layer composed of materials with different refractive indices, the ratio of the refractive indices of the materials for the A layer and the B layers is ≥1.15, characterized in that the A layer partially covers the substrate, thus forming a combined body of the A layer and the substrate, the B layer covers an upper side of the combined body, the A layer has a rectangular or trapezoid cross section, and a width W of a contact surface between the A layer and the substrate, a thickness H of the A layer of the waveguide core, and a thickness C of the B layer of the waveguide core are configured in such a way that the broadband dispersion controlling waveguide has a chromatic dispersion curve whose dispersions are controlled within a range of −100˜+100 ps/nm/km in a wavelength range.

2. The broadband dispersion controlling waveguide according to claim 1, characterized in that an upper part of the substrate has a through groove along a light transmission direction.

3. The broadband dispersion controlling waveguide according to claim 2, characterized in that a top part of the substrate comprises a support layer for the waveguide core.

4. The broadband dispersion controlling waveguide according to claim 1, characterized in that the materials of the A layer and the B layer are selected from the same combination or from different combinations of a first combination, a second combination and a third combination; the first combination is a chalcogenide glass combination comprising S-based glass of lower refractive index and Se-based glass and Te-based glass of higher refractive index; the second combination at least comprises TiO.sub.2, HfO.sub.2, Al.sub.2O.sub.3, SiO.sub.2, Ga.sub.2O.sub.3, Ta.sub.2O.sub.3, and Bi.sub.2O.sub.3; and the third combination at least comprises Ge, SiC, Si, Ge.sub.x Si.sub.y, Diamond, GaN, AlN, Si.sub.x N.sub.y, InP, GaAs, LiNbO.sub.3.

5. The broadband dispersion controlling waveguide according to claim 4, characterized in that the S-based glass at least comprises Ge.sub.2S.sub.3, As.sub.2S.sub.3, Ge.sub.x As.sub.yS.sub.z and Ge.sub.x P.sub.yS.sub.z, the Se-based glass at least comprises Ge.sub.2Se.sub.3, As.sub.2Se.sub.3, Ge.sub.x As.sub.ySe.sub.z, Ge.sub.x Sb.sub.ySe.sub.z and Ge.sub.x P.sub.ySe.sub.z, and the Te-based glass at least comprises Ge.sub.x Sb.sub.yTe.sub.z, Ge.sub.x Se.sub.yTe.sub.z and As.sub.x Se.sub.yTe.sub.z, wherein x, y, z represent different mole percentage, and x+y+z=100; and the x and y in the third combination represent different mole percentage, and x+y=100.

6. The broadband dispersion controlling waveguide according to claim 1, wherein the wavelength range is larger than 0.3 octave.

7. The broadband dispersion controlling waveguide according to claim 1, wherein the chromatic dispersion curve is convex from a shortest wavelength of the wavelength range to a first wavelength of the wavelength range, and is concave from the first wavelength to a second wavelength of the wavelength range.

8. The broadband dispersion controlling waveguide according to claim 7, wherein the chromatic dispersion curve is convex from the second wavelength to a third wavelength of the wavelength range.

9. The broadband dispersion controlling waveguide according to claim 8, wherein the chromatic dispersion curve is concave from the third wavelength to a fourth wavelength of the wavelength range.

10. The broadband dispersion controlling waveguide according to claim 1, wherein the chromatic dispersion curve has 5 zero-dispersion wavelengths.

11. The broadband dispersion controlling waveguide according to claim 1, wherein the chromatic dispersion curve has dispersions within a range of −100˜+100 ps/nm/km over a broadband wavelength range of two octaves.

12. An optical resonance device and an optical interference device based on a broadband dispersion controlling waveguide, characterized in that a cross section of the optical resonance device and the optical interference device uses a cross section of a broadband dispersion controlling waveguide comprising a waveguide core located on a substrate, wherein: the waveguide core is provided with a cladding layer; the waveguide core comprises an A layer and a B layer composed of materials with different refractive indices, a ratio of the refractive indices of the materials for the A layer and the B layers is ≥1.15, the A layer partially covers the substrate, thus forming a combined body of the A layer and the substrate, the B layer covers an upper side of the combined body, the A layer has a rectangular or trapezoid cross section; and the width W of the contact surface between the A layer and the substrate, the thickness H of the A layer of the waveguide core, and the thickness C of the B layer of the waveguide core are configured in such a way that the broadband dispersion controlling waveguide has a chromatic dispersion curve whose dispersions are controlled within a range of −100˜+100 ps/nm/km in a wavelength range.

13. The optical resonance device and the optical interference device based on the broadband dispersion controlling waveguide according to claim 12, characterized in that the optical resonance device includes at least micro-ring resonator cavity and a FP cavity, the optical interference device includes at least Mach-Zindel Interferometer.

14. A method for controlling chromatic dispersion based on a broadband dispersion controlling waveguide, characterized in that, the broadband dispersion controlling waveguide comprises a waveguide core located on a substrate, wherein the waveguide core is provided with a cladding layer; the waveguide core comprises an A layer and a B layer composed of materials with different refractive indices, a ratio of the refractive indices of the materials for the A layer and the B layers is ≥1.15; the A layer partially covers the substrate, thus forming a combined body of the A layer and the substrate, the B layer covers an upper side of the combined body, the A layer has a rectangular or trapezoid cross section; and the method comprises: by using the broadband dispersion controlling waveguide, first, designing a set of structural size parameters of the waveguide, the set of structural size parameters comprising the width W of the contact surface between the A layer and the substrate, the thickness H of the A layer of the waveguide core, and the thickness C of the B layer of the waveguide core; and then obtaining a chromatic dispersion curve based on the second derivative of the transmission constant of light in the waveguide with respect to wavelength.

15. The method for controlling the chromatic dispersion based on a broadband dispersion controlling waveguide according to claim 14, characterized in that the chromatic dispersion curve is a chromatic dispersion curve with up to 5 zero-dispersion wavelengths, and the chromatic dispersion curve is flat in a broadband wavelength range of two octaves.

16. The method for controlling the chromatic dispersion based on a broadband dispersion controlling waveguide according to claim 15, characterized in that, by increasing the width W of the contact surface between the A layer and the substrate, the chromatic dispersion curve is shifted as a whole in the direction in which an anomalous dispersion value increases; by increasing the thickness H of the A layer of the waveguide core, the chromatic dispersion curve is shifted as a whole in the direction in which the anomalous dispersion value increases; and by increasing the thickness C of the B layer of the waveguide core, the chromatic dispersion curve is rotated counterclockwise with the wavelength λ.sub.0 as the center of rotation, where when the wavelength is less than λ.sub.0, the chromatic dispersion curve moves in the direction in which the anomalous dispersion value decreases, and when the wavelength is greater than λ.sub.0, the chromatic dispersion curve moves in the direction in which the anomalous dispersion value increases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1-1 is a schematic cross-sectional view of Structure 1 of the optical waveguide structure according to the present disclosure;

(2) FIG. 1-2 is a schematic cross-sectional view of Structure 2 of the optical waveguide structure according to the present disclosure;

(3) FIG. 1-3 is a schematic cross-sectional view of Structure 3 of the optical waveguide structure according to the present disclosure;

(4) FIG. 2-1 is a graph showing chromatic dispersion varies along with a width W of a contact surface between a waveguide core and a substrate;

(5) FIG. 2-2 is a graph showing chromatic dispersion varies along with a thickness H of the high-index material; and

(6) FIG. 2-3 is a graph showing chromatic dispersion varies along with a thickness C of the low-index material.

DETAILED DESCRIPTION

(7) A further detailed description will be made to the technical solution of the present disclosure in conjunction with drawings and specific embodiments, and the described specific embodiments are used merely to explain the present disclosure, but not to limit the present disclosure.

(8) As shown in FIG. 1-1, the present disclosure provides a broadband dispersion controlling waveguide comprising a waveguide core located on the substrate 3, wherein the waveguide core comprises an A layer 1 and a B layer 2, the A layer has a sidewall angle α, α≥90°, the A layer 1 and B layer 2 are composed of materials with different refractive indices, and the refractive index ratio of the materials of the A layer 1 and the B layer 2 is ≥1.15; it is characterized in that the A layer 1 partially covers the substrate 3, thus forming a combined body of the A layer 1 and the substrate 3, the B layer 2 covers the upper side of the combined body; and the A layer 1 has a rectangular or trapezoid cross section.

(9) As shown in FIG. 1-2, an upper part of the substrate in a broadband dispersion controlling waveguide according to the present disclosure has a through groove along a light transmission direction, and it is recommended to use etching process with etching liquid to form the through groove in the present disclosure. Therefore, a material within the range of the height of the through groove uses a material 3 that can be etched by a selected etching liquid, while a material 4 at the bottom of the substrate uses a material that can not be etched by this etching liquid. In addition, the top part of the substrate comprises a support layer for the waveguide core, and in order to facilitate processing, a material of the support layer is preferably the same as that of the A layer.

(10) As shown in FIG. 1-3, an upper part of the substrate in a broadband dispersion controlling waveguide according to the present disclosure has a through groove along the light transmission direction, and it is recommended to use etching process with etching liquid to form the through groove in the present disclosure. Therefore, a material within the range of the height of the through groove uses a material 3 that can be etched by a selected etching liquid, while the material 4 at the bottom of the substrate uses a material that can not be etched by this etching liquid. In addition, the top part of the substrate comprises a support layer for the waveguide core, and in order to facilitate processing, a material of the support layer is preferably the same as that of the A layer.

(11) In the present disclosure, the materials of the A layer and the B layer are selected from the same combination or from different combinations of a first combination, a second combination and a third combination.

(12) The first combination is a chalcogenide glass combination comprising S-based glass of lower refractive index and Se-based glass and Te-based glass of higher refractive indices; the S-based glass at least comprises Ge.sub.2S.sub.3, As.sub.2S.sub.3, Ge.sub.xAs.sub.yS.sub.z and Ge.sub.xP.sub.yS.sub.z, the Se-based glass at least comprises Ge.sub.2Se.sub.3, As.sub.2Se.sub.3, Ge.sub.xAs.sub.ySe.sub.z, Ge.sub.xSb.sub.ySe.sub.z and Ge.sub.xP.sub.ySe.sub.z, the Te-based glass at least comprises Ge.sub.xSb.sub.yTe.sub.z, Ge.sub.xSe.sub.yTe.sub.z and As.sub.xSe.sub.yTe.sub.z, wherein x, y, z represent different mole percentage, and x+y+z=100.

(13) The second combination at least comprises TiO.sub.2, HfO.sub.2, Al.sub.2O.sub.3, SiO.sub.2, Ga.sub.2O.sub.3, Ta.sub.2O.sub.3, and Bi.sub.2O.sub.3.

(14) The third combination at least comprises Ge, SiC, Si, Ge.sub.xSi.sub.y, Diamond, GaN, AlN, Si.sub.xN.sub.y, InP, GaAs, and LiNbO.sub.3, wherein the x and y in the third combination represent different mole percentage, and x+y=100.

(15) A method for controlling chromatic dispersion is obtained by using the broadband dispersion controlling waveguide according to the present disclosure, in which first, designing a set of structural size parameters of an optical waveguide, the set of structural size parameters comprising a width W of a contact surface between the waveguide core and the substrate, a thickness H of the A layer 1 of the waveguide core, and a thickness C of the B layer 2 of the waveguide core; and then, obtaining a chromatic dispersion curve based on a second derivative of a transmission constant of light in the optical waveguide with respect to wavelength.

(16) By reasonably adjusting value(s) of one or more of the width W of the contact surface between the waveguide core and the substrate, the thickness H of the A layer 1 of the waveguide core, and the thickness C of the B layer 2 of the waveguide core, the resulted chromatic dispersion curve can be a chromatic dispersion curve with up to 5 zero-dispersion wavelengths, and moreover, the chromatic dispersion curve is relatively flat in a broadband wavelength range, that is, the chromatic dispersion curve is flat in a broadband wavelength range of two octaves.

(17) Based on the resulted chromatic dispersion curve, by increasing the width W of the contact surface between the waveguide core and the substrate, the chromatic dispersion curve is shifted as a whole in the direction in which the anomalous dispersion value increases; by increasing the thickness H of the A layer 1 of the waveguide core, the chromatic dispersion curve is shifted as a whole in the direction in which the anomalous dispersion value increases; by increasing the thickness C of the B layer 2 of the waveguide core, the chromatic dispersion curve is rotated counterclockwise with the wavelength λ.sub.0 as the center, wherein when the wavelength is less than 4, the chromatic dispersion curve moves in the direction in which the anomalous dispersion value decreases, and when the wavelength is greater than 4, the chromatic dispersion curve moves in the direction in which the anomalous dispersion value increases.

Example

(18) As shown in FIG. 1-1, the core region of the selected optical waveguide structure comprises a double-layer structure of the A layer and the B layer formed of two different materials, where the material 2 of the B layer, i.e., the outer layer, is Ge.sub.15Sb.sub.20S.sub.65, and its refractive index is about 2.2; the material 1 of the A layer, i.e., the inner layer, is Ge.sub.30Sb.sub.10Se.sub.60, and its refractive index is about 2.65; the refractive index ratio of the two materials is about 1.2; the material of the substrate 3 is CaF.sub.2, and its refractive index is about 1.43; the cladding layer is air; and the sidewall angle α of the waveguide core is 87°. The FEM algorithm is used to calculate the effective refractive index of the TE mode fundamental mode in this waveguide structure, and a chromatic dispersion is calculated according to the obtained effective refractive index. First, a set of parameters are preset, including the width W of the contact surface between the waveguide core and the substrate 3 being 2350 nm, the height H of the A layer 1 being 1800 nm, and the height C of the B layer 2 being 1350 nm, and then with the above method, a curve of chromatic dispersion with respect to wavelength can be obtained. This curve has 5 zero-dispersion wavelengths, which are 2.94, 4.18, 7.36, 11.32 and 14.86 μm, respectively. And the chromatic dispersion curve is very flat, as shown with the solid line in the middle position in FIG. 2-1. The difference between the maximum and the minimum of the chromatic dispersion is 23 ps/nm/km, while the corresponding bandwidth is 3 to 15 μm, which exceeds two octaves.

(19) By merely increasing the width W of the contact surface between the waveguide core and the substrate 3 to W=2500 nm, the chromatic dispersion curve is shifted as a whole in the direction in which the anomalous dispersion value increases, with an amount of shifting being about 15 ps/nm/km, on the contrary, by reducing the width to W=2200 nm, the curve is shifted as a whole in the direction in which the anomalous dispersion value decreases, with an amount of shifting being about −15 ps/nm/km, as shown in FIG. 2-1.

(20) By merely increasing the thickness H of the high-index material (that is, the inner layer material 1) to H=1900 nm, the curve is shifted as a whole in the direction in which the chromatic dispersion value increases, with an amount of shifting being about 12 ps/nm/km, on the contrary, by reducing the thickness H to H=1700 nm, the curve is shifted as a whole in the direction in which the anomalous dispersion value decreases, with an amount of shifting being about −12 ps/nm/km, as shown in FIG. 2-2.

(21) By merely increasing the thickness C of the low-index material (i.e., the layer B) to C=1400 nm, the dispersion curve rotates counterclockwise with the specific wavelength λ.sub.0=10 μm as the center of rotation, where when the wavelength is less than 10 μm, it moves in the direction in which the anomalous dispersion value decreases, and the overall average movement amount is about −6 ps/nm/km, and when the wavelength is greater than 10 μm, it moves in the direction in which the anomalous dispersion value increases, and the overall average movement amount is about 9 ps/nm/km. On the contrary, by reducing the thickness to C=1300 nm, the dispersion curve rotates clockwise with the wavelength λ.sub.0=10 μm as the center of rotation, where when the wavelength is less than 10 μm, it moves in the direction in which the anomalous dispersion value increases, and the overall average movement amount is about 6 ps/nm/km, and when the wavelength is greater than 10 μm, it moves in the direction in which the anomalous dispersion value decreases, and the overall average movement amount is about −9 ps/nm/km, as shown in FIG. 2-3.

(22) With the present disclosure, controlling of the chromatic dispersion can be realized by flexibly changing the values of the three structural parameters (W, H, and C).

(23) Optical resonance devices and optical interference devices derived based on the cross section of the optical waveguide structure of the present disclosure include at least micro-ring resonator, Mach-Zindel Interferometer and a FP cavity using the cross section of the optical waveguide structure of the present disclosure.

(24) Although the present disclosure has been described above in conjunction with the accompanying drawings, the present disclosure is not limited to the specific embodiments described above. The described specific embodiments are only illustrative, but not restrictive. Under the enlightenment of the present disclosure, the skilled in this art could make many modifications without departing from the purpose of the present disclosure, which all fall into the protection scope of the present disclosure.