JP-2026075933-A - Optical waveguide element

JP2026075933AJP 2026075933 AJP2026075933 AJP 2026075933AJP-2026075933-A

Abstract

[Problem] To provide an optical waveguide element that can perform mode conversion between a strip waveguide section and a slot waveguide section, which have different layers. [Solution] An optical waveguide element according to one embodiment comprises a substrate, a strip waveguide portion formed in a first layer located above the substrate, a slot waveguide portion formed in a second layer located above the substrate and different from the first layer, and a mode conversion portion connected between the strip waveguide portion and the slot waveguide portion. The mode conversion portion includes a first optical confinement portion formed in the first layer and connected to the strip waveguide portion, and a pair of second optical confinement portions formed in the second layer and connected to the slot waveguide portion. The width of the first optical confinement portion decreases as it approaches the slot waveguide portion from the strip waveguide portion. The pair of second optical confinement portions include the first optical confinement portion on the inside in a plan view of the substrate. [Selection Diagram] Figure 1

Inventors

藤澤燦
田中啓二
杉本良之

Assignees

住友電気工業株式会社

Dates

Publication Date: 20260511
Application Date: 20241023

Claims (7)

circuit board and A strip waveguide portion formed on the first layer located above the substrate, A slot waveguide portion is located above the substrate and formed in a second layer different from the first layer, A mode conversion unit connected between the strip waveguide and the slot waveguide, Equipped with, The mode conversion unit includes a first optical confinement unit formed in the first layer and connected to the strip waveguide unit, and a pair of second optical confinement units formed in the second layer and connected to the slot waveguide unit. The width of the first optical confinement section decreases as it approaches the slot waveguide section from the strip waveguide section. The pair of second light confinement portions include the first light confinement portion on the inside when viewed in plan of the substrate. Optical waveguide element.
The strip waveguide, the mode conversion unit, and the slot waveguide are arranged in this order along the X-axis direction. Along the Y-axis direction intersecting the X-axis direction, one of the pair of second light confinement sections, the first light confinement section, and the other of the pair of second light confinement sections are arranged in this order. With respect to a reference line that passes through the center of the first light confinement portion in the Y-axis direction and extends along the X-axis direction, each of the pair of second light confinement portions is formed to be symmetrical with respect to the other. The optical waveguide element according to claim 1.
The difference between the distance between the pair of second optical confinement sections aligned along the Y-axis and the width of the first optical confinement section decreases monotonically as you move from the strip waveguide towards the slot waveguide. The optical waveguide element according to claim 2.
The width of each of the pair of second optical confinement sections decreases monotonically from the slot waveguide section toward the strip waveguide section. The optical waveguide element according to any one of claims 1 to 3.
In a cross-section perpendicular to the X-axis direction, which is the direction in which the strip waveguide, the mode conversion section, and the slot waveguide are aligned, the first layer is formed above the second layer. The optical waveguide element according to any one of claims 1 to 3.
The slot waveguide has the same mode of optical propagation as the strip waveguide. The optical waveguide element according to any one of claims 1 to 3.
The substrate comprises a cladding formed on the substrate, The first layer and the second layer are provided within the cladding. The optical waveguide element according to any one of claims 1 to 3.

Description

This disclosure relates to optical waveguide elements. Patent Document 1 describes a waveguide coupler configured to optically couple a strip waveguide to a first slot photonic crystal waveguide. The waveguide coupler is positioned between the first slot photonic crystal waveguide and the strip waveguide. The waveguide coupler includes a tapered region having a second slot photonic crystal waveguide aligned with the first slot photonic crystal waveguide and the strip waveguide. Non-patent document 1 describes a structure in which a tapered section is provided between a slot waveguide and a strip waveguide. A strip waveguide uses a strip section with a high refractive index as its core, and increasing the width of the strip section strengthens optical confinement. In a slot waveguide, a low refractive index section is sandwiched between two strip sections with high refractive index as its core. As the distance between the two strip sections increases, the optical confinement in the slot waveguide weakens. In the tapered section, the width of the strip waveguide is gradually narrowed to weaken optical confinement, while the distance between the slot waveguide sections is gradually narrowed to strengthen optical confinement in the slot waveguide, thereby converting light between the two waveguides. U.S. Patent Application Publication No. 2014/0219602 Q.Deng et al., “Strip-slotwaveguide mode converter based on symmetric multimode interference”, OpticsLett. Vol.39, Issue 19, pp.5665-5668(2014) Figure 1 is a plan view showing an optical waveguide element according to an embodiment.Figure 2 is a cross-sectional view taken along the line B-B in Figure 1.Figure 3 schematically shows the beam shape in the sections along lines A-A, B-B, C-C, and D-D in Figure 1.Figure 4 is a graph showing an example of the relationship between the length of the mode conversion section of an optical waveguide element and its conversion efficiency. [Description of Embodiments in this Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. (1) An optical waveguide element according to one embodiment includes a substrate, a strip waveguide portion formed in a first layer located above the substrate, a slot waveguide portion formed in a second layer located above the substrate and different from the first layer, and a mode conversion portion connected between the strip waveguide portion and the slot waveguide portion. The mode conversion portion includes a first optical confinement portion formed in the first layer and connected to the strip waveguide portion, and a pair of second optical confinement portions formed in the second layer and connected to the slot waveguide portion. The width of the first optical confinement portion decreases as it approaches the slot waveguide portion from the strip waveguide portion. The pair of second optical confinement portions include the first optical confinement portion on the inside in a plan view of the substrate. In this optical waveguide element, a strip waveguide section and a slot waveguide section are formed above the substrate, and a mode conversion section is located between the strip waveguide section and the slot waveguide section. The mode conversion section includes a first optical confinement section and a second optical confinement section. The first optical confinement section is connected to the strip waveguide section, and the second optical confinement section is connected to the slot waveguide section. The width of the first optical confinement section decreases as it approaches the slot waveguide section from the strip waveguide section, and the second optical confinement section contains the first optical confinement section internally in a plan view of the substrate. Therefore, the width of the first optical confinement section decreases as it approaches the slot waveguide section, and the distance between the second optical confinement section and the first optical confinement section in a plan view of the substrate decreases as it approaches the slot waveguide section. Consequently, optical conversion can be performed smoothly in the mode conversion section located between the strip waveguide section and the slot waveguide section. (2) In (1) above, the strip waveguide, mode conversion section, and slot waveguide section may be arranged in this order along the X-axis direction, and one of the pair of second optical confinement sections, the first optical confinement section, and the other of the pair of second optical confinement sections may be arranged in this order along the Y-axis direction intersecting the X-axis direction. Each of the pair of second optical confinement sections may be formed so as to be symmetrical with respect to a reference line that passes through the center of the first optical confinement section in the Y-axis direction and extends along the X-axis direction. In this case, the rotation of the mode,